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EARTH FROM SPACE: Like You've Never Seen Before

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A random vistor asks:"How did earth get its name?"

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A random vistor asks:"How did earth get its name?"

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Peppa: So basiclly we don't know how it gets it name, there is a fact that earth is named after a roman or greek god.

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People think earth is a prefect circle, but It's not

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People think earth is a prefect circle, but It's not

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Reference:
Twitter, @SpaceHub_SL

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Not sure if it's real or not

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A year ago the #Fagradalsfjall #eruption in #Iceland started! and here a little video we made so you can appreciate it at its best!! #volcano #science #lava

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A year ago the #Fagradalsfjall #eruption in #Iceland started! and here a little video we made so you can appreciate it at its best!! #volcano #science #lava https://t.co/nLaY2nPrBn

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A year ago the #Fagradalsfjall #eruption in #Iceland started! and here a little video we made so you can appreciate it at its best!! #volcano #science #lava pic.twitter.com/nLaY2nPrBn
— GeoLchat (@geolchat) March 20, 2022

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A year ago the #Fagradalsfjall #eruption in #Iceland started! and here a little video we made so you can appreciate it at its best!! #volcano #science #lava https://t.co/nLaY2nPrBn

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A year ago the #Fagradalsfjall #eruption in #Iceland started! and here a little video we made so you can appreciate it at its best!! #volcano #science #lava https://t.co/nLaY2nPrBn

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A year ago the #Fagradalsfjall #eruption in #Iceland started! and here a little video we made so you can appreciate it at its best!! #volcano #science #lava

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5 layers and they have different colour

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We don't know, because nobody has every tried to enter it

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The discussion of black holes is one that still confuses and stumps scientists. Therefore, asking whether or not you could survive a black hole is also tricky. Black holes bend time and space, which leaves scientists with unanswered questions about what happens in them. In fact, physicists have debates on paradoxes and unanswered questions that black holes present.

What happens when you fall into a black hole is dependent upon the size of the black hole and the perspective you take. The strength of a black hole's gravity depends on the size. A black hole's gravity decreases as size increases; this means that larger black holes have weaker a gravity. Smaller black holes have a stronger gravity.

You would most likely not survive either a small or a large black hole. Remember, light cannot even escape a black hole-that is why it is called a black hole. From an outside perspective, time would slow down as you moved closer to the center of the black hole. Time and space begin to warp and stretch as they are pulled towards the center of the black hole: this means that you too would warp and stretch. This bending and stretching is called spaghettification. Someone outside the black hole would see your body begin to stretch and bend like a spaghetti noodle. As you approach the edge of the event horizon, you will freeze in space and time. You will appear to be unmoving and stretched like a noodle forever. After some time, heat and radiation would then destroy your body and turn you into ash.

However, time becomes strange as you get closer to the event horizon, or the end of the black hole before the large pit. In your eyes, as the one who is falling into the black hole, you would experience time normally. Additionally, once you reach the event horizon, you may survive. To outside observers, you are gone. However, in your perspective, you are alive and well. The issue in this case is that once you pass the event horizon, you cannot turn back. While you are alive and well within the black hole, you may never return. To return would mean to travel against time and space. We all know that you cannot time travel into the past. Light cannot even do this. To outside observers, you are dust. You may not tell them that you are alive in your new reality within the black hole because you cannot travel against time.

The image is confusing. How can you be alive and not alive at the same time? Physicists are still debating it. Regardless of the explanation, we do know that it is highly unlikely that anyone entering a black hole would survive. Nothing escapes a black hole. Any trip into a black hole would be one way. The gravity is too strong and you could not go back in space and time to return home. Aside from this, your body would be stretched and destroyed by the warping of space and the amount of radiation surrounding the event horizon.

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Can You Survive A Black Hole? | Will You See, Survival & Facts

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The discussion of black holes is one that still confuses and stumps scientists. Therefore, asking whether or not you could survive a black hole is also tricky. Black holes bend time and space, which leaves scientists with unanswered questions about what happens in them.

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a place where matter is compressed down to an infinitely tiny point, and all conceptions of time and space completely break down.

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(Image credit: Shutterstock)

Paul M. Sutter is an astrophysicist at Stony Brook and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of . Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.

The singularity at the center of a is the ultimate no man's land: a place where matter is compressed down to an infinitely tiny point, and all conceptions of time and space completely break down. And it doesn't really exist. Something has to replace the singularity, but we're not exactly sure what.

Let's explore some possibilities.
Related: Black holes of the universe (images)
Planck stars

It could be that deep inside a black hole, matter doesn't get squished down to an infinitely tiny point. Instead, there could be a smallest possible configuration of matter, the tiniest possible pocket of volume.

This is called a Planck star, and it's a theoretical possibility envisioned by loop quantum gravity, which is itself a highly hypothetical proposal for creating a quantum version of gravity. In the world of loop quantum gravity, space and time are quantized - the universe around us is composed of tiny discrete chunks, but at such an incredibly tiny scale that our movements appear smooth and continuous.

This theoretical chunkiness of space-time provides two benefits. One, it takes the dream of quantum mechanics to its ultimate conclusion, explaining gravity in a natural way. And two, it makes it impossible for singularities to form inside black holes.

As matter squishes down under the immense gravitational weight of a collapsing star, it meets resistance. The discreteness of space-time prevents matter from reaching anything smaller than the Planck length (around 1.68 times 10^-35 meters). All the material that has ever fallen into the black hole gets compressed into a ball not much bigger than this. Perfectly microscopic, but definitely not infinitely tiny.

This resistance to continued compression eventually forces the material to un-collapse (i.e., explode), making black holes only temporary objects. But because of the extreme time dilation effects around black holes, from our perspective in the outside universe it takes billions, even trillions, of years before they go boom. So we're all set for now.

Related: What is gravity?

Gravastars

Another attempt to eradicate the singularity - one that doesn't rely on untested theories of quantum gravity - is known as the gravastar. It's such a theoretical concept that my spell checker didn't even recognize the word.

The difference between a black hole and a gravastar is that, instead of a singularity, the gravastar is filled with dark energy. Dark energy is a substance that permeates space-time, causing it to expand outward. It sounds like sci-fi, but it's real: dark energy is currently in operation in the larger cosmos, causing our entire universe to accelerate in its expansion.

As matter falls onto a gravastar, it isn't able to actually penetrate the event horizon (due to all that dark energy on the inside) and therefore just hangs out on the surface. But outside that surface, gravastars look and act like normal black holes. (A black hole's event horizon is its point of no return - the boundary beyond which nothing, not even light, can escape.)
The universe: Big Bang to now in 10 easy steps
However, recent observations of merging black holes with gravitational wave detectors have potentially ruled out the existence of gravastars, because merging gravastars will give a different signal than merging black holes, and outfits like LIGO (the Laser Interferometer Gravitational-Wave Observatory) and Virgo are getting more and more examples by the day. While gravastars aren't exactly a no-go in our universe, they are definitely on thin ice.

Let's go for a spin

Planck stars and gravastars may have awesome names, but the reality of their existence is in doubt. So maybe there's a more mundane explanation for singularities, one that's based on a more nuanced - and realistic - view of black holes in our universe.

The idea of a single point of infinite density comes from our conception of stationary, non-rotating, uncharged, rather boring black holes. Real black holes are much more interesting characters, especially when they spin.

The spin of a rotating black hole stretches the singularity into a ring. And according to the math of Einstein's theory of general relativity (which is the only math we've got), once you pass through the ring singularity, you enter a wormhole and pop out through a white hole (the polar opposite of a black hole, where nothing can enter and matter rushes out at the speed of light) into an entirely new and exciting patch of the universe.

One challenge: the interiors of rotating black holes are catastrophically unstable. And this is according to the very same math that leads to the prediction of the traveling-to-a-new-universe stuff.

The problem with rotating black holes is that, well, they rotate. The singularity, stretched into a ring, is rotating at such a fantastic pace that it has incredible centrifugal force. And in general relativity, strong enough centrifugal forces act like antigravity: they push, not pull.

This creates a boundary inside the black hole, called the inner horizon. Outside this region, radiation is falling inward toward the singularity, compelled by the extreme gravitational pull. But radiation is pushed by the antigravity near the ring singularity, and the turning point is the inner horizon. If you were to encounter the inner horizon, you would face a wall of infinitely energetic radiation - the entire past history of the universe, blasted into your face in less than a blink of an eye.

The formation of an inner horizon sows the seeds for the destruction of the black hole. But rotating black holes certainly exist in our universe, so that tells us that our math is wrong and something funky is going on.

What's really happening inside a black hole? We don't know - and the scary part is that we may never know.

Additional resources

You can learn more about black holes at this NASA explainer page. This BBC Earth piece has good basic information about black holes as well, and it also describes what would happen to you if you fell into one of these light-gobbling monsters. And the Stanford Encyclopedia of Philosophy has a good, detailed breakdown of black holes and singularities.

Rovelli, C. and Vidotto, F, 2014. "Planck stars," International Journal of Modern Physics D, Vol. 23, No. 12. https://doi.org/10.1142/S0218271814420267

Sakai, N. et al, 2014. "Gravastar shadows," Physical Review D, Vol. 90. https://journals.aps.org/prd/abstract/10.1103/PhysRevD.90.104013

Taylor, E. and Wheeler, J. "Exploring Black Holes: Introduction to General Relativity." Addison Wesley Longman, 2000. https://www.amazon.com/Exploring-Black-Holes-Introduction-Relativity/dp/020138423X

Editor's note: Learn more by listening to the episode What really happens at the center of a black hole? on the Ask A Spaceman podcast, available on and on the Web at http://www.askaspaceman.com. Thanks to Andy P., Brittany, Jeff J., Robert S., Vladimir B., Jack S., @Grobillard, and James L. for the questions that led to this piece! Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter. This story was first published on Oct. 27, 2020. It was updated and republished on Feb. 8, 2022.
Bibliography

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What happens at the center of a black hole?

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(Image credit: Shutterstock) Paul M. Sutter is an astrophysicist at Stony Brook and the Flatiron Institute, host of Ask a Spaceman and Space Radio , and author of . Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.

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There isn't any method to escape, because no one has entered it, and scitenist hasn't conform whats inside there.

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What would happen if you fell into a black hole? | BBC Earth

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The black hole; fascinating, mysterious, deadly. But what would happen if you fell into one?

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The outside of black hole it's incredidly hot, but the inside it's probably really cold.

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What is the temperature of a blackhole? - Wonder Wall - TPL Kids

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TPL Kids is a website for kids. Discover great books, get homework help, enjoy fun activities and more.

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It was called worm hole, because in the earlies people didn't get a chance to go to the space and check whats it look like. So they that the hole its made by a worm.

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Wormhole Tunnels in Spacetime May Be Possible, New Research Suggests

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There may be realistic ways to create cosmic bridges predicted by general relativity

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Will the time freeze if you go into the black?

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Will the time freeze if you go into the black?

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Time does stop at the event horizon of a black hole, but only as seen by someone outside the black hole.

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This post may contain affiliate links to books or other resources I personally recommend.

Black holes are some of the most intriguing, yet not very well-understood objects in the universe, which are best described by Einstein's theory of general relativity.

One of the more interesting predictions of the theory is that even time will slow down near a black hole. But why, exactly?
Time slows down near a black hole due to the extremely strong gravitational field of the black hole. According to the theory of general relativity, this phenomenon is due to the gravity of the black hole curving spacetime in a way that affects all measurements of time and space near the black hole.
In this article, we'll be discussing all about this slowing down of time -thing in great detail (namely the interesting geometry behind it) as well as looking at some consequences of this phenomenon (such as how it affects aging).

We'll also look at some concrete examples of how much time actually slows down near a black hole as well as how different properties of black holes affect this (such as electric charge and spin).

Gravitational Time Dilation Explained

If you've ever heard of general relativity or black holes before, you've probably also heard about the phenomenon called gravitational time dilation.

This is the effect a gravitational field has on the passing of time around it, namely that a clock will "tick" slower near, for example, a black hole than it would far away from the black hole.

The real question is, however, why such a phenomenon actually occurs and the answer is quite subtle but has a nice geometric explanation.

But, we need to first discuss the underlying ideas behind this geometric explanation.

The Geometry of Spacetime According To General Relativity

In general relativity, we model everything through a concept called spacetime. Essentially, this means that both space and time are "combined" together into a 4-dimensional geometry known as a manifold.

The effects of gravity are then modeled by the curvature of this spacetime manifold. If you wish to understand the underlying ideas behind this, I recommend reading this introduction to general relativity.

This is a sketch of a curved spacetime manifold, which has a time dimension and a spacial dimension. Note that in reality, spacetime is 4-dimensional with one time dimension and three spacial dimensions, but this cannot really be pictured in any sensible way.

Anyway, if we wish to actually describe a point (these are called events) on a curved spacetime manifold, we need coordinates (one time coordinate and three space coordinates) or a coordinate system.

In a coordinate system, there are always basis vectors, which are used to generally describe any vector and its components in that system.

However, if the spacetime and thus, the coordinate system is curved (such as in a gravitational field in general relativity), these basis vectors are going to vary from point to point, which means their length and direction aren't constant anymore.

Here, we have again a 2-dimensional spacetime with et denoting the basis vector in the time direction and ex the basis vector in the x-direction.

We describe how these basis vectors are different from point to point by using a metric tensor, which is essentially just a function that allows us to define a notion of length on any curved manifold.

The components of this metric tensor (at any point) are defined as the dot product between basis vectors:

Since the dot product is a measure of how much two vectors are "aligned" (for more on this, you can check out this article on the physical meaning of the dot product), this means that the metric tensor measures the alignment of basis vectors at any given point. Also, more importantly for our discussion, the metric gives a measure of the lengths of basis vectors at a point.

Now, the changes of these basis vectors from point to point also have direct physical implications.

Namely, this means that measurements of physical quantities that are described by these spacetime coordinates (so time intervals and lengths) are going to differ from point to point.

We'll discuss this (and most importantly how this can help us understand time dilation near a black hole) in the next section.

Quick tip: If you really wish to build a deep understanding of general relativity, you need to have a strong mathematical foundation first and one of the most important topics to learn is vector calculus.

This is why I created my own online course Vector Calculus For Physics that aims to teach all of the most foundational mathematical concepts in a way that anyone will be able to understand them. You'll also get to discover how all of the mathematical tools can be directly applied to physics through intuitive step-by-step examples as well as a workbook with tons of practice problems

The Geometric Explanation Behind Gravitational Time Dilation

For our discussion regarding black holes, the curved spacetime geometry near a spherical black hole is such that the basis vectors in the time direction get shorter as one moves closer to the black hole (more on this down below).

You can sort of picture this geometrically as the time dimension getting "squeezed" as one moves radially towards the black hole. This then results in the effect we call gravitational time dilation.

All of this is described by the usual metric from general relativity called the Schwarzschild metric. This is the metric describing spacetime (and gravity) around a spherically symmetric massive body.

Why Do The Basis Vectors Get Shorter? (Mathematical Explanation)

The geometry of these basis vectors can be understood quite easily. Now, to really understand the mathematics here, you may need a little bit of an understanding of general relativity first. For that, I'd recommend checking out this step-by-step guide on self-studying general relativity.

Anyway, to describe what happens to the basis vectors in the time direction, we need the g tt-component of the Schwarzschild metric, which is defined as follows:

Here, rs is a parameter known as the Schwarzschild radius and r is the radial coordinate (basically the distance from the center of the black hole).

On the other hand, the g tt-component of the metric can also be defined as the dot product between the e t-basis vectors:

This gives a nice expression for the length of the e t-basis vector through the metric. As a technical detail, the length (squared) of a basis vector is given by the absolute value of the metric component (since the metric components can be negative):

This absolute value sign denoted the length of the et-basis vector, which is the dot product between the et-basis vector with itself. This is, of course, just the metric component gtt, however, the "true length" of the basis vector requires taking the absolute value, which is really just a technical detail.

From this and the one equation above, we get a formula for the length of the e t-basis vector as a function of the coordinate r by inserting the g tt-component of the Schwarzschild metric into this (note that due to the absolute value, the negative sign changes to a positive since the g tt-component of the metric is generally negative):

From this, we can see that as r gets smaller (getting closer to the black hole), the length of the e t-basis vector gets shorter.

At the point r=r s (this is the event horizon of the black hole), the length of the e t-basis vector actually shrinks to zero, which physically corresponds to time dilation going to infinity. This is the origin of the idea that an outside observer would never actually see anything cross the horizon of a black hole.

It's also worth noting that all of this is perfectly valid for not just black holes, but for any spherically symmetric mass, like the Earth. In this case, the e t-basis vectors also get shorter as one approaches the Earth.

The only difference here between the Earth and a black hole would be the parameter r s. In fact, a black hole is defined as any object that has its rs greater than its actual physical radius.

Therefore, for something like the Earth, the basis vectors will never shrink to a length of zero at any physically sensible value of r, because this would mean actually having to go inside the Earth to reach the Schwarzschild radius r s, in which case the Schwarzschild metric wouldn't even be valid anymore.

But why does this happen? Why would the basis vectors getting shorter actually imply time itself passing slower near a black hole?

The answer to this really comes from the fact that time itself is only a coordinate in general relativity, not a universal concept.

Thus, any change in the coordinate system we use to describe spacetime will have an effect on the specific measured values of the coordinates.

In our case, the basis vectors changing length in the time direction means that the measured values of time at different points will also be affected.

Now, this may seem counter-intuitive, but if you actually wish to understand time dilation, you have to just accept the fact that time really is only a coordinate.

However, there is a concept of proper time, which can be thought of as the closest thing there is to a universal notion of time. I explain this later in this article (I also discuss this in my articles " Special Relativity For Dummies" and " Is Time a Vector? ").

Anyway, we can understand the geometry behind this time dilation effect through a simple example, which you'll find down below.

Example: The Geometry Behind Time Dilation

If we're talking about basis vectors changing in the time direction, surely this must have some kind of effect on actual vectors also, vectors after all being expressed through basis vectors?

The answer is actually somewhat more subtle, since a vector itself does not change even if the coordinate system (basis vectors) change but the vector components do.

To understand this, I need to first make clear that by vectors, I'm talking about four-vectors, which are basically vectors in spacetime (that have one time component and three spacial components).

Also, by a vector not changing, I'm essentially talking about its length (and direction, but that's not too important for us) remaining constant. The length of a vector being invariant is one of the most fundamental geometric properties of vectors, so it will be true generally.

Anyway, let's look at a concrete example of how time dilation actually occurs from this.

We'll consider an object described by a spacetime displacement four-vector, which has a time component describing "displacement in the time direction" (which basically just means a time interval) and spacial components describing spacial displacements.

Moreover, we'll take the object in question to be stationary in space, so the spacial displacements are all zero (the time component is not zero, however, since all objects "move in time"). You can physically think of this as an object that is essentially just "floating" above a black hole, for example.

The components of this four-vector are therefore:

The c here is the speed of light, which is just a constant that is needed to give the right units to this expression.

The length of this four-vector is simply the total spacetime interval or line element, ds ² (actually, the square of the length). We can calculate this by the following formula:

This formula is basically the curved spacetime equivalent of the Pythagorean theorem. For more on this, I recommend reading my general relativity article. This metric tensor, gµν, is required here since the basis vectors are not constant.

Since the only non-zero component of the displacement four-vector is the time component, we get:

From the example from earlier, we know that the g tt-component of the metric gives the square of the length of the time basis vector e t. Inserting this and also the dx t-component, we get:

Now, here comes the interesting part. Since the basis vectors get shorter as one moves closer to the black hole (this e t ² -term gets smaller) but ds ² has to remain constant, this means that the dt ² MUST get bigger to account for the decrease in this basis vector length term.

But what does this mean physically? Essentially, this dt-term represents a displacement in time, in other words, a time interval. This term getting bigger the closer one moves to the black hole means time intervals are passing slower the closer one is to the black hole. This is the effect of time dilation!

This was just one example, of course, but the same concept still applies to other situations as well. Intuitively, you can think of the geometry of this time dilation effect the following way; since the basis vectors are shorter closer to the black hole, all vectors require "more of the time component" to describe that same vector.

Basically, the logic here is; shorter basis vector="more" of the component to describe the same vector in that direction. This then results in actual physical effects in quantities that are described by components of four-vectors, such as time.

If you're interested in learning more about black holes, I have afull guide on orbits around black holes. In this article I cover what kinds of orbits are possible around a black hole (such as the little-known zoom-whirl orbits) and explain various phenomena such as orbital precession as well as how the spin or charge of a black hole affects these orbits. I also have anarticle on orbits of light specifically, which covers topics such as null geodesics and the notion of a photon sphere around a black hole.

Does Time Stop In a Black Hole?

As one moves closer and closer to a black hole, the passing of time will also slow down more and more. So, does time therefore stop as one falls into a black hole?
Time does stop at the event horizon of a black hole, but only as seen by someone outside the black hole. This is because any physical signal will get infinitely redshifted at the event horizon, thus never reaching the outside observer. Someone falling into a black hole, however, would not see time stop.
Now, to understand what actually happens to time dilation at the black hole's event horizon, we need to discuss an important distinction made by general relativity and that is the distinction between coordinate time and proper time.

Coordinate Time vs Proper Time

Coordinate time, in this context, is the time passing for the observer near the black hole as measured by another observer far away. In this sense, it is the amount of time an observer on Earth, for example, would measure to pass for the other observer near the black hole.

Proper time, on the other hand, is the time measured by the observer itself that is near the black hole. It's worth noting that proper time is an invariant quantity, so in a sense, it is a more "objective" measure of the actual time that passes.

In a sense, proper time is a more meaningful measure of time as it is always the time measured by an observer themselves. However, for time dilation, what really matters is the difference in the proper time and coordinate time measurements. Also, don't ask me why these observers happen to be fruits.

That being said, what really matters is the difference in the time measurements between the two observers, which results in the phenomenon of gravitational time dilation.

Mathematically, it's possible to derive an equation for both the coordinate time (t) and proper time (τ) as a function of the distance (r) from the black hole's center (note that these are only valid for stationary observers, because otherwise we'd have to account for other time dilation effects also):

Here, rs is the Schwarzschild radius, which describes the event horizon of the black hole (the radius beneath which nothing, not even light, can escape).

From these, we can look at what happens near the event horizon of the black hole (in other words, the limit as r approaches r s).

Because of the logarithmic term in the first equation, the coordinate time blows to infinity, while nothing particularly special happens to the proper time.

So, the physical implication of this is that the far away observer would see the time passed for the observer near the event horizon slow down indefinitely, while the observer at the event horizon would not see anything special happening.

But why does such a thing happen? There is actually a fairly intuitive explanation for this, which all comes down to how we think of the concept of time; fundamentally, time can only be measured through changes.

Any measurement of a physical change is, however, limited by a "signal" having to travel between two points (between the observer and the point where the physical change occurs) and these signals are limited to travel at (or under) the speed of light.

This is the basic idea behind how the speed of light defines the way that the passing of time is measured (this is also the basis behind the idea of Einstein's clock synchronization procedure).

This also helps us understand the phenomenon of gravitational time dilation.

Gravitational time dilation only happens between two observers at different points under different gravitational potentials and this is fundamentally due to how light (or any other signal) travels between these two points.

So, an observer far away (essentially not influenced by gravity at all) would observe the passing of time of another observer close to a black hole as being slower simply because light (or any other signal) is slowed down due to the gravitational potential difference between the observers.

Intuitively, you could think of this resulting from the gravity of the black hole "pulling" the outgoing light rays towards the center, thus "slowing them down", but really this is due to the light being redshifted as it climbs out of the black hole's gravitational well.

Now, while the far away observer would see any light rays or any other physical signals being slowed down due to gravity, thus resulting in the passing of time being seemingly slower, the observer near the black hole would not see such an effect.

This is because, locally, the speed of light is always c (a constant), so the time dilation effect is only due to the coordinate differences between the two observers.

The observer itself that is close to the black hole does not see his own time passing any slower, but the far away observer does see this other observer's time passing slower.

But which one of them is right? Well, the answer is that both of them are correct.

See, the question isn't about which one is more correct than the other because the whole premise behind this question does not make sense (relativistically, that is).

Neither one of them is more correct because this would require one observers frame being somehow "superior" to the other's and the whole idea behind the theory of relativity is that all reference frames are equivalent.

So, it's simply not possible to say how much time has "universally" passed, we can only say how much time passes in one particular frame and then compare those differences.

However, an objective fact is that there is a difference in the passing of time between the two observers. So, in fact, the two observers WILL see each other physically age at a different pace. This is discussed more later in the article.

How Much Does Time Actually Slow Down Near a Black Hole?

How much time actually slows down near a black hole will depend on a few things, such as the motion and position of the observer in question as well as the type of black hole and its properties.

We will keep considering the simplest types of black holes here, the Schwarzschild black hole, which are uncharged and non-rotating.

It's worth noting, however, that the electric charge and rotation will play a role in time dilation for other black hole types, but these we will look at later in this article.

The simplest case we can do is consider an observer at a fixed position near the black hole (meaning that the observer's spacial coordinates are constant, but the time coordinate is not; we're essentially just ignoring all velocity-induced time dilation effects) and then compute the gravitational time dilation.

If this is the case, the gravitational time dilation is only affected by two things:

The mass of the black hole

The (radial) distance from the black hole

The formula for calculating the exact time dilation is as follows (note; this gives the time dilation factor, which is a dimensionless number):

Here, rs is again the Schwarzschild radius (which depends on the black hole's mass, since rs=2GM/c²), which gives the event horizon of the black hole. Note also that this formula is only valid for r>rs (i.e. outside of the black hole).

This time dilation factor essentially gives the ratio of proper time to the coordinate time (we talked about the differences between these earlier).

So, we can calculate the coordinate time that would pass for a given amount of proper time near the black hole by multiplying it with this time dilation factor:

As a reminder; proper time (τ) is the time that passes for the observer who is near the black hole, while coordinate time (t) is the time a far away observer would see pass for this observer near the black hole.

It's interesting to look at some actual numerical values for the time dilation and how they depend on the distance from the black hole.

The most general way to do this is by specifying the distances from the black hole in terms of its Schwarzschild radius. This way we don't have to specify a mass for the black hole or calculate the Schwarzschild radius explicitly.

Below I've collected a table of different values of the time dilation for different distances.

Distance from the black hole
(measured in units of rs)

Time passed on Earth for
24 hours near the black hole

Here we're comparing the time passed in 24 hours near the black hole to how much time passes on Earth in this same period (so we're taking Δτ=24 h, which is the time passed near the black hole and Δt is the time passed on Earth that we get from our formula above).

The interesting thing about the above values is that the time dilation increases quite slowly, but as you get closer and closer to the black hole, the effects become much more significant and over time the effect sort of "compunds" on itself.

For example, if you were to spend 1 year near the black hole at the distance 1.00005 r s (which is probably unrealistic, since it is so close to the event horizon), in this time, 141 years would have passed on Earth!

Time Dilation Near Rotating and Charged Black Holes (Interactive Tool)

If we take into account other properties that a black hole may have (in general, a black hole can have a mass, charge and angular momentum), these will affect the time dilation experienced by an observer near the black hole, although the significance of these effects might vary.

Now, how would we calculate the time dilation in these more general cases? The general formula for the time dilation factor is:

If you're not familiar with the mathematics of general relativity, this may look quite complicated. Implicitly, this formula contains a summation over both the µ and ν indices, which run from 0 to 3. These time derivatives of the coordinates describe the coordinate velocities.

This formula indeed gives the time dilation in any spacetime for any observer, moving or not. We can, however, simplify this a lot by only looking at observers that are stationary near the black hole (relative to the far away observer).

Doing this, the time dilation factor simplifies to:

For stationary observers, the time dilation is only given by the g₀₀-component of the metric.

Now, rotating and charged black holes in general relativity are described by the Reissner-Nordström metric (non-rotating black hole with charge), the Kerr metric (rotating uncharged black hole) and the most general one, the Kerr-Newman metric (rotating and charged black hole).

The g ₀₀-components of these metrics are:

The parameters a and r Q ² describe the angular momentum ("rate of spinning") and charge of the black hole and they are defined as follows:

Here, J is the black hole's angular momentum, Q is its charge and M is its mass.

The time dilation factors obtained from these g ₀₀-metric components are then as follows:

Note that if we choose θ=π/2, this actually reduces to the Schwarzschild time dilation factor, meaning that in the θ=π/2-plane, the time dilation would appear as if the black hole was not rotating at all.

Here are a few noteworthy details about these time dilation factors:

All of these reduce to the Schwarzschild time dilation factor if we take Q=0 and a=0.

The time dilation factors for the rotating black holes depend on the θ-coordinate, which we'll take as the angle relative to the z-axis (which is also the spin-axis of the black hole).

Physically, this means that the time dilation as seen by a far away observer will be different depending on the relative angle between the far away observer and the observer near the black hole.

This is due to a phenomenon called frame dragging, which can be thought of as the rotating black hole "dragging" the spacetime around it as it rotates (a nice analogue of this is like water "circling" around a drain in a pool).

Also, due to this frame-dragging effect, all observers are naturally "dragged" to rotate with the black hole; thus, for an observer to remain stationary, it has to oppose the rotation of the black hole such that it remains still. This is only possible outside a certain distance called the stationary limit surface.

Here we've taken the Earth (the observer far away from the black hole) to be sitting still in the xy-plane, which lies at the value of θ=π/2.

I explain the effect of frame dragging in more detail in this article. In there, I also go over how frame dragging actually results in some extremely interesting and complicated 3D orbital mechanics around a black hole.

To get an idea of how these time dilation factors for the different types of black holes actually differ from the simple Schwarzschild black hole, I've made a little interactive tool for you to play around with (which you'll find down below).

This tool allows you to see the graphs of all the time dilation factors (plotted as functions of the r-coordinate) for different values of the black hole's mass M and the angle θ. This allows you to visualize how these values actually affect the time dilation.

To turn on the animations in the graphs below, press either one of the sliding scales, then the top right corner with 3 bars, then the little gear icon (which reads "Object Properties") and tick the "Animation On" -box.

Note; these functions plotted in the graph all describe extremal black holes (this makes it easier to compare them). This means that the black holes have the maximum possible allowed angular momentum and charge:

The explicit time dilation factors are then (for simplicity, I've also set the constants c and G equal to 1):

Would You Really Age Slower Near a Black Hole?
In short, a person near a black hole will age slower compared to someone far away from the black hole. This is because the passing of time is slowed down due to the extremely strong gravitational field near the black hole and thus, any physical aging processes will also happen slower.
Since black holes will affect the rate of time, it makes sense to think that they would also affect the way someone near the black hole ages. The question is, would you age slower or faster near a black hole?

Now, let's try to understand this more deeply.

When we talk about time dilation and time "slowing down", we're really talking about all physical processes slowing down to the same extent. In fact, we're talking about all measurements of time being "slowed down".

By time measurement, I don't necessarily mean someone measuring seconds with a wristwatch, I'm rather talking about the fundamental nature of how time is even observed in the first place; through physical changes.

Think about it; if nothing were to ever change in any way, time would not even exist. There wouldn't be any way of distinguishing the past from the present.

So, the passing of time itself can fundamentally only be observed by things changing and therefore, time slowing down really means that all physical changes happen slower.

The same applies to processes in your body as well. Essentially, this comes down to what aging really is in the first place; a series of physical processes that change your body over time.

These, on the other hand, are regulated by signals that your cells are sending across your body.

Now, it doesn't really matter what these physical signals are; whether they are neuron impulses or hormone binding proteins travelling around your body, these are still physical processes of change, which too will be affected by gravitational time dilation as anything else would.

So yes, being near a black hole (or any other strong gravitational field) does affect aging. Now, the key point here is that a person near a black hole won't themselves notice anything different in their OWN aging process, but another observer far away will.

It's the difference in the passing of time that really matters when comparing who ages faster or slower.

In the language of general relativity, it's the difference in the proper time (time as measured by the observer near the black hole) and the coordinate time (time as measured by some far away observer) that determines who ages at what rate COMPARED TO someone else (the word compared matters here, as the rate of aging is always relative to something).

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Why Time Slows Down Near a Black Hole: The Physics Explained | Profound Physics

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This post may contain affiliate links to books or other resources I personally recommend. Black holes are some of the most intriguing, yet not very well-understood objects in the universe, which are best described by Einstein's theory of general relativity. One of the more interesting predictions of the theory is that even time will slow down near a black hole.

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Human survival on Mars would require living in artificial Mars habitats with complex life-support systems.

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The colonization of Mars (or settlement of Mars) has received interest from public space agencies and private corporations and has received extensive hypothetical treatment in science fiction writing, film, and art.

Organizations have proposed plans for a human mission to Mars, the first step towards any colonization effort, but no person has set foot on the planet nor have any return journeys been achieved. However, landers and rovers have successfully explored the planetary surface and delivered information about conditions on the ground.

Reasons for colonizing Mars include curiosity, the potential for humans to provide more in-depth observational research than uncrewed rovers, economic interest in its resources, and the possibility that the settlement of other planets could decrease the likelihood of human extinction. Difficulties and hazards include radiation exposure during a trip to Mars and on its surface, toxic soil, low gravity, the isolation that accompanies Mars' distance from Earth, a lack of water, and cold temperatures.

Commitments to researching permanent settlement have been made by public space agencies- NASA, ESA, Roscosmos, ISRO, the CNSA, among others-and private organizations- SpaceX, Lockheed Martin, and Boeing.

Since the 20th century, there have been several proposed human missions to Mars both by government agencies and private companies.

Most of the human mission concepts as currently conceived by national governmental space programs would not be direct precursors to colonization. Programs such as those being tentatively planned by NASA, Roscosmos, and ESA are intended solely as exploration missions, with the establishment of a permanent base possible but not yet the main goal.

Colonization requires the establishment of permanent habitats that have the potential for self-expansion and self-sustenance. Two early proposals for building habitats on Mars are the Mars Direct and the Semi-Direct concepts, advocated by Robert Zubrin, an advocate of the colonization of Mars.

At the February 2017 World Government Summit, the United Arab Emirates announced a plan to establish a settlement on Mars by 2117, led by the Mohammed bin Rashid Space Centre.

SpaceX has proposed the development of Mars transportation infrastructure in order to facilitate the eventual colonization of Mars. The mission architecture includes fully reusable launch vehicles, human-rated spacecraft, on-orbit propellant tankers, rapid-turnaround launch/landing mounts, and local production of rocket fuel on Mars via in situ resource utilization (ISRU). SpaceX's aspirational goal as of 2017 was to land their cargo Starships on Mars by 2024 and the first 2 crewed starships by 2026.

The surface gravity of Mars is just 38% that of Earth. Although microgravity is known to cause health problems such as muscle loss and bone demineralization, it is not known if Martian gravity would have a similar effect. The Mars Gravity Biosatellite was a proposed project designed to learn more about what effect Mars' lower surface gravity would have on humans, but it was cancelled due to a lack of funding.

Mars has a surface area that is 28.4% of Earth's, which is only slightly less than the amount of dry land on Earth (which is 29.2% of Earth's surface). Mars has half the radius of Earth and only one-tenth the mass. This means that it has a smaller volume (~15%) and lower average density than Earth.

Due to the lack of a magnetosphere, solar particle events and cosmic rays can easily reach the Martian surface.

Atmospheric pressure on Mars is far below the Armstrong limit at which people can survive without pressure suits. Since terraforming cannot be expected as a near-term solution, habitable structures on Mars would need to be constructed with pressure vessels similar to spacecraft, capable of containing a pressure between 30 and 100 kPa. The atmosphere is also toxic as most of it consists of carbon dioxide (95% carbon dioxide, 3% nitrogen, 1.6% argon, and traces totaling less than 0.4% of other gases, including oxygen).

This thin atmosphere does not filter out ultraviolet sunlight, which causes instability in the molecular bonds between atoms. For example, ammonia (NH ₃) is not stable in the Martian atmosphere and breaks down after a few hours. Also due to the thinness of the atmosphere, the temperature difference between day and night is much larger than on Earth, typically around 70 °C (125 °F). However, the day/night temperature variation is much lower during dust storms when very little light gets through to the surface even during the day, and instead warms the middle atmosphere.

The climate is much colder than Earth, with mean surface temperatures between 186 and 268 K (−87 and −5 °C; −125 and 23 °F) (depending on the season and latitude). The lowest temperature ever recorded on Earth was 184 K (−89.2 °C, −128.6 °F) in Antarctica.

Because Mars is about 52% farther from the Sun, the amount of solar energy entering its upper atmosphere per unit area (the solar constant) is only around 43.3% of what reaches the Earth's upper atmosphere. However, due to the much thinner atmosphere, a higher fraction of the solar energy reaches the surface as radiation. The maximum solar irradiance on Mars is about 590 W/m ² compared to about 1000 W/m ² at the Earth's surface; optimal conditions on the Martian equator can be compared to those on Devon Island in the Canadian Arctic in June. Mars' orbit is more eccentric than Earth's, increasing temperature and solar constant variations over the course of the Martian year. Mars has no rain and virtually no clouds, so although cold, it is permanently sunny (apart from during dust storms). This means solar panels can always operate at maximum efficiency on dust-free days.

Global dust storms are common throughout the year and can cover the entire planet for weeks, blocking sunlight from reaching the surface. This has been observed to cause temperature drops of 4 °C (7 °F) for several months after the storm. In contrast, the only comparable events on Earth are infrequent large volcanic eruptions such as the Krakatoa event which threw large amounts of ash into the atmosphere in 1883, causing a global temperature drop of around 1 °C (2 °F). These dust storms would affect electricity production from solar panels for long periods, and interfere with communications with Earth.

Mars has an axial tilt of 25.19°, similar to Earth's 23.44°. As a result, Mars has seasons much like Earth, though on average they last nearly twice as long because the Martian year is about 1.88 Earth years. Mars' temperature regime is more similar to Earth's than all other planets' in the solar system. While generally colder than Earth, Mars can have Earth-like temperatures in some areas and at certain times.

The Martian soil is toxic due to relatively high concentrations of chlorine and associated compounds, such as perchlorates, which are hazardous to all known forms of life.

Plants and animals cannot survive the ambient conditions on the surface of Mars. However, some extremophile organisms that survive in hostile conditions on Earth have endured periods of exposure to environments that approximate some of the conditions found on Mars.

The Martian day (or sol) is very close in duration to Earth's. A solar day on Mars is 24 hours, 39 minutes and 35.244 seconds.

Conditions on the surface of Mars are closer to the conditions on Earth in terms of temperature and sunlight than on any other planet or moon, except for the cloud tops of Venus. However, the surface is not hospitable to humans or most known life forms due to the radiation, greatly reduced air pressure, and an atmosphere with only 0.16% oxygen.

In 2012, it was reported that some lichen and cyanobacteria survived and showed remarkable adaptation capacity for photosynthesis after 34 days in simulated Martian conditions in the Mars Simulation Laboratory (MSL) maintained by the German Aerospace Center (DLR). Some scientists think that cyanobacteria could play a role in the development of self-sustainable crewed outposts on Mars. They propose that cyanobacteria could be used directly for various applications, including the production of food, fuel and oxygen, but also indirectly: products from their culture could support the growth of other organisms, opening the way to a wide range of life-support biological processes based on Martian resources.

Humans have explored parts of Earth that match some conditions on Mars. Based on NASA rover data, temperatures on Mars (at low latitudes) are similar to those in Antarctica. The atmospheric pressure at the highest altitudes reached by piloted balloon ascents (35 km (114,000 feet) in 1961, 38 km in 2012) is similar to that on the surface of Mars. However, the pilots were not exposed to the extremely low pressure, as it would have killed them, but seated in a pressurized capsule.

Human survival on Mars would require living in artificial Mars habitats with complex life-support systems. One key aspect of this would be water processing systems. Being made mainly of water, a human being would die in a matter of days without it. Even a 5-8% decrease in total body water causes fatigue and dizziness and a 10% decrease physical and mental impairment (See Dehydration). A person in the UK uses 70-140 litres of water per day on average. Through experience and training, astronauts on the ISS have shown it is possible to use far less, and that around 70% of what is used can be recycled using the ISS water recovery systems. (For instance, half of all water is used during showers.) Similar systems would be needed on Mars but would need to be much more efficient, since regular robotic deliveries of water to Mars would be prohibitively expensive (the ISS is supplied with water four times per year). Potential access to on-site water (frozen or otherwise) via drilling has been investigated by NASA.

Mars presents a hostile environment for human habitation. Different technologies have been developed to assist long-term space exploration and may be adapted for habitation on Mars. The existing record for the longest consecutive space flight is 438 days by cosmonaut Valeri Polyakov, and the most accrued time in space is 878 days by Gennady Padalka. The longest time spent outside the protection of the Earth's Van Allen radiation belt is about 12 days for the Apollo 17 moon landing. This is minor in comparison to the 1100-day journey to Mars and back envisioned by NASA for possibly as early as the year 2028. Scientists have also hypothesized that many different biological functions can be negatively affected by the environment of Mars colonies. Due to higher levels of radiation, there are a multitude of physical side-effects that must be mitigated. In addition, Martian soil contains high levels of toxins which are hazardous to human health.

The difference in gravity may negatively affect human health by weakening bones and muscles. There is also risk of osteoporosis and cardiovascular problems. Current rotations on the International Space Station put astronauts in zero gravity for six months, a comparable length of time to a one-way trip to Mars. This gives researchers the ability to better understand the physical state that astronauts going to Mars would arrive in. Once on Mars, surface gravity is only 38% of that on Earth. Microgravity affects the cardiovascular, musculoskeletal and neurovestibular (central nervous) systems. The cardiovascular effects are complex. On Earth, blood within the body stays 70% below the heart, but in microgravity this is the not case due to nothing pulling the blood down. This can have several negative effects. Once entering into microgravity, the blood pressure in the lower body and legs is significantly reduced. This causes legs to become weak through loss of muscle and bone mass. Astronauts show signs of a puffy face and chicken legs syndrome. After the first day of reentry back to earth, blood samples showed a 17% loss of blood plasma, which contributed to a decline of erythropoietin secretion. On the skeletal system which is important to support our body's posture, long space flight and exposure to microgravity cause demineralization and atrophy of muscles. During re-acclimation, astronauts were observed to have a myriad of symptoms including cold sweats, nausea, vomiting and motion sickness. Returning astronauts also felt disoriented. Journeys to and from Mars being six months is the average time spent at the ISS. Once on Mars with its lesser surface gravity (38% percent of Earth's), these health effects would be a serious concern. Upon return to Earth, recovery from bone loss and atrophy is a long process and the effects of microgravity may never fully reverse.

Because of so much radiation reaching Mars' surface, the planet has lost its inner dynamo despite its far distance from the Sun compared to Earth. Due to this, Mars has a weaker global magnetosphere than Earth does. Combined with a thin atmosphere, this permits a significant amount of ionizing radiation to reach the Martian surface. There are two main types of radiation risks to traveling outside the protection of Earth's atmosphere and magnetosphere: galactic cosmic rays (GCR) and solar energetic particles (SEP). Earth's magnetosphere protects from charged particles from the Sun, and the atmosphere protects against uncharged and highly energetic GCRs. There are ways to mitigate against solar radiation, but without much of an atmosphere, the only solution to the GCR flux is heavy shielding amounting to roughly 15 centimeters of steel, 1 meter of rock, or 3 meters of water, limiting human colonists to living underground most of the time.

The Mars Odyssey spacecraft carries an instrument, the Mars Radiation Environment Experiment (MARIE), to measure the radiation. MARIE found that radiation levels in orbit above Mars are 2.5 times higher than at the International Space Station. The average daily dose was about 220 μGy (22 mrad)-equivalent to 0.08 Gy per year. A three-year exposure to such levels would exceed the safety limits currently adopted by NASA, and the risk of developing cancer due to radiation exposure after a Mars mission could be two times greater than what scientists previously thought. Occasional solar proton events (SPEs) produce much higher doses, as observed in September 2017, when NASA reported radiation levels on the surface of Mars were temporarily doubled, and were associated with an aurora 25-times brighter than any observed earlier, due to a massive, and unexpected, solar storm. Building living quarters underground (possibly in Martian lava tubes) would significantly lower the colonists' exposure to radiation.

Much remains to be learned about space radiation. In 2003, NASA's Lyndon B. Johnson Space Center opened a facility, the NASA Space Radiation Laboratory, at Brookhaven National Laboratory, that employs particle accelerators to simulate space radiation. The facility studies its effects on living organisms, as well as experimenting with shielding techniques. Initially, there was some evidence that this kind of low level, chronic radiation is not quite as dangerous as once thought; and that radiation hormesis occurs. However, results from a 2006 study indicated that protons from cosmic radiation may cause twice as much serious damage to DNA as previously estimated, exposing astronauts to greater risk of cancer and other diseases. As a result of the higher radiation in the Martian environment, the summary report of the Review of U.S. Human Space Flight Plans Committee released in 2009 reported that "Mars is not an easy place to visit with existing technology and without a substantial investment of resources." NASA is exploring a variety of alternative techniques and technologies such as deflector shields of plasma to protect astronauts and spacecraft from radiation.

Due to the communication delays, new protocols need to be developed in order to assess crew members' psychological health. Researchers have developed a Martian simulation called HI-SEAS (Hawaii Space Exploration Analog and Simulation) that places scientists in a simulated Martian laboratory to study the psychological effects of isolation, repetitive tasks, and living in close-quarters with other scientists for up to a year at a time. Computer programs are being developed to assist crews with personal and interpersonal issues in absence of direct communication with professionals on Earth. Current suggestions for Mars exploration and colonization are to select individuals who have passed psychological screenings. Psychosocial sessions for the return home are also suggested in order to reorient people to society.

Various works of fiction put forward the idea of terraforming Mars to allow a wide variety of life forms, including humans, to survive unaided on Mars' surface. Some ideas of possible technologies that may be able to contribute to the terraforming of Mars have been conjectured, but none would be able to bring the entire planet into the Earth-like habitat pictured in science fiction.

To be self-sustaining, a colony would have to be large enough to provide all the necessary living services. These include

Ecosystem management: producing appropriate gases, controlling air composition pressure and temperature, collecting and producing water, growing food and processing organic wastes.

Energy production: this includes extracting methane for vehicles and if photovoltaic cells are used to produce energy this would include the extraction and processing of silicates, to augment or replace any original equipment.

Industry: extracting and processing appropriate ores, manufacturing tools and other objects; producing clothes, medicine, glass, ceramics, plastics.

Building: even if the base is constructed before arrival, it will need frequent adaptation according to the evolution of the settlement as well as inevitable replacement.

Social activities: this includes raising children and educating them, health care, preparing meals, cleaning, washing, organizing the work and making decisions. Time for sport, culture and entertainment can be minimized but not eliminated.

As the number of individuals grows, both activities and objects can be shared between them. Growth also will offset the risks of collapse of the society, caused by sudden deaths, accidents, infertility or inbreeding. But this may not prevent mortal combat between different groups of individuals, or the loss of efficiency due to inappropriate social organization.

By mathematical modelling of the time spent by people on these issues and by keeping things simple, Salotti concludes that the minimum number for a colony on Mars is 110. This is close to other studies of the genetic problems involved in the longer journey to Proxima Centauri b (6,000+ years).

Mars requires less energy per unit mass ( delta V) to reach from Earth than any planet except Venus. Using a Hohmann transfer orbit, a trip to Mars requires approximately nine months in space. Modified transfer trajectories that cut the travel time down to four to seven months in space are possible with incrementally higher amounts of energy and fuel compared to a Hohmann transfer orbit, and are in standard use for robotic Mars missions. Shortening the travel time below about six months requires higher delta-v and an increasing amount of fuel, and is difficult with chemical rockets. It could be feasible with advanced spacecraft propulsion technologies, some of which have already been tested to varying levels, such as Variable Specific Impulse Magnetoplasma Rocket, and nuclear rockets. In the former case, a trip time of forty days could be attainable, and in the latter, a trip time down to about two weeks. In 2016, a University of California, Santa Barbara scientist said they could further reduce travel time for a small robotic probe to Mars down to "as little as 72 hours" with the use of a laser propelled sail (directed photonic propulsion) system instead of the fuel-based rocket propulsion system.

During the journey the astronauts would be subject to radiation, which would require a means to protect them. Cosmic radiation and solar wind cause DNA damage, which increases the risk of cancer significantly. The effect of long-term travel in interplanetary space is unknown, but scientists estimate an added risk of between 1% and 19% (one estimate is 3.4%) for males to die of cancer because of the radiation during the journey to Mars and back to Earth. For females the probability is higher due to generally larger glandular tissues.

Mars has a surface gravity 0.38 times that of Earth, and the density of its atmosphere is about 0.6% of that on Earth. The relatively strong gravity and the presence of aerodynamic effects make it difficult to land heavy, crewed spacecraft with thrusters only, as was done with the Apollo Moon landings, yet the atmosphere is too thin for aerodynamic effects to be of much help in aerobraking and landing a large vehicle. Landing piloted missions on Mars would require braking and landing systems different from anything used to land crewed spacecraft on the Moon or robotic missions on Mars.

If one assumes carbon nanotube construction material will be available with a strength of 130 GPa (19,000,000 psi) then a space elevator could be built to land people and material on Mars. A space elevator on Phobos (a Martian moon) has also been proposed.

Colonization of Mars would require a wide variety of equipment-both equipment to directly provide services to humans and production equipment used to produce food, propellant, water, energy and breathable oxygen-in order to support human colonization efforts. Required equipment will include:

In order to function at all the colony would need the basic utilities to support human civilization. These would need to be designed to handle the harsh Martian environment and would either have to be serviceable while wearing an EVA suit or housed inside a human habitable environment. For example, if electricity generation systems rely on solar power, large energy storage facilities will also be needed to cover the periods when dust storms block out the sun, and automatic dust removal systems may be needed to avoid human exposure to conditions on the surface. If the colony is to scale beyond a few people, systems will also need to maximise use of local resources to reduce the need for resupply from Earth, for example by recycling water and oxygen and being adapted to be able to use any water found on Mars, whatever form it is in.

Communications with Earth are relatively straightforward during the half- sol when Earth is above the Martian horizon. NASA and ESA included communications relay equipment in several of the Mars orbiters, so Mars already has communications satellites. While these will eventually wear out, additional orbiters with communication relay capability are likely to be launched before any colonization expeditions are mounted.

The one-way communication delay due to the speed of light ranges from about 3 minutes at closest approach (approximated by perihelion of Mars minus aphelion of Earth) to 22 minutes at the largest possible superior conjunction (approximated by aphelion of Mars plus aphelion of Earth). Real-time communication, such as telephone conversations or Internet Relay Chat, between Earth and Mars would be highly impractical due to the long time lags involved. NASA has found that direct communication can be blocked for about two weeks every synodic period, around the time of superior conjunction when the Sun is directly between Mars and Earth, although the actual duration of the communications blackout varies from mission to mission depending on various factors-such as the amount of link margin designed into the communications system, and the minimum data rate that is acceptable from a mission standpoint. In reality most missions at Mars have had communications blackout periods of the order of a month.

A satellite at the or Earth-Sun Lagrangian point could serve as a relay during this period to solve the problem; even a constellation of communications satellites would be a minor expense in the context of a full colonization program. However, the size and power of the equipment needed for these distances make the L4 and L5 locations unrealistic for relay stations, and the inherent stability of these regions, although beneficial in terms of station-keeping, also attracts dust and asteroids, which could pose a risk. Despite that concern, the STEREO probes passed through the L4 and L5 regions without damage in late 2009.

Recent work by the University of Strathclyde's Advanced Space Concepts Laboratory, in collaboration with the European Space Agency, has suggested an alternative relay architecture based on highly non- Keplerian orbits. These are a special kind of orbit produced when continuous low-thrust propulsion, such as that produced from an ion engine or solar sail, modifies the natural trajectory of a spacecraft. Such an orbit would enable continuous communications during solar conjunction by allowing a relay spacecraft to "hover" above Mars, out of the orbital plane of the two planets. Such a relay avoids the problems of satellites stationed at either L4 or L5 by being significantly closer to the surface of Mars while still maintaining continuous communication between the two planets.

The path to a human colony could be prepared by robotic systems such as the Mars Exploration Rovers , Opportunity, and Perseverance. These systems could help locate resources, such as ground water or ice, that would help a colony grow and thrive. The lifetimes of these systems would be years and even decades, and as recent developments in commercial spaceflight have shown, it may be that these systems will involve private as well as government ownership. These robotic systems also have a reduced cost compared with early crewed operations, and have less political risk.

Wired systems might lay the groundwork for early crewed landings and bases, by producing various consumables including fuel, oxidizers, water, and construction materials. Establishing power, communications, shelter, heating, and manufacturing basics can begin with robotic systems, if only as a prelude to crewed operations.

Mars Surveyor 2001 Lander MIP (Mars ISPP Precursor) was to demonstrate manufacture of oxygen from the atmosphere of Mars, and test solar cell technologies and methods of mitigating the effect of Martian dust on the power systems.

Before any people are transported to Mars on the notional 2020s Mars transportation infrastructure envisioned by SpaceX, a number of robotic cargo missions would be undertaken first in order to transport the requisite equipment, habitats and supplies. Equipment that would be necessary would include "machines to produce fertilizer, methane and oxygen from Mars' atmospheric nitrogen and carbon dioxide and the planet's subsurface water ice" as well as construction materials to build transparent domes for initial agricultural areas.

As with early colonies in the New World, economics would be a crucial aspect to a colony's success. The reduced gravity well of Mars and its position in the Solar System may facilitate Mars-Earth trade and may provide an economic rationale for continued settlement of the planet. Given its size and resources, this might eventually be a place to grow food and produce equipment to mine the asteroid belt.

Some early Mars colonies might specialize in developing local resources for Martian consumption, such as water and/or ice. Local resources can also be used in infrastructure construction. One source of Martian ore currently known to be available is metallic iron in the form of nickel-iron meteorites. Iron in this form is more easily extracted than from the iron oxides that cover the planet.

Another main inter-Martian trade good during early colonization could be manure. Assuming that life doesn't exist on Mars, the soil is going to be very poor for growing plants, so manure and other fertilizers will be valued highly in any Martian civilization until the planet changes enough chemically to support growing vegetation on its own.

Solar power is a candidate for power for a Martian colony. Solar insolation (the amount of solar radiation that reaches Mars) is about 42% of that on Earth, since Mars is about 52% farther from the Sun and insolation falls off as the square of distance. But the thin atmosphere would allow almost all of that energy to reach the surface as compared to Earth, where the atmosphere absorbs roughly a quarter of the solar radiation. Sunlight on the surface of Mars would be much like a moderately cloudy day on Earth.

Space colonization on Mars can roughly be said to be possible when the necessary methods of space colonization become cheap enough (such as space access by cheaper launch systems) to meet the cumulative funds that have been gathered for the purpose.

Although there are no immediate prospects for the large amounts of money required for any space colonization to be available given traditional launch costs, there is some prospect of a radical reduction to launch costs in the 2020s, which would consequently lessen the cost of any efforts in that direction. With a published price of US$62 million per launch of up to 22,800 kg (50,300 lb) payload to low Earth orbit or 4,020 kg (8,860 lb) to Mars, SpaceX Falcon 9 rockets are already the "cheapest in the industry". SpaceX's reusable plans include Falcon Heavy and future methane-based launch vehicles including the Starship. If SpaceX is successful in developing the reusable technology, it would be expected to "have a major impact on the cost of access to space", and change the increasingly competitive market in space launch services.

Alternative funding approaches might include the creation of inducement prizes. For example, the 2004 President's Commission on Implementation of United States Space Exploration Policy suggested that an inducement prize contest should be established, perhaps by government, for the achievement of space colonization. One example provided was offering a prize to the first organization to place humans on the Moon and sustain them for a fixed period before they return to Earth.

Mars Odyssey found what appear to be natural caves near the volcano Arsia Mons. It has been speculated that settlers could benefit from the shelter that these or similar structures could provide from radiation and micrometeoroids. Geothermal energy is also suspected in the equatorial regions.

Several possible Martian lava tube skylights have been located on the flanks of Arsia Mons. Earth based examples indicate that some should have lengthy passages offering complete protection from radiation and be relatively easy to seal using on-site materials, especially in small subsections.

Hellas Planitia is the lowest lying plain below the Martian geodetic datum. The air pressure is relatively higher in this place when compared to the rest of Mars.

Robotic spacecraft to Mars are required to be sterilized, to have at most 300,000 spores on the exterior of the craft-and more thoroughly sterilized if they contact "special regions" containing water, otherwise there is a risk of contaminating not only the life-detection experiments but possibly the planet itself.

It is impossible to sterilize human missions to this level, as humans are host to typically a hundred trillion microorganisms of thousands of species of the human microbiome, and these cannot be removed while preserving the life of the human. Containment seems the only option, but it is a major challenge in the event of a hard landing (i.e. crash). There have been several planetary workshops on this issue, but with no final guidelines for a way forward yet. Human explorers would also be vulnerable to back contamination to Earth if they become carriers of microorganisms should Mars have life.

Ethical, political and legal challenges

It is unforeseen how the first human landing on Mars will change the current policies regarding the exploration of space and occupancy of celestial bodies. In the 1967 United Nations Outer Space Treaty, it was determined that no country may take claim to space or its inhabitants. Since the planet Mars offers a challenging environment and dangerous obstacles for humans to overcome, the laws and culture on the planet will most likely be very different from those on Earth. With Elon Musk announcing his plans for travel to Mars, it is uncertain how the dynamic of a private company possibly being the first to put a human on Mars will play out on a national and global scale. NASA had to deal with several cuts in funding. During the presidency of Barack Obama, the objective for NASA to reach Mars was pushed to the background. In 2017, president Donald Trump promised to return humans to the Moon and eventually Mars, effectively taking action by increasing NASA budget with $1.1 billion, and mostly focus on the development of the new Space Launch System.

Space colonization in general has been discussed as continuation of imperialism and colonialism, especially regarding Mars colonial decision making and reasons for colonial labor and land exploitation have been questioned with postcolonial critique. Seeing the need for inclusive and democratic participation and implementation of any space and Mars exploration, infrastructure, or colonialization, many have called for dramatic sociological reforms and guarantees to prevent racism, sexism, and other forms of prejudice and bigotry.

The narrative of space exploration as a " New Frontier" has been criticized as unreflected continuation of settler colonialism and manifest destiny, continuing the narrative of colonial exploration as fundamental to the assumed human nature.

The predominant perspective of territorial colonization in space has been called surfacism, especially comparing advocacy for colonization of Mars opposed to Venus.

One possible ethical challenge that space travelers might face is that of pregnancy during the trip. According to NASA's policies, it is forbidden for members of the crew to engage in sex in space. NASA wants its crew members to treat each other like coworkers would in a professional environment. A pregnant member on a spacecraft is dangerous to all those aboard. The pregnant woman and child would need additional nutrition from the rations aboard, as well as special treatment and care. The pregnancy would impinge on the pregnant crew member's duties and abilities. It is still not fully known how the environment in a spacecraft would affect the development of a child aboard. It is known however that a fetus would be more susceptible to solar radiation in space, which would likely have a negative effect on its cells and genetics. During a long trip to Mars, it is likely that members of craft may engage in sex due to their stressful and isolated environment.

Mars colonization is advocated by several non-governmental groups for a range of reasons and with varied proposals. One of the oldest groups is the Mars Society who promote a NASA program to accomplish human exploration of Mars and have set up Mars analog research stations in Canada and the United States. Mars to Stay advocates recycling emergency return vehicles into permanent settlements as soon as initial explorers determine permanent habitation is possible.

Elon Musk founded SpaceX with the long-term goal of developing the technologies that will enable a self-sustaining human colony on Mars. Richard Branson, in his lifetime, is "determined to be a part of starting a population on Mars. I think it is absolutely realistic. It will happen... I think over the next 20 years," [from 2012] "we will take literally hundreds of thousands of people to space and that will give us the financial resources to do even bigger things".

Author Robert Zubrin has been a major advocate for Mars exploration and colonization for many years. He is a member of the Mars society and has authored several fiction and nonfiction books about the subject. In 1996 he wrote The Case for Mars: The Plan to Settle the Red Planet and Why We Must. He continues to advocate for Mars and space exploration with his most recent book being The Case for Space: How the Revolution in Spaceflight Opens Up a Future of Limitless Possibility.

In June 2013, Buzz Aldrin, American engineer and former astronaut, and the second person to walk on the Moon, wrote an opinion, published in The New York Times, supporting a human mission to Mars and viewing the Moon "not as a destination but more a point of departure, one that places humankind on a trajectory to homestead Mars and become a two-planet species". In August 2015, Aldrin, in association with the Florida Institute of Technology, presented a "master plan", for NASA consideration, for astronauts, with a "tour of duty of ten years", to colonize Mars before the year 2040.

A few instances in fiction provide detailed descriptions of Mars colonization. They include:

''Away'' (2020), published by Netflix

Surviving Mars (2018), developed by Haemimont Games, published by Paradox Interactive

The Expanse (2016-2021) airing originally on Syfy, then Amazon Prime

TerraGenesis (2016) developed by Edgeworks Entertainment, published by Tilting Point

'' Colony One Mars: A SciFi Thriller '' (2016), by Gerald Kilby

The Martian (2011), by Andy Weir (and the 2015 film, directed by Ridley Scott)

Tom and Jerry: Blast Off to Mars (2005) animated science fiction comedy film by Warner Bros. Animation and Turner Entertainment

Red Faction (2001), developed by Volition, published by THQ

Martian Gothic: Unification (2000), developed by Creative Reality for Microsoft Windows and Coyote Developments for PlayStation, published by TalonSoft for Microsoft Windows and Take-Two Interactive for PlayStation

(1985), the Mars trilogy (Red Mars, Green Mars, Blue Mars, 1992-1996), and The Martians (1999), by Kim Stanley Robinson

The Destruction of Faena (1974), by Alexander Kazantsev

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# data[].attributes.attachment_link.description
The colonization of Mars (or settlement of Mars) has received interest from public space agencies and private corporations and has received extensive hypothetical treatment in science fiction writing, film, and art. Organizations have proposed plans for a human mission to Mars, the first step towards any colonization effort, but no person has set foot on the planet nor have any return journeys been achieved.

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Temperatures on Mars average about -81 degrees F. However, temperatures range from around -220 degrees F. in the wintertime at the poles, to +70 degrees F.

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You cannot breath in Mars, because the amount of air are a few and the air have too much carboine dioxide, so its toxic. Inorder to live there you have to wear a space suit.

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The fact about the water in Moon and Mars

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The fact about the water in Moon and Mars

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Theres a fact that if the Moon or Mars water touch blood, it will start to duplocate. So if you drink the water there, you will drown