Next Question: How and why does gravity warp/deform space-time?

Next Question:

How do Gravitational Waves interact with other forms of energy or matter in the universe such as dark matter? Why do some forms of energy or matter have a bigger stretch/compression factor than others?

1. Gravitational wave astrophysics at UBC - https://gravitational-waves.phas.ubc.ca/research/

2. A Spacetime Surprise: Time Isn’t Just Another Dimension - https://www.forbes.com/sites/startswithabang/2020/08/12/a-spacetime-surprise-time-isnt-just-another-dimension/?sh=6430bc947dc8

Content:

The model of spacetime being 2D or 3D is generally used for common understanding. In reality it is 4D. 3 spatial dimensions, and 1 chronal.

The four dimensional fabric of spacetime works in a very weird way, leaving the spatial dimensions all interacting with each other easily, and the chronal dimension needing a conversion to go from one to the other.

Essentially you have time using one set of units and space using another set of units, to get from time to space you need to convert from the units that mean space, (m, in, etc.) to units that mean time (c, s, ms, etc)

The impact of a gravitational wave is fundamentally the increasing or decreasing of gravity in a localized area (or the stretching/compression of spacetime) If a gravitational wave were to pass over earth, essentially it would squeeze and stretch the areas that align with peaks or valleys of the wave.

Follow Up:

What dimensional axis does spacetime change in when a gravitational wave passes through it (Spatial, Chronal, both or neither)

Next question:

How should we think about spacetime? What is the difference between spacetime and space?

HOW

To sum up how mass warps spacetime, every particle has a mass, that mass curves spacetime around itself, when you add up a bunch of particles, the curvature also adds up. Essentially you end up with a "gravity well"

As said in the NASA article and also your answer, this can be visualized in a simply way by placing a heavy object on a mattress or a rubber sheet, and then adding another object, they seem to "Attract each other" (gravity isn't an attractive force but something a little more interesting)

This "gravity well" is an area of high curvature, although the typical images of a ball on a grid help to understand, in reality the curve occurs across all axes, creating more of a gravity bubble, really hard to imagine.

WHY 

To save everybody's time, we don't know. I spent about 2 or 3 hours trying a bunch of different search terms and even went to ChatGPT to try and get some help. The conclusion is that we know that gravity curves spacetime, we don't know what causes it, the reasons that ChatGPT provided were that it may be due to "string theory" or "quantum gravity" (don't bother, they're a bunch of hodgepodge) but this is the limit of our current understanding.

(My source is not ChatGPT, I was just desperate to see the tool could help me narrow my search, it helped me realize there's literally nothing)

FOLLOW UP QUESTION:

Our best analogy of how gravity works due to spacetime curvature is with the bowling ball on rubber sheet analogy, but in that case, the smaller ball is being pushed by the normal force exerted on it by the rubber sheet

How can less massive objects seemingly accelerate into gravity wells given there's no force pushing it in (Very hard question, start by looking up "geodesics in spacetime" and "can anything completely stop moving")

Spacetime: straight path is longest elapsed time between two events; flip from shortest distance to longest time is difference between time and space

Next Question:

What experimental evidence supports the concept of gravity bending spacetime, as predicted by Einstein's general theory of relativity?

Next question:

How is the physics of moving masses different from stationary masses?

• Creates gravity, not affected by electromagnetic forces (gravity is a weak electromagnetic force)

• Dark matter is invisible, inferred matter that does not interact with electromagnetic waves/forces

• This means it does not emit, reflect, absorb, or bend when light hits it which makes it hard to spot (we do not have the techno

• Scientists believe that the dark matter is the extra mass which generates extra gravity to hold the universe together

• We need more experimentation with dark matter to determine more of its properties, our best bet is to run experiments in the world’s largest particle accelerator, the Large Hadron Collider

• One theory is that dark matter contains “supersymmetric particles”, ones that are partners to known standard model particles, hypothetically

• Many theories describe that dark matter would be light enough to be created in the particle accelerator and escape undetected. If this happened, the missing momentum and the missing energy could be inferred to be dark matter

• Seems to outweigh visible matter 6:1 and makes up roughly 27% of the universe

• The matter known to mankind makes up roughly 5% of the universe

What is dark energy?

• Dark energy is thought to be related to the vacuum in space and makes up 68% of the universe

• Throughout the entire universe, dark energy is spread equally through space and time, which means that as the universe expands it is not diluted

• Has a global effect on gravity of the universe and not in a specific area due to it’s even distribution

• Leads to a repulsive force which seems to quicken the rate of expansion of the universe 

• Using Hubble law, we can calculate the rate change

• Along with other scientific data, Hubble law calculations have confirmed the existence of dark energy in the universe

TL:DR - Gravity has no effect on dark matter for some reason (did not discover it because more experimentation needs to be done to discover the properties of dark matter)

Next question:

Does the magnitude of mass of impacted objects increase the effect of gravity's stretch/compression?

• Another way to imagine gravity is like acceleration, if you were accelerating upwards in a spaceship at the same speed as gravity, you would weight the same on a scale meaning you experience the same amount of force

• Based on this fact, einstein theorized that acceleration also causes the same kind of warp in space time as gravity does

Next question:

Would an accelerating mass have a greater force of gravity than another identical mass that is stationary?

1. Why do Objects increase in mass as they get faster? - https://futurism.com/why-do-objects-increase-in-mass-as-they-get-faster-2

2. What is the difference between the inertial and gravitational mass? - https://www.physlink.com/education/askexperts/ae305.cfm

Content:

Objects fundamentally have something called a rest mass, this is what its mass is when it's relativistically at rest. 

When you increase the speed, you increase the energy of that object, thereby increasing its mass when you look at E = mc^2

When you increase the energy (in this case kinetic) you must increase the mass, thereby increasing how much it has an effect on spacetime. 

One caveat is that there are two types of mass, inertial mass and gravitational mass. Rather, there is one kind of mass expressed and measured in two different ways.

However in the second article linked, we can see that throughout all of our experiments, they are numerically the same. Meaning that it would also have an effect on the gravitational mass, thereby influencing how much it warps spacetime.

As we know that gravity is essentially the magnitude of how much spacetime is warped. So the answer is yes, the apparent force of gravity on a relativistically stationary object will be weaker than that of an accelerating object.

Follow-up Question:

How do we know if an object is accelerating or decelerating (going against the velocity that we are already traveling in), does this affect whether or not its mass increases or decreases. And if this is the case could we not use this information to find our objective velocity.

The force of gravity changes when an object moves closer to (stronger) or further away from (weaker) the source because of the curving of spacetime being more severe closer to the centre of the mass. Did not touch on accelerating masses. 

Next Question:

How do planets collapse to form black holes and how is time affected? What is the difference in time at the outskirts of a black hole compared to the inner core? Is it even possible to find out?

Next Question:

How does Stephen Hawking's theory collide and intersect Einstein's theory? What similarities and differences do they share and why is that the case?

Next Question:

Are there any phenomena to explain why General Relativity is not a complete picture of the universe? If not, why is General Relativity still a theory with so much evidence to back it up?

• String theory also states that there are two types of strings, closed and open

• Closed strings are like a circle and can travel through dimensions

• Open strings have ends and are therefore confined to the dimensions in which they exist

• Gravitons are closed strings and photons are open 

• This theory explains why gravity is the weakest of the four fundamental forces since it would leak into other dimensions only leaving a fraction for us to feel

• This theory also offers a solution to dark matter, it could be gravitons from other dimensions leaking into our 3 dimensions

Next question:

Is gravity a combination of gravitons and the warping of space-time? Do the gravitons cause the warping of space time?

1. The Silent Black Hole - https://www.science.org/content/article/silent-black-hole#:~:text=According%20to%20theory%2C%20a%20black,into%20an%20infinitely%20dense%20speck.

2. The Effect Density Has on the Speed of Light, Time, and the Dimensions of the Multiverse - https://www.scirp.org/journal/paperinformation?paperid=120196#:~:text=As%20density%20increases%2C%20gravity%20increases,same%20factor%20that%20dt%20increases.

Content

First note is that black holes cannot be formed from a planet. The reason that stars are able to not implode is because they have constant nuclear fusion going on in the core of the star. This is the only force preventing it from turning into a black hole.

It's essentially a MASSIVE fusion reactor going on at all times, and fusion in of itself is even stronger that what we use to generate massive amounts of energy with small quantities, which is nuclear fission.

The fusion is like constant nuclear bombs being exploded inside of the star and it pushes the mass outwards. Heavier stars do rely on this force to prevent themselves from being imploded, lighter stars like our sun will simply shrink when it dies, it simply does not have enough mass to overcome its structure.

To summarize, the bigger celestial objects will always try to collapse, the thing holding it in balance is the fusion going on inside the star

In terms of how time is affected, we can look at the second paper linked, citing that as the density of an object increases, its effect on spacetime also increases, thereby forcing time to run slower.

This would mean that before the collapse and after the collapse (assuming no matter and energy is lost which it typically is) there would be a shift in how much time is dilated. Rather, an increase.

Follow up

Given the relationship between density and time dilation, how might this be applied to a singularity? Given its supposed infinite density, would it not cause time to completely stop, in this case, how would any matter reach it. Does the progressively approach a complete stop? Or is our assumption of infinite density simply erroneous. 

• Anything that crosses the apparent horizon of a black hole will never escape the black hole

• As you approach the horizon the flow of time progressively slows down compared to the flow of time far away from the black hole

• This effect of time distortion is true for any massive object in the universe including earth

• Using very accurate clocks we observed this effect her on earth

• However near black holes the fabric of space-time is distorted to such a magnitude that one would be able to see visible changes in the flow of time

What happens to time near black holes?

• To someone observing the black hole, the time would seem to stop for a supposed object falling into the black hole, making it appear frozen in time

• According to Einstein’s theory of relativity, inside the black hole, space-time is so heavily distorted that time and space switch places

• Inside the black hole, the flow of time would act as the primary dimension through which an object would fall

• Instead of falling through space, it would fall through time towards the singularity

• No force in the universe would be able to stop this fall because all forces act in the three spatial dimensions, there is no force that can affect time

What happens at the singularity (centre of the black hole)?

• Our understanding of black holes does not extend beyond this point, at the singularity nobody knows what would happen

• Einstein’s theory of gravity no longer applies at these very small scales in the singularity

• Einstein theorised that time would be destroyed in the singularity

• Other scientists have theorised that the singularity leads to a new universe

• We cannot conduct direct experiments on black holes because anything that enters the black hole would never be able to communicate with the outside universe, and no information can ever escape the black hole

• New research must me done on the laws of the universe to devise more accurate theories of what may happen in the centre of a black hole

Next question:

Similar to black holes, neutron stars(the second densest objects in the universe after black holes) also cause extreme distortions in space time that even light bends around the star. Could research be conducted on these stars to improve our understanding of black holes and how they affect time?

• Albert Einstein discovered that time is not constant -> it will not go in the same speed at different spots in the universe

  • Einstein proved that gravity and acceleration are able to change the way which time travels

  • because of the warping of time due to gravity, people who are on the international space station are actually aging slower than people on earth

  • this is because of the idea of general relativity

• the theory of general relativity is the idea that instead of objects beings connected to each other by an invisible force, they are connected by gravity curving and warping space 

  • the more massive the object, the more it warps space around it. This also changes the way time warps

• gravity is formed by any massive object in the universe

  • Every planet makes its own gravity. The planet pulls space towards itself, making it accelerate at increasing speeds

• Every object in the universe has a gravitational field

  • For example, a pencil has a gravitational field, but the pull of that gravitational field is so small that it basically affects nothing surrounding it. It's so small that it also cannot be measured by modern technology

Next Question: What is the relationship between acceleration and the warping of space-time?

• The universe is expanding at rate that is accelerating rate 

  •  this fact contradicts what researchers understand about the effect of gravity on the universe 

  • The universe's expansion accelerating can be compared to throwing an apple in the air and it continuing and accelerating upwards

  • The cause of the acceleration of the universe is a result of dark matter. The logistics behind this phenomena is still a mystery

• The universe's accelerating expansion contradicts the current understanding we have of gravity's effect on the universe 

  • It hints that the understanding we have of gravity at the universal level is incomplete

  • This potential misunderstanding may help scientists explain dark matter

• Einstein's theory of general relativity has up until this point been able to accurately describe gravity (has been able to predict things like the orbit of mercury and the existence of black holes) until this point. 

  • The theory cannot explain dark energy however, so some scientists have argued that they may need to modify some equations or add new components to the theory 

  • To find out whether or not the theory needs modifications, scientists would have to look for evidence that the strength of gravity has varied throughout the history of the universe or over cosmic distances

• So far, the research scientists have conducted has shown that Einstein's theory of general relativity still works. This means that there is no explanation for dark energy yet

• Most of the matter in our universe is dark matter which is matter that does not reflect, emit or absorb light (this makes it really hard for us to observe or determine what it's made of)

  • We know it exists because gravity gives it away

  • Large masses of dark matter warp space itself. When light travels through space, it encounters these portions of warped space. These cause images of distant galaxies to appear curved or smeared to us, which is something that proves the existence of dark matter 

• The strength of gravity determines the size and distribution of dark matter structures and then those dark matter structures determine the warping of light and how distant galaxies appear to us 

  • The subtle distortions due to dark matter bending space are called weak gravitational lensing

Next Question: Why does the strength of gravity affect the size and structures of dark matter?

• Einstein's theory of general relativity and the quantum theory (describes the subatomic world) have contradictions with each other

  • Each theory takes radically different view of the force of gravity 

  • Einstein theorized that matter distorts the fabric of space time around it -> creating the effect of a force field

  • The quantum theory describes all forces in terms of -exchange particles' that move around from place to place (in the case of the force of gravity, those particles are known as gravitons)

  • The existence of gravitons would be the bridge between the differences in these to theories 

• The main reason theorists believe gravitions must exist is because quantum theory has successfully explained every other force in nature.

  • Proving gravitons exist would unify the quantum theory with the theory of general relativity 

  • Not scientists agree with gravitons existing; this is because no theory that claims to unify the quantum theory with GR has ever been successfully proven -> this has caused suspicions that maybe gravity does not exist like all other forces. In that case gravitons may not exist 

• Even if gravitons exist, finding them and actually roving they exist is very hard to do. 

  • Quantum theory predicts that gravity essentially has an infinite range. This means the graviton must have an extremely low mass 

  • Studies that came from gravitational waves from colliding black holes suggest that the mass of a graviton should be approximately a billion, billion, billion times lighter than a electron

  • A graviton detector has to be extremely massive and has to be placed near a source with a ton of gravitons to 

    • Even a detector the size of jupiter placed near a neutron star (good source of gravitons) would have a hard time finding anything

• To answer the question: graviton is a particle of gravity. Since the warping of spacetime occurs because of gravity, and gravity is made up of gravitons, therefore gravitons cause warping of gravity. The higher the density of gravitons, the more warping of spacetime occurs

Next Question: How does the quantum theory affect gravity and explain the warping of space-time?