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Section:1

Team:38

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Book name:Very high energy gamma radiation
Author-F.A Ahronian
Publication-World Scientific
Year of publication-2000

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Gamma ray astronomy, the branch of high energy astrophysics that studies the sky in energetic ?-ray photons, is destined to play a crucial role in the exploration of nonthermal phenomena in the Universe in their most extreme and violent forms. The great potential of this discipline offers impressive coverage of many OC hot topicsOCO of modern astrophysics and cosmology, such as the origin of galactic and extragalactic cosmic rays, particle acceleration and radiation processes under extreme astrophysical conditions, and the search for dark matter."

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Gamma ray astronomy, the branch of high energy astrophysics that studies the sky in energetic ?-ray photons, is destined to play a crucial role in the exploration of nonthermal phenomena in the Universe in their most extreme and violent forms. The great potential of this discipline offers impressive coverage of many OC hot topicsOCO of modern astrophysics and cosmology, such as the origin of galactic and extragalactic cosmic rays, particle acceleration and radiation processes under extreme astrophysical conditions, and the search for dark matter."

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-Shanthan Kumar

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We would like to thank our teacher Mrs. Amutha for giving us such a wonderful opportunity to explore and share information on astronomy.

I would also thank all you attentive viewers for watching this patiently.

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1)How effective was our communication?

2)How do you appreciate our study on astronomy?

3)How was our team work?

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1)On a scale of 1 to 10,how much would you rate our padlet?
2)Were the concepts made clear?
3)Would you recommend anyone interested in astronomy to take a look at our work?

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1)www.youtube.com
2)www.nasa.com
3)www.sciencedaily.com
4)www.skyandtelescope.com
5)www.mitcoursware.com
6)www.astronomynow.com
7)www.slate.com

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Gamma ray applications in everyday life.-Sayan 

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Gamma ray applications in everyday life.-Sayan 

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We've all heard of radiotherapy, but what is it? This is the story of how Gamma Rays kill cancer cells. and briefly explain DNA mutation.

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The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself changes. This is different from other examples of expansions and explosions in that, as far as observations can ascertain, it is a property of the entirety of the universe rather than a phenomenon that can be contained and observed from the outside

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When most people believed in an essentially static and unchanging universe, the question of whether or not it had a beginning was really one of metaphysics or theology. One could account for what was observed either way. Either the universe had existed forever, or it was set in motion at some finite time in such a manner as to look as though it had existed forever.By measuring the distances between the galaxies using red shift and dopplers' effect phenomena,we can say thatthe universe is expanding. This means that at earlier times objects would have been closer together. In fact, it seemed that there was a time about ten or twenty thousand million years ago when they were all at exactly the same place.

One may say that time had a beginning at the big bang, in the sense that earlier times simply could not be defined. It should be emphasized that this beginning in time is very different from those that had been considered previously. In an unchanging universe, a beginning in time is something that has to be imposed by some being outside the universe.

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I feel that, the universe is expanding so rapidly that the gravitational attraction can never stop it, though it does slow it down a bit. The separation between neighbouring galaxies in this model starts at zero, and eventually the galaxies are moving apart at a steady speed. Though the dark matter increases with the ageing of universe, we can say that new stars and massive bodies get created to overcome these gravitational interactions.

REASON: We can determine the present rate of expansion by measuring the velocities at which other galaxies are moving away from us, using the Doppler effect. This
can be done very accurately. However, the distances to the galaxies are not very well known because we can only measure them indirectly. So all we know is that the universe is expanding by between 5 percent and 10 percent every thousand million years. However, our uncertainty about the present average density of the universe is even greater.

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I would like to present my ideas on the advancements in the study of astronomy, specially its formation and amendments in the rocket technology.

First of all I want to tell about the rocket technology and its improvements.

In this field the main problem is due to the fuel. We

have to control its usage for efficiency. My idea is to use simple physics principles to get motion. we can use the principle of conservation of momentum.

Then I would like to say you regarding the study of universe. this topic is really a vast one to discuss. Beginning from its formation to expansion and different stages. And still the study is running. There is actually no end to this topic but the theories go on evolving to explain the things.

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1. Is the padlet easy to understand?

2.  Is the language used easy to convey the information?

3.  Are the video links interesting?

4.  Is this padlet interesting and can be ?

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I say that the universe is expanding so sufficiently
slowly that the gravitational attraction between the different galaxies causes the expansion to slow down and eventually to stop. The galaxies then start to move toward each other and the universe contracts. The distance between two neighboring galaxies starts at zero, increases to a maximum, and then decreases back down to zero again.
REASON:
If we add up the masses of all the stars that we can see in our galaxy and other galaxies, the total is less than one-hundredth of the amount required to halt the expansion of the universe, even in the lowest estimate of the rate of expansion. But we know that our galaxy and other galaxies must contain a large amount of dark matter which we cannot see directly, but which we know must be there because of the influence of its gravitational attraction on the orbits of stars and gas in the galaxies. Moreover, most galaxies are found in clusters, and we can similarly infer the presence of yet more dark matter in between the galaxies in these clusters by its effect on the motion of the galaxies. When we add up all this dark matter, we still get only about one-tenth of the amount required to halt the expansion. However, there might be some other form of matter which we have not yet detected and which might still raise the average density of the universe up to the critical value needed to halt the expansion

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ROCKETS

TELESCOPES

SPACE SHUTTLES

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Observing planets: optimising your views

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The NASA/ESA Hubble Telescope's skeleton (artist's rendering)

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The NASA/ESA Hubble Telescope's skeleton (artist's rendering)

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History and locations of various telescopes in world

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History and locations of various telescopes in world

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-Bhavi tej

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There is a great need to have advancements in this technology as we are evolving with time along with our needs.

To fulfil these needs we have to improve our technology too.

For ex.

The Fuel Crisis- To control the usage of fuel we need to develop new techniques like some magnetic motion which can attract a rocket into space .

-Shanthan Kumar

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Like many other engines, a rocket produces thrust by burning fuel. Most rocket engines turn the fuel into hot gas. Pushing the gas out of the back of the engine makes the rocket move forward.

Then later in its journey it uses basic physics laws to go forward. It starts losing its mass to go forward with a higher speed and carries satellites with it.

-Shanthan Kumar

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As promised earlier that I would discuss about the application of mechanical engineering in this astronomy field, I would like to present it.

My main moto is to show ways to improve the rockets and discuss their launching procedure.

Here is an article from NASA , an introduction to rockets.

-Shanthan Kumar

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A rocket is a vehicle that launches into space. A rocket also can be a type of engine.

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neutron star-A compact star that forms due to the collapse of a massive star

Supernova-An explosion that outshines an entire galaxy.

Afterglow-The glow of a star a long time after its burst.

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Our universe has an entirely different way of expanding and what's interesting is that the rate of expansion is not constant!

https://en.wikipedia.org/wiki/Metric_expansion_of_space

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The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not expand "into" anything and does not require space to exist "outside" it. This expansion involves neither space nor objects in space "moving" in a traditional sense, but rather it is the metric (which governs the size and geometry of spacetime itself) that changes in scale. As the spatial part of the universe's spacetime metric increases in scale, objects become more distant from one another at ever-increasing speeds. To any observer in the universe, it appears that all of space is expanding, and that all but the nearest galaxies (which are bound by gravity) recede at speeds that are proportional to their distance from the observer. While objects within space cannot travel faster than light, this limitation does not apply to the effects of changes in the metric itself. Objects that recede beyond the cosmic event horizon will eventually become unobservable, as no new light from them will be capable of overcoming the universe's expansion, limiting the size of our observable universe.

According to inflation theory, during the inflationary epoch about 10 −32 of a second after the Big Bang, the universe suddenly expanded, and its volume increased by a factor of at least 10 ⁷⁸ (an expansion of distance by a factor of at least 10 ²⁶ in each of the three dimensions). This would be equivalent to expanding an object 1 nanometer (10 −9 m, about half the width of a molecule of DNA) in length to one approximately 10.6 light years (about 10 ¹⁷ m or 62 trillion miles) long. A much slower and gradual expansion of space continued after this, until at around 9.8 billion years after the Big Bang (4 billion years ago) it began to gradually expand more quickly, and is still doing so. Physicists have postulated the existence of dark energy, appearing as a cosmological constant in the simplest gravitational models, as a way to explain this late-time acceleration. According to the simplest extrapolation of the currently favored cosmological model, the Lambda-CDM model, this acceleration becomes more dominant into the future. In June 2016, NASA and ESA scientists reported that the universe was found to be expanding 5% to 9% faster than thought earlier, based on studies using the Hubble Space Telescope.

In 1912, Vesto Slipher discovered that light from remote galaxies was redshifted, which was later interpreted as galaxies receding from the Earth. In 1922, Alexander Friedmann used Einstein field equations to provide theoretical evidence that the universe is expanding.

Swedish astronomer Knut Lundmark was the first person to find observational evidence for expansion in 1924. According to Ian Steer of the NASA/IPAC Extragalactic Database of Galaxy Distances, "Lundmark's extragalactic distance estimates were far more accurate than Hubble's, consistent with an expansion rate (Hubble constant) that was within 1% of the best measurements today."

In 1927, Georges Lemaître independently reached a similar conclusion to Friedmann on a theoretical basis, and also presented observational evidence for a linear relationship between distance to galaxies and their recessional velocity. Edwin Hubble observationally confirmed Lundmark's and Lemaître's findings in 1929. Assuming the cosmological principle, these findings would imply that all galaxies are moving away from each other.

Based on large quantities of experimental observation and theoretical work, the scientific consensus is that space itself is expanding, and that it expanded very rapidly within the first fraction of a second after the Big Bang, approximately 13.8 billion years ago. This kind of expansion is known as "metric expansion". In mathematics and physics, a " metric" means a measure of distance, and the term implies that the sense of distance within the universe is itself changing.

The modern explanation for the metric expansion of space was proposed by physicist Alan Guth in 1979 while investigating the problem of why no magnetic monopoles are seen today. Guth found in his investigation that if the universe contained a field that has a positive-energy false vacuum state, then according to general relativity it would generate an exponential expansion of space. It was very quickly realized that such an expansion would resolve many other long-standing problems. These problems arise from the observation that to look as it does today, the universe would have to have started from very finely tuned, or "special" initial conditions at the Big Bang. Inflation theory largely resolves these problems as well, thus making a universe like ours much more likely in the context of Big Bang theory. According to Roger Penrose, inflation does not solve the main problem it was supposed to solve, namely the incredibly low entropy (with unlikeliness of the state on the order of 1/10 ⁠) of the early Universe contained in the gravitational conformal degrees of freedom (in contrast to fields degrees of freedom, such like the cosmic microwave background whose smoothness can be explained by inflation). Thus, he puts forward his scenario of the evolution of the Universe: conformal cyclic cosmology.

No field responsible for cosmic inflation has been discovered. However such a field, if found in the future, would be scalar. The first similar scalar field proven to exist was only discovered in 2012-2013 and is still being researched. So it is not seen as problematic that a field responsible for cosmic inflation and the metric expansion of space has not yet been discovered.[citation needed ]

The proposed field and its quanta (the subatomic particles related to it) have been named . If this field did not exist, scientists would have to propose a different explanation for all the observations that strongly suggest a metric expansion of space has occurred, and is still occurring much more slowly today.

To understand the metric expansion of the universe, it is helpful to discuss briefly what a metric is, and how metric expansion works.

A metric defines the concept of distance, by stating in mathematical terms how distances between two nearby points in space are measured, in terms of the coordinate system. Coordinate systems locate points in a space (of whatever number of dimensions) by assigning unique positions on a grid, known as coordinates, to each point. Latitude and longitude, and x-y graphs are common examples of coordinates. A metric is a formula that describes how a number known as "distance" is to be measured between two points.

It may seem obvious that distance is measured by a straight line, but in many cases it is not. For example, long haul aircraft travel along a curve known as a " great circle" and not a straight line, because that is a better metric for air travel. (A straight line would go through the earth). Another example is planning a car journey, where one might want the shortest journey in terms of travel time - in that case a straight line is a poor choice of metric because the shortest distance by road is not normally a straight line, and even the path nearest to a straight line will not necessarily be the quickest. A final example is the internet, where even for nearby towns, the quickest route for data can be via major connections that go across the country and back again. In this case the metric used will be the shortest time that data takes to travel between two points on the network.

In cosmology, we cannot use a ruler to measure metric expansion, because our ruler's internal forces easily overcome the extremely slow expansion of space, leaving the ruler intact. Also, any objects on or near earth that we might measure are being held together or pushed apart by several forces that are far larger in their effects. So even if we could measure the tiny expansion that is still happening, we would not notice the change on a small scale or in everyday life. On a large intergalactic scale, we can use other tests of distance and these do show that space is expanding, even if a ruler on earth could not measure it.

Example: "Great Circle" metric for Earth's surface

For example, consider the measurement of distance between two places on the surface of the Earth. This is a simple, familiar example of spherical geometry. Because the surface of the Earth is two-dimensional, points on the surface of the Earth can be specified by two coordinates - for example, the latitude and longitude. Specification of a metric requires that one first specify the coordinates used. In our simple example of the surface of the Earth, we could choose any kind of coordinate system we wish, for example latitude and longitude, or X-Y-Z Cartesian coordinates. Once we have chosen a specific coordinate system, the numerical values of the coordinates of any two points are uniquely determined, and based upon the properties of the space being discussed, the appropriate metric is mathematically established too. On the curved surface of the Earth, we can see this effect in long-haul airline flights where the distance between two points is measured based upon a great circle, rather than the straight line one might plot on a two-dimensional map of the Earth's surface. In general, such shortest-distance paths are called " geodesics". In Euclidean geometry, the geodesic is a straight line, while in non-Euclidean geometry such as on the Earth's surface, this is not the case. Indeed, even the shortest-distance great circle path is always longer than the Euclidean straight line path which passes through the interior of the Earth. The difference between the straight line path and the shortest-distance great circle path is due to the curvature of the Earth's surface. While there is always an effect due to this curvature, at short distances the effect is small enough to be unnoticeable.

On plane maps, great circles of the Earth are mostly not shown as straight lines. Indeed, there is a seldom-used map projection, namely the gnomonic projection, where all great circles are shown as straight lines, but in this projection, the distance scale varies very much in different areas. There is no map projection in which the distance between any two points on Earth, measured along the great circle geodesics, is directly proportional to their distance on the map; such accuracy is possible only with a globe.

In expanding space, proper distances are dynamical quantities that change with time. An easy way to correct for this is to use comoving coordinates, which remove this feature and allow for a characterization of different locations in the universe without having to characterize the physics associated with metric expansion. In comoving coordinates, the distances between all objects are fixed and the instantaneous dynamics of matter and light are determined by the normal physics of gravity and electromagnetic radiation. Any time-evolution however must be accounted for by taking into account the Hubble law expansion in the appropriate equations in addition to any other effects that may be operating ( gravity, dark energy, or curvature, for example). Cosmological simulations that run through significant fractions of the universe's history therefore must include such effects in order to make applicable predictions for observational cosmology.

In principle, the expansion of the universe could be measured by taking a standard ruler and measuring the distance between two cosmologically distant points, waiting a certain time, and then measuring the distance again, but in practice, standard rulers are not easy to find on cosmological scales and the timescales over which a measurable expansion would be visible are too great to be observable even by multiple generations of humans. The expansion of space is measured indirectly. The theory of relativity predicts phenomena associated with the expansion, notably the redshift-versus-distance relationship known as Hubble's Law; functional forms for cosmological distance measurements that differ from what would be expected if space were not expanding; and an observable change in the matter and energy density of the universe seen at different lookback times.

The first measurement of the expansion of space came with Hubble's realization of the velocity vs. redshift relation. Most recently, by comparing the apparent brightness of distant standard candles to the redshift of their host galaxies, the expansion rate of the universe has been measured to be = 73.24 ± 1.74 (km/s)/Mpc. This means that for every million parsecs of distance from the observer, the light received from that distance is cosmologically redshifted by about 73 kilometres per second (160,000 mph). On the other hand, by assuming a cosmological model, e.g. Lambda-CDM model, one can infer the Hubble constant from the size of the largest fluctuations seen in the Cosmic Microwave Background. A higher Hubble constant would imply a smaller characteristic size of CMB fluctuations, and vice versa. The Planck collaboration measure the expansion rate this way and determine H ₀ = 67.4 ± 0.5 (km/s)/Mpc. There is a disagreement between the two measurements, the distance ladder being model-independent and the CMB measurement depending on the fitted model, which hints at new physics beyond our standard cosmological models.

The Hubble parameter is not thought to be constant through time. There are dynamical forces acting on the particles in the universe that affect the expansion rate. It was earlier expected that the Hubble parameter would be decreasing as time went on due to the influence of gravitational interactions in the universe, and thus there is an additional observable quantity in the universe called the deceleration parameter, which cosmologists expected to be directly related to the matter density of the universe. Surprisingly, the deceleration parameter was measured by two different groups to be less than zero (actually, consistent with −1), which implied that today the Hubble parameter is converging to a constant value as time goes on. Some cosmologists have whimsically called the effect associated with the "accelerating universe" the "cosmic jerk". The 2011 Nobel Prize in Physics was given for the discovery of this phenomenon.

In October 2018, scientists presented a new third way (two earlier methods, one based on redshifts and another on the cosmic distance ladder, gave results that do not agree), using information from gravitational wave events (especially those involving the merger of neutron stars, like GW170817), of determining the Hubble Constant, essential in establishing the rate of expansion of the universe.

At cosmological scales, the present universe conforms to Euclidean space, what cosmologists describe as geometrically flat, to within experimental error.

Consequently, the rules of Euclidean geometry associated with Euclid's fifth postulate hold in the present universe in 3D space. It is, however, possible that the geometry of past 3D space could have been highly curved. The curvature of space is often modeled using a non-zero Riemann curvature tensor in Curvature of Riemannian manifolds. Euclidean "geometrically flat" space has a Riemann curvature tensor of zero.

"Geometrically flat" space has 3 dimensions and is consistent with Euclidean space. However, spacetime on the other hand, is 4 dimensions; it is not flat according to Einsten's general theory of relativity. Einstein's theory postulates that "matter and energy curve spacetime, and there are enough matter and energy lying around to provide for curvature."

In part to accommodate such different geometries, the expansion of the universe is inherently general relativistic. It cannot be modeled with special relativity alone: though such models exist, they are at fundamental odds with the observed interaction between matter and spacetime seen in our universe.

The images to the right show two views of spacetime diagrams that show the large-scale geometry of the universe according to the ΛCDM cosmological model. Two of the dimensions of space are omitted, leaving one dimension of space (the dimension that grows as the cone gets larger) and one of time (the dimension that proceeds "up" the cone's surface). The narrow circular end of the diagram corresponds to a cosmological time of 700 million years after the Big Bang, while the wide end is a cosmological time of 18 billion years, where one can see the beginning of the accelerating expansion as a splaying outward of the spacetime, a feature that eventually dominates in this model. The purple grid lines mark off cosmological time at intervals of one billion years from the Big Bang. The cyan grid lines mark off comoving distance at intervals of one billion light years in the present era (less in the past and more in the future). Note that the circular curling of the surface is an artifact of the embedding with no physical significance and is done purely for illustrative purposes; a flat universe does not curl back onto itself. (A similar effect can be seen in the tubular shape of the pseudosphere.)

The brown line on the diagram is the worldline of Earth (or more precisely its location in space, even before it was formed). The yellow line is the worldline of the most distant known quasar. The red line is the path of a light beam emitted by the quasar about 13 billion years ago and reaching Earth at the present day. The orange line shows the present-day distance between the quasar and Earth, about 28 billion light years, which is a larger distance than the age of the universe multiplied by the speed of light, ct.

According to the equivalence principle of general relativity, the rules of special relativity are locally valid in small regions of spacetime that are approximately flat. In particular, light always travels locally at the speed c; in the diagram, this means, according to the convention of constructing spacetime diagrams, that light beams always make an angle of 45° with the local grid lines. It does not follow, however, that light travels a distance ct in a time t, as the red worldline illustrates. While it always moves locally at c, its time in transit (about 13 billion years) is not related to the distance traveled in any simple way, since the universe expands as the light beam traverses space and time. The distance traveled is thus inherently ambiguous because of the changing scale of the universe. Nevertheless, there are two distances that appear to be physically meaningful: the distance between Earth and the quasar when the light was emitted, and the distance between them in the present era (taking a slice of the cone along the dimension defined as the spatial dimension). The former distance is about 4 billion light years, much smaller than ct, whereas the latter distance (shown by the orange line) is about 28 billion light years, much larger than ct. In other words, if space were not expanding today, it would take 28 billion years for light to travel between Earth and the quasar, while if the expansion had stopped at the earlier time, it would have taken only 4 billion years.

The light took much longer than 4 billion years to reach us though it was emitted from only 4 billion light years away. In fact, the light emitted towards Earth was actually moving away from Earth when it was first emitted; the metric distance to Earth increased with cosmological time for the first few billion years of its travel time, also indicating that the expansion of space between Earth and the quasar at the early time was faster than the speed of light. None of this behavior originates from a special property of metric expansion, but rather from local principles of special relativity integrated over a curved surface.

Over time, the space that makes up the universe is expanding. The words ' space' and ' universe', sometimes used interchangeably, have distinct meanings in this context. Here 'space' is a mathematical concept that stands for the three-dimensional manifold into which our respective positions are embedded while 'universe' refers to everything that exists including the matter and energy in space, the extra-dimensions that may be wrapped up in various strings, and the time through which various events take place. The expansion of space is in reference to this 3-D manifold only; that is, the description involves no structures such as extra dimensions or an exterior universe.

The ultimate topology of space is a posteriori - something that in principle must be observed - as there are no constraints that can simply be reasoned out (in other words there can not be any constraints) on how the space in which we live is connected or whether it wraps around on itself as a compact space. Though certain cosmological models such as Gödel's universe even permit bizarre worldlines that intersect with themselves, ultimately the question as to whether we are in something like a " Pac-Man universe" where if traveling far enough in one direction would allow one to simply end up back in the same place like going all the way around the surface of a balloon (or a planet like the Earth) is an observational question that is constrained as measurable or non-measurable by the universe's global geometry. At present, observations are consistent with the universe being infinite in extent and simply connected, though we are limited in distinguishing between simple and more complicated proposals by cosmological horizons. The universe could be infinite in extent or it could be finite; but the evidence that leads to the inflationary model of the early universe also implies that the "total universe" is much larger than the observable universe, and so any edges or exotic geometries or topologies would not be directly observable as light has not reached scales on which such aspects of the universe, if they exist, are still allowed. For all intents and purposes, it is safe to assume that the universe is infinite in spatial extent, without edge or strange connectedness.

Regardless of the overall shape of the universe, the question of what the universe is expanding into is one that does not require an answer according to the theories that describe the expansion; the way we define space in our universe in no way requires additional exterior space into which it can expand since an expansion of an infinite expanse can happen without changing the infinite extent of the expanse. All that is certain is that the manifold of space in which we live simply has the property that the distances between objects are getting larger as time goes on. This only implies the simple observational consequences associated with the metric expansion explored below. No "outside" or embedding in hyperspace is required for an expansion to occur. The visualizations often seen of the universe growing as a bubble into nothingness are misleading in that respect. There is no reason to believe there is anything "outside" of the expanding universe into which the universe expands.

Even if the overall spatial extent is infinite and thus the universe cannot get any "larger", we still say that space is expanding because, locally, the characteristic distance between objects is increasing. As an infinite space grows, it remains infinite.

The expansion of space is sometimes described as a force that acts to push objects apart. Though this is an accurate description of the effect of the cosmological constant, it is not an accurate picture of the phenomenon of expansion in general.

In addition to slowing the overall expansion, gravity causes local clumping of matter into stars and galaxies. Once objects are formed and bound by gravity, they "drop out" of the expansion and do not subsequently expand under the influence of the cosmological metric, there being no force compelling them to do so.

There is no difference between the inertial expansion of the universe and the inertial separation of nearby objects in a vacuum; the former is simply a large-scale extrapolation of the latter.

Once objects are bound by gravity, they no longer recede from each other. Thus, the Andromeda galaxy, which is bound to the Milky Way galaxy, is actually falling towards us and is not expanding away. Within the Local Group, the gravitational interactions have changed the inertial patterns of objects such that there is no cosmological expansion taking place. Once one goes beyond the Local Group, the inertial expansion is measurable, though systematic gravitational effects imply that larger and larger parts of space will eventually fall out of the " Hubble Flow" and end up as bound, non-expanding objects up to the scales of superclusters of galaxies. We can predict such future events by knowing the precise way the Hubble Flow is changing as well as the masses of the objects to which we are being gravitationally pulled. Currently, the Local Group is being gravitationally pulled towards either the Shapley Supercluster or the " Great Attractor" with which, if dark energy were not acting, we would eventually merge and no longer see expand away from us after such a time.

A consequence of metric expansion being due to inertial motion is that a uniform local "explosion" of matter into a vacuum can be locally described by the FLRW geometry, the same geometry that describes the expansion of the universe as a whole and was also the basis for the simpler Milne universe, which ignores the effects of gravity. In particular, general relativity predicts that light will move at the speed c with respect to the local motion of the exploding matter, a phenomenon analogous to frame dragging.

At the end of the early universe's inflationary period, all the matter and energy in the universe was set on an inertial trajectory consistent with the equivalence principle and Einstein's general theory of relativity and this is when the precise and regular form of the universe's expansion had its origin (that is, matter in the universe is separating because it was separating in the past due to the inflaton field).[citation needed ]

While special relativity prohibits objects from moving faster than light with respect to a local reference frame where spacetime can be treated as flat and unchanging, it does not apply to situations where spacetime curvature or evolution in time become important. These situations are described by general relativity, which allows the separation between two distant objects to increase faster than the speed of light, although the definition of "distance" here is somewhat different from that used in an inertial frame. The definition of distance used here is the summation or integration of local comoving distances, all done at constant local proper time. For example, galaxies that are farther than the Hubble radius, approximately 4.5 gigaparsecs or 14.7 billion light-years, away from us have a recession speed that is faster than the speed of light. Visibility of these objects depends on the exact expansion history of the universe. Light that is emitted today from galaxies beyond the more-distant cosmological event horizon, about 5 gigaparsecs or 16 billion light-years, will never reach us, although we can still see the light that these galaxies emitted in the past. Because of the high rate of expansion, it is also possible for a distance between two objects to be greater than the value calculated by multiplying the speed of light by the age of the universe. These details are a frequent source of confusion among amateurs and even professional physicists. Due to the non-intuitive nature of the subject and what has been described by some as "careless" choices of wording, certain descriptions of the metric expansion of space and the misconceptions to which such descriptions can lead are an ongoing subject of discussion within the fields of education and communication of scientific concepts.

At a fundamental level, the expansion of the universe is a property of spatial measurement on the largest measurable scales of our universe. The distances between cosmologically relevant points increases as time passes leading to observable effects outlined below. This feature of the universe can be characterized by a single parameter that is called the scale factor, which is a function of time and a single value for all of space at any instant (if the scale factor were a function of space, this would violate the cosmological principle). By convention, the scale factor is set to be unity at the present time and, because the universe is expanding, is smaller in the past and larger in the future. Extrapolating back in time with certain cosmological models will yield a moment when the scale factor was zero; our current understanding of cosmology sets this time at 13.799 ± 0.021 billion years ago. If the universe continues to expand forever, the scale factor will approach infinity in the future. In principle, there is no reason that the expansion of the universe must be monotonic and there are models where at some time in the future the scale factor decreases with an attendant contraction of space rather than an expansion.

The expansion of space is often illustrated with conceptual models that show only the size of space at a particular time, leaving the dimension of time implicit.

In the " ant on a rubber rope model" one imagines an ant (idealized as pointlike) crawling at a constant speed on a perfectly elastic rope that is constantly stretching. If we stretch the rope in accordance with the ΛCDM scale factor and think of the ant's speed as the speed of light, then this analogy is numerically accurate - the ant's position over time will match the path of the red line on the embedding diagram above.

In the "rubber sheet model" one replaces the rope with a flat two-dimensional rubber sheet that expands uniformly in all directions. The addition of a second spatial dimension raises the possibility of showing local perturbations of the spatial geometry by local curvature in the sheet.

In the "balloon model" the flat sheet is replaced by a spherical balloon that is inflated from an initial size of zero (representing the big bang). A balloon has positive Gaussian curvature while observations suggest that the real universe is spatially flat, but this inconsistency can be eliminated by making the balloon very large so that it is locally flat to within the limits of observation. This analogy is potentially confusing since it wrongly suggests that the big bang took place at the center of the balloon. In fact points off the surface of the balloon have no meaning, even if they were occupied by the balloon at an earlier time.

In the "raisin bread model" one imagines a loaf of raisin bread expanding in the oven. The loaf (space) expands as a whole, but the raisins (gravitationally bound objects) do not expand; they merely grow farther away from each other.

Hubble's law

Technically, the metric expansion of space is a feature of many solutions[which? ] to the Einstein field equations of general relativity, and distance is measured using the Lorentz interval. This explains observations that indicate that galaxies that are more distant from us are receding faster than galaxies that are closer to us (see Hubble's law).

The first general relativistic models predicted that a universe that was dynamical and contained ordinary gravitational matter would contract rather than expand. Einstein's first proposal for a solution to this problem involved adding a cosmological constant into his theories to balance out the contraction, in order to obtain a static universe solution. But in 1922 Alexander Friedmann derived a set of equations known as the Friedmann equations, showing that the universe might expand and presenting the expansion speed in this case. The observations of Edwin Hubble in 1929 suggested that distant galaxies were all apparently moving away from us, so that many scientists came to accept that the universe was expanding.

Hubble's concerns over the rate of expansion

While the metric expansion of space appeared to be implied by Hubble's 1929 observations, Hubble disagreed with the expanding-universe interpretation of the data:

[...] if redshifts are not primarily due to velocity shift [...] the velocity-distance relation is linear; the distribution of the nebula is uniform; there is no evidence of expansion, no trace of curvature, no restriction of the time scale [...] and we find ourselves in the presence of one of the principles of nature that is still unknown to us today [...] whereas, if redshifts are velocity shifts which measure the rate of expansion, the expanding models are definitely inconsistent with the observations that have been made [...] expanding models are a forced interpretation of the observational results.

[If the redshifts are a Doppler shift ...] the observations as they stand lead to the anomaly of a closed universe, curiously small and dense, and, it may be added, suspiciously young. On the other hand, if redshifts are not Doppler effects, these anomalies disappear and the region observed appears as a small, homogeneous, but insignificant portion of a universe extended indefinitely both in space and time.

Hubble's skepticism about the universe being too small, dense, and young turned out to be based on an observational error. Later investigations appeared to show that Hubble had confused distant H II regions for Cepheid variables and the Cepheid variables themselves had been inappropriately lumped together with low-luminosity RR Lyrae stars causing calibration errors that led to a value of the Hubble Constant of approximately 500 km/ s/ Mpc instead of the true value of approximately 70 km/s/Mpc. The higher value meant that an expanding universe would have an age of 2 billion years (younger than the Age of the Earth) and extrapolating the observed number density of galaxies to a rapidly expanding universe implied a mass density that was too high by a similar factor, enough to force the universe into a peculiar closed geometry that also implied an impending Big Crunch that would occur on a similar timescale. After fixing these errors in the 1950s, the new lower values for the Hubble Constant accorded with the expectations of an older universe and the density parameter was found to be fairly close to a geometrically flat universe.

However, recent measurements of the distances and velocities of faraway galaxies revealed a 9 percent discrepancy in the value of the Hubble constant, implying a universe that seems expanding too fast compared to previous measurements. In 2001, Wendy Freedman determined space to expand at 72 kilometers per second per megaparsec - roughly 3.3 million light years - meaning that for every 3.3 million light years further away from the earth you are, the matter where you are, is moving away from earth 72 kilometers a second faster. In the summer of 2016, another measurement reported a value of 73 for the constant, thereby contradicting 2013 measurements from the European Planck mission of slower expansion value of 67. The discrepancy opened new questions concerning the nature of dark energy, or of neutrinos.

Until the theoretical developments in the 1980s no one had an explanation for why this seemed to be the case, but with the development of models of cosmic inflation, the expansion of the universe became a general feature resulting from vacuum decay. Accordingly, the question "why is the universe expanding?" is now answered by understanding the details of the inflation decay process that occurred in the first 10−32 seconds of the existence of our universe. During inflation, the metric changed exponentially, causing any volume of space that was smaller than an atom to grow to around 100 million light years across in a time scale similar to the time when inflation occurred (10 −32 seconds).

In expanding space, distance is a dynamic quantity that changes with time. There are several different ways of defining distance in cosmology, known as distance measures, but a common method used amongst modern astronomers is comoving distance.

Theoretical cosmologists developing models of the universe have drawn upon a small number of reasonable assumptions in their work. These workings have led to models in which the metric expansion of space is a likely feature of the universe. Chief among the underlying principles that result in models including metric expansion as a feature are:

Scientists have tested carefully whether these assumptions are valid and borne out by observation. Observational cosmologists have discovered evidence - very strong in some cases - that supports these assumptions, and as a result, metric expansion of space is considered by cosmologists to be an observed feature on the basis that although we cannot see it directly, scientists have tested the properties of the universe and observation provides compelling confirmation. Sources of this confidence and confirmation include:

Hubble demonstrated that all galaxies and distant astronomical objects were moving away from us, as predicted by a universal expansion. Using the redshift of their electromagnetic spectra to determine the distance and speed of remote objects in space, he showed that all objects are moving away from us, and that their speed is proportional to their distance, a feature of metric expansion. Further studies have since shown the expansion to be highly isotropic and homogeneous, that is, it does not seem to have a special point as a "center", but appears universal and independent of any fixed central point.

In studies of large-scale structure of the cosmos taken from redshift surveys a so-called "End of Greatness" was discovered at the largest scales of the universe. Until these scales were surveyed, the universe appeared "lumpy" with clumps of galaxy clusters, superclusters and filaments that were anything but isotropic and homogeneous. This lumpiness disappears into a smooth distribution of galaxies at the largest scales.

The isotropic distribution across the sky of distant gamma-ray bursts and supernovae is another confirmation of the Cosmological Principle.

The Copernican Principle was not truly tested on a cosmological scale until measurements of the effects of the cosmic microwave background radiation on the dynamics of distant astrophysical systems were made. A group of astronomers at the European Southern Observatory noticed, by measuring the temperature of a distant intergalactic cloud in thermal equilibrium with the cosmic microwave background, that the radiation from the Big Bang was demonstrably warmer at earlier times. Uniform cooling of the cosmic microwave background over billions of years is strong and direct observational evidence for metric expansion.

Taken together, these phenomena overwhelmingly support models that rely on space expanding through a change in metric. It was not until the discovery in the year 2000 of direct observational evidence for the changing temperature of the cosmic microwave background that more bizarre constructions could be ruled out. Until that time, it was based purely on an assumption that the universe did not behave as one with the Milky Way sitting at the middle of a fixed-metric with a universal explosion of galaxies in all directions (as seen in, for example, an early model proposed by Milne). Yet before this evidence, many rejected the Milne viewpoint based on the mediocrity principle.

More direct results of the expansion, such as change of redshift, distance, flux, angular position and the angular size of astronomical objects, have not been detected yet due to smallness of these effects. Change of the redshift or the flux could be observed by Square Kilometre Array or Extremely Large Telescope in the mid-2030s.

Eddington, Arthur. The Expanding Universe: Astronomy's 'Great Debate', 1900-1931. Press Syndicate of the University of Cambridge, 1933.

Liddle, Andrew R. and David H. Lyth. Cosmological Inflation and Large-Scale Structure. Cambridge University Press, 2000.

Lineweaver, Charles H. and Tamara M. Davis, "Misconceptions about the Big Bang", Scientific American, March 2005 (non-free content).

Mook, Delo E. and Thomas Vargish. Inside Relativity. Princeton University Press, 1991.

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The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not expand "into" anything and does not require space to exist "outside" it.

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http://missionscience.nasa.gov/ems/12_gammarays.html

-sayan

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1)Why are we humans not constantly bombarded with GRBs(gamma ray bursts)?
a)GRBs lose their intensity with time and distance
b)GRBs have  a very focused directional path.
c)GRBs are sucked in by the black holes.
d)GRBs hit us all the time but it does not affect us in anyway.
ANSWER-b

2)How many kinds of GRBs are produced in nature?
a)one
b)two
c)three
d)five
ANSWER-b

3)What is the maximum GRBs' distance possible from earth today?
a)100 years
b)10 million light  years
c)10 billion light years
d)16 billion light years
ANSWER-d

4)which of the following helps us determine precisely where the GRB was emmited from?
a)redshift
b)blueshift
c)afterglow frequency
d)none
ANSWER-a

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This video shows us how the blackholes result in slowing of time.

-Shanthan Kumar

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Stephen Hawking - Black Hole Time Travel

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Einstein's idea on worm holes and Black holes. 

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Einstein's idea on worm holes and Black holes. 

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This video is an addition info. regarding the black holes and wormholes and also describes Einstein's idea on this.

-Shanthan Kumar

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In the early 1990s, one thing was fairly certain about the expansion of the universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Gr…

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Chandrashekhar Limit- 1.4 times mass of the sun.

Wormhole- a shortcut through which long distances can be travelled in space time.

Dark Matter-it is a hypothetical kind of matter that cannot be seen with telescopes but would account for most of the matter in the universe.

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Q.1 Which observation provides the best evidence that Earth rotates?

1.   The position of the planets among the stars changes during the year.

2.   The location of the constellations in relationship to Polaris changes from month to month.

3.   The length of the shadow cast by a flagpole at noontime changes from season to season.

4.   The direction of swing of a freely swinging pendulum changes during the day.

Correct Answer Number: 4
Q.2 The best evidence that Earth spins on its axis is provided by

1.   variations in atmospheric density

2.  apparent shifts in the swing of a Foucault pendulum

3.   changes in the position of sunspots on the Sun

4.   eclipses of the Moon

Correct Answer Number: 2

Q.3A cycle of Moon phases can be seen from Earth because the

1.   Moon’s distance from Earth changes at a predictable rate

2.   Moon’s axis is tilted

3.   Moon spins on its axis

4.   Moon revolves around Earth

Correct Answer Number: 4

Q.4 Energy is transferred from the Sun to Earth mainly by

1.   molecular collisions

2.   density currents

3.  electromagnetic waves

4.   red shifts

Correct Answer Number: 3

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This padlet is interesting!

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Which planet is approximately thirty times farther from the Sun than Earth is?

1. Jupiter

2. Saturn

3. Uranus

4. Neptune

Ans-4. Neptune

Which object is located at one foci of the elliptical orbit of Mars?

1. Sun

2. Earth

3. Mercury

4. Moon

Ans- 1. Sun

Summer days in New York State are likely to be hotter than winter days because in summer

1.   Earth is closer to the Sun

2.  the number of sunspots increases

3.   Earth’s northern axis is tilted toward the Sun

4.   the Sun gives off more energy

Ans-3

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Supernova Remnant-supernova remnant is the structure resulting from the explosion of a star in a supernova.

Interstellar- between the stars.

Supersonic- involving or denoting a speed greater than that of sound.

-Shanthan Kumar

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Closest and Brightest gamma rays recorded.

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Closest and Brightest gamma rays recorded.

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The brightest ever recorded gamma rays promise to reveal the secret behind the production of gamma rays.

-Sayan Ray

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The Universe clearly works weekends; delivering one of the brightest and closest gamma ray bursts yet on Saturday, March 29, at 6:37 a.m. EST.

NASA's High-Energy Transient Explorer (HETE) detected the burst, signaling the birth of a black hole, in the constellation Leo. For more than 30 seconds, the burst out shone the entire Universe in gamma rays, and its afterglow was still over a trillion times brighter than the Sun two hours later. This was the brightest burst yet detected by HETE and is in the top one percent of all bursts in terms of intrinsic brightness. Within seconds, HETE nailed down a location and subsequently relayed the coordinates to the astronomy community, allowing hundreds of scientists and amateur astronomers to join the observation, from Australia to Finland and across the ocean to America. Observations poured in as scientists attempted to unravel what caused the burst. The burst was later identified with a new supernova in a distant galaxy.

"This was our biggest one ever, and it didn't get away," said Dr. George Ricker of the Massachusetts Institute of Technology (MIT), Cambridge, Mass., and principal investigator for the HETE mission. "With scores of observations now completed and more on the way, we should get a rather clear picture of what triggered this burst."

Gamma ray bursts are the most powerful explosions in the Universe; likely caused by the death of a massive star, in which the core implodes to form a black hole. Bursts appear to occur randomly, and few last more than a minute, making them hard to study.

HETE detects the fleeting gamma ray and X-ray portions of these bursts, and its prompt localization enables scientists to study the burst afterglow, which can linger from days to weeks in optical light and radio waves. Most bursts originate in the early universe, traveling upwards of 10 billion years at light speed to reach us.

The burst on March 29 was named GRB 030329. Both the burst and its afterglow were brilliant. The burst poured out a thousand trillion, trillion times the gamma rays seen in a solar flare. When measured more than one hour after the burst, the afterglow was still about as bright as a 12th magnitude star. This means it was only about 10 to 100 times dimmer than what can be seen with the naked eye, visible with backyard telescopes. At its peak, the afterglow may have been visible to the naked eye.

The burst originated approximately two billion light years from Earth, which is relatively close. The GRB 030329 redshift measurement was 0.168, making this the second closest burst with a known redshift measurement. (Redshift is a measurement of how light from distant regions of the Universe is "shifted" to lower energy as the Universe expands; the greater the redshift, the greater the distance from Earth.) "Few amateur astronomers are treated to an event that originated billions of light years away," said Ricker.

Bruce Peterson and Paul Price of the Research School of Astronomy and Astrophysics at the Australian National University, Canberra, first identified the burst afterglow. An automated telescope at Japan's RIKEN science institute quickly confirmed the location. Finnish amateur astronomers provided even tighter constraints on the properties of the afterglow. Multiple observations enable a thorough study of the burst environment.

Gamma ray burst hunters are aided by three new developments: fast triggers from orbiting detectors; fast relays to observers worldwide via the Gamma ray burst Coordinates Network (GCN); and fast responses from ground-based robotic telescopes. HETE is the first satellite to provide and distribute accurate burst locations within seconds.

The GCN, developed and maintained at NASA's Goddard Space Flight Center in Greenbelt, Md., serves as a gamma ray burst hub. HETE signals the GCN, which sends out "phone calls" and email messages to scientists and amateurs worldwide. The GCN Web site also posts scientific information from the astronomers making observations.

HETE was built by MIT as a mission of opportunity under the NASA Explorer Program, with collaboration among U.S. universities, Los Alamos, N.M. National Laboratory, scientists and organizations in Brazil, France, India, Italy and Japan.

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The Universe clearly works weekends; delivering one of the brightest and closest gamma ray bursts yet on Saturday, March 29, at 6:37 a.m. EST. NASA's High-Energy Transient Explorer (HETE) detected the burst, signaling the birth of a black hole, in the constellation Leo.

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This video explains my reference book in short. Its a video from the youtube channel minute physics. Mr. Neil deGrasse Tyson explains the reference.

-Shanthan Kumar

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A Brief History of Everything, feat. Neil deGrasse Tyson

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-Bhavitej

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How To Time Travel | National Geographic

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Bhavi Tej,the chances of a gamma ray burst taking place anywhere near our milky way are close to zero,and if it were to take place anywhere nearby then yeah,lifeform could be destroyed.

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This video gives us a short explanation on my journal. Its explains in short about the life cycle of a star, beginning from its birth to death and conditions to form a black hole or a supernova to take place.

Explains the fusion reaction which takes place in a star and how it emits energy from it.

-Shanthan Kumar

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Bhavitej

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Bhavitej-2015A7PS021H

Sayan Ray-2015AAPS274H

Shanthan Kumar-2015ABPS672H

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Sayan ,if gamma ray burst were to happen in our neighbouring Andromeda galaxy,what would be the consequences on earth?

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Those people who need basic requirements can refer to the book 'The grand design' by Stephen Hawking.

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Physics has been classified into quantum mechanics and classical mechanics just for our ease. But we can generalise that classical mechanics is an ideal situation of quantum mechanics.I mean quantum mechanics can be extended to explain classical mechanics under certain constraints and conditions.

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Every few seconds, a supernova emits jets of deadly gamma rays somewhere in the universe. If one of these gamma ray bursts should happen sufficiently close to the solar system, all life would perish.<br>             -Sayan

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My interests are mainly centric about gamma ray burst.
-Sayan

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Gamma Ray bursts are the  biggest explosions after the Big Bang.It pushes observational astronomy to it's limits.These were discovered by accident,yet it  managed to grab most of the leading astrophysicists' attention.Gamma rays are very high energy waves with the wavelength equal to the size of an atomic nuclei.Initially it was thought that gamma rays were emitted only by nuclear explosions.But then satellites detected similar high energy radiations coming from outer space.With the help of red shifts ,it was determined that these are billions of lights years away almost on the edge of the universe.There are two ways of producing such gamma rays.
1)Degrading of massive stars into blackholes
2)Collision of two neutron stars.
These gamma ray bursts are bright enough to be brighter than the entire universe when they occur.

-Sayan Ray

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Talk by Edo Berger (Hardvard univ.)
-Sayan Ray

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Edo Berger: Gamma-Ray Bursts: The Biggest Explosions Since the Big Bang

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Bhavitej, how do you explain this to the public who are not aware of all this but need some requirements from this?

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Well my journal is basically about the formation of universe, how the bigbang has occurred.

It even describes the life of a star from its birth to death.

it discusses the conditions to form a black hole or for a supernova to occur.

It even discusses the different stages of the supernova and proves mathematically the conditions for it to exists.

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Shanthan, can you please summarize your journal too

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Bhavitej, how is it possible to find such a type of theory which include both quantum and classical mechanics at the same time, which actually contradict each other?

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This shows you how universe was formed.

-Bhavitej

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The History of the Universe in 10 Minutes

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This deals with a quick discussion of our universe from big bang to black holes.

This describes how Newton's and Einstein's theories of gravity led to the conclusion that universe should be either expanding or contracting.

This also deals with the black holes that are formed when a massive star or an even larger body collapses into itself under its own gravitational pull.

This also tells that quantum mechanics allows energy to leak out of black holes.

The author tries to find a unified theory that will include quantum mechanics, gravity and all other interactions of physics

-Bhavitej (2015A7PS021H)

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My Reference for the project, "The Theory Of Everything " by "Stephen Hawking"

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My Reference for the project, "The Theory Of Everything " by "Stephen Hawking"

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Book Name-The Theory Of Everything

Author-Stephen Hawking

Year Of Publication-2006

Publisher-Jaico Publishers

Place of publication-Mumbai

-Bhavitej

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This gives a short idea how the universe was created and discusses different stages of a star.

-Shanthan Kumar

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-Shanthan Kumar

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(Jordi Prat-Camps/Autonomous University of Barcelona)

Back in 2015, researchers in Spain created a tiny magnetic wormhole for the first time ever. They used it to connect two regions of space so that a magnetic field could travel 'invisibly' between them.

Before you get too excited, it wasn't the kind of gravitational wormhole that would theoretically allow humans to travel rapidly across space in science fiction TV shows and films such as Stargate, Star Trek, and Interstellar, and it wouldn't have been able to transport matter.

But the physicists managed to create a tunnel that allowed a magnetic field to disappear at one point, and then reappear at another, which is still a pretty huge deal.

A wormhole is effectively just a tunnel that connects two places in the Universe. So far scientists have simulated this process, but are nowhere near creating a gravitational wormhole, as it would require us to create huge amounts of gravitational energy - something we don't yet know how to do.

But what physicists are good at is generating and manipulating electromagnetic energy, and so the team from the Autonomous University of Barcelona decided to see if they could build a magnetic wormhole in the lab instead.

In 2014, they managed to create tunnels that directed magnetic fields from one place to another, but these weren't true wormholes because they didn't keep the magnetic field undetectable or magnetically 'invisible' while it was travelling inside the tunnel.

This is something they managed to overcome in 2015, by using metamaterial and metasurfaces to build their tunnel.

That meant that they could make the magnetic field from a source, such as a magnet or an electromagnet, appear at the other end of the wormhole with no trace of it in between.

This created the illusion that the magnetic field must be travelling through some kind of extra dimension. Oddly enough, it also meant that an isolated magnetic monopole - a magnet with only one pole, North or South - appeared randomly at the end of the tunnel.

"This result is strange enough in itself, as magnetic monopoles do not exist in nature," a press release explained at the time.

"The overall effect is that of a magnetic field that appears to travel from one point to another through a dimension that lies outside the conventional three dimensions."

To be clear, the wormhole in this experiment isn't really invisible to the human eye - it's a sphere made up of an outer ferromagnetic surface, an inner superconducting layer, and then a ferromagnetic sheet rolled into a cylinder internally.

But the way that it's been designed means that it, and its contents, is totally undetectable magnetically.

In other words, it's magnetically invisible from the outside, but to us it looks more like this:

Jordi Prat-Camps/Autonomous University of Barcelona

And while the tunnel isn't anywhere near to the kind of wormhole that would take us across space, it does have a lot of features in common.

"[It] changes the topology of space, as if the inner region has been magnetically erased from space," lead researcher Àlvar Sánchez explained.

The research has potential practical applications in areas that use magnetic fields - for example, it could lead to the creation of MRI machines that don't require people to lie inside the claustrophobic machine, or more targeted MRI scans.

But importantly, it also teaches us more about ways we can tunnel our way through space - an endeavour that holds countless exciting possibilities.

The research was published in Scientific Reports.

A version of this story was first published in September 2015.

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A Magnetic ‘Wormhole’ That Connects Two Regions of Space Was Created in The Lab

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Back in 2015, researchers in Spain created a tiny magnetic wormhole for the first time ever. They used it to connect two regions of space so that a magnetic field could travel ‘invisibly’ between them.

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I will even explore and suggest some innovative ideas of using mechanical engineering in the field of astronomy, basically related to the machinery and equipment which are used in this field.

- Shanthan Kumar

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This Video is just to show that how big bang has taken place and created the known universe

-Shanthan Kumar

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This book which I have chosen deals with the change of ideologies of people regarding universe with the time . Many theories have tried to explain the universe part wise, but none of them could explain it as a whole .

This continues with the various theories which were proposed by different scientists and the drawbacks which came due to them.

Physicists continue to seek a complete, unified theory of the universe, although this may not be possible to discover. The driving motivation is the thirst for knowledge, while another human motivation, the discomfort of uncertainty, resists the discovery of what may be taken as the mind of God. The author is fully aware of what scientific discovery means to the world's religions that cling to older models of the universe, and mentions this often. The author uses humour and friendly tone to make it interesting.

-Shanthan Kumar

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The  reference which I will be using for this is "A Brief History Of Time" by "Stephen Hawking".

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The  reference which I will be using for this is "A Brief History Of Time" by "Stephen Hawking".

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Book Name-A Brief History Of Time

Author-Stephen Hawking

Year Of Publication- 1988

Publisher- Bantam Dell Publishers

Place Of Publication- New York

-Shanthan Kumar