What determines whether the universe will expand forever or recollapse?

Answer 1

The universe is expanding, and it was recently discovered that the universe is expanding much faster than was originally thought. Also, objects within the universe are constantly changing, such as the birth and death of stars, expanding and/or contraction of gas clouds, and objects in motion (the spinning of galaxies and solar systems, rogue stars or planets) are constantly changing.

Answer 2

THEORY 1: If you observe 2 galaxies, and note their distance from each other, after some time (maybe an hour) you will notice that the distance has dramatically increased. The rate of increase of distance suggests that they are almost moving away from each other at the speed of light. This was observed in 1929 through telescopes, and the only explanation for this was the the overall containment for all galaxies (or the Universe itself) was expanding. Think a of balloon. Fill it partially with air, then mark it with black dots which represents galaxies. Now continue to fill the balloon and you will notice that the dots move away from each other. Same assumption applies to Universal expansion.

THEORY 2: Einstein's theory of relativity was applied to the Universal energy singularity in 1920's. The numbers that resulted from his application mathematically proved the fact that the Universe was functioning under unstable energy. The only way to accommodate this energy was only if the Universe expands, or contracts. Contraction of Universe is not practical as it suggests that the starting size of the Universe was infinite. However, considering that Universe is expanding is much more sensible as it suggests that Universe started as a single point which exploded into a huge size (supporting the Big-Bang and Entanglement Theory)

THEORY 3: Most of the lights from other galaxies we receive are in a Red spectrum. According to the works of Edwin Hubble on the light spectrum, if a light is received of a Reddish spectrum, the object is moving away from the receiving observer which further supports the notion that galaxies are moving away from each other.

Answer 3

There are several pieces of evidence. One important piece of evidence is the redshift of distant galaxies. That is, the change in the color of the light that reaches us indicates that far-away galaxies are receding (going away) from us.

Answer2.

The redshift itself is misunderstood and is weak evidence for an expanding universe. Hubble is the authority on the redshift data and Hubble does not support the redshift interpretation of an expanding universe. The universe is not expanding it is in scalar equilibrium and the redshift is evidence of this equilibrium. At the speed of light the universe is also in vector equilibrium, F= ma= 0.

See Alan Sandage on Hubble reference in related links..

Hubble believed that his count data gave a more reasonable result concerning spatial curvature if the redshift correction was made assuming no recession. To the very end of his writings he maintained this position, favouring (or at the very least keeping open) the model where no true expansionexists, and therefore that the redshift "represents a hitherto unrecognized principle of nature". This viewpoint is emphasized (a) in The Realm of the Nebulae, (b)in his reply (Hubble 1937a) to the criticisms of the 1936 papers by Eddington and by McVittie, and (c)in his 1937 Rhodes Lectures published as The Observational Approach to Cosmology(Hubble 1937b). It also persists in his last published scientific paper which is an account of his Darwin Lecture (Hubble 1953).

Answer 4

People know that the solar system is expanding because of astronomers looking through telescopes. Light takes a certain time to get to earth, so the light from a really long way away could have been produced a hundred years ago. But you can only look a certain distance away because before a certain time the universe was very cloudy, so you can't see much. But as the universe expands, more of it is seen, so that is why we know it is expanding.

Answer 5

We know the universe is expanding for several reasons. The first is galactic red shift. The light of galaxies far away is Doppler shifted towards the red end of the light spectrum. The further away a galaxy is, the further down the spectrum the light from it is shifted.

A second reason we know the universe is expanding is due to Einstein's equations for General Relativity. Had Einstein the courage to stand by his initial results, he would have won credit for the discovery of the expansion of the universe instead of Edwin Hubble.

Answer 6

The spectra of Cepheid variables, which are found in all galaxies, are red-shifted.

This is an optical effect that indicates they are moving rapidly away from Earth and from the center of the known universe.

*This interpretation was not shared by astronomer Edwin Hubble (see discussion).

Answer 7

In a very general sense, this is an unavoidable consequence of the Second Law of Thermodynamics!

More specifically, several processes are known to work in the Universe. For example, stars will gradually use up their fuel - they will burn hydrogen, converting it into helium and heavier elements. Also, at the end of their lives, most stars leave a remain, a "corpse", which contains matter that is no longer available to form new stars.

Answer 8

The amount of matter (or more exactly the density of matter) in the Universe is very important.

That determines the gravitational attraction, which tends to stop the Universe expanding.

The other important thing is how fast the Universe is expanding.

The discovery of "dark energy" in the last few years suggests that the rate of expansion is actually increasing.

See "Sources and related links", below.

Answer 9

A proper Theory of the Universe is the only way to know. Measurements must be interpreted in the context of a Theory, so measurements themselves like the redshift do not in themselves provide a way to "know.

My Theory of Quaternion Physics claims the Universe is not expanding or collapsing. The Universe has a lower bound in size of 158E24 and a upper bound of 3E30 meters.

Answer 10

By observing the relative positions of galaxies.