why the universe is expanding?

Question

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Answer 1

According to the experiments the groups of galaxies are found to move away from each other. Hence it can be concluded that the universe is expanding.

Answer 2

OK......I'l make this as easy as I can, as an explanation without going too much into theory. But you'll have to put up with some:)

Before the Inflation Era (10^-37 to 10^-32 secs), the universe was under the influence of some rather exotic conditions, known as Supersymmetry. Now, what this was, is that all the forces of nature.....gravity, the electroweak force (electromagnetism and the weak nuclear force) and the strong nuclear force were unified as one overriding force of nature (thus as defined in GUT's......Grand Unified Theories). This condition extends all the way back to the Planck Era (10^-43 secs) and is as far as we can tell what the universe was like. Now Supersymmetry states that all the natural forces and spacetime itself were in a state of perfect symmetry with one another. This means that all the energies present were in equilibrium, all forces were one unified force and all the dimensions of reality were of equal size and importance. The energy state of the universe was extremely high and space itself was comprised of a state called a false vacuum.

Now, this supersymmetry was inherently unstable, because its initial energy state was highly positive. Now, what happened next was that this highly positive energy state couldn't sustain its own existence. To rid itself of all the energy that it contained, the early universe had to do something. What it did was to break the symmetry that it was under. What had to happen was the false (positive) vacuum had to change and convert itself into the lowest energy state it could possibly exist as. This state is what we have now......the true vacuum. This vacuum has a bulk negative energy value ie: it's energy is in its lowest state of existence. To achieve this, to break symmetry, the false vacuum produced a ultra heavy particle called the Higgs Boson. This particle (which still hasn't been observed) carried the energy of the false vacuum as mass.....the Higgs Boson is believed to be the particle which gives matter/energy mass.

This broke the symmetry of the false vacuum, releasing an unimaginably collossal amount of energy into the true vacuum. Also at this stage, the 4 dimension of the true vacuum, space itself, rapidly expanded whilst the other 7 dimensions of spacetime shrank to below Planck dimensions (10^-37m). The 4 dimensions of spacetime (hence the true vacuum) underwent an explosive expansion from a size 10^-33 times smaller than a proton to an object 10^100 times larger (about 100 million light years) in about 10^-50 seconds. Also at this inflationary stage, the 4 forces of nature began to "defrost" out of the previously high positive energy state.......first gravity, followed by the strong nuclear, weak nuclear then the electromagnetic forces. Meanwhile, what we see of the universe.....the "observable universe" grew to about the size of a grapefruit. It is this explosive initial expansionary episode that is still driving the expansion today.

However, what has been recently found is that for the first 2 billion years of its existence, gravity was the main player in universal expansion, slowing it down. After 2 billion years, it appears that a factor, known as the Cosmological Constant, represented by what is known as "dark energy", has taken over and now the universe is accelerating its expansion.

That's the fairly simple answer to your question......:)

Answer 3

Not only is the universe expanding from the original big bang, but it's expanding at an ever increasing rate. That's one of science's greatest mysteries.

For expansion to be accelerating there must be a force pushing it.
But there is no known force to account for it.

So we call it 'dark energy'.

Answer 4

According to the Big Bang theory,
all matter originated at a point and then due to an explosion all matter started to move away from each other.
so the universe is expanding.

Answer 5

Because after the Big Bang, all matter expanded out from that point, and continues to do so.

Answer 6

The universe is expanding due to bigbang theory.

Answer 7

we know that the universe IS expanding and we know about some of the forces that are involved but no one knows WHY it is expanding

Answer 8

the universe is expanding cause time moves forward not back.

Answer 9

All the hot air from the politicians

Answer 10

After big-bang too many mat rial speed in space and in this space many stars born , live and die..