The Big Bang and the Expansion of the Universe

The universe we live mediante is expanding. We know this because we see galaxies and groups of galaxies steadily moving apart con the universe. This expansion has been occuring since the universe was formed 14 billion years ago in per very hot, dense event known as the Big Bang.

(1) Where is the center of the Universe?

There mai centre of the universe because there is mai edge of the universe. Durante verso finite universe, space is curved so that if you could travel billions of light years mediante verso straight line you would eventually finish back where you started. It is also possible that our universe is infinite. Per both examples, groups of galaxies completely fill the universe and are moving apart at all points making the universe expand (see question 2).

(2) Where did the Big Bang occur sopra the Universe?

There is a common assumption that the Big Bang was an explosion that occured durante empty space and that the explosion expanded into the empty space. This is wrong.

Although space may have been concentrated into verso celibe point at the Big Bang, it is equally possible that space was infinite at the Big Bang. Sopra both scenarios the space was completely filled with matter which began puro expand.

There is giammai centre of the expansion, the universe is simply expanding at all points. Observers sopra any galaxy see most of the other galaxies durante the universe moving away from them.

The only answer sicuro the question "Where did the Big Bang happen?" is that it occured everywhere durante the Universe.

(3) Is the Earth expanding with the universe?

The Earth is not expanding and neither is the solar system, nor the Milky Way galaxy. These objects formed under the influence of gravity and stopped moving apart. Gravity also holds galaxies together into groups and clusters. It is mainly the groups and clusters of galaxies that are moving apart mediante the universe.

(4) What exists outside the universe?

Space was created durante the Big Bang. Our universe has no edge or boundary - there is per niente outside of our universe (see question 1). It is possible that our universe is part of an infinity of universes (see question 5), but these universes do not necessarily need per space preciso exist in.

(5) What existed before the Big Bang?

Time was created per the Big Bang - we do not know if it existed before the Big Bang. This question is therefore hard puro answer. Some theories suggest that our universe is part of an infinity of universes (called a multiverse) which are being continuously created. This is possible but very hard preciso prove.

(6) If the universe is 14 billion years old, how could galaxies have travelled more than 14 billion light years?

It is possible that our universe is infinite and has been filled with matter everywhere since the Big Bang (see question 2). But there is also nothing stopping the universe expanding faster than the speed of light. Although at any local point within the universe, nothing can travel faster than the speed of light, this is not true for the entire universe. There is no limit on how fast space can expand.

We can imagine galaxies are like balls sitting on per rubber sheet which represents space. If we stretch the sheet, the balls move apart. Balls which are close together will only move apart slowly. Balls which are widely separated will seem onesto move apart very quickly.

People living on any one of the balls will see their own ball as stationary. They will see nearby balls moving away slowly and they will see distant balls moving away quickly. Very distant balls (beyond the horizon) can be moving away faster than the speed of light, but the people cannot see them - locally per their own part of the universe nothing is travelling faster than the speed of light.