big bang

[deegee]

Is there any evidence that the big bang has happened more than once? Are there any reasons why not ??

[Area54]

A google search for Big Bang, which I assume you  would have conducted  (if not, why not?), should have returned items that mentioned the Big Bounce. There is no evidence for this that I am aware of, but it is not precluded by current theory.

[Strange]

2 hours ago, deegee said:

Is there any evidence that the big bang has happened more than once?

No. But it does form part of several models. Area54 has mentioned the "big bounce" or cyclical models. There are also "eternal inflation" models where multiple universes could be continuously created: https://en.wikipedia.org/wiki/Eternal_inflation

It seems unlikely that there could ever be evidence for any of these ideas though.

Quote

Are there any reasons why not ??

Not currently. Although Stephen Hawking's last paper suggests it may not be a necessary consequence of inflation.

[deegee]

Is there any evidence that the expansion from the "Big Bang" is slowing down ?

[Strange]

2 minutes ago, deegee said:

Is there any evidence that the expansion from the "Big Bang" is slowing down ?

Quite the reverse. Google "dark energy"

Is this really homework? (Much more interesting homework topics than when I was at school!)

[deegee]

Well it started as homework with my daughter ,the question re big bang happening before.But we both had our eyes opened a bit with more questions.

[Strange]

Well, if this bit isn't homework ...

In 2011 three guys (Perlmutter, Riess and Schmidt) got the Nobel Prize in physics for finding evidence that the expansion of the universe is accelerating. Previously it had been assumed that gravity would cause it to slow down and then, possibly reverse (leading to the "big bounce"). But instead they found that, starting about 4 billion years ago, the rate of expansion started increasing. This can most easily be explained by the presence of a fixed amount of energy in empty space - so, as the universe expands and there is more space then there is more of this energy. No one knows what this energy is so it is called "dark energy". The presence of this energy causes the rate of expansion to increase (which means more dark energy and faster expansion ...)

http://www.bbc.com/news/science-environment-15165371

[deegee]

"Facts don't come " etc...... in many cases facts are preceded by theories and in many cases theories are accepted as facts.is that not so ?

[Strange]

5 minutes ago, deegee said:

"Facts don't come " etc...... in many cases facts are preceded by theories and in many cases theories are accepted as facts.is that not so ?

Hmmm.... Not sure. In science "facts" are usually the evidence that theories are based on (and tested against). Theories shouldn't really be accepted as facts (or true) because they are always provisional - further evidence could show them to be wrong (although this doesn't happen very often). But some theories are so well established that it is hard to see how they could ever be overturned.

The quote in my signature is from Hans Rosling, pointing out that many of the ideas we have about the world around us (about, for example, the relative wealth and health of countries) is based on inaccurate stereotypes and out-of-date information.

Edited March 20, 2018 by Strange

[deegee]

"In 2011" etc. Could it not be because that the further you get from the source of the attraction the less restraining influence there is,thus the  increase in acceleration ?

[Strange]

1 minute ago, deegee said:

"In 2011" etc. Could it not be because that the further you get from the source of the attraction the less restraining influence there is,thus the  increase in acceleration ?

That can only reduce the rate at which expansion is slowing, not speed it up. So, if the density of the universe were low enough (and there were no dark energy) then expansion could continue forever at the same rate. With a higher density it would slow down and eventually collapse again. With dark energy it looks as if it will continue to expand at an ever increasing rate.

http://astronomy.swin.edu.au/cosmos/C/Critical+Density

https://www.physicsoftheuniverse.com/topics_bigbang_accelerating.html