# What triggered the Big Bang?

1. Apr 1, 2012

### curiouschris

As far as I am aware the current theory (most popular) for the creation of the universe was that it arose from a singularity. This singularity exploded (The Big Bang) and created the universe as we know it.

Now for all changes that occur, whether it be an explosion, a landslide, an earthquake or even the thoughts of a poster, something must trigger it. This is an application of logic not physical laws (debatable) and therefore I believe a trigger or flaw or impurity in the singularity would be necessary. In other words it can't suddenly decide to go bang.

Is that thinking correct?
What would give rise to such a external force or inherent flaw?

CC

p.s. Its hard to talk about events without invoking a time element like 'suddenly'.

2. Apr 1, 2012

### Drakkith

Staff Emeritus

Not really. The singularity is most likely a product of our incomplete knowledge at the temperature and density scales that the early universe existed in. All we really know is that the universe was once very hot, very dense, and expanded from there.

The simple answer is that we don't know.

3. Apr 2, 2012

### skydivephil

I think the problem is not that we have no idea how the big bang was triggered but we have far too many ideas, none of them verified by any data. The ideas do seem to me to be falling under two areas though:
mutiverse, our big bang is just one of many: look up "eternal inflation " for this
cyclic: many diffferent versions of cyclic cocmoslogy exist , google "Loop quanutm cosmology" "Conformal cyclic cosmology" or "ekpyrotic".
There is a book coming out which is supposed to be for a lay audience but I suspect will be more academic than that, alink is here:
https://www.amazon.com/Beyond-Big-Bang-Competing-Collection/dp/3540714227
But if you cant afford it or dont want to wait, there is an ok summary here:
http://philsci-archive.pitt.edu/1910/1/VAASTIME.PDF

Last edited by a moderator: May 5, 2017
4. Apr 2, 2012

### Chronos

Most scientists consider the initial 'singularity' thing unrealistic, but, the 'we have no clue' proposition remains popular.

5. Apr 2, 2012

### phyzguy

While you may consider this proposition that "All events must have a cause" to be self-evidently true, it is not, and it appears not to be true in our universe. Orthodox quantum mechanics rejects this proposition - things can 'just happen'. An excited atom sits there for a while, and then just emits a photon, with no apparent trigger. A uranium atom just sits there for a billion years and then decays for no apparent reason. As others have said, we really have no clue what triggered the big bang, but one possibility is that it arose through a quantum fluctuation, meaning that it 'just happened' with no previous event having triggered it.

6. Apr 2, 2012

### bapowell

And for the record, the big bang was not an explosion in any traditional sense of the word.

7. Apr 2, 2012

### Drakkith

Staff Emeritus
I disagree with this. While we may not be able to predice when a specific atom will decay, I wouldn't say that it decays for no reason.

8. Apr 2, 2012

### Mark M

Chris,

When you say Big Bang, are you referring to the absolute beginning of the universe, or the beginning of the rapid expansion?

If you are referring to expansion, the 'Bang' part, inflation is the excepted theory on how this occurs. Inflation theorizes that a field, called the inflaton field, produced an enormous negative-pressure vacuum energy, after getting stuck on a false vacuum. This would have expanded the universe by a factor of up to 100100, for about 10-36 seconds, estimated to be 10-33 seconds after the big bang.

If you are referring to the absolute beginning, then that is a highly speculative question. But no 'trigger' is necessary. One proposal from the cosmologist Sean Carroll is that the universe began as a time-symmetric de Sitter space, so the idea of a cause is not necessary. There are also the cyclic models, such as Paul Steinhardt's proposal of the Ekpyrotic universe, in which two 3-branes collide every 1 trillion years. Obviously, this dependent on M-Theory.

Also, singularity is a breakdown of general relativity. Stephan Hawking and Roger Penrose had originally convinced many of the idea that the universe began in a singularity, but today it is mostly recognized as an example of extending a theory beyond its range of applicability. We still need quantum gravity to analyze conditions of the Planck Epcoh.

Correct, but I believe phyzguy was trying to say that quantum mechanics says it could happen for now apparent reason.

9. Apr 2, 2012

### bapowell

There was no "bang" part. Using this kind of language confuses people into thinking that the big bang was some sort of explosion. Inflation, as a process, is completely separate from the big bang, and neither were explosions.
Where'd you get this number? Inflation grew the universe by a factor of least $e^{60} \sim 10^{23}$, but could have lasted longer. Your number is closer to the number of vacua predicted to exist in the string landscape, which is a completely different problem.

10. Apr 2, 2012

### Mark M

Bad terminology, though what I was trying to convey by 'bang' was the beginning of expansion. I can see how this could be misinterpreted as some kind of explosion.

First line of the article, "at least 1078 in volume"

http://en.wikipedia.org/wiki/Inflation_(cosmology))

Where did you get 1023? Also, the number of vacua predicted in string theory is closer to 10500.

11. Apr 2, 2012

### bapowell

Yes, the volume expanded by at least that factor, but the number that is usually quoted is the number of e-folds of expansion, which is the amount of increase of the scale factor -- this is what I thought you were referring to. I mistyped -- that should be $10^{26}$.
Great. I was only off by 400 orders of magnitude.

Last edited: Apr 2, 2012
12. Apr 3, 2012

### curiouschris

Wow thanks guys. I now have a whole bunch of stuff to go through. Maybe I shouldn't be so curious.

I am not a fan of m theory for no other reason than it seems to much like, Hey this equation doesn't work out, I'll throw in another universe or two and maybe an extra dimension. There you go now it works.... well almost anyway.

I read in Paul Davies book "The mind of God" about gaps in our knowledge being attributed to God and he introduced me to the phrase "God of the Gaps" This resonated with me and has stuck. but I apply it to not only religion but all endeavors of man. Thus I believe theories like M Theory, String theory and similar are "Theories of the Gaps". I sincerely doubt their correctness.

I hope I haven't offended in my previous paragraph.

In a similar vein I view singularities as being a creation of gaps rather than having any real basis. So I am heartened by the response.

I have no problem per se with inflation and my original question was to see whether I was wrong in my misgivings over a singularity. I felt a singularity was an impossibility and even if it wasnt it needed something to initiate the 'inflation' (I wont use bang). I do believe all actions are preceded by an initiator, so I also do not agree with phyzguy. Whether we are able to determine what the initiator is or can predict the onset is another thing altogether.

I guess I am more of a fan of the expanding contracting universe. in the end it will collapse until the density and temperature reaches such a high level a change is triggered and inflation starts again.
Perhaps each iteration results in a different set of physical laws. Except now I sound like a theoretical physicist.

13. Apr 3, 2012

### phyzguy

You may disagree, but I believe that this is what standard quantum mechanics says. Also, the Bell inequalities put strong constraints on any type of 'hidden variable' theories that would allow you to predict the outcome of an experiment on a specific particle.

14. Apr 3, 2012

### skydivephil

I would advise against letting your personal prefences get in the way of conclusions. The data tells us whats correct. Its not like going to the movies where your subejctive preferences are important. We shouldnt believe our universe is going to collapse unless the data demands it. at the moment the data is the other way. That doesnt mean there havent been previous collapses but again the data must tell us that.
As I udnerstand it M theory was invesnted to show how different string theories were equivalent. Hence is not equiavlent to a god of the gaps argument. That doenst mean its correct, again we shall have to wait and see. There are certianly ways to criticise M theory, but Im not sure this is an appropriate one.

15. Apr 3, 2012

### Mark M

Although I can not argue against that, it does not matter what you 'feel' about a theory. If it is self-consistent, solves the problem at hand, and is consistent with data, we stay with it until a better theory is proposed.
They are not anything like a 'god of the gaps'. I don't see where you are drawing any comparison.
They aren't created to fill gaps, they are the gap. They are regions that appear because a particular theory is taken out of it's area of applicably.
This is misguided, you're equating your experiences of cause an effect to something that is totally different. Similar to the way I stated earlier that singularities arise, you are using something beyond where it applies. If the universe had absolute maximum entropy at t=0, then nothing would happen for a reason, quantum processes would dominate.

The universe is accelerating, ruling out any re collapse ideas.

16. Apr 3, 2012

### Drakkith

Staff Emeritus
I believe QM explains exactly why a particle decays, it just doesn't let us know exactly when it will happen. This has nothing to do with hidden variables.

17. Apr 3, 2012

### phyzguy

OK. In reference to the OP's original statement that 'All events must have a cause', explain to me the trigger that causes a Uranium atom to decay after not decaying for a billion years.

18. Apr 3, 2012

### Drakkith

Staff Emeritus
It's unstable and it's decay is governed by statistics and probability. That is "cause" to me. I'm sure someone more educated in the details of QM could explain it better.

19. Apr 3, 2012

### phyzguy

So maybe the OP would be satisfied with the answer, "The quantum vacuum is unstable and its decay into an inflating universe is governed by the laws of statistics and probability". Curiouschris, does this answer your question?

20. Apr 3, 2012

### bapowell

It's likely closer to the opposite: while the universe is trapped in a metastable false vacuum, it inflates. It stops inflating when it decays to the true vacuum, nucleating a non-inflationary universe.