Entry 1609, on 2013-12-19 at 23:22:55 (Rating 3, Science)
For many years now I have been intrigued by the idea of multiple universes. If they exist it would answer a lot of the problems we have with current theories, such as what happened before the Big Bang, what caused it, what it formed from, and why our universe seems so special (in terms of the physical constants seemingly being fine-tuned to allow life).
First I should briefly explain these problems. A question people often ask about the Big Bang is what happened before it and what caused it. If it really was the origin of our universe and there no other universes then those questions have no obvious answer, in fact the questions themselves may make no sense (because time and space didn't exist before our universe began).
Then there is the puzzling observation that many of the constants, such as the strength of gravity and electromagnetism, are not predicted by theory so could have any value. Yet if their values were much different to what they actually are life anywhere in the universe would not be possible. And that isn't just "life as we know it", it is any reasonable type of life (for reasons I won't go into here to save space).
But a multiverse theory can answer these questions in a rather elegant way.
If our universe is just one part of a multiverse, with an infinite number of universes in it, and ours "broke off" from the multiverse during the Big Bang then we avoid the origin problems. The multiverse would be infinite in time and space so asking what is outside the universe or what happened before is no problem: outside is just more universes embedded in a multiverse which has always existed.
We still can't say for sure what "caused" our universe to "break off" but I think it's fair to suggest it was one of those causeless, random quantum events. This idea is supported by the fact that the total energy in our universe seems to be zero.
So what about the fine tuning argument? This has been used as a reason to believe in a god. Some people say that the universe could only be the way it is if an intelligent entity had deliberately made it that way. Of course, like most theological theories, this one is absurd because it just pushes the problem back one step: we know why the universe is the way it is but why is god the way he is? It's really nothing more than a "god of the gaps" argument.
A multiverse answers this question very easily. If there are an infinite number of universes all with slightly different values for the constants then there is sure to be one which suits life. We live in that one because we couldn't live in any other, just like we evolved here on Earth because Venus is too hot and Mars too cold.
The whole idea is just perfect, except for one small issue: there has never been the slightest piece of evidence to support it! Perhaps until now...
Scientists who have studied radiation data gathered by Planck telescope think they have found evidence of other universes (although this is disputed). The theory says that during the first seconds of the universe it would be affected by other universes in the area and that would be detectable in background radiation patterns. And that's what some researchers think they have found.
I really do have to say that this stuff is rather speculative and quite preliminary at this point but I think I have noticed a trend over the last 10 years for multiverse theories to be taken more and more seriously. Maybe in the near future the evidence will be much better and the theory will be generally accepted. It's certainly an interesting idea and the best explanation yet of some of the most puzzling questions we have.
Comment 1 by richard on 2013-12-22 at 21:56:25:
I am continually surprised by the lack of comments in alot of your blog entries Owen. I certainly enjoy your posts, and any ensuing discussion (in spite of some ridicule), and am amazed (and disappointed) that others don't feel encouraged to join in. I would have thought this was what was hoped for - certainly more than just me anyway!
May I say, this is another nice article, and my questions here are motivated by genuine interest in the topic, in spite of some obvious skepticism in my background (ideology?) :-)
Firstly, can you point us to the particular paper(s) that describe the multi-verse theory you describe. This isn't a veiled criticism in any way Owen, but am sincerely interested in more info, as your phrase 'one part of a multi-verse' and 'broke off' was different to my original thinking of the idea, which was more around an 'infinite number of universes' happening one after the other - the cyclic universe - which I think would also satisfy the fine-tuning requirements in a similar way to the (bubbly?) multi-verse you describe, wouldn't it? Similarly, do you have a particular preference for this idea say over the cyclic version? I don't have an opinion either way on which might seem more reasonable.
Secondly can I ask, (although this might be made more clear in the papers): Do they describe how they can make a sure distinction from any observed unusual background radiation pattern artifacts, between any adjacent universes in a multi-verse, and any other 'pre-big bang' cause, that could be come up with, like the 'causeless random quantum event' you mention. I am not sure how this could be distinguished, given the problem (perhaps?) that all observations, become a part of our ever increasingly observed (but single) universe?
One more question: Can you explain why the multi-verse theory is any less a 'gaps' theory, than any other? i.e. Does this also not just put the idea one step back? Don't you now have a requirement to explain the origin (or the why?) for a multi-verse, that has an infinite number of universes, one of which has the almost ungraspable finely-tuned physical constants combination required for life. It currently seems to me that in order for a multi-verse to produce that smorgasbord, it too must have been finely tuned? So, I'm just not sure how that 'elegantly answers the question'? Cheers, Rich.
Comment 2 by OJB on 2013-12-23 at 09:13:28:
I am also disappointed at the lack of comments! :( I know there are been over 2 million views of this blog (although many could be automated searches, etc) so I know it is being looked at.
Try this as a starting point. Let me know if you want more detailed stuff. The papers are very technical!
The old "oscillating" or "cyclic" universe theory seems to be less popular now than the parallel multiple universes have gained support, but you are right, both would give varying physical laws and allow for particular universes apparently being fine-tuned for life.
There are specific observations, beyond the usual "patchiness" of the CMB which indicate other universes exist. Have a look at the article.
Multiple universes naturally arise out of several different areas of science and math, including string theory. It isn't just an arbitrary idea which can fill any gap in knowledge like "god did it" theories!
The elegance of the multiverse is that the fine tuning fits in with similar phenomena on a smaller scale. For example: why is the Earth so fine tuned for life? 1. because millions of other planets aren't but some planets had to be. 2. because life adapted to the conditions here. The same arguments apply to the universe. And the second elegant result is the removal of a beginning to the universe. If the multiverse (including all its physical meta-laws) has always existed and always will, then no origin theory is necessary.
I should repeat here that this is highly speculative and no firm evidence yet exists supporting the idea! :) Plus this all gets back to my ultimate question I discussed a while back: why is there anything?
Comment 3 by richard on 2013-12-24 at 10:09:47:
Thanks. Interesting article. Lets not get into another multi post 'God' debate, which I realise might start turning people away from your blog, and I honestly don't want that to happen. Especially as this post is in the science category. I guess you are asking for it in the religion category, but folk can choose to run a mile then if they wish :)
I would just say, that the your characterisation of God as merely an 'arbitrary gap filling' idea, is while granted your opinion, hardly a fair one, given the briefest look around the world and all the other areas of discussion on the topic of reality and theistic apologetics. :)
So lets stick to the science. I certainly have no problem with 'highly speculative' ideas, and appreciate your heads up on that, and the answers to some of my questions. I will resist commenting in detail on your fine tuning answer (for the reason above).
I must confess though that I cannot work out how that answered my original questions at all.
First one: Is there any sound reasoning to assume that the boundary of our visible universe, equates to the actual limits of our universe? I am not aware of any such clear evidence. If not, we have no idea just how much 'bigger' it is, and what other artifacts might be present in it, could account for the CMB variations we observe in our visible portion? Just saying how do we distinguish that from a multi-verse? I recognise this is too just speculation, but fair I think, given the speculative nature of the proposal in the first place? Is this an unfair question?
Secondly - Yes, IF the multi-verse always existed, then no origin theory is necessary, but this is exactly the same argument as IF the single universe existed, isn't it? I am not clear on why is there any more reason to 'assume' that a multi-verse 'always existed', than our 'child' one? Aren't we (unfortunately) in exactly the same boat - again - strictly scientifically speaking? :)
Comment 4 by OJB on 2013-12-24 at 12:28:35:
People don't actually "run" when they see these debates, but they don't tend to read the long and complex comments either. We need to try to keep them short: one or two paragraphs preferably. So, OK, I won't start on the "god of the gaps" thing here.
No, the boundary of the universe is not its actual limit but there is a limit beyond that because of the speed of expansion since the Big Bang. If we accept (based on very good evidence) that the expansion started 13.7 billion years ago, plus factor in inflation, there is a specific size it must be. We expect random CMB fluctuations at a certain level. The effects which are used to support other universes are bigger and less random than these.
One multiverse theory states there would be an infinite number of universes appearing over infinite time. The CMB anomalies only potentially show one other universe but string theory predicts many (an infinite number maybe). Did I mention this is highly speculative? :)
No matter what theory you accept, religious or scientific, the ultimate question always remains: why is there anything? (that could be why is there a multiverse or why is there a god). In fact there are possible explanations but they are highly speculative! :) Want me to list some?
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