Marcus Chown writing in this week's New Scientist [subscribers only link] about the so-called Goldilocks Paradox (i.e. why do the laws of physics seem fine-tuned for life?):
The most likely explanation for fine-tuning is […] that our universe is merely one of a vast ensemble of universes, each with different laws of physics. We find ourselves in one with laws suitable for life because, again, how could it be any other way?
The multiverse idea is not without theoretical backing. String theory, our best attempt yet at a theory of everything, predicts at least 10500 universes, each with different laws of physics. To put that number into perspective, there are an estimated 1025 grains of sand in the Sahara desert.
I don't think that puts it into perspective at all. Do you? What Chown is saying is that the number of grains of sand in the Sahara is 10475 times smaller than the theoretically predicted minimum number of universes in the multiverse (10500 ÷ 1025 = 10475).
I don't think 10475 is much easier to envisage than 10500. That's a 1 followed by 475 zeroes, as opposed to a 1 followed by 500 zeroes.
Chown might almost as well have said, "To put that number into perspective, I only have two legs". Two is much closer to 1025 than 1025 is to 10500. Several hundreds of orders of magnitude closer, in fact.
In other words, as I'm sure Chown would agree, 10500 is an unimaginably vast number. You can't really put it into any sort of perspective.
Nice try, though, Mr Chown: you certainly got me thinking.
It got me thinking — didn't you give up your subscription to NS!
The grains of sand thing seems to be a staple of people trying to get big numbers across but it's fairly meaningless as you say.
I'm also not convinced that multiverses are the most likely explanation for 'fine tuning' either. The fact that our Universe is favourable to life is curious but, if the Universe hadn't been so, no one would ever had the chance to ponder the opposite!
I must have missed the announcement that String theory has been crowned our best attempt yet at a theory of everything. So far, as I understand it, it's predicting nothing that can be tested and that is not the way progress is usually made (Einstein just had frame dragging confirmed a cool 93 years after he predicted it). Until and if we ever can understand the constraints upon the formation of a new Universe we can't really say how improbable this one is; if you've ever assembled Ikea furniture you know that there are lots of ways of doing it – but only one that hangs together :*)
I like multiverses, it's a fun thought and I also like the music of The Eels but no need to get carried away.
P.S. I'm assuming your NS subscription is tailing off :*)
I am with you on multiverses and string theory, and am a huge Eels fan. Personally, I don't have a problem with saying that the universe must be tuned in such a way that life is possible, otherwise we wouldn't be talking about it. But a lot of physicists don't like that, apparently.
I studied physics at university, before string theory caught on. And to think I thought quantum dynamics was weird! 10500 universes! Really?!
New Scientist has a very irritating habit of asking you to renew your subscription several months before it expires. I still have no intention of renewing.
If total energy of the universe is zero, then it can be shown that multiverse theory cannot be true. This is because total energy being zero, total mass will also be zero due to mass-energy equivalence. Scientists have shown that anything having mass will always occupy some space. So anything that fails to occupy any space cannot have any mass. Our universe perhaps fails to occupy any space, and that is why its mass is zero. But if multiverse theory is true, then our universe will definitely occupy some space within the multiverse, and thus in that case its mass cannot be zero. But as this mass is zero, therefore multiverse theory cannot be true.
Here it may be argued that radiation occupies space but its mass is zero. So here is an example that something occupying space can still be without mass. So our universe can also be without mass even if it occupies some space within the multiverse. In reply we will say that the example cited here is a bad example, because our universe is not any kind of radiation. So if it is without mass, then that can only be due to its not occupying any space, and not due to its being some sort of radiation.
Well, my point exactly!
Recently I have read in a blog post that some quantum theorists say that space cannot exist at the most fundamental level. If what these theorists are saying is indeed correct, then this gives us another strong reason to assert that multiverse theory must be false. This is because if this theory is true, then there will be pre-existing space at the fundamental level within which all the universes of the multiverse will be placed. Only if our universe is the sole universe, then there will be no space outside our universe, in which case it will be in the real sense of the word a "spaceless" universe, and in that case only we can say that there will be no space at the fundamental level.
You people are all dogmatic idiots. Of course there are multiverses, it's basically been proven. It's not the 70's anymore, condolences, you lost. Now grow up and accept the truth.