Testing the Multiverse

Here's an interesting article from Quanta. It's about efforts by physicists to test the idea of the multiverse:

If modern physics is to be believed, we shouldn’t be here. The meager dose of energy infusing empty space, which at higher levels would rip the cosmos apart, is a trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion times tinier than theory predicts. And the minuscule mass of the Higgs boson, whose relative smallness allows big structures such as galaxies and humans to form, falls roughly 100 quadrillion times short of expectations. Dialing up either of these constants even a little would render the universe unlivable.

To account for our incredible luck, leading cosmologists like Alan Guth and Stephen Hawking envision our universe as one of countless bubbles in an eternally frothing sea. This infinite “multiverse” would contain universes with constants tuned to any and all possible values, including some outliers, like ours, that have just the right properties to support life. In this scenario, our good luck is inevitable: A peculiar, life-friendly bubble is all we could expect to observe.

Many physicists loathe the multiverse hypothesis, deeming it a cop-out of infinite proportions. But as attempts to paint our universe as an inevitable, self-contained structure falter, the multiverse camp is growing.

The problem remains how to test the hypothesis. Proponents of the multiverse idea must show that, among the rare universes that support life, ours is statistically typical. The exact dose of vacuum energy, the precise mass of our underweight Higgs boson, and other anomalies must have high odds within the subset of habitable universes. If the properties of this universe still seem atypical even in the habitable subset, then the multiverse explanation fails.

I'm afraid I don't understand the physics well enough to comment on the minutiae of what the physicists are up to. It's that part about some physicists loathing the idea of a multiverse that caught my eye. I've commented on this before, but it's an attitude I simply don't understand. It's one thing to say the idea is speculative, or that it is difficult to impossible to test in practice. But it is quite another to talk like this:

Paul Steinhardt, a theoretical physicist at Princeton University and one of the early contributors to the theory of eternal inflation, saw the multiverse as a “fatal flaw” in the reasoning he had helped advance, and he remains stridently anti-multiverse today. “Our universe has a simple, natural structure,” he said in September. “The multiverse idea is baroque, unnatural, untestable and, in the end, dangerous to science and society.”

Dangerous to society? Doesn't that seem just a little overwrought?

We get a partial explanation for the hostility in the next paragraph:

Steinhardt and other critics believe the multiverse hypothesis leads science away from uniquely explaining the properties of nature. When deep questions about matter, space and time have been elegantly answered over the past century through ever more powerful theories, deeming the universe's remaining unexplained properties “random” feels, to them, like giving up. On the other hand, randomness has sometimes been the answer to scientific questions, as when early astronomers searched in vain for order in the solar system's haphazard planetary orbits. As inflationary cosmology gains acceptance, more physicists are conceding that a multiverse of random universes might exist, just as there is a cosmos full of star systems arranged by chance and chaos.

I don't buy this at all. The multiverse idea is not driving people away from uniquely explaining the properties of nature. It is precisely the opposite. It is our consistent failure to uniquely explain those properties that is driving people toward the multiverse idea. That, coupled with the fact that every currently fashionable theory in cosmology seems to have a multiverse as a consequence, of course.

The article continues:

“When I heard about eternal inflation in 1986, it made me sick to my stomach,” said John Donoghue, a physicist at the University of Massachusetts, Amherst. “But when I thought about it more, it made sense.”

Sick to his stomach? Can we please stop with the melodrama?

But the rest of Donoghue's statement seems exactly right to me. The multiverse seems like an outre idea when you first here it, but with a bit of thought it comes to seem natural, even obvious. Why should there be only one universe, after all? We know that there is some sort of universe-generating mechanism out there. Why should that mechanism have operated only once?

Back in July I wrote a post titled, “The Multiverse is a Done Deal.” At the time I stated that the title was meant facetiously. The more I read articles like this, however, the more I think I needn't have added that caveat.


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It’s that part about some physicists loathing the idea of a multiverse that caught my eye. I’ve commented on this before, but it’s an attitude I simply don’t understand.

I think what you're seeing here is probably a reporter's manufactured controversy. At worst, what we're probably seeing here is a generational issue, where most older scientists aren't going to embrace the odd ramifications of a current theory but the young scientists do. That's pretty much par for the course in science, we may just be watching it happen in regards to inflation.

But AFAIK your earlier article was basically correct: inflation is the best theory we have for explaining the universe's structure, and inflation predicts that there will be other universes, so a multiverse is consistent with the best available cosmological theory we have today.

And the minuscule mass of the Higgs boson, whose relative smallness allows big structures such as galaxies and humans to form, falls roughly 100 quadrillion times short of expectations.

That's utter crap. The Higgs boson was found at exactly the mass that physics predicted it to be. The rest of the article is, by proxy, questionable at minimum.

These comments take a very narrow view of life. Life as we know it is the natural consequence of the evolution of universe we are in. We are as much as anything just a part of our universe. The idea that we are lucky to be in our universe is a non sequitur. We are not independent of our universe. It is not the case that life was roaming around and got lucky that it was dropped into a "good" universe.

Seems rather arrogant to imply/state that other universes are not livable.

#2 Makeino

I am not expert, but as I recall finding the Higgs boson was a search because its mass was not known?

Multiverse hypotheses are untestable, unfalsifiable stories made up to explain the universe. In other words, because they are just like religion. It is natural and reasonable that most scientists should reject them.

Indeed the circulation of unfalsifiable ideas is dangerous to society, and arguments such as "Why should there be only one universe, after all?", as a substitute for proof, are dangerous to society.

By Sheldon Cooper (not verified) on 07 Nov 2014 #permalink

Attn: Makeinu

You stated above " .... The Higgs boson was found at exactly the mass that physics predicted it to be. The rest of the article is, by proxy, questionable... blah, blah, blah." Only one, MAJOR problem with your observation. Breaking news reports from Phys.Org state the following.." Physicists agree that the CERN experiments DID find a new particle that had never been seen before, but according to an international research team, there is NO conclusive evidence that the particle was indeed the Higgs particle...." Sounds like nothing more than the typical, science fiction bullshit, from a bunch of geeks, who can't even agree on their own propaganda material.

By Joseph Alden (not verified) on 07 Nov 2014 #permalink

The multiverse has been a failure when it comes to predicting things. It does not explain anything since it does not predict anything and we have no independent evidence for the existence of the multiverse.

Note by the way that inflation (which is still unproven) does not lead to a multiverse with different laws of nature, just that there may be parts of the universe which can not communicate with each other.

If scientists claim to have an explanation for the laws of nature in term of some more basic theory they somehow need to have evidence for this basic theory.

Maybe the empty-space (i.e. a near-perfect vacuum) is as mistaken as the many other cosmological theories which were thought true --unitl they fell apart.


Also-- I join what in Jr wrote above.


George, I think you have it backwards. The import of the Higgs boson derived from the fact that it was premissed as fulfilling a precise (but theretofore undiscovered) mass-value which, if found, would effectively rescue the structure of the accepted standard theory, and, conversely, if not found, would, by that failure, leave the standard theory in a computational shambles. I think the Higgs boson--though its presumed mass may be correct as a measurement, may also be a misleading indicator of consistency in the standard theory. A little like the fact that you actually found your missing car keys under the street-lamp is a false basis in fact on which to found the idea that the best place to look for missing car keys is always beneath a street-lamp.

Scientists don't always reason very well merely because they're scientists.

By proximity1 (not verified) on 09 Nov 2014 #permalink

Anti-evolutionist: I don't understand how (fill in the blank) could have evolved - therefore God

Multiverse proponent: I don't understnad why (fill in the blank) has the value it has - therefore multiverse.

I agree with my friend Paul Steinhardt. His statement about dangerous to society may be an overstatement but its not hyperbole.

As I say, I am not an expert. But this from the Atlas experiment - one of the two at CERN seems clear. The mass of the Higgs was not known in advance of its discovery and thus there was a search for this boson mass.

"The Standard Model does not predict the mass of the Higgs boson, but does predict the production cross section once the mass is known. The "cross section" is the likelihood of a collision event of a particular type."

The multiverse hypothesis is not much like a religion. It has no sacred texts and demands or proscribes no types of behaviors. I can only predict this, but I don't think it will be adhered to by faith in the face of conflicting evidence. As Dr. Sean Carroll has explained at his blog, it is a natural consequence of other ideas, such as inflation, which have some testable consequences. Plus it is an interesting, mind-expanding idea.

Re the Higgs Bosun, if I recall correctly its value was predicted quite closely by a paper published a few years before the experiments, based on the Standard Model, but many scientists were hoping for a much larger value which would require new physics beyond the Standard Model, such as Super Symmetry. I don't think anyone was expecting a value quadrillion times as large as found, however. As always, Google will be more reliable than my memory, but that's my recollection.

Any new idea might have bad effects, but to make progress we must be open to new ideas. It's just another form of evolution.