More To The Universe Than Meets The Eye

The universe is full of invisible stuff—dark matter, for example, outnumbers visible matter by a ratio of five to one. Some theoretical physicists think dark matter may be lurking in extra dimensions. Cosmologist Michael Turner discusses the dark side of the universe, and how physicists are studying it.

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IRA FLATOW, HOST:

This is SCIENCE FRIDAY. I'm Ira Flatow. There's much more to the universe than meets the eye. Take dark matter. You can't see it or touch it or hold it, but there's five times more dark matter out there than the visible matter we are made of. But where is it hiding? Maybe some of it's lurking in extra dimensions, as some cosmologists have theoretized. Or what about parallel worlds, mirror worlds? A recent paper in the European Physics Journal - Physical Journal hypothesized that a particle might be able to morph into its invisible twin and pass into a parallel world and back again, turning into a mirror of itself.

If we can't see the stuff, how can we prove it? How close are we to discovering the hidden these dimensions, if they exist at all? These are the sort of things my next guest ponders at his day job, and he's here to tell us a bit about the dark side of the universe. Michael Turner is a cosmologist and professor of astrophysics at the University of Chicago in Illinois. Welcome back to SCIENCE FRIDAY, Michael.

MICHAEL TURNER: Great to be here, Ira.

FLATOW: Always good to talk to you. What do you make of the idea that a particle could turn into an invisible twin of itself in a parallel world?

TURNER: Well, as we often say in cosmology or theoretical physics, that idea might be crazy enough to be true.

(LAUGHTER)

FLATOW: How would it work?

TURNER: Well, the idea that is talked about in this paper is that there's kind of a parallel universe out there with very similar laws of physics to ours, but it only communicates with our universe by a very feeble interaction. So it's almost invisible. So it could be occupying the same space. But without very sensitive experiments, we cannot perceive that. And this paper talks about such an experiment done at a laboratory in Grenoble, France, where they bottle neutrons. They bottled about a half million neutrons in an ultracold neutron trap, and they monitored them for about five minutes, and they see some of them disappear.

FLATOW: And the idea is that they could be leaking into this parallel universe?

TURNER: And so the idea is that the neutrons in that bottle are morphing into their mirror or their shadow counterpart in this shadow world, and then they come back. This is all done by a magnetic field - not in our world, but in the shadow world. And to say the least, this is a really extraordinary claim. I'm not sure the evidence has - in fact, I am sure the evidence has not risen to the extraordinary level that it should. But I think it plays along the theme that you mentioned that would summarize well our exploration of the universe for the past 20, 30 or even 50 years, and that theme being there's much more to the universe than meets the eye, and we keep discovering new things.

FLATOW: Speaking of discovering new things, I want to get your take on the rumors circulating that the Large Hadron Collider may have actually made a discovery. You want to talk about that a little bit? You can...

TURNER: I can certainly talk about the rumors. For about a week, the Internet has been abuzz with rumors that the two experiments at the Large Hadron Collider - CMS and ATLAS - looked at two months of data that they've taken since they started running. They call it opening the box. And the rumor is that each one of them, when they opened their little Christmas box - or I guess this isn't Christmas - found a Higgs. And what - we just all got an email today that CERN will have a press conference on July 4th - I guess that must be acknowledging the very important American role in these experiments - to talk about what they have.

But you may remember last December, they had a press conference and a seminar that was very exciting. And basically, both experiments said - I'm doing this tongue-in-cheek. We found a - the Higgs has a mass of 125 GeV, but we still don't - we still aren't sure it exists. And they've now taken more than - they've now more than doubled their data. And so on July 4th, we are hoping that there will be a big announcement with the discovery of the Higgs particle.

FLATOW: Wow. That's been, as you say, lighting up Twitterdom these days, all kinds of rumors. So you're - do you know that for a fact? Or are you just guessing that's what's going to happen on July 4th?

TURNER: No. The director general of CERN sent out an email that I can forward to you announcing that there will be a press conference and a seminar and to update the status of the Higgs search. So it doesn't say to announce the discovery of, but if you put that together with the rumors, we're - we've got all our fingers crossed that the particle that Leon Lederman called the God particle may well have been discovered. And that announcement will happen on July 4th.

FLATOW: All right. We're circling our calendars and getting ready for that SCIENCE FRIDAY week, which is, what, not a week from now or so. 1-800-989-8255, talking with Michael Turner about dark matter. And can you talk about dark matter and not talk about dark energy or do you, basically, do you have to talk about them both?

TURNER: I can do it either way.

(LAUGHTER)

TURNER: There are two different puzzles. You know, they are the dominant forms of matter and energy in the universe. Roughly speaking, dark matter accounts for about 25 percent of the universe, and dark energy 70 percent with the stuff you and I are made of, weighing in at 4.5 percent. And, you know, dark matter holds things together. Dark matter holds together our galaxy, and it's the dark energy that's causing the expansion of the universe to speed up. So they're doing very different things. But as you alluded to, they're both big mysteries and who knows? They might be related.

We think that in terms of the puzzles that were at different stages, as long as we're talking about the LHC, one of cosmology's big hopes is that the LHC stands for dark matter factory. Let's see, I guess those letters don't quite work. Maybe in some language they do. But we're hoping that the LHC, after it finds the Higgs, will actually find the dark matter particle so that this mystery that started some 70 years ago with Fritz Zwicky will be finished off and that we will have identified the dark matter. The dark energy is one of those puzzles where, who knows, it could get solved this decade, but my hunch is it will be another 30 years or maybe even longer.

FLATOW: Are you saying that the Large Hadron Collider can actually make dark matter?

TURNER: So we have a very simple hypothesis: that the dark matter particle is something called a WIMP, a weakly interacting massive particle. And that that WIMP weighs about - maybe 100, maybe 1,000 times what the proton does. And so the ideal place to make one and to bottle it, I'm speaking figuratively, would be the LHC. And that's why we're so excited about this - some of us call this the dark matter decade where the LHC is poised to actually produce the dark matter particle if it's a WIMP.

We also have very sensitive detectors that are deep underground in laboratories that shield the detectors from cosmic rays where we could detect the interaction of the WIMPs that hold together our galaxy with these detectors. And then also, it could be that these WIMPs, when they bump into each other, turn into particles that are much easier to see, like photons or positrons, and we could detect those with satellites, like the Fermi Gamma-ray Observatory. And so we kind of feel like we have the full court press on this decade, and all three techniques could yield a signal.

In fact, I'm hoping for the trifecta, that we get all three signals. And that by the end of this decade, we can convince somebody in Missouri that the - most of the matter in the universe is dark matter. And even though we can't see it with our telescopes, that it really does hold together the universe.

FLATOW: Mm-hmm. But dark energy will have to wait for the next generation or two to show itself.

TURNER: It's a big puzzle and it - I don't want to discourage people, but - and it's such a big puzzle that you - it's hard to predict breakthroughs in science. It could come in 10 years, or it could just take a very long time.

FLATOW: Mm-hmm. Is there any way going - getting back to the beginning of our conversation about a mirror universe or a parallel universe, is there any - are there any experiments that could prove the existence of one of those?

TURNER: You know, let's come back to the Large Hadron Collider because if you talk about things, if you talk about this theme, there's much more to the universe than meets the eye, the other one that you know well is the prediction from string theory and similar theories that there are extra dimensions. And one of the ways to look for things like extra dimensions or shadow universes is to look for the leakage of material from our universe into their universe.

And let me use the LHC. One way to look for evidence of extra dimensions would be to carefully look at collisions that take place at the Large Hadron Collider and look for some of the energy to disappear. And what's interesting about that technique is when I put there's - when I say there's much more to the universe than meets the eye, the top of my list would be neutrinos, and we now know neutrinos exist. We can't see them with the eye, but we can build detectors to detect them. And the original evidence for the neutrino was missing energy in beta decays that were observed in the early part of the last century and then poly-hypothesize this particle, the neutrino. And eventually, we built detectors that were sensitive enough. So this technique of looking for energy leaking out of our universe going elsewhere is a very powerful technique for looking for things that we can't see.

FLATOW: Michael Turner, a pleasure as always to come have you come on and explain this stuff to us. Thanks a lot, Michael.

TURNER: Glad to be on.

FLATOW: And we'll be waiting for the Fourth of July with you in mind.

(LAUGHTER)

TURNER: Good.

FLATOW: Michael Turner, cosmologist and professor of astrophysics at the University of Chicago in Illinois. Have a happy Fourth, and maybe it'll be happier for other reasons.

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