Planetary Radio: Space Exploration, Astronomy and Science - A Hole In The Universe

Episode Date: September 3, 2007

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I've got a hole in my universe, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. We mentioned last week that a team of astronomers has found what appears to be a gigantic hole in the universe, or more strictly speaking, a billion light-year-wide void containing, well, nothing. This week we'll talk to Lawrence Rudnick, the discoverer of this vast expanse of nada. He and his colleagues at the University of Minnesota will soon have their paper published by the Astrophysical Journal.

Later today, Bruce Betts will report on the night sky from the annual convention of the Mars Society, and he'll have lots of red planet trivia for us, including a spanking new contest. We turn to news from around the solar system. If Mars Exploration Rover's spirit and opportunity could sing, a spanking new contest. We turn to news from around the solar system. If Mars Exploration Rovers Spirit and Opportunity could sing, they would certainly be singing,

I can see clearly now the dust is gone. We've been following the planet-encircling dust storm on Mars for weeks. It turned day into night above the rovers, putting them in serious risk of running out of solar power. The storm has finally dissipated, and both MERS are back to normal, doing science, taking pictures, and talking to Earth. Opportunity is once again on the verge of descending into Victoria Crater, an adventure that is likely to be its most dangerous ever. You can read much more at planetary.org.

That's also where you can learn how an Arctic test of new rover instruments was temporarily interrupted by a polar bear. Still more from Mars. Take a look at Emily's August 30 blog entry for a fascinating follow-up to the story about holes in the planet that we covered in June. The amazing high-rise camera on the Mars Reconnaissance Orbiter has taken another picture, and it shows fairly conclusively

that at least one of these is not a cave skylight, but a very deep pit, extending at least 78 meters, or 225 feet, down. It's an amazing image. Emily is away this week, so we've dipped deep into the Q&A archives for this great installment that last aired in 2003. I'll be right back with Lawrence Rudnick. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, could the asteroid impact that killed the dinosaurs have sent earthly debris, soil microbes, and dinosaur guts out into the solar system?

We asked Dr. Jay Milosz, a planetary geophysicist at the University of Arizona, to answer this excellent question. He explained that the impact, known as the KT impact, blasted debris over the entire Earth. known as the KT impact, blasted debris over the entire Earth. Most of this debris was melt droplets and individual little mineral crystals, but a few rock fragments and even pieces of the asteroid have been found tens of thousands of kilometers from ground zero. Therefore, it's quite plausible that some material was also blasted entirely free of Earth. The discovery of Martian and moon meteorites in Antarctica makes it clear that impacts can eject material from planets. But could there really be dinosaur guts in space from the KT impact?

Stay tuned to Planetary Radio to find out. Ready for a heavy-duty abbreviation? The NVSS is the National Radio Astronomy Observatory Very Large Array Sky Survey. The project swept the entire sky visible to the VLA, that network of big radio telescopes spread across the New Mexico desert. Lawrence Rodnick and his colleagues believe survey data confirms their discovery of a truly humongous anomaly in the universe. I called Larry a few days ago to learn more about this hole in the cosmos, reaching him

at his University of Minnesota office, where he is a distinguished teaching professor in the Department of Astronomy. Larry, I think I already mentioned that we carried the story about this so-called hole in space that you and your team found on last week's show, and I said then we're going to have to talk to these folks. So thank you for responding so quickly. Quite welcome. Here we are. Is that a fair description, calling this billion-light-year-wide thing a hole? Sure. It's as good as anything else. The more formal term we sometimes use is void, which really implies the same thing. But it's missing all of its matter, as best we can tell. So that's a good description. This void is truly devoid of matter. You're saying that probably there isn't even dark matter in there. Right. There were two observations, actually,

that we put together. One was a survey of radio galaxies that we used publicly available data from the what's called the NVSS survey from NRAO. And we put that together with the WMAP measurements of the cosmic microwave background. And our argument was that a cold spot in the background corresponded to a lack of radio galaxies in the same direction. If our physics is right in connecting those two, then we really need to empty out the whole of all kinds of matter, whether it's visible matter or dark matter. So that's the inference. We really haven't seen a place where we can show that the dark matter isn't there except through its indirect effects.

How empty would this void have to be to give you those results? Could there be a stray galaxy or two in there? Sure. In fact, let me, I'll be a little bit more precise in what we actually had to calculate. What we had to do was to say, if we're going to create this colder spot in the microwave background, then we need to create a place where there is very little gravity. And we calculated exactly how much gravity would we have to get rid of, basically, in order to create the effect, how much gravitational force, actually the depth of the gravitational well.

If we were to stick in some galaxies into that hole, then we'll simply have to make the hole bigger, because in the end there has to be a certain amount of matter that was missing. Now, there are constraints on that, but yes, you could throw some matter into the hole, but then I'm going to say, okay, but we need a bigger hole now. You referred to this as the cold spot, because indeed that's what it is compared to the surrounding region of the universe, but we're not talking about a huge difference in temperature here. It's really quite a testament to the incredible capabilities of radio astronomy nowadays.

Absolutely. The WMAP satellite really was a tour de force, and it's actually a very personal connection for me because one of the key members of the team was David Wilkinson, who helped design and build the satellite, saw it get launched, and the initial data started coming in, and then died of cancer in the middle of the first year before the actual first pictures were put together. And they renamed the satellite the Wilkinson Microwave Anisotropy Probe, so it's now known as WMAP. And Dave was my thesis advisor. So it was really sort of a poignant thing for me to be able to actually do some research that's connected with what came out of the WMAP satellite. And, yes, the precision is just astounding.

What we're talking about now, we're talking about a temperature coming from the early universe of on average 2.7 degrees Kelvin, and is above absolute zero. But the fluctuations in there that we're talking about are simply parts in 100,000. So it is almost perfectly smooth with these tiny little ripples that have been the source of so much information about the early universe. Now and then during, on this program, my Star Trek fixation sneaks in. Good for you. Thank you. I remember, I think it was an episode of Voyager, where that ship, which was still in our galaxy,

found itself in a void, and there were no stars to be seen. Now, that was a bit of an exaggeration, I would say, within our galaxy, but what if you were to find yourself in a very fast ship in the middle of this void? Have you thought about what you would see? Would there be not stars, but even galaxies in the sky? Right. A little bit. It would be very dark in there because the light reaching you from the walls of the void would be so far away that it would be a very sort of poor environment. If you were inside a galaxy, then you might see lots of stars like we see our own Milky Way.

But as you trained your telescope to go deeper and to see what was beyond them, similar to what we've discovered as we point our telescopes and find that we're surrounded by all these galaxies, you'd find yourself in a big empty area. And it would really be shocking. And then you'd maybe find some little specks very far away and wonder sort of what was the whole universe like? You'd have a very biased picture of the universe. Perhaps even more interesting would be, what would it be like if you were near the edge, one of the edges of this void? Because then half of the sky would have no galaxies visible in it,

and the other half would be very rich with galaxies. That would be an exciting view. Fascinating stuff, and there's more to come when we rejoin University of Minnesota astronomy professor Lawrence Rudnick in a minute. This is Planetary Radio. I'm Robert Picardo. I traveled across the galaxy as the doctor in Star Trek Voyager. Then I joined the Planetary Society to become part of the real adventure of space exploration. The Society fights for missions that unveil the secrets of the solar system.

It searches for other intelligences in the universe and it built the first solar sail. It also shares the wonder through this radio show, its website and other exciting projects that reach around the globe. I'm proud to be part of this greatest of all voyages and I hope you'll consider

joining us. You can learn more about the Planetary Society at our website, planetary.org slash radio, or by calling 1-800-9-WORLDS. Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio t-shirt. Our nearly 100,000 members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Astronomy professor Lawrence Rudnick and two University of Minnesota colleagues believe they have found a hole or void

in the universe that is far larger than any human mind can really comprehend. It's also larger than anyone ever expected one of these could be. You can see a representation of the void at planetary.org slash radio. One of the most interesting things about this find, and you've said in your paper that it does need to be confirmed by other observers or other actually analysts of the data. You know what? Let's talk about that first, the fact that really you're taking data which was collected as a part of this long-term study,

and that's where you found the evidence for this. Right. So let me talk. I mean, I think it's very important when you look at any kind of scientific discovery to understand the caveats, the warnings that go along with it. We think that we have analyzed the data appropriately, interpreted it in the most straightforward way, and come to these conclusions which look very surprising on their surface. very surprising on their surface. However, it really needs the scrutiny of the community in a variety of different ways to see whether this thing really will hold up long term. So, for example, at the very simplest level, we said that there are a smaller number of radio galaxies in the same direction as the cold spot and inferred that they are physically connected.

Those two effects are physically connected with each other. Well, they might not be. It could be a statistical fluke. We don't think it is, and we've made arguments to suggest that it isn't, but it could be that somebody would come along and argue, no, it's really very difficult to rule out, and maybe it's just a statistical fluke, and we really can't come to any of the conclusions we did about the existence of the void. So there's a variety of things like that that really need to be done, and that's the job of the community. I mean, it's partly the job of our team as well, but you really need sort of a wide range of minds and people who don't like the result who should come and challenge it and poke holes in it. And only if it survives that process will we consider it sort of part of the standard picture. And isn't science glorious? Oh, absolutely. I mean, I do stay up all night worried about

what they're going to poke in this a bit, but that's the name of the game. If this interpretation of this data holds up, one of the most interesting things about this find is that it does not seem to fit current theory. Right. There are a couple of things which it appears to be in contradiction with. If you look at voids in the universe, so in fact most of the time most people concentrate on the structures in the universe. We look at, in our own galaxy, we look at stars and planets in our own solar system.

As we go outside, we look at galaxies on larger scales. We look at clusters and superclusters and filaments and sheets of galaxies, all different kinds of structures. But what they have left behind are a bunch of empty places, voids. And a handful of people around the world have studied the distribution of those voids because they help tell you they are the flip side of studying the question of structure, and they help tell you about how all these structures developed. And when you look at the voids, they behave very similar to almost any other kind of object that you would look at. There are lots and lots of small ones, and then a smaller number of bigger ones, and yet a smaller number of yet bigger ones. And typically, for almost any kind of physical object, the number

of voids that we observe falls off dramatically as you get larger and larger. So that by the time you're done counting all these voids, it's very, very rare to find something that's bigger than about 150 million light years across. That itself is enormous, but that's about the biggest that you normally see. And then we found one that's about six times the diameter of that. And I think that's similar, for example, if you were wandering along the surface of the earth and you'd go up hills and valleys and you'd count the number of hills and then you'd explore mountains. And then you'd find things like Everest at close to 30,000 feet. And then all of a sudden you find one more and it's close to 200,000 feet high. And you go, where did that come from? Where does that fit?

And so we really do have a puzzle from just the raw observations about why would this one thing just sort of stand out so far from all the rest. Have you begun to even conjure up how theory would have to be modified to allow for a void this large. No, that's not, I mean, that wasn't part of our original work, and it's probably something that we would leave to people whose business this really is, is calculating structure formation. One of the interesting things, though, is that one of the ways that people study structure formation is by simulating it in a computer, putting laws of physics in, running simulations, putting in gravity and other effects, and letting the thing run and see what kind of universe comes out of that. And then they look in there and say, well, what kind of voids got created? And they don't

find voids this large. So you might say, well, then there's some physics that's missing. There's some conditions that are missing or something that's missing. On the other hand, most of the boxes, the cubic volume that they run these simulations in, are actually not big enough to even find these voids. If you didn't make a big enough box, then you can't find a hole, you know, essentially that's this big. So there's been very little work on these kinds of large scales. And it will be interesting to see as people try to simulate larger volumes of the universe whether these things will start popping up. What else would you like to know about this void, or what does it lead you to want to know more about in our universe? Well, I certainly want to know are there more like it.

We found what is perhaps the easiest one to find because we took, again, a modest effect in the radio survey, the NBSS survey, put it together with the cold spot, and said, this is our evidence for the void. If we didn't have the cold spot from the microwave background, we couldn't have reached that conclusion. And so the problem is going to be, if you look at other cold areas from the microwave background, none of them are as extreme as the one that we studied. and it's going to be harder and harder than to separate out just normal fluctuations in the microwave background from very special cases where a void has perturbed it and made it even colder.

So it's going to be a hard game, but absolutely one thing I'd like to know is how many more are there like that out there? And so that's one thing. The second thing is we'd really like to know where it is, meaning basically how far away it is. Right now, we have a rough guess that it's somewhere between 6 and 10 billion light years away. But it's a very rough estimate. The problem is how do you measure the distance of something that you can't see? And so it's very indirect reasoning we use to estimate that. And we're going to be, we just proposed to do some new observations with a very large array that may help pin that down a bit. Again, it's a very tricky business because we're trying to figure out what is the distance of the things that are missing that we can't see, as opposed to the things that we do see.

Absolutely fascinating. We're just about out of time. Let me give you just a moment to mention your co-authors in this paper, which will, I guess, soon be appearing in the Astrophysical Journal. Right. It's scheduled for December, and I'd love to say a few words, because when I first found this effect, I was the one that discovered it. I had no idea what

I was looking at. And I was just scratching my head, called my graduate student, Shea Brown, and he immediately said, you are looking at the integrated Saks-Wolf effect. And I said, what? And he said, we just studied that in cosmology. And here's how it works, and here's why that's the explanation. And so at that moment, we knew we had a void, because I didn't know that beforehand. And then we said, oh, my gosh, where is it? How far away is it? How do we calculate how big it is? How much mass is really missing?

And so we marched down the hall to Lily Williams and said, you need to work with us on this, because she studies structure formation, and so she was the one that did all the calculations, put in the right physics, and did the calculations for us. Wonderful. Larry, keep up the good work, and congratulations on this terrific find. Great. Thank you very much. Lawrence Rudnick is Distinguished Teaching Professor in the Department of Astronomy at the University of Minnesota. That's also where his co-authors of this paper are. And we will follow this progress as he and other astronomers look for other bits of emptiness, large bits of emptiness in this universe that we call home.

We will be right back with Bruce Betts for this week's edition of What's Up after a return visit by Emily. Hi, I'm Emily Lakdawalla, back with Q&A about whether microbes were sent to space in the KT impact. When asteroids collide with the Earth at speeds of several kilometers per second, the shock of the impact can create tremendous heat and pressures. But in a process called spallation, solid rock can be ejected at very high speed, but with little heating or shock damage. Spallation happens when the shock wave created by the collision reflects from the ground surface near the impact site.

Therefore, material located right at the ground surface can be ejected from the Earth while staying intact. Based on research that Dr. Malosh performed, it seems very probable that microbes could survive this experience. As for dinosaur guts, they might indeed have graced the moons of the solar system if the KT impact had occurred on land. However, the actual strike appears to have been in a shallow sea, which means that the KT impact probably blasted out mostly seawater and whatever was living in the upper ocean. So instead of vacuum-dried dinosaur parts, future astronauts should probably be looking for broken ammonite shells in space. Got a question about the universe?

Send it to us at planetaryradio at planetary.org, and you may hear it answered by a leading space scientist or expert. And now, here's Matt with more Planetary Radio. Bruce Betts is here for What's Up. He's the director of projects for the Planetary Society, and he's out there doing his job today. What are you doing at UCLA? Well, I was giving a talk at the Mars Society convention here. You got all those wild and crazy Mars guys out there, like Bob Zubrin? Oh, yeah. Oh, yeah.

Lots of good Mars enthusiasm. So I was telling him about some of our current Mars projects, including with Phoenix and then future Russian Phobos mission. Yeah, excellent. Well, I hope everybody was excited about that. They were giddy. And you know what else, Matt? As I always do nowadays when I go to these talks,

I met some avid listeners, so thanks to all them. No kidding. Yeah, and they said they love you. Yeah. Yeah, it's a success. So how is mom? She's doing well. She says you should call her.

How's the night sky? No, it's been fun. That eclipse, I just have to say again, really cool. A total lunar eclipse. I enjoyed it, but I got up in the middle of the night, and I carried each of my boys out in sequence on my shoulder and forced them to look at it. No, they wanted me to. That's so sweet. No, that's wonderful. Are you sure you want me to wake you up?

So anyway, it was fun. We checked out some of the eclipse. If you're in South America, there's a partial solar eclipse coming up on September 11th, 12th in there. Check that out on the web. We've got other things up in the sky. Of course, Jupiter is still lovely. And check out near Jupiter the bright star in Scorpius and Peres. So if you look below Jupiter, you'll see a reddish, much dimmer-looking star.

Jupiter, the brightest star-like object up in the evening sky right now. Then we've got other things coming up later around midnight. Mars, that red place, is coming up and will keep brightening until December when we reach opposition. If you get up before dawn, you might catch Venus out there. It'll get much easier as the months come. It's starting to get higher and higher, so we'll check back with you on that one, and also as the others come back into the sky. That, I think, leads us on to random space facts! You know what I thought I'd do?

I've been getting into a lot of detailed space facts lately, and I just wanted to review. Let's just get a few quick Mars space facts in honor of being here. Mars hits some of the Earth-like characteristics. Mars, of course, its day is about only 40 minutes, not 40 hours, 40 minutes longer than the Earth's day. Its axial tilt, almost identical to Earth. And its gravity, about 38% that on Earth, which means I am spelt if I'm on Mars. So it's a groovy place.

What do you think? I want to go, as you know. I would have fit right in there. I should have driven out there today. Not to Mars, to the conference. Oh, I was going to say, are you hiding something? Did you have a blow to the head recently? Did you have a blow to the head recently?

No. And also, Mark, there's those nasty characteristics, especially that 1% of the atmospheric pressure, and pretty much all carbon dioxide, and the freezing temperatures, and other nasties like that. But, hey, it's got polar caps, even if the seasonal ones are made of carbon dioxide. Should we go on to the trivia contest? Yeah. We asked you which to the trivia contest? Yeah. We asked you which Apollo launch was hit by lightning. How'd we do? What did people tell us?

They told us, to a person, to a listener, they told us it was Apollo 12. No, I take it back. One person did say Apollo 13, which had bigger problems than lightning hits on launch to worry about. Although, now that I mention it, now, anyway, but it was Apollo 12. You're not going to start calling out people's names if they get it wrong. We want to encourage people to submit. Of course we do. But I will call out their name if they win.

And in this case, it was our old friend Tom Hendricks. He has been entering many many times he is past winner although i think it's been i don't know over a year i think since he's won the contest so uh persistence paid off again uh tom indeed said that uh he uh that it was apollo 12 hit not once but twice in the first minute or so of its trip to the moon. And got some other interesting stuff. Torsten Zimmer, who we can always count on for a laugh, said that, you know, after all, Apollo was the son of Zeus.

He says lightning must run in the family. Indeed, indeed. Yeah, I thought it was a funny quote from Pete Conrad, who was the commander of the mission, who really feels that Skylab was a much more challenging mission for them, and they had to fix a broken space station, basically. His comment about Apollo 12 was, you know, after the lightning strikes, it really just was simple. It went well, something to that effect. Sorry, I don't have the exact quote.

Just kind of matter-of-factly, you know, except for the lightning strikes. I think they call it the right stuff. Yeah, I think that would be the test pilot. Oh, yeah. For next week, I have the following question, keeping our Martian theme. We'll go to the moons. In what year or years were Mars' moons discovered, Phobos and Deimos? What year or years were they discovered?

Go to planetary.org slash radio. Find out how to enter and try to compete for the amazing and beautiful Planetary Radio t-shirt. People have got until 2 p.m. on Monday, September 10, to get us that answer. That's it. We're out of time. All right, everybody, go out there, look up in the night sky, and think about circles, lots, on Monday, September 10, to get us that answer. That's it. We're out of time. All right, everybody, go out there, look up in the night sky, and think about circles, lots and lots of circles. Thank you, and good night.

We're going round and round with Bruce Betts, the Director of Projects for the Planetary Society, and he joins us every week here for What's Up today from the Mars Society Conference at UCLA. Planetary Radio is produced by the Planetary Society in Pasadena, California. Did you know we're coming up on our fifth anniversary? That ought to be worth more than a t-shirt, wouldn't you agree? Stay tuned and have a great week. Thank you.