Science Talk August 16, 2006 -- Is the Universe Bigger and Older?; The Status of Pluto
Welcome to Science Talk, the podcast of Scientific american for the seven days starting August 16th. I am Steve Mirsky. This week on the podcast, the universe, now available in the large economy size. The news started coming out about 10 days ago. Papers appearing in an upcoming issue of The Astrophysical Journal that had a pretty impressive implication: The universe might be about 15 percent bigger than previously thought. The work was funded by NASA and the National Science Foundation and the research team included scientists from institutions around the globe. Fortunately, Scientific American has its own astronomy institution, editor George Musser. I asked him to help me understand what was going on out there in the universe. We'll also talk about the status of Pluto; not Mickey's dog, the planet—or is it a planet? Plus, we'll test you on some recent science in the news. First up, George Musser and the entire universe.
Steve: George, thanks for coming into my office here to explain this to me.
George: Thanks for letting me fit into your office Steve.
Steve: It's not a big office. So these folks came out with the story this week that the universe, according to their calculations, may be significantly bigger than we thought it was.
George: So what this latest group has done is measuring the distance to a galaxy, it's about three million light-years away. It's the farthest object for which humans have direct distance measurement. So specifically what they are looking at is the Triangulum Galaxy; it is also called M33. It's one of the three large galaxies in our local neighborhood. There is the Milky Way; there is Andromeda—which is M31—and there is M33, the Triangulum or the Pinwheel galaxy. It's actually [a] really beautiful galaxy if you look at [it] through a telescope.
Steve: It is popular on the astronomy calendars.
George: Exactly. Pinwheel, it's called.
Steve: Okay. They are looking at that galaxy, and they are estimating how far away it is.
George: Exactly. So they look specifically at a binary star—a pair of mutually orbiting stars in the galaxy—and what's special about this binary pair is that one of [the] star[s] passes in front of the other one, so it is called an eclipsing binary system. And what's cool about an eclipsing binary system—I suppose it is just an ordinary one—is that it allows you to estimate the size and the shape of the actual stars themselves because their light its modified as they pass in front, if one passes in front of the other.
Steve: So they're looking at this system and their estimates are that its further away than anybody thought before, and because that's further away everything is further away and the whole universe is somewhat—I mean I was going to say, slightly but 15 percent is more than slightly.
George: Well, actually, in the context of astronomy 15 percent is pretty slight. What you have to understand in this kind of debate over distance is that it has been factors of two. It has been a 100 percent at certain points, so getting down at 15 percent, is making some progress. The age of the universe, when you work through all the calculations that this would employ, goes up from 13.7 billion years to about 15.8 billion, so it's a couple of billion years.
Steve: Okay, so they're looking at this binary star
s system, they are looking at the stars rotating around each other, and when one star is eclipsing the other star, you get information because of the way that light is changing during that eclipse movement. Can you describe exactly how the information that you see during those eclipse movements winds up making the researchers think that this system is somewhat further away than the old calculations made them think it was?
George: Okay. We'd just walk through kind of the process they look at;
is and they are taking a variety of measurements of all sorts. They're looking at the colors; they're looking at the amount of light; they're looking at the spectra of the light. And one thing they get from scenes from the spectra is the velocity of the star to and from us, the old Doppler effect question.
Steve: Doppler effect—this would be [when] you're driving down the highway [and] a truck comes at you from the other side (mmmmm).
George: Precisely. You sound like a truck.
Steve: Right, thank you.
George: So that gives you the velocity to and from you and the question
what[with] the Doppler effect has always been, there is another component of the velocity that might be up and down, for example, not just to and from you; so there is an ambiguity in the velocity of the star that comes about from just a Doppler measurement. So you can resolve that ambiguity by knowing exactly where the orbit of the star is oriented relative to your line of sight. Now an eclipsing star has to be almost edge on ...
George: ... otherwise, it wouldn't eclipse.
George: So already the very mere fact it's eclipsing lets you get at the actual velocities and thereby the actual masses of the stars. And then what they can do is, they can use the way those lights dim
s and brighten s more precisely, to say, well the stars are, they seem to be a little bit out of alignment because when they come on top of one another, they are not directly blocking each other, there is a little bit of light. It's a partial eclipse. That's exactly it, and they can also say that the stars are spherical or [a] little bit oblong; they can get a lot of detailed information on the size. So out of this you can get the mass on the star precisely; there is no ambiguity left. You can get the radius of the star; you can get the temperature of the star, and the temperature just comes from the color and the spectrum of the star. Now based on those attributes, mass, size and temperature, you can get how bright the star is intrinsically, how much light is it [is] giving off just at its distance. Then you know how much light you get because you just measure the brightness as seen on Earth. You put the two together, you get the distance, and the distance is that much further than thought it would be.
Steve: So any idea why all the old measurements didn't come up with the same number? Why is this new methodology giving us the new numbers?
George: I mean, that's really the question
s astronomers need to answer now. One possibility is that the obvious measurements are confounded by dust. There is dust between us and the star and the dust will make the star look little bit dimmer than it truly is.
George: And the astronomers try to correct for that, but maybe their correction process is flawed or maybe previous correction efforts were flawed. It's also possible that the actual expansion rate of the universe varies from position to position. We might live in an area of the universe that's expanding more quickly or less quickly than the universe as a whole is and that's not really a mystery. There might be little patches of universe that are expanding at different rates even if the overall universe is expanding at some overall rate.
Steve: Because it's a patch with more mass in it, so it's slowing down.
George: Right—more mass or less mass compared to other patches. So what matters for the age of the universe is the obvious thing—the overall rate. so there may not be a contradiction after all; but that's really what they have to address in the next you know years.
Steve: Okay, so these things we'll put on the table. It is going to be years of other researchers trying to duplicate their work looking at other galaxies, finding other binary star systems and other galaxies. Duplicating the methodology, seeing if they get results that agree and then hashing it out and coming up with a new figure that's pretty much accepted universally, no pun intended.
George: Yep! That's basically the process. The question is really—and I think, you got it; you got at it earlier—they have to resolve why there are these differences. So it's not just enough to average and get at some kind of value. They have to understand why there is a spread around that value. And maybe it's because of this dust effect, maybe it's because of some peculiarity in the galaxy having to do with its chemical composition that leads to [a] different type of star, and then there is someone uncertainty associated with that. So I think I would say there is two things that you need to do. They need to take more measurements, and they need to reconcile the differences among those different measurements.
that the distance to the size of the universe is related to the age of the universe, so how does this possibly change the accepted figure for the age of the universe and make the universe older?
George: So, the key is in understanding something called the Hubble constant, and that basically tells you the rate at which the universe is expanding. Now to get that constant you take speed and you divide by distance, so they know the speed at which that galaxy—the M33 galaxy—is moving away from us due to the expansion. Now they have the distance, and they do that division and they get the so called Hubble constant. The Hubble constant then tells you the size and the age of the universe. Now it's interesting. If you take speed and divide by distance you get the reciprocal of time, so
they [you] need for you to take the reciprocal of the Hubble constant , you [to] get time. That's when you get the 15.8 billion years since the Big Bang.
Steve: Okay. So and the previous accepted figure is about ...
Steve: Okay, so we maybe, you know, throw another billion and half years or two billion years around; you know, that's a lot of time for things to happen.
George: In a sense, but on the other hand, all the ages you read about in the papers, you know, galaxy Y is at a distance X and it's time Z billion years ago. It's all a scale, so this
is just scales everything out; doesn't really change anything fundamental.
Steve: Okay. So it doesn't give us more time for processes to happen. It just means that the processes we know happened took longer.
George: You got it.
Steve: Okay. Are they are any practical consequences of the universe being 15 percent bigger and/or older than we thought?
George: No, there is no practical consequence (laughs) whatsoever. It's just a cool thing to know. I guess if I really had to come up with a practical consequence, it is that understanding cosmology and the universe and its age and its character help us develop a theory of physics; and
if[a] theory of physics might then have practical consequences.
Steve: George Musser, thanks for illuminating this whole issue.
George: Thank you, Steve.
Steve: Check out George Musser's musings in the pages of Scientific American and at our blog, blog.sciam.com. This August 3rd post in particular will gabble few. Now it is time to play TOTALL.......Y BOGUS. Here are four science stories; only three are true. See if you know which story is TOTALL.......Y BOGUS.
Story number 1: There are now more obese people worldwide than undernourished people.
Story number 2: London cabbies are shooing GPS, figuring their own navigation abilities are better.
Story number 3: The original films of Neil Armstrong's first steps on the moon are missing.
And Story number 4: Depressed people who get married tend to fall into a deeper depression.
We'll be back with the answer, but first—Pluto, planet or not a planet?
The controversy has been ongoing for a few years now. One of the youngest members of my extended family is Ari Mirsky, who turns three in October. He loves Pluto. I thought this was really unusual until I heard a report last week on National Public Radio about Pluto, and it turns out many little children besides Ari love Pluto. In the NPR report, Harvard astronomer and science historian Owen Gingrich said that people said to him that little children love Pluto; they'll be brokenhearted if you take it away; and science writer, Dava Sobel said people love Pluto, children identify with its smallness. Now this past Sunday, I visited Ari—again he'll be three in October—and I asked him about Pluto while he munched a cookie.
Steve: Hey buddy. Can you tell me about the planet Pluto?
Ari: He's my favorite.
Steve: It's your favorite?
Ari: Uh ...
Ari: Can't talk anymore.
Steve: Can't talk anymore?
Steve: Because your mouth is full.
Steve: Okay. Will you tell me why he's your favorite when your mouth isn't full?
Ari: Because he is my favorite.
Steve: (laughs) So there you have it. Although, I have it on the authority of his parents with whom he has been somewhat more expansive that he does indeed love Pluto because it's "so small, so cute" and Ari did tell his father Jason
an another reason why Pluto was his favorite planet.
Jason: Which one is your favorite? Is it Earth?
Ari: No. It's Pluto.
Jason: Why is Pluto your favorite?
Ari: Because it—because it's cold.
Steve: Because it is cold. Well we're still recovering from a week of 100 degree temperatures in New York, so Pluto's coldness might seem pretty cool indeed. Anyway, new Pluto news came out of Prague Wednesday morning, the 16th. Richard Binzel is a Pluto expert at M.I.T. and a member of the International Astronomical Union's Planetary Definition Committee. I spoke to him Tuesday morning while the information was still hush-hush.
Steve: Professor Binzel, thanks so much for talking to me, especially on such short notice.
Binzel: You're very welcome. Good morning.
Steve: Good morning. So tell me what's the up[shot]
show. What is the status of Pluto officially?
Binzel: Pluto is a planet.
Steve: The little children are gonna be so happy. (laughs)
Binzel: Yes. In fact for thousands of years, the definition of planet has just simply meant an object that moves in the sky. And now modern science—as we've learnt more and more about our own solar system, we found lots of other large objects beyond Pluto, and we have to decide whether or not they are planets; and that forces us to make a new definition.
Steve: And how does the new definition work?
Binzel: The new definition of planet says that an object is a planet if it is big enough or massive enough for its own gravity to pull it into a sphere.
Steve: By that definition, how many planets are in our solar system?
Binzel: So, this definition is now a proposal before the International Astronomical Union; and if approved, there are now 12 planets in our solar system.
Steve: And the approval process—how does that work?
Binzel: [The] definition is now being put forth before the International Astronomical Union as a resolution—kind of like a UN resolution—where over the next week or so, there will be [a] discussion; they'll take input on the proposed resolution and at which point a final version, if amendments are[n't] needed, will go forth for a vote on Thursday, August 24th.
Steve: And who votes on this?
Binzel: This will be voted by the membership of the International Astronomical Union,
your present year [here] in Prague.
Steve: So this is a community of professional astronomers.
Binzel: That's correct. It's the international Committee of professional astronomers.
Steve: Tell me—on one level, what difference does it make, what we call these things. They are what they are, regardless of our naming of them.
Binzel: Exactly. They are what they are no matter what we call them; but it is useful in a scientific sense to group things that are somewhat alike, and so it just helps focus our thinking even though Pluto is Pluto no matter what we call it.
Steve: Tell me Dr. Binzel, have the proceedings been acrimonious in anyway? I mean how emotionally charged is [it] to try to decide this kind of thing?
Binzel: Well there had been official discussions within the IAU for nearly two years to try to come to a single, concise, simple definition of what a planet is; and the early attempts at this effectively deadlocked and we were able to break that deadlock with a small planet definition committee early this summer that actually formed the definition and brought it forward to the IAU to make it, you know, to allow a formal resolution to be voted by the membership.
Steve: And that committee did not solely include scientists—you had, I know, at least one science writer on it.
Binzel: The committee was chaired by Dr. Owen Gingrich, a historian of astronomy at Harvard [and] includ[ed]
ing myself a Pluto scientist from M.I.T., Dr. Dav a[id] Sobel, the well-known author of Galileo's Daughter, Longitude, and a wonderful book on the planet, as well as representatives from France, Germany, England and Japan.
Steve: Terrific. Thank you very much. I really appreciate your taking the time, especially under the circumstances.
I know, Thanks for hopping over there to talk to us.
Binzel: You're very welcome.
Steve: For more Pluto news, see David Biello's story on the Scientific American Web site, www.sciam.com.
Now it's time to see which story was TOTALL.......Y BOGUS. Let's review the four stories.
Story number 1: Obese people outnumber malnourished.
Story number 2: London cabbies trust themselves over GPS.
Story number 3: Original moonwalk movies mislaid.
And Story number 4: Depressed people who marry get more depressed.
Story number 1 is true. Obesity now outweighs malnourish[ment]
ed; that's according to the University of North Carolina, Chapel Hill's Barry Popkin, who spoke last week in Australia at the Conference of the International Association of Agricultural Economists. He said there were now a billion overweight people and 800 million undernourished people.
Story number 2 is true. London cabbies have pretty much rejected GPS in the cars. London cabbies are incredibly well trained, spending years learning the maps of the city; and they also know that the shortest route on the map may not be the quickest one depending on traffic patterns at a particular time of day. For more, check out the story on our Web site, sciam.com, entitled "Satnav No Match for London Cabbies, Yet!"
Story number 3 is true. Apparently, the original films of Neil Armstrong setting foot on the moon have gone missing. According to the British paper, The Guardian, the movies were transferred to magnetic tape in 1970 and sent to the Goddard Space Flight Center in Maryland and the folks over at SPACE.com had a quote from someone who has been looking for the tapes. He said, "I would simply like to clarify that the tapes are not lost as such. We are confident that they are stored at Goddard, we just don't know where precisely." Ladies—sound like your husband, when he is driving in circles?
Speaking of marriage, story number 4 about depressed people who marry getting more depressed is TOTALL.......Y BOGUS. Because a new study out of Ohio State University found that depressed people got a big mood bounce from marriage—bigger than nondepressed people got. It had been assumed that one partner's depression would put a big strain on the relationship, but it looks like, in this study anyway, it really is good to have a better half. We'll be right back.
Rennie: Hi, I am John Rennie, editor in chief of Scientific American. Our magazine is now available in a digital edition. Not only does your Scientific American Digital subscription include the full contents of every new printed issue, it also entitles you to access our digital archives from 1993 to the present. For more information, visit www.sciamdigital.com.
Steve: Well that's it for this edition of the Scientific American podcast. Our e-mail address is firstname.lastname@example.org; and also remember that science news is updated daily on the Scientific American Web site, www.sciam.com. For Science Talk, the podcast of Scientific American, I am Steve Mirsky. Thanks for clicking on us. "Can't talk anymore."