SGU Episode 41

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SGU Episode 41
May 3rd 2006
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SGU 40                      SGU 42
Skeptical Rogues
S: Steven Novella
B: Bob Novella
R: Rebecca Watson
P: Perry DeAngelis
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Introduction

You're listening to the Skeptics' Guide to the Universe, your escape to reality.

Questions and E-mails

Bubble Universes (17:24)

S: Well, we... let's move on; we have a lot of e-mail, and some excellent questions we've been getting in e-mail, so I want to try to cover a few of those this week. The first question comes from Elias Luna in Bronx, New York, from nearby. He writes:

I have a couple of questions which I would love to hear you guys discuss. What's your view on Michio Kaku's [pronounced kuh-ku] view of the universe as a multiverse, that we are nothing but a bubble in a sea of bubbles.

B: I believe it's pronounced "Michio Kaku".

S: Is it kah-ku?

B: I believe.

S:

If there is a so-called multiverse, when did it begin? I'm not speaking of our universe, because we all know the universe began with the Big Bang. But let's say there is a multiverse. What is beyond the multiverse and beyond what's beyond the multiverse and etc.? You see, it's a paradox and only way to escape is to say there's always been something somewhere, literally for infinite and will be, so there is no end or beginning in the grand scheme of things. And if there is an infinite amount of universes or multiverses there, there's an infinite amount of civilizations.

Then he goes on along—basically, that's his question. He asks a couple of other questions. So let's talk about that first. Bob, do you wanna start?

B: Well, yeah, his main question in the beginning is: if there is a multiverse, when did it begin? And you really can't ask that question, because, by definition, you have no contact to any of these other bubble universes within the multiverse or meta-verse. So how could you determine how old it is. I mean, our universe could have been created 15 billion years ago, but it might be a baby compared to other universes. Or it could be the first universe in a bubble universe. So you really can't know how old this multiverse might be. You just can't get outside of your universe, by definition.

S: Right. And just to clarify, that's because, by definition, our universe is everything that we can interact with. Anything that can affect us, everything that we can affect, everything that we can see is, by definition, part of our universe. So, from a theoretical point of view, another universe that was part of a grander multiverse would be forever inaccessible to us.

B: Right. And imagine if somehow you could contact another bubble universe within the multiverse, even that wouldn't help you, because who knows how old that universe is and how long that bubble has been around. You'd have to literally examine every one and find out what the oldest is and say, "OK, this is how old the multiverse is", so it's really inconceivable.

S: The other possibility is that—and Stephen Hawkings [sic] wrote about this—that the age of the universe or the multiverse may be finite but unbound. This is kind of a hard concept to get across, but it's kind of like the surface of a sphere. It's finite; the amount of space that it occupies is finite, but there's no beginning or end that you can point to; it's continuous. There's no specific boundary, but it's finite. So the time dimension of our universe may be the same thing. Maybe we didn't have a beginning and we won't have an end, even though the amount of time that it occupies could still be finite.

R: So does that mean that we're going to get around to the beginning again at some point?

S: I don't know. I don't know. When you start to talk about cosmology like that, whenever physicists write about that kind of cosmology, they always say something to the effect "you could really only express these ideas in, like, 12-dimensional derivative calculus, but I'm going to try to sort of paraphrase in English".

B: (chuckles)

S: So I mean, these are concepts that you can't really even understand, except on a very sophisticated mathematical level. So who knows what it all really means. But... This is also, by the way, Kaku is the guy—he was one of the co-originators of string theory, right? That's what it says on his website, anyway.

B: OK. I'm not sure if he was one of the originators.

P: So what is the point of positing the hypothesis—

S: That's exactly what I was going to get to next, Perry. This all very interesting, but unless you can derive from these notions a testable hypothesis, some way to test it, then it doesn't really enter the realm of empirical science. At best it's a mathematical construct and it's just a mathematical theorem. Now, mathematical theorems can be the beginning of a scientific exploration or a scientific investigation; it could say, "here's a model that's internally consistent and is consistent with what we observe". But you still have to then test it against something. You have to find some way to find out if it's actually real or not. And no one's been able to figure out a way to test string theory or the multi-universe theory or any of these other sort of big ultimate cosmological questions. So, at the moment, they still lie in the realm of theoretical mathematics and not empirical science.

Limits of Black Holes (22:16)

S: So let's go on to the second e-mail. This one's a lot shorter. This one is from Dan Hanch in California, and he writes,

Is there a limit to the amount of mass that a black hole can consume? Why don't the super-massive black holes in the center of galaxies gobble up all the surrounding highly dense stars, gases, etc.?

B: Let me grab that one again, Steve.

S: Oh, go ahead, Bob.

B: If that's all right. I know of no limit, and I can't think of why there would be a limit. As you just keep feeding a black hole matter, there's no reason why it's just not going to just keep sucking it up. Now I've heard—I've read estimates of super-massive black holes that have millions of Solar masses, and of course, a Solar mass is the matter equivalent in our sun. That's generally how they rate them, by Solar masses. I've seen them listed as millions of Solar masses and even billions, but recently, they found a super-massive black hole that is generating energy at the rate of 20 trillion suns. I've never heard an amount that huge. They never went into the trillions; I've only seen billions. But 20 trillions is truly staggering.

P: That's a lot of suns.

S: Was that part of the recent discovery, Bob, that some black holes generate more energy than they consume?

B: No, that's unrelated to Hawking radiation.

S: Yeah.

P: Are you doing about free energy there?

R: Yeah, are you saying we could have black-hole-powered cars one day?

P: Is that what you're talking about?

B: That would be interesting.

S: Theoretically. It was a recent discovery that's also been on a lot of the news sites recently. So-called green or energy-efficient black holes. But the implications of that, obviously, are unclear.

B: So I don't think there's any limit. I mean, a black hole could conceivably hold the entire universe worth of matter. There's no reason why it couldn't do that. So there is no limit. The other question that he had was: why doesn't it just keep on sucking up everything. People seem to think that black holes—I mean, they do have immense gravitational pull, but they seem to think they their reach is just beyond what anything else with mass has, but that's not true. If our sun turned into a black hole at this moment, I don't see any reason why the Earth wouldn't still continue to orbit around it. It wouldn't necessarily increase its gravitational pull and suck us it. Now, of course, it would have an event horizon and things like that. It'd have all these wacky features of a black hole, but it doesn't mean it's going to reach out any farther than anything else with that much gravitational pull. So, generally a black hole will clean out the area around it, and it'll create and produce lots of energy in the form of X-rays and things, things that... it's not leaving the black hole, it's just being created and emitted before it crosses the event horizon. So once it sweeps out that area, then the black hole become quiescent and pretty much just waits around for more matter to slowly get a little closer and closer and closer.

R: So it really is... it's more like a hole and not like a vacuum. Some people seem to think that it kind of acts like it's sucking, but it's really more of a hole.

S: No more than any other object with similar gravity, basically.

B: Right. Exactly.

S: And the gravity still falls off as the square of the distance, which is...

B: Right. Exactly. That's not violated with a black hole.

S: And also, another way to think about it is that it kind of is sucking in everything that's around it, that's close to it, as you say, but also, you know... things are really far away in the galaxy and outer space, and there's still the speed of light that can't be violated, so. Even if things do move towards the gravitational pull of a black hole, it would take a long time to draw in things that are very, very far away.

B: Right. And beyond a certain distance, you're essentially... it's just not there to you, gravitationally, because once you go a certain distance away—

S: You would orbit around it, but it wouldn't draw you in.

Origin of Life (26:15)

S: A closer question; this one regards the origin of life. This one is from Jeremy Freeman of Springfield, Illinois. Jeremy writes:

I recently discovered your podcast and just got caught up to your most recent. I'm disappointed that now I have to wait for you to release a new one, but you guys put on a great show; very interesting and entertaining.

Thanks.

In one of your podcasts and in your article, "The Starchild Project"

That's an article, by the way, that you could find on the NESS website, on our Articles page.

You refer to a point that Carl Sagan made and said that it would be incredibly unlikely that human and alien DNA would be compatible because it would be from two completely different evolutionary genetic code sequences. I agree with that line of thinking, but it got me thinking about a related question that maybe you could shed some light on. If I understand correctly, we share a genetic code with every other known form of life on Earth.

That is correct.

Therefore, we assume that an alien life form would have a genetic code from its planet of origin. What prevented multiple starting points of life on Earth? I mean, why is there only one set of genetic code? Why on a planet as hospitable to life as Earth, wouldn't life have started from multiple points? Why doesn't life spark even now, to create a new random microbe with different code to start a new evolutionary chain? I would like to know if scientists have attempted to answer this in the past and what their conclusions or theories were. Without an answer to that question and no evidence that shows that this has happened and that life died out, the likelihood of life on other planets decreases dramatically, at least in my mind. I'm not ready to go to the creationist route, but without a good answer, it's really bugging me.

R: We've got one on the cusp here, guys—

S: We need to draw him in.

R: —we need to pull him back and save him from the creationists.

S: So let me start with this one. So it is true that all life on Earth shares the same genetic code, and what we mean by that is the DNA sequence—you know, the DNA has four base pairs; like, four letters to the alphabet and each sequence of three base pairs codes for a specific either amino acid and then there are a few that regulate the transcription of that. Like for example, they may tell the transcription process to stop at a certain point. So that's the code. Which three letters equal which amino acid. There is absolutely no reason, by the way, why any two different species on this planet would have the same genetic code, except because of heredity. So therefore, we can conclude that all life on Earth is related to itself, to each other. Life that evolved on another planet—first of all, we wouldn't even know that they would have DNA. They may have some completely other molecule serving as their genetic code.

B: Could be a triple helix.

S: Whatever. It could be proteins. It could be something other than deoxyribonucleic acid, right? It could be some other chemical compound. And even if it was something like DNA, there's no reason why they would have randomly come up with the same genetic code, the same three letters equaling the same amino acid. They may, in fact, use a different... we use twenty—all life on Earth is derived from twenty amino acids. They may have a different set of amino acids then what we have. They may use some that we don't and not use some that we do. Now, in terms of has life arisen multiple times on this planet and why doesn't it. Well, one reason is that the conditions which were suitable for the origin of life on the early planet are no longer present. For examine, there probably was a lot more electrical storms early on. There was no oxygen in the atmosphere. There were probably lots more ammonia and methane and other compounds. So the early Earth, which may have been more suitable for the generation of life is not the conditions that exist now. Also, once life did arise, it would use up a lot of the resources in the environment. It would basically fill all the niches pretty quickly on the planet. And that would crowd out any new life trying to get a foothold. So whichever life arose first would have probably just crowded out any other later attempts at life arising.

Also, interestingly, there is one form of life that has a slightly different genetic code than everything else. Do you guys know what that is? I know Bob does.

R: A fundamentalist?

B: (chuckles)

S: That's not a bad guess. It's actually mitochondria. Mitochondria, which are organelles inside of our cells—they're the energy factories of our cells. They were probably a primitive form of bacteria that then formed a symbiotic relationship with larger cells. And they have a slightly different genetic code than does all other life. So, probably mitochondria represent a very early side branch of the branch of life that led to all existing life today. It's possible that they were a completely separate branch of life, but probably not, because they're still too similar. The genetic code's not totally randomized; it's very similar to other life; just a few differences. So what that also implies is that... Well, you know, there could've been multiple origins of life, multiple early branching points with different genetic codes, but only one branch survived. The one that is—later gave rise to all of life. So the early sort of chaotic biological systems on this world may have been competing and one branch survived. And that's why we only have genetic code at this point in time. So, those are some possible answers. Probably the most far out answer, which is still a possibility, is that life on Earth was actually seeded from outer space. If a meteorite landed on Earth that had some templates of DNA or whatever, that could have then seeded this planet with life. And then of course, if life on this planet arose from one point of seeding, it would all have the same genetic code. That's still very hypothetical, but that's another sort of possibility compatible with that. So, interesting question, and yeah, there's quite a bit of speculation that is compatible with what we see.

Science or Fiction (51:50)

S: The Skeptics' Guide to the Universe is produced by the New England Skeptical Society. For information on this and other podcasts, please visit our website at www.theskepticsguide.org. Please send us your questions, suggestions, and other feedback; you can use the "Contact Us" page on our website, or you can send us an email to info@theskepticsguide.org. 'Theorem' is produced by Kineto and is used with permission.

References