The Great Debate 2010: Are We Alone?

[QuietIce]

This is a debate that outlines the basic premise of SETI as well as the current, opposing view. It includes an extensive review of the Drake Equation and, more importantly, focuses on the current values assigned to the variables in the Equation - values assigned on both sides of the argument. On the Pro-SETI side is Dan Werthimer, the chief SETI scientist at Berkeley, who has been running the program since it's inception. On the Anti-SETI side is Geoff Marcy, a very predominate astronomer to say the least. Dr. Marcy's team has been leading the research and discovery of extra-solar planets. Some of the slides are particularly interesting (and one funny is attached below). Whichever way you choose to watch it's worth the time - enjoy!

YouTube video - in ~10 minute chunks

Berkeley's video



PS
If you're interested in the monthly science lectures at Berkeley, here's the website:
http://scienceatcal.berkeley.edu/lectures
.

 

[Voodoo Rufus]

Oh boy, a lot of video to occupy my time. Thanks for posting it.

 

[Sephis]

I just finished the whole thing, and I found both presenters to have very good arguments. It essentially boils down to a lack of data. We have no idea what good parameters are for the Drake equation, or even if that equation contains all of the necessary variables. In the coming decades, we will learn more and more about extrasolar planets, and the debate may be very different then. At the moment though, there are just too many unknowns. The best approach to finding an answer IMO, is to keep collecting as much data as possible.

 

[Bobnova]

Thing is... As far as we can tell the universe is infinite. Given that, there are an infinite number of civilizations as well.


Now if you confine it to our galaxy, it's much harder.

I say we have company, personally.
Odds are it doesn't use water, and may live somewhere like the liquid hydrogen seas inside gas giants. Or even under those seas on the metallic hydrogen core.
Or why not in the sun?

 

[QuietIce]

I think the better question they asked was more to the point than "Is there life out there?". Both scientists agreed there almost certainly is other life out there and, given the size of the universe, intelligent life at that. The real question they posed was "How far away is it?" That's where the real question lies and I think, as Sephis said it, there are just too many unknowns in our equation to answer that question - all we can do is guess.


I also agree that just because we have no proof of alien exploration of our system doesn't mean they haven't been here. We know about the planets of our own solar system, some in fair detail, but we've only landed on the Moon and that was more for a "Can we do it?" dare than anything else. We put robots on Mars and we've shot a probe into Jupiter's atmosphere. In a thousand years could we go back and find any of evidence of them on those planets? Will we ever bother shooting a probe into Saturn, Uranus, or Neptune? Doubtful unless there's something peculiar we see from orbit that we'd like to investigate. Do you suppose we could even find traces of an African expedition from the 1800's, even knowing the route that was taken? I doubt it. I've spent the last 25 years of my life land surveying, part of which is keeping land corners monumented. Even when we know exactly where the corner should be we sometimes can't find it - and this is only after a few decades of time, at most a century. Even if there is one to find what are the odds of randomly stumbling across a space probe from millennia ago? Ain't gonna' happen ...

 

[Cheator]

Thing is... As far as we can tell the universe is infinite. Given that, there are an infinite number of civilizations as well.

The universe isn't infinite as far as we know. For something to be infinite, it would have to start from an infinite size. From what we can tell its growing, therefore its gigantic beyond any measure we have, bigger than anyone can imagine, however not infinite.

I just watched a very interesting BBC horizon on Infinity and they have a good point about making that distinction.

No we're not alone, they're just far away and possibly not inteligent

 

[QuietIce]

Both scientists pretty much conceded that life, as in basic cellular or equivalent types, are probably fairly abundant out there. The compounds needed just for our kind of life is readily available in the universe and the extremophiles on planet Earth have shown it doesn't take a Goldilocks environment for life to exist.

Starting at intelligent life is where the big questions come. Up to that point the Drake equation is pretty straightforward with all sides agreeing on rough values. When we hit the f_i, f_c, and L variables - representing intelligent life, communicative life, and Longevity of a communicative species - that's when the speculation really starts. Intelligence (not necessarily human-level intelligence!) is rare in earth life considering the number of species we have and technology is very limited, being present only in primates, with longevity being the biggest question mark of all ...

 

[Sephis]

Thing is... As far as we can tell the universe is infinite. Given that, there are an infinite number of civilizations as well.

This is a bit misleading. The scientific community believes that there is no "edge of the universe." However, there is only a finite amount of mass and energy. Whatever was released in the big bang is all there will ever be. So while the size of the universe may be infinite, the number of stars and planets is not.

 

[Bobnova]

Assuming the big bang theory is correct, and the matter wasn't infinitely compressed, yes.

The big bang theory seems to be the current favorite, but it is by no means proven (nor will it be, really).
I've never understood how it could compress matter past the official maximum for a black hole, and then allow it to escape.

 

[Voodoo Rufus]

I don't understand why the big bang theory is not proven. We know that matter in our known universe started accelerating from a single point. We also know that we're not slowing down as the universe expands.

You can either chalk that up to some effect of dark matter, but I'm a fan of the multiple universe hypothesis.

 

[wingman99]

I say it's just like the movie men in black, and are galaxy could just be on a key cain around a cat's neck.

 

[Sephis]

I say it's just like the movie men in black, and are galaxy could just be on a key chain around a cat's neck.

This is the most logical theory I have ever heard.
It is my great honor to name wingman99 the smartest person in this thread.


The big bang theory is currently the accepted theory for how the universe began. Is is also the only universe creation theory (AFAIK) that has actual evidence to back its claims. There are many respected scientists who have put forward many ideas on the creation of our universe. Most of them fail to explain the visible movement of the cosmos in a radial pattern from a single point. They also fail to explain the easily detectable background radiation present in every place we have ever pointed a radio telescope.

 

[QuietIce]

Assuming the big bang theory is correct, and the matter wasn't infinitely compressed, yes.

The big bang theory seems to be the current favorite, but it is by no means proven (nor will it be, really).
I've never understood how it could compress matter past the official maximum for a black hole, and then allow it to escape.

In some of the wilder theories about the origin (not formation!) of our universe they postulate a super-universe and our universe is what has fallen into their equivalent of a black hole.

Other theories include a type of spontaneous creation, kind of like what happens here at the quantum level with matter/anti-matter particle pairs. Enough energy builds up in one small spot then "bang" there's a new universe floating around - but since the super-universe has different phyical properties than ours there's no paradox.

Most of them fail to explain the visible movement of the cosmos in a radial pattern from a single point. They also fail to explain the easily detectable background radiation present in every place we have ever pointed a radio telescope.

???????????

The CMB, yes, that's a BIG fact in favor of the Big Bang - but you'll have to provide a link to the other. AFAIK there is no "center" to the Universe except that which we create through Relativity.

I say it's just like the movie men in black, and are galaxy could just be on a key chain around a cat's neck.

The Truth is probably even stranger than that ...

 

[Sephis]

The CBR, yes, that's a BIG fact in favor of the Big Bang - but you'll have to provide a link to the other. AFAIK there is no "center" to the Universe except that which we create through Relativity.

I seem to have messed up my own explanation. That's pretty easy to do when discussing these sorts of things. I should have said "most of them fail to provide a universe that could expand radially from a single point." I do realize that is very different from what I described earlier, and I apologize.

In 1927 Georges Lemaître found solutions of Einstein's equations of general relativity in which space expands. He went on to propose the Big Bang theory with those solutions as a model of the expanding universe. The best known class of solutions that Lemaître looked at were the homogeneous solutions now known as the Friedman-Lemaitre-Robertson-Walker (FLRW) models. (Friedmann found the solutions first but did not think of them as reasonable physical models). It is less well known that Lemaître found a more general class of solutions that describe a spherically symmetric expanding universe. These solutions, now known as Lemaître-Tolman-Bondi (LTB) models, describe possible forms for a universe that could have a centre. Since the FLWR models are actually a special limiting case of the LTB models, we have no sure way of knowing that the LTB models are not correct. The FLWR models may just be good approximations that work well within the limits of the observable universe but not beyond.

The FLRW models would provide for a homogeneous universe with no center, but the more general case (the LTB models) describe a universe that expands spherically. In college, my physics professor taught that the LTB models were probably the reality of the situation, but our limited range of detection fit the FLRW models better.

And now we have dragged this topic wayyyy off of the OP.

 

[Cheator]

I don't understand why the big bang theory is not proven.

Actually, because of some recent observations, they're not sure that the big bang is a perfect theory that explains it. Many people like to belive the balloon model.

 

[QuietIce]

I seem to have messed up my own explanation. That's pretty easy to do when discussing these sorts of things. I should have said "most of them fail to provide a universe that could expand radially from a single point." I do realize that is very different from what I described earlier, and I apologize.



The FLRW models would provide for a homogeneous universe with no center, but the more general case (the LTB models) describe a universe that expands spherically. In college, my physics professor taught that the LTB models were probably the reality of the situation, but our limited range of detection fit the FLRW models better.

And now we have dragged this topic wayyyy off of the OP.

Well, somewhat off topic but not completely. An infinite Universe virtually guarantees the existence of other intelligent life - in fact, it would guarantee the existence of every kind of life imaginable and then some. However, even if the Universe were only as big as what we can see, almost as impossible as an infinite Universe (it almost HAS to be bigger than what we can see) both sides of the argument agree that intelligent life is out there. Again, this goes back to what I'd said earlier - the discussion isn't really about whether "ET" is out there or not, it's about how far away ET is from us ...

 

[4GHZ_or_bust]

The problem with infinity universe theory is we'd likely have seen some ancient lights long ago but as seeing we haven't found anything much older than some 15 trillions (quassars for example) which would mean nothing existed as far as light or radio source before the big bang.

If there is an infinite universe, then the probably explanation would be they existed in a form that we have not discovered or proven as of yet (ie not atom, proton, electron, etc)

 

[wingman99]

How do we know the infinite distance light travels for sure.

 

[QuietIce]

It is almost certain there are light sources farther away than the 15-18 billion ly we can see. The simple fact that our sight distance stops at that range in all directions dictates that either there are light sources beyond that OR that we are the center of the Universe, which would be a truly cosmic stroke of luck if true!

The reason we can't see those light sources farther away is a matter of time - enough of it hasn't elapsed yet for light from those sources to reach us. In large part the distance to those distant objects that we can see is probably the most significant "fact" we have for determining the age of the Universe.

Experiments have been done to try and determine the size (actually the curvature) of the Universe but the results were that space is flat, meaning space is infinite. Most astrophysicists believe it's more likely that our experiments simply aren't sufficiently refined to detect the curvature but the error of those experiments does set a lower limit on the size, which is much larger than the 15-18 billion ly we can see.

How do we know the infinite distance light travels for sure.

It's no more of a "fact" than gravity. Since we have no "proof" of it's existance all gravity is to us for now is a phenomina that seems to always hold. It could just be a cosmic coincidence that every time we've tested it it's been working ...

 

[wingman99]

How do we know the infinite distance light travels for sure.

It's no more of a "fact" than gravity. Since we have no "proof" of it's existance all gravity is to us for now is a phenomina that seems to always hold. It could just be a cosmic coincidence that every time we've tested it it's been working ...

Yes, however with light we can't jump up and come down. Are not some stars brighter and darker than others.