Mars Odyssey Detects Signs of Water

BBC ^ | Friday, 14 December, 2001, 16:50 GMT | David Whitehouse

[Joe Hadenuf]

but as I mentioned, naturalism is a scientific philosophy, not empirically verified by science with respect to biology.

Lot of things have not been proven or verified by science yet. Sometimes the more we discover or prove, the more questions it creates.

[TigerDSL]

How large is the Universe? Is it infinite? If not, what is "outside" the Universe? How can we envision something being beyond the Universe?

[Joe Hadenuf]

How large is the Universe?

I don't have a clue.

Is it infinite? If not, what is "outside" the Universe?

I have heard two different trains of thought, one a closed universe and another open. I think the current belief is that its an open ever expanding universe.

How can we envision something being beyond the Universe?

I have tried that, but after a while it hurts my brain. When I was very young, it was the brick wall, but then, it was always, well whats behing the wall?

[RadioAstronomer]

The universe is estimated at between 11 and 15 billion years old and has been expanding (spacetime) ever since an event called the Big Bang.

[Joe Hadenuf]

His other question was how large is the universe?

[Joe Hadenuf]

What is the current age estimate of Earth. 3 or 4 billions years keeps coming to mind. Is this close or are there updated figures?

[Arthalion]

The problem is that the numbers most people enter for the Drake equation overlook some very fundamental facts about our galaxy. The very first entry into the equation, the rate at which suitable stars are formed, is MUCH lower than most people assume. To wit: Much as our solar system has a "band of life," or a region of space where life can exist, so does the galaxy itself.

Deep in the center of our galaxy, for example, is a large black hole. Any planets in this region would be heavily irradiated and subject to massive stresses that aren't exactly conducive to life. Move out of the core and into the "bulge", and your radiation problems die down, but gravitational interaction between the densely packed stars makes stable planetary orbits very difficult to achieve. Novas are also somewhat common in the core region which can't be healthy for nearby life bearing planets. Moreover, the vast majority of stars in this region are Population II type stars with very little metal, and are therefore not likely to support planets, much less life.

Move out of the bulge, and into the inner disk, and the problem reverses...you run into a plethora of metal-heavy but hydrogen-deficient Population I stars. Some of these are very old and have burned out their hydrogen, others have gone dwarf, and still others simply formed in this relatively hydrogen-free section of the galaxy and are distinctly "below average". A star with below average hydrogen content is far less likely to contain water-bearing planets, which is practically a requirement for complex multicellular life forms. Tack on to that the fact that hydrogen-deficient stars burn much cooler than "normal" stars, and we can effectively rule them out as a likely home for E.T.

Moving into the central part of the disk, you find an equilibrium. This region is far enough from the maelstrom of the galactic core and bulge that the hydrogen hasn't been burned or blown away. Its stars are all moving in mostly stable orbits, and enough Population II stars have died in the area to provide plenty of metals. The primary phase of Population I star formation in this part of the galaxy ended several billion years ago, meaning that gamma radiation is relatively low and that this section of the galaxy is comparatively clear of debris. This is, of course, where we are and where any other life is to be found.

And if we move out further? The outer portions of our galactic disk are characterized by immense clouds of dust, many radiation spewing stellar nurseries, more unstable orbits than you'd care to count, and a population of stars that, in whole, is far too young to support complex, intelligent life. Even if a stable and life bearing planet could arise out there, the fact is that nearly all of them are too young to have done so yet.

I remember that when my astronomy professor was teaching this to us, he mentioned its effect on the Drake equation. By refactoring the rate of star formation to limit it to only the portion of the galaxy where complex organic life has a realistic probability of surviving, while leaving the rest of the numbers to the generally accepted probablilities, the equation stated that there were only seven intelligent species in our entire galaxy. Given the massive size of our galaxy, the probability of achieving any kind of meaningful two way communication with one of those seven are effectively nil.

Don't get me wrong. I run Seti@Home on four of my computers and hope against hope that we'll someday make contact with one of those species, but at the same time I'm a realist. The numbers don't lie, and they don't look good.

[farmfriend]

Just had a horid thought. If they find life on Mars, will it be considered an endangered species?

[RadioAstronomer]

Here are some notes that will give a better explanation ass to expansion and size that a two liner from me:

http://phyun5.ucr.edu/~wudka/Physics7/Notes_www/node102.html

[RadioAstronomer]

What is the current age estimate of Earth. 3 or 4 billions years keeps coming to mind. Is this close or are there updated figures?

The generally accepted age for the Earth and the rest of the solar sytem is about 4.55 billion years (plus or minus about 1%).

[RadioAstronomer]

I have read the some same thoughts on this. I don't have enough information to make the assertion that life is non-viable in those regions. An interesting paper you might enjoy can be found here:

http://www.aip.de:8080/groups/sternphysik/stp/PDFFILES/2000/gaia_paper.pdf

[Exnihilo]

This makes the odds of life elsewhere great.

No, I'm sorry. It doesn't. Have you ever taken a course in statistical probability?

[Exnihilo]

Again, it would be illogical to use science, which assumes naturalism, to prove naturalism. In that respect, science will forever be vulnerable because in the end, the entire body of science is based on the assumption of naturalism. Where experiments can be carried out, and repeated, we can trust that in those cases naturalism holds true. For instance, this is the case with gravitational pull on Earth. However, in the realm of biology, naturalism is a philosophical assumption that cannot be verified. I find it amusing that one looks at major morphological similarities in fossilized forms in the Earth's strata and say "Ah ha! Those must be ancestors!". The entire theory of evolution, and abiogenesis as well, rests *entirely* on the philosophical presupposition of naturalism. I don't fault science for this assumption since this is the essence of science, however I am always struck by how many people do not seem to realize this major achilies heel of science, especially in the realm of biology. At any rate, you have your faith, I have mine. Good luck!

[Arthalion]

Thanks, I've actually been looking for something a little more definitive on habitable zone forecasting, and that definitely works. This information is useful because, while I don't believe that there are many intelligent life forms in our galaxy, I do believe that there are a large number of human habitable planets awaiting colonization.

I don't have enough information to make the assertion that life is non-viable in those regions.

It's not so much that life is "non-viable" - heck, research on our own planet has showed us that life can pop up in the most unexpected of places - it's that complex, intelligent, multicellular life is unlikely in much of the galaxy. Life of this type requires long burning, metal and hydrogen rich stars. It requires stable orbits. It requires a quiet area unaffected by nearby gravity wells, radiation bursts, or swarms of interstellar debris. Moreover, it requires time...a planet may need more than three billion years before it can raise an intelligent species capable of communication with the stars. There is only one region in our galaxy that meets all these requirements, and that region is contained in a relatively narrow band in the middle of the galactic disk.

The presence of life on planetary bodies outside of this band is indeed possible, but the odds of intelligent life are very, very low. They are so low, in fact, that radio astronomers searching for signs of intelligent extrasolar life would be better off ignoring these to focus their search on the more likely areas first...as astrophysicists and visual astronomers have been recommending for more than a decade.

[Scully]

I cannot remember where I heard about this poll, but Christians (an unknown numbers and denominations) were asked if discovering life on other planets would shake their faith. More than 80% said that it would. An amazing number considering that God is supposedly all powerful. Personally, I can't understand why we must be the only sentient life in the Universe, or how anyone could imagine God as incapable of creating other life forms elsewhere.

[asneditor]

#2 LMAO

[Scully]

Wonderful reference! Thank you for including it!

[Joe Hadenuf]

Have you ever taken a course in statistical probability?

Lol, no, and I don't think I need to, to understand that the chances of life are much greater if you have a trillion planets, as opposed to say, 3 planets :o

[tberry]

"I can't understand why we must be the only sentient life in the Universe, or how anyone could imagine God as incapable of creating other life forms elsewhere."

Off all the things both physical and organic that have been observed, has there been anything that we have just found one of, that we have not found there to be more than one?

If the answer is that there is no provable thing of which there is just one, why do we believe that life which, is found on the earth, is the one and only example of life that is?

[Johnny Shear]

I can only assume it's because the Bible doesn't SAY God crated Martians on the 8th day.