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Lacy33
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Was wondering if "Astrobiology", as in SETI and The movie Contact is a "real" science?
lisab said:Nope, it's no joke. You can study Astrobiology at my alma mater, the University of Washington.
http://depts.washington.edu/astrobio/
tribdog said:Oh I believe in aliens. I believe i alien civilizations more advanced than ours even. I don't believe any have ever visited us, but I believe they are out there. I don't even think that is considered fringe anymore. Fringe would be believing that we are the only ones in the Universe.
Chronos said:Apologies, Shoshana, I forgot to include links:
http://www.markelowitz.com/exobiology.htm
http://biocab.org/Exobiology.html
Arch2008 said:http://en.wikipedia.org/wiki/Drake's_Equation
People always spend a lot of effort explaining how there must be intelligent life elsewhere for a lot of intelligent reasons, and then sort of gloss over Fermi’s point.
http://en.wikipedia.org/wiki/Fermi_paradox
I believe there is no reason to doubt in simple life elsewhere in the universe. Chemistry and physics should conspire to create exobiology in lots of places. However, intelligent life eventually leads to advanced civilizations. That’s the whole point, right?
http://en.wikipedia.org/wiki/Kardashev_scale
A type III civilization would be here in our solar system right now. Their Dyson sphere around the Sun would be a little hard to miss. There are about a hundred million galaxies within a billion light years of us and not one single type IV/V civilization anywhere in that sphere has spread here. Either interstellar/intergalactic transportation is impossible for some unknown reason, or there simply are none.
Of course, one could argue that the universe is larger than a sphere with a diameter of a mere two billion light years or that only a few septillion planets in such a sphere are too small a sample, or that a few billion years was too short a time for them to get here. Maybe intelligent life/advanced civilizations are everywhere in the parts of the universe that are beyond our Hubble sphere, i.e., where we will never find each other. Their existence would remain forever a belief.
Chronos said:I have more dire solutions to the Fermi paradox - 1: Advanced civilizations learn how to destroy themselves before learning how to resist the urge. 2: Interstellar travel is as difficult as it appears to be. I agree with Arch2008 that intelligence is not necessary for survival, but, it does appear to be an evolutionary trend - e.g.,
http://www.space.com/searchforlife/seti_intelligence_030821.html
Arch2008 said:...
http://en.wikipedia.org/wiki/Kardashev_scale
A type III civilization would be here in our solar system right now. Their Dyson sphere around the Sun would be a little hard to miss. ...
Lacy33 said:On our very own planet we have we have so many species. Does anyone know how many recorded?
I don't know if I would make that assumption. If ice is trapped in a pocket within a rocky comet, and the temperature of the rock begins to warm, the ice will indeed sublimate to gas. However, if this gas cannot escape the pocket, the gas will form a trapped "atmosphere," with pressure increasnig as more ice sublimates. At sufficient pressures, ice begins to melt to form liquid water.Widdekind said:...Now, the Triple Point of water is (613 Pa , 273.01 K)*. Below pressures of 613 Pa, ice sublimates straight to a gas. Thus, comets must be big enough, to produce enough core pressure, to allow liquid water to form from melting ice.
LURCH said:I don't know if I would make that assumption. If ice is trapped in a pocket within a rocky comet, and the temperature of the rock begins to warm, the ice will indeed sublimate to gas. However, if this gas cannot escape the pocket, the gas will form a trapped "atmosphere," with pressure increasnig as more ice sublimates. At sufficient pressures, ice begins to melt to form liquid water.
Just saying; gravity is not the only way to create the required pressure.
Widdekind said:Prof. Wickramasinghe et al have calculated that Comets must be 2 km across to generate sufficient core pressures, and 8 km across to generate sufficient heat for "millions of years*".
* International Journal of Astrobiology (2007). The Origin of Life in Comets.If Biogenesis happened in comet cores, then those primary microbes were probably Chemosynthesizers (??). This is consistent w/ claims, that the earliest Earth Life formed around volcanic vents (??).
LURCH said:I'll follow the link after I get through the forums today. However, it sounds as though we're counting on gravitational pressure to generate heat and core of the comet. Is that the model used in that article? I was assuming an external heat source, like the sun (or other star, in the case of solar comets).
Chronos said:I seriously doubt there is enough fissile material in your typical comet to be of any consequence.
Vanadium 50 said:Pity the thread got hijacked.
Lurch, you're right. Gravity is not the only way to create that pressure. In fact, comets are too small to be held together by gravity; it's largely chemical bonds that keep them together.
Also, the calculation done by Mr. Widdekind uses his own...um...highly speculative model for densities. Observations, such as those made on 19P/Borrelly, 9P/Tempel 1 and Shoemaker-Levy 9 indicate that the densities of these comets are lower than Mr. Widdekind predicts, by possibly an order of magnitude or more.