Careful, there. Physics exerting itself on biology means something like gravity making leaves fall to the ground rather than fly off into space, no matter whether the leaves are on earth or Mars. It does not mean that if there are leaves on earth there must be leaves on Mars as well.
I think you have to presume that life is rare, unless you believe in magic or God. 
Think of it this way. Would leaves evolve on a dark moon heated by tidal energy? Did they evolve on deep sea black smokers?
What about on a radioactive world with gamma rays as a primary energy source? There’s earth based fungi that metabolize gamma rays.
HULK SHROOM
Sure, but given long enough time scales it would be moot anyway. After all, if it happened here with perhaps seed life propagating from the Earth to Mars/Europa/some other solar life friendly spot (or vice versa I guess) then it would happen everywhere…even if for some odd reason the Earth was the starting point for all life. It probably took hundreds of millions of years for the meteorite to get from Mars to the Earth after all…if life could survive that long after being blown off a planet it would essentially be immortal…and so every life friendly niche out there would eventually be covered I should think.
I think though that in my lifetime someone is going to manage completely artificial life which should strongly indicate that given the right conditions and time life is going to result…and given what we know of evolution that eventually complex life will arise as long as the entire biosphere doesn’t get whacked by some kind of cosmic disaster. Whether intelligent life will also arise…that’s probably not something we’ll be able to answer (or the actual probability of it arising), and I could certainly see intelligent live as being VERY rare with extremely low probabilities. Even so…well, it’s a really big universe out there (and perhaps an infinite number of parallel universes as well).
As to why they don’t call, maybe they got ambushed by Indians on the way to California and their bleached bones are sitting right next to the burned out wagon (obscure reference to Dances with Wolves that I think of every time I see the title of this thread)…
-XT
If physics created leaves on earth I see no reason why physics wouldn’t create leaves somewhere else. There are pretty good reasons why physics didn’t create leaves on Mars specifically, but you seem to be saying “be careful, physics won’t create rocks on Mars.” But physics did.
This is a very important point, but it’s pretty easy to address, at least if we get living specimens rather than just fossils. All life on Earth uses the same genetic code: In Earthly organisms, CCG always codes for the amino acid proline, and and GAA always codes for glutamic acid, and so on. There’s no inherent reason this must be the case; any codon could in principle code for any amino acid. If we were to find some alien species, even if they implausibly used the same sort of DNA that we do, the odds would be astronomical against them using the same code to interpret it. So in practical terms, we can say that if Europan life uses the same genetic code that we do, then it’s related to us, and if it doesn’t use the same genetic code (or even uses a completely different genetic material), then it’s not related to us.
And the argument, repeated by many, that maybe we just don’t have the appropriate technology to communicate with aliens doesn’t really address the question. Fermi’s paradox doesn’t ask why we don’t hear aliens talking on the radio; it asks why we don’t have an alien standing right in front of us and waving.
Yes, but the laws of physics have been the same since after the first few seconds of the big bang, and have been the same for the first 4 billion years of Earth’s existance. Yet despite abundant life for 4 billion years there were no leaves on planet Earth. Leaves have only existed for a small fraction of the time that Earth has been an Earth-like planet. Land plants only date from the Silurian, about 450 million years ago, that would mean that leaves did not exist for something like 9/10ths of Earth’s existance. And these earliest land plants didn’t really have structure differentiated into leaf, root and stem, but were just branching filaments.
Perhaps you are hearing your own voice, certainly not mine. Physics creates nothing that I know of, least of all leaves.
I think he’s using the word ‘physics’ in a different (and unusual) way than you are Liberal.
To paraphrase…I dinna think that word means what you think it means…
-XT
What? In my universe we have laws. They control the fall of leaves just as they control the molecules that make up the leaves. I’m not sure what the laws of physics are in Liberal’s universe. I’d like to pin them down though. I think in both universes they create planets, but it would appear that in his universe, biology falls under some other law.
Yes, but even things like kelp have broad flat structures evolved to maximize the amount of surface area exposed to the Sun. Even though those structures are not evolutionarily connected to land-plant leaves, I don’t think it’s much of a stretch to call them “leaves”.
The universe has existed for what, 15 billion years? Earth has existed for what, 4 billion years? So? The laws of physics said earth would be created when the conditions were right for earth to be created. Nothing magical going on here. Move, along, move along.
Higher order life only got going 500 million years ago. Okay, I get that. What is your point? That makes it really rare? Well, if a black hole only becomes a black hole one second after 5 billion years, that means what? It happens when it happens.
Life on earth remained primitive up until recently. Fine. Life likes spurts, I guess.
Are you suggesting that the Scala naturae is not only real, but is a physical/biological law?
If so, I think a few hundred years of progress in the biological sciences would disagree with you. If not, I don’t know what makes you think plants, let alone leafy plants, are an inevitable byproduct of evolution.
Huh?
To everyone: don’t bother reading that link. It’s some hair-brained thing about medieval concepts and God.
What it has to do with this discussion, I don’t know.
And no, I don’t think anything is inevitable unless it’s inevitable. Didn’t I already point out the sun didn’t turn into purple jello? Yeah, that would be physics raining on that particular fanciful parade.
Sorry, that link isn’t a great explanation of the biological side of the concept. Basically the scala naturae is a concept which says life is divided into certain stages, from “primitive” to “advanced”, and that it is some kind of ‘natural order’ for life to progress from mineral to vegetable to lower animal to higher animal, etc. Outdated classification systems that use concepts like Class, Order, Phylum, etc. are based on this.
In the modern conception, life is life. There’s no “order” as such, just a wide diversity of essentially random evolutionary pathways. There’s no law or scale that says life must “progress” from bacteria to worm to fish to reptile to mammal, that just happens to be the way it all shook out on earth.
Is the current classification system really considered “outdated?” I didn’t know that. Interesting.
Anyway, I can get behind the idea that life doesn’t really lead to this or that direction. But, when we talk about things like the Drake Equation, we can’t safely make assumptions about anything other than what we can observe and know to be true, and that’s earth, and how things work here.
I wonder what earth would be like if we had no land above water. Still, you can’t deny evolution.
We’re actually a long way from the idea of panspermia being proved viable. Everywhere in space, there is ambient radiation. Within a solar system, there is additional solar radiation. Either one would be sufficient to kill off any life form that we know during a long space journey.
Furthermore, there’s the question of temperatures. Any meteor traveling from Mars to Earth gets heated up twice. Once when the initial collision knocks it loose from Mars, and the second time when the meteor crashes into Earth. Any life forms on board would get cooked.
We’ve already identified and classified extremophiles. Heat, cold, radiation resistant and/or living in rocks organisms exist.
Polyextremophiles can handle several extreme conditions.
As I understand it, physics deals with physical laws — regarding such things as forces, fields, waves, and particle behavior. Biology deals with biological laws — regarding such things as life, evolution, taxonomy, and reproduction. Those aren’t exhaustive lists, by any means, but they should give a clue.
Biology laws are just a subset of physical laws. Nothing happens in biology that can’t be explained by physics.
We have much more testing ground with physics. We can look ten billion light years in any direction and see galaxies held together by gravity. We can see that the speed of light is the same there as here.
We only have one planet with life, and all that life has one common ancestor at some point. There’s no way to know if we’re freaks or not.