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Loren Booda
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What single observable (such as complexity) might characterize Earth as unlike any other planet in the universe?
And some reason to suspect that all of them are unique in some way. We have a very small sample to observe here in our neighborhood, and there are some vast differences between them in many metrics. There is no reason to assume that other planetary systems would not have significant differences, as well. We have discovered extra-solar planets by lots of means, not the least of which is tracking light-curves to discover large planets partially occulting their stars when their orbits are aligned with our line-of-sight. Are we going to find a "Mercury" orbiting a large star that way? Probably not for a very long time.Xnn said:There's roughly 10^24 planets in the universe.
No reason to suspect that ours is unique.
Xnn said:There's roughly 10^24 planets in the universe.
No reason to suspect that ours is unique.
Andre said:The large moon, stabilizing it's spin axis, preventing Earth from getting into the chaotic zone
Earth has both cyrus and evo - that must be pretty unique!Loren Booda said:What single observable (such as complexity) might characterize Earth as unlike any other planet in the universe?
Loren Booda said:Might such a large moon - having its genesis in the coalescing debris of a planetary impact - be more likely suited to avoid chaos by stabilizing the spin axis of the resultant planet?
Read section 2.2 of the paper that Andre cited. It is Earth's obliquity rather than its orbit that the Moon acts to stabilize. Lasker is claiming that Venus' rather anomalous rotation is due solely to gravitational effects by the other planets. The Moon acts to stabilize the Earth's rotation.Integral said:I am not sure what the deal is with the moon and stability? We have moonless Venus and Mercury, clearly a moon is not a necessary thing.
Integral said:I am not sure what the deal is with the moon and stability? We have moonless Venus and Mercury, clearly a moon is not a necessary thing
Integral said:I am not sure what the deal is with the moon and stability? We have moonless Venus and Mercury, clearly a moon is not a necessary thing.
Andre said:But are Venus and Mercury anywhere near Earthlike? The only thing that Venus shares with Earth is the order of magnitude of its size
That was pithy.negitron said:No, it's not.Andre said:But it is the subject of the thread.
Loren Booda said:What single observable (such as complexity) might characterize Earth as unlike any other planet in the universe?
D H said:That was pithy.
The subject of this thread is the uniqueness of the Earth. Loren asked
I agree that that is the hidden agenda behind his original post. That is not what Loren asked in the original post. What Loren asked was "What single observable (such as complexity) might characterize Earth as unlike any other planet in the universe?"SW VandeCarr said:The subject here is really whether there are any other planets having characteristics friendly to intelligent life as we know it.
D H said:The end result is the same: We are alone. The only way we are not alone is if there are hundreds of billions of Earth-like planets spread around the universe.
That's a better question, but you are still eliminating a lot of explanations for why some say the Earth is rare. The word "physics" pretty much eliminates geological, chemical, and biological concerns (assuming you don't consider geology, chemistry, and biology to be branches of physics). The words "Earth's physics" pretty much eliminates attributes of the parent star and perturbing effects by other planets in the star system.Loren Booda said:How might Earth's physics be most unlike that of any practically observable planet?
What does this number mean? That one out of every 10 billion stars has an Earth-like planet?Xnn said:By that definition, Earth is probably 1 in a 10 billion.
You are once again stating highly hypothetical things as if they are fact. This is not the site for doing that.However, consider that the visible Universe is not the only Universe in existence. Instead, it is just a single Universe of the greater Multiverse.
But the dynamic role of the gravity of considerable moon on the Earth physics is worth mentioning.
http://en.wikipedia.org/wiki/Tidal_accelerationThere is geological and paleontological evidence that the Earth rotated faster and that the Moon was closer to the Earth in the remote past.