Slashdot Mirror
Evidence of Protoplanet Found On Moon
mrspoonsi (2955715) writes 'Researchers have found evidence of the world that crashed into the Earth billions of years ago to form the Moon. Analysis of lunar rock brought back by Apollo astronauts shows traces of the "planet" called Theia. The researchers claim that their discovery confirms the theory that the Moon was created by just such a cataclysmic collision. The accepted theory since the 1980s is that the Moon arose as a result of a collision between the Earth and Theia 4.5bn years ago. It is the simplest explanation, and fits in well with computer simulations. The main drawback with the theory is that no one had found any evidence of Theia in lunar rock samples. Earlier analyses had shown Moon rock to have originated entirely from the Earth whereas computer simulations had shown that the Moon ought to have been mostly derived from Theia. Now a more refined analysis of Moon rock has found evidence of material thought to have an alien origin.'
I haven't read the Science article yet, but from the BBC report it seems that the differences between the isotope ratios in moon rocks and earth are still a lot smaller than expected. This would suggest the Theia hypotheses to not be true, contrary to what the title says. I'm going to track down the original paper, because this BBC article has me somewhat confused.
And the rest of the article discusses the skepticism of this "evidence". To sum it all up, the evidence is the different ratios of oxygen isotopes found between 3 moon rocks and Earth. Most experts are saying the difference in the ratios should be much, much larger, because of how different the ratios of isotopes are in meteorites and other outer solar system bodies. The difference between the earth and moon is so small that other theories are just as likely for explaining it. The counter argument is that maybe all of the inner planets have the same ratios of oxygen isotopes as one another, and it was an inner planet that struck Earth and basically everything involved was made of the same stuff so the differences are small.
I think that until we have actually measured the ratios from Mecury or Venus, we can't assume that every inner planet is exactly the same in that regard, and thus the "evidence" this study has found is actual evidence one way or another. The only thing we know for certain is all the extraterrestrial material we have analyzed so far from the rest of the solar system has had very different ratios of the isotopes, and so this evidence requires a whole new theory about the homogeneousness of the solar system to be true.
Better known as 318230.
That's like asking, "how do we know that the Cretaceous period was called the Cretaceous period, the dinosaurs didn't have written language".
No kidding!!! What do you say at this point?
... where all those pesky Thetans came from
I'm ignorant, but today's science seems like "Tell me what is your theory, and i will find data to prove it's true"...
Yes, like that famous current scientist Einstein produced a theory of gravitation and then several years later they found data to prove it was true.
Or as a law predicts, "Given an enough amount of data, ANY theory can be proved"... :-)
There is no law that predicts such a thing. Given enough data, almost all theories are disproven. The only ones that remain are the ones that fit the data.
Given enough data, almost all theories are disproven. The only ones that remain are the ones that fit the data.
Given enough data, almost all hypotheses are disproven. The ones which remain and have not yet been disproven by evidence become theories.
If Slashdot were chemistry it would look like this:Cadaverine
This means two things: firstly we can now be reasonably sure that the Giant collision took place; secondly, it gives us an idea of the geochemistry of Theia
Earth isn't large enough to capture an object the size of the moon in such a close orbit. and the moon was orbiting in a much much closer orbit 4 billion years ago.So, no, it was the most complex explanation.
Well they have The Doctor and I am sure he knows, he probably watched it happen
And that's how baby planets are made.
Get free satoshi (Bitcoin) and Dogecoins
Also consider that the proto-earth and Theia originated from the same material overall, which means that it would be hard to distinguish them from each other.
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
Given enough data, almost all theories are disproven. The only ones that remain are the ones that fit the data.
Given enough data, almost all hypotheses are disproven. The ones which remain and have not yet been disproven by evidence become theories.
Nope, the AC was right.
By your definition, there is ultimately no such thing as a theory. Newtonian physics don't fit as they've been invalidated by Einstein's general relativity, which itself is known to be wrong as it is inconsistent with quantum mechanics (which are also wrong for the same reason).
You can't claim that former theories that were refined / invalidated never were theories in the first place : The "not yet" in your second sentence is problematic as it only allows theories to be defined with hindsight.
Therefore :
When data doesn't fit current theories, you're forming hypotheses, and test them. If your hypothesis fits the data better than former theories on some domain of validity (whose boundaries might not be completely known at the time of formulation, and will be refined with time and experimentations), good for you: you now have a new theory. It will ultimately be replaced by better theories, usually with an extended domain of validity (data that were missing at the time of formulation and testing).
And that was well summed up by the GP.
I have discovered a truly marvelous proof of killer sig, which this margin is too narrow to contain.
No, this is simply the definition of a theory. If it's simply "I think that mice cause global warming", that's a hypothesis, but as soon as you add "you could test this by doing this, this and this, it predicts this result from the above tests" it becomes a theory. Once you do the testing it may stay a theory, or become simply wrong.
But they would be spherical cows!
Wow. A physics approximation that actually works.
Faster! Faster! Faster would be better!
Given enough data, almost all hypotheses are disproven. The ones which remain and have not yet been disproven by evidence become theories.
Science is the discipline of publicly testing ideas by systematic observation, controlled experiment, and Bayesian inference. The last one is important, because Bayesian inference never "proves" or "disproves" anything in the Cartesian (or Poperian) sense of those terms. It instead increases or decreases the plausibility of propositions.
At best, "proof" and "disproof" are convenience terms that mean "overwhelmingly plausible with no alternative that has remotely similar plausibility" and "hugely implausible regardless of alternatives."
The asymmetry that Popper pointed out still exists on the Bayesian view: an extremely plausible idea may turn out to be in competition with unknown alternative ideas (think Newtonian gravity vs General Relativity) that are incrementally more plausible. Newtonian gravity (in its modified form) is still fairly plausible (although I don't think anyone really accepts it is better than GR), unlike, say, phlogiston theory, which is utterly implausible.
This is important because it means we don't have to accept the "most plausible" idea as "true"--the Bayesian standard of plausibility is absolute, not relative. It just never reaches a value of 1.0, only 1 - epsilon (or conversely epsilon for a maximally implausible idea.)
Bayesianism is compatible with "I don't know" as an answer when all current ideas have very low plausibility, and with "This is good enough for going on with" when one idea alone has high absolute plausibility, and "Could be this or that" when two or more ideas have similarly high plausibilities.
Blasphemy is a human right. Blasphemophobia kills.
I thought the simplest explanation was that it was captured by Earths Gravity
Thats only simple until you figure out that that sort of thing isnt actually possible. In cases where gravitational capture is possible, it is the gravity of a 2nd body (such as a moon) that enables a 3rd body (such as an asteroid) to lose enough velocity to orbit a 1st body (such as a planet.) Conservation of energy means any body that wasnt in a planets orbit will by default have escape velocity if it ever approaches that planet, and this is true unless it is acted upon by a force external to the mutual gravity of the planet and would-be capturer.
"His name was James Damore."
Right, while the simplest explanation was "That's no moon..."
Violence is the last refuge of the incompetent. Polar Scope Align for iOS
Damn, I had to give up modding this to answer, but I can't leave this.
One cannot "capture" a body the size of the moon by any two body elastic (e.g. gravitational) interaction. Within irrelevant perturbations such as gravitational wave radiation (presuming such a thing to exist), energy is conserved, and if it starts out unbound to the Earth it will end up unbound to the Earth.
One can capture in a three (or more) body interaction, but in that case the missing energy has to go someplace, and we are talking about a LOT of energy in the case of an orbiting moon. Enough energy to basically melt the moon and the earth and then some. One would expect to see some sort of orbital remnants of such a many-body event, and all of the other bodies in the solar system are a bit too far away to be good candidates in terms of the forces needed, and show none of the orbital perturbation one would expect as a consequence.
That leaves inelastic events. Tidal interaction is inelastic over time, but to make it strong enough to mediate a "capture" it would damn near be a collision anyway, brushing up on Roche's Limit (look that up). Also, that too would leave the nascent moon in an orbit much closer than the initial radius of its apparent orbit. Also, it wouldn't explain the apparent deficit of heavier elements and an iron core in the moon (thought to have been literally blown out of the incoming body in the collision and either ejected altogether to carry away the missing energy and momentum needed to leave the remnant in orbit or absorbed into the Earth) and a bunch of other things.
So really, the collision hypothesis makes "enough" sense and is consistent with enough data that it is AFAIK the "accepted" explanation of the moon's origin, with the usual caveat that contrary evidence or a better argument in the future might change that as we cannot easily be certain about events 4.5 billion years ago.
rgb
Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.