How is molecular hydrogen detected?

[twofish-quant]

I think that you still don't "get it."

On the northwest corner of 1st Avenue and 14th Street in New York City, there is fast food place that sells hot dogs. Now someone argues that there is a French restaurant there.

You cannot by any purely mathematical or philosophical argument refute that position.

It is perfectly mathematically and philosophically possible for there to be a French restaurant at the corner of 1st ave and 14th street. There is no logical contradiction for there to be a French restaurant at the NW corner of 1st and 14th. If you ask me to prove through logical arguments that there isn't a French restaurant there, I can't.

But there isn't. You can go to that location, and see that it's a hot dog joint. If you can't get a plane ticket to NYC, you can go onto google maps, and see that there isn't one there.

Same goes with cosmology. I cannot by pure mathematics or logic show that Milne is wrong. I can just look a the sky and show that he is wrong about how the universe is set up, and most of those measurements were taken decades after Milne was around.

Also, the point of theory is to tell the observers what to look for. You are asserting (incorrectly) that we can't see distant galaxies because our telescopes aren't good enough. Now even if that were true, then the question should be "how good do our telescopes have to be?"

One of the points that I'm trying to make here is that cosmology is not philosophy. It's grounded in observations in much the same way that oceanography is.

 

[Chronos]

My apologies for referring to you as James, Jonathan. I perceive your error as one of philosophy, not science - e.g., I agree with twofish. Cosmology is a conjecture founded on observation. While I agree cosmology is still largely a matter of conjecture, it is a conjecture based on observational evidence. Once you leave the realm of observational evidence you enter the realm of metaphysics.

 

[SpiffyKavu]

Golly, this thread has gone off topic. I was going to say that the Fermi telescope has good things to say about molecular hydrogen (not always well traced by CO), but I have a feeling a new topic would be better...

 

[twofish-quant]

While I agree cosmology is still largely a matter of conjecture, it is a conjecture based on observational evidence. Once you leave the realm of observational evidence you enter the realm of metaphysics.

And this is a serious, serious philosophical problem when you deal with things like multiverses, pre-event zero, and the anthropic principle stuff.

However, once you get past the very, very early universe, you don't have to worry about these issues.

One problem with the way that cosmology is presented to the general public is that there is so much focus on the "this is *WEIRD* and *SPOOKY* stuff" that people aren't aware that most of cosmology isn't different from oceanography or planetary science, and observing the big bang isn't any different from observing the moon. We know the moon is there because we can see it. We know the big bang happened because we see that too. In some ways, we know more about the formation of the universe than we do about the formation of the moon.

 

[JDoolin]

My apologies for referring to you as James, Jonathan. I perceive your error as one of philosophy, not science - e.g., I agree with twofish. Cosmology is a conjecture founded on observation. While I agree cosmology is still largely a matter of conjecture, it is a conjecture based on observational evidence. Once you leave the realm of observational evidence you enter the realm of metaphysics.

There IS an error of philosophy here, but I don't think it is mine.

The problem is that you are doing philosophy rather than physics. You are treating isotropy and homogenity as if they were mathematical axioms when they aren't.

If homogeneity is NOT a mathematical axiom, then it should not be possible to make a mathematical argument with it as your premise.

Once you start with the premise that the universe is isotropic and homogenous, then at large distances things are going to be flying away from each other at > c, and Lorenz transformation will break down.

The issue here is that your cosmology professor actually IS using the idea of an infinite homogeneous universe as an axiom. He then uses that axiom to draw logical consequences. He then uses those logical consequences to throw out the idea of Special Relativity applied at large scales.

 

[George Jones]

I have closed this thread. There have been several pages of violations of Physics Forums Rules, which I explicitly posted earlier in this thread (post #26).