Recent content by alantheastronomer

From the observed intensity of the microwave background radiation, you can approximate the number density of hydrogen atoms that produced it...

Oh well THAT clears things up! The paper you referenced is arguing that the dynamics needed to explain the observed properties of the collision, aren't statistically compatible with a universe with large scale structure determined by dark matter. They're saying that the probability is too low...

Peebles determined the dark matter to baryonic matter ratio to be 5:1 based on acoustic oscillations in the cosmic microwave background radiation for which he won a Nobel prize. Only after the recombination of electrons with protons to produce neutral hydrogen was this radiation able to be...

I was in the process of trying to develop such a model when I realized that redshift is not time independent and would also be affected by any type of time variation; I had erroneously thought that the light curves and velocity dispersions would diverge at larger redshifts but I see that's not...

I thought I was...I'm attempting to describe a model where proper time varies as a function of redshift. I think I see...like attributing it to a variation in distance or curvature? The hypothetical variation of cluster velocity dispersion with redshift that I posited, which admittedly was...

Just affirming that it is... You can compare observations of clusters of galaxies at different redshifts and see if there are systematic trends over and above what could be accounted for by the Hubble relation, though admittedly any effect I might attribute to an increase in the time interval...

I'm not sure I understand...these are observations made from Earth! How can you choose to observe from any other location? If you mean hypothetically, then if the universe is isotropic, the redshift you're measuring would be different which would account for your result, but if you chose to...

Yes, but this would be an effect that would be evident even after redshift is taken into account. Something more speculative and the result more uncertain, would be the effect on local thermodynamics and how that would impact star formation, structure and evolution. The strength of the...

What I mean by "there is none"... is that we're not making a coordinate transformation in the situation the op is positing. Well, I don't want to get into areas that are too speculative, but if the expansion of space were to cause clocks to tick slower with increasing distance, that would...

That's a very thoughtful and insightful question...you've noticed that space and time are connected and so if space is expanding doesn't that affect time somehow? What you are thinking of is the spacetime interval, and the way they're connected is that the interval is invariant - unchanging -...

@Filip Larsen has provided an excellent reference in post #14...I highly recommend it!

Interesting idea to 'backtrace' the origin of the elements from the Earth to their source. Unfortunately on the Earth there are too many geologic processes for a 'pristine' example to have survived, but I remember reading about a study done using the abundances of radioactive Al 26, and it's...

Phase space, not physical space...

Have you tried Wikipedia under "star formation" ?

Why does mass "curve" spacetime?...I don't know either!