Recent content by zhermes

Yes. Temperature is a quantitative measure of a material's thermal energy. Heat is the transfer of thermal (internal) energy between materials.

I'm not familiar with any work that does this in more than order of magnitude sense. The general idea is to estimate the star formation rate as the molecular-gas infall rate - with some efficiency factor, e.g. \rm{SFR} \sim \epsilon \cdot M_{H} \cdot t_\rm{dyn}^{-1} Where \epsilon is the...

Your question is unclear.

Of course the gravity stays the same in that case---because the energy is conserved. If instead you are considering the difference between two scenarios, one with more energy and the other with less, then obviously the former will have stronger gravity. Period. If you have a neutron star's...

Yes, it does. Because pressure does contribute to the stress-energy tensor---as Ich eloquently points out. If the pressurized cylinder contains the same rest-mass of gas, it must be at a higher temperature to maintain the higher pressure. As I tried to elucidate with the 'hot rock', that...

In both general relativity and the standard model, space-time is always continuous. Thus, the standard, excepted picture is continuous. There are many indications (namely from quantum mechanics) that space-time might be quantized at the Planck-scale, as is described by theories like loop...

But we're concerned with pressure, which is related to the internal energy density.

Hi AustinJones, welcome to PhysicsForums! 1) Individual Light rays don't 'dissipate'. They can be absorbed, scattered, etc, but otherwise they stay the same (energy/momentum have to be conserved, right?) 2) A collection of light-rays can 'dissipate', in a way, by the individual 'rays' being...

Oh, damn. Thanks Chronos!

For a precise result, you would use a stellar evolution simulation to calculate the result numerically. For an approximate result, you can use an order of magnitude scaling for how long stars live---which is determined primarily by its mass. \tau \sim 10^{10} \textrm{ yrs} \left(...

A rock on a mountain top at a high temperature, does have stronger gravity than a cold rock on a mountain top. No? (Note, mountain top superfluous)

This doesn't make sense. Things don't become 'egg-shaped' when they spin. And the 'egg-shape', if spinning along the axis of symmetry, still has no quadrupole moment. About 10% (http://www.physics.drexel.edu/~bob/Term_Reports/Whitehead_hw1.pdf)

The outward nature of the expansion is (in this case) unrelated to the isotropy and homogeneity of the universe. It could be either inward or outward, and still both isotropic and homogenous. Remember that isotropic means the same in all directions (i.e. no matter which direction you look...

Sweet; thanks marcus

I made no such claim. And once again, to draw you back to Hilbert's Hotel---the entire point of that 'paradox' is establishing that there are degrees of infinite, some larger than others---and thus some which contain contain the others. At no point did I even suggest that all infinities are...