New answers tagged

0

Stars orbiting black holes (I assume that's what you mean) and observed from afar will have their light doppler shifted due to (i) gravitational redshift; (ii) the relativistic doppler effect due to their orbital motion. Effect (i) becomes more important the closer a star gets to the event horizon of the black hole. The redshifted frequency is given by ...


0

Yes, they absolutely would. In general, a light-ray which passes at a minimum distance $x$ to the BH will have all of the same effects as a light-ray emitted at the same distance $x$.


2

Excited nuclei don't get that way on their own: you have to hit them with a beam. Your reference starting on page 689, refers to beams of oxygen, silicon, calcium, and nickel, with energies of several MeV per nucleon, on stationary lead targets. Pick a target, beam, beam energy, and reasonable excitation energies for the target and beam nucleus, then use ...


1

In Stephen Weinberg's well-known book "The First Three Minutes," he talks solely about Doppler shifts. A good review and analysis of the "expanding space" vs. Doppler shift question was provided by Bunn and Hogg, "The kinematic origin of the cosmological red shift," Am. J. Phys. 77 (8), 2009, pp. 688-694. They make convincing arguments that the red shift ...


0

There are two parts to understanding this: Space is expanding - we know this to be true because as distance increases, so does recessional velocity (Hubble's law). So the more space in-between, the faster it recedes. Therefore the space itself is responsible for the recessions, and thus must be expanding. There is simply so much evidence for Hubble's law, ...



Top 50 recent answers are included