Which label belongs in the area marked x? radiation is x

a. must involve temperature differences between substances or objects

b. only occurs when molecules are in direct contact

c. involves the movement of fluids based on density differences

d. can occur where there is little or no matter

Why are some galaxies’ spectra blueshifted rather than redshifted? question 4 options:

The “death throes” of stars are amongst the most complex phenomena in all of astronomy, and the “corpses” of stars amongst the most energetic and exotic objects in existence. beginning at the end of the core helium fusion stage in a star’s life, describe in detail the post-main sequence development of both (a) a 1.0 solar mass star, and (b) a 25.0 solar mass star. in what significant ways do they differ? what role does each of these types of stars play in the "star-gas-star" cycle and the evolution of chemical elements in our galaxy?

An inclined plane wrapped around a metal shaft is a a. lever b. screw c. pulley d. wedge