8. Astronomers have found, on a Universal scale, that spacetime is presently stretching at the rate of about 70 km per second for any pair of points separated by 1 mpc. Assuming this rate has been constant, the age of the Universe can be simply estimated by
a. dividing 70 km/sec by 1Mpc
b. dividing 1 Mpc by 70 km/sec
c. multiplying 70 km/sec by the SOlar Systems age
d. adding the Sun's age to the ratio of 1 Mpc to 70 km/sec
9. According to the density-wave hypothesis, a pinwheel-shaped family of waves of high pressure is traveling through our Galay and
a. removing matter located between the spiral arms
b. triggering star formation
c. propagating mainly in the Galaxy's halo
d. causing spiral arms to unwind
10. According to the Special Theory of Relativity, it is impossible to accelerate a solid object to "c", the speed of light. This is because, as the objct's speed approaches "c":
a. its size approaches zero
b. the amount of energy needed to accelerate it becomes infinite
c. its mass becomes infinite
d. its length becomes infinite
11. The redshift in the spectrum of a distant galaxy is primarily due to
a. the galaxy's intense gravity
b. the galaxy's extreme velocity relative to Earth
c. the expansion of the Universe's spacetime
d. the "tiring" of light as the Universe ages
12. A typical stellar spectrum (like the Sun's) consists of
a. a continuous spectrum only
b. emission and absorption lines
c. emission lines only
d. a continuous spectrum with absorption lines
13. A simple result of General Relativity is that light observed to have cosmological redshift z was emitted when things were 1 + z times closer together than at the present time. Thus, if a galaxy's spectrum shows a redshift of 3, we know that, compared to today, that galaxy was _____ times closer to us, and the original wavelength of its light was ____ by the same factor as it traveled to us.
a. 2... shortened
b. 4... shortened
c. 2... lengthened
d. 4... lengthened