Final answer:
An astronaut moving at speeds close to the speed of light relative to Earth would experience time dilation and Lorentz contraction but would not notice changes in his time or space dimensions. Black holes can explain the luminous nature of quasars due to the energy released when material accelerates and falls into them, and though unlikely, the Milky Way could become as luminous as a quasar if its central black hole starts actively feeding on material.
Step-by-step explanation:
When considering the effects of traveling at speeds close to the speed of light, a field known as relativity explains some non-intuitive phenomena that astronauts would experience. If an astronaut is moving relative to Earth at a significant fraction of the speed of light, time dilation occurs due to the principles outlined by Einstein's theory of special relativity.
- (a) The astronaut does not observe the rate of his clocks to have slowed. To him, time passes normally.
- (b) Observing Earth-bound clocks, the astronaut would see that they are moving faster than his own clocks.
- (c) The astronaut's ship would not appear shortened to him, but an Earth-bound observer would see it as shortened in the direction of motion.
- (d) The distance between stars lying along his line of motion would also appear shorter to the astronaut - this is known as the Lorentz contraction.
- (e) He and an Earth-bound observer would not agree on his velocity relative to Earth due to relativistic effects on their measurements.
Discussing black holes, they are known to be regions of spacetime where gravity is so strong that nothing, not even light, can escape from it. The intense gravitational pull of a black hole can, under certain conditions, accelerate material around it to high speeds, causing the release of vast amounts of energy, observable as quasars. Quasars are among the most luminous objects in the universe because of the supermassive black hole at their center consuming surrounding material. It is this accretion of matter that turns potential energy into other forms of energy, such as light, making quasars exceptionally bright.
The Milky Way galaxy contains a supermassive black hole at its center but currently does not display the extreme characteristics of a quasar. However, if our galaxy were to start actively feeding on a significant amount of material at its center, it could potentially become an active galaxy. As for matching the luminosity of a quasar, it is theoretically possible, but such events are rare and would likely be temporary.