Someone in Earth's rest frame says that a spaceship's trip between two planets took 10.0 y, while an astronaut on the space ship says that the trip took 6.27 y. Find the speed of the spaceship in terms of the speed of light.
A) 0.779c
B) 0.687c
C) 0.975c
D) 0.384c
Question 2
In Ptolemy's theory, retrograde planetary motion is explained as
A) the backward part of the planet's loop-the-loop orbits around Earth.
B) due to the back-and-forth or oscillatory motion that planets make as they move along their circular orbits around Earth.
C) due to the natural wandering of the celestial sphere of background stars.
D) a result of Earth's motion: as Earth passes another planet, that planet appears to move backward as seen against the background stars.
E) Actually he didn't have an explanation for this.
The greenhouse effect: heat trapping by earth's atmosphere.
The Inner Planets: A Comparison
The Oceans of Earth
Formation of the Early Earth
Earth 200 Million Years Ago
Earth Present