If astronauts could travel at  v = 0.956c,  we on Earth would say it takes  (4.20/0.956) = 4.39  years to reach Alpha Centauri, 4.20 light-years away. The astronauts disagree. (a) How much time passes on the astronauts' clocks?  years (b) What is the distance to Alpha Centauri as measured by the astronauts?  light-years

Suppose you decide to travel to a star 85 light-years away at a speed that tells you the distance is only 25 light-years. How much is that speed?

You are an astronomer on planet Tirth, which orbits a distant star. It has recently been accepted that Tirth is spherical in shape, though no one knows its size. One day, you learn that on the equinox your sun is directly overhead in the city of Tyene, located 450 kilometers due north of you. On the equinox, you go outside in Alectown and observe that the altitude of your sun is 85 ∘∘. What is the circumference of Tirth? Express your answer in kilometers to two significant figures.

Spacecraft 1 passes spacecraft 2 at 0.855c relative to spacecraft 2.  An astronaut on spacecraft 1 measures the length of spacecraft 2 to be 485m.  Calculate the proper length of spacecraft 2.

Your clocks and calendars are synchronized with the clocks and calendars in a star system exactly 10 ly from earth that is at rest relative to the earth. You receive a TV transmission from the star system that shows a date and time display. The date it shows is June 17, 2050. When you glance over at your own wall calendar, what date does it show?

A day on the Earth has 24 hours. How fast must a spacecraft travel so that the spacecraft clocks tick through 23 hours (on spacecraft clocks) while the earth clocks tick through 24 hours from the viewpoint of an observer on the Earth?

The remaining lifetime of the Sun in seconds is 1.5 x 10¹7 sec. Convert this value into years. 0000000000000000 PLS HELP!

For an astronaut traveling to a star 10 lightyears away at v=0.99c  and returning, spending negligible amount of time at the destination, describe the journey as the astronaut would observe it. In particular, describe what the astronaut would observe as happening on Earth during the journey

You are in a rocket moving away from Earth at one-third the speed of light relative to Earth. A friend is on Earth, and an astronaut in another rocket is moving toward Earth at one-third the speed of light (in the Earth reference frame), on a path collinear with your path. If each of you records the duration of your journey in your three respective reference frames, which of you records the proper time interval?

A space probe with a diameter of 2.50m is moving past Saturn's moon Enceladus. An observational platform on Enceladus measures the shortest length of the ellipsoidal probe to be 1.25m. How fast is the probe moving relative to the moon? a) .999c b) .995c c) .957c d) .883c e)  .866c