# Traveling through space

1. Oct 11, 2010

### jeremyfox4392

Ok This is my first post and I wanted to first say hello to every one :) Next my knowledge of physics is self taught I am not a student or teacher just a guy that that enjoys this subject and breaking down all the complicated math to huge basic problems any one can do :) lol

Now this question I have has been bothering me lately and I can not find an answer any where I look so I hope someone can help me.

In side our solar system earth and the other planets move around the sun. I have also read that our Galaxy with everything that it contains is rotating around the cosmos (possibly the center of the universe). Now a rocket ship leaves earth for say Mars with people on it. This ship moves in a relatively straight line from point A to point B. Is this rocket ship not effected by the rotation of the Galaxy. If not not what kind of side effects would the people inside suffer upon landing?

This makes sense in my head I hope it does to someone on here :) I will Elaborate a little bit more.

the earth rotates at roughly 66660mph on its axes and around the sun at roughly 67000mph
and our galaxy rotates at 552 km/s (Speed relative to CMB rest frame Wiki).

Now in our tiny spaceship are we cutting straight through (from point A to point B) and not being effected by everything rotating around us? If so there would (in my mind) be adverse effects on the people inside the ship what would they be ?

2. Oct 11, 2010

### HallsofIvy

We measure the space ships motion relative to the earth. As long as that is true, the motion of earth and spaceship relative to the rest of the universe, and vice-versa, is not relevant.

The circumference of the earth is about 25000 miles and it rotates in 24 hours. That means its rotational speed is 25000/24 or a little more that 1000 mph. Where did you get that "66660 mph"?

The circumference of the earth's orbit is about 565200000 mi and the earth travels that distance in 365.4 days= (365.4)(24)= 8769.6 hours. The earth's speed in its orbit is about 6500 mph, not 67000.

3. Oct 11, 2010

### ghwellsjr

Any spacecraft that leaves earth to travel anywhere else in the solar system, does not travel "in a relatively straight line" but rather, it is in orbit around the sun following approximately the path of an ellipse (oval), just like every other object in the solar system that is not near another object. When the spacecraft is near another object like earth or Mars, its trajectory becomes more and more influenced by the gravitation of the closer object. Why are you concerned that the particular path that people take from earth to Mars might have some kind of side effects for the people inside and that as a result they might suffer upon landing?

And what does this all have to do with relativity?

Last edited: Oct 11, 2010
4. Oct 11, 2010

### jeremyfox4392

first I wanted to say thank you I added in another 0 by mistake :)

What all this has to do with relativity you answered clearly for me in your post :) The space ships speed is and trajectory are all relative to everything els in the solar system. Thank you I wish I thought of it before I wrote this out lol.

5. Oct 11, 2010

### Passionflower

The rocket could not travel on a straight line because spacetime is curved, but when it is not accelerating it would travel on a geodesic, the straightest possible line between two events. They would not notice anything, as they would be free falling because they travel on a geodesic. But of course as soon as the engines are working to slow down or speed up the rocket there would be an acceleration which they would feel.