View Full Version : How far from the earth would you have to be

03-09-2009, 22:12
Let's say you are Spaceman Spiff, and you were on a spaceship that left the earth.

How far away from the earth would you have to be before the earth's gravity is insufficient to keep pulling you with it, and instead you begin to see the earth recede in the distance?

Does it differ by the amount of your mass? Or is it the same irregardless of your mass? i.e. if both the moon and Spaceman Spiff were stranded, they both would see the earth recede away at the same speed?

Thanks! This is driving me crazy

03-09-2009, 22:16
your homework? ;)

03-09-2009, 22:16
Sounds like homework to me :rolleyes:

03-09-2009, 22:21
Yeaah this is homework, just take your physics book and this http://en.wikipedia.org/wiki/Newton%E2%80%99s_law_of_gravitation

Do 125 exercises, repeat , and you're done.

03-09-2009, 22:22
No this is not my homework :)

It was just driving me nuts.

Since the gravitation acceleration of you to the earth is never 0, (gravity is endless so its like .000000000000000000~1 repeating), it would be the point where some other object overtakes the earth's acceleration on you.

Would that be the sun, or would you be drawn to something like Mars first?

03-09-2009, 22:22
When you look out of your spaceship and see this huge blueish spiral, you are far enough

03-09-2009, 22:25
When you look out of your spaceship and see this huge blueish spiral, you are far enough

Not good enough, sorry..I need exact numbers :(

03-09-2009, 22:25
Lies! Everybody knows that the Earth is flat and the stars are about 6000 km away.

03-09-2009, 22:38
Not good enough, sorry..I need exact numbers :(

Exact numbers... ask this guys : www.nasa.gov

Anyway you are complicating the question since you will have to know where all planets / stars / blackholes / etc are located in the universe and their mass and radius to resolve the problem.

03-09-2009, 22:46
Well, we need numbers too, how heavy is the Earth, how heavy is your craft and how fast are you traveling...

Poorly scripted question if that's your assignment verbatim.

03-09-2009, 22:49
If we just launched surly into space the weight of the earth would be a calculable number...

03-09-2009, 22:57
If you are just looking for distance, the Suns gravity is about 28 (27.90 or something specifically) that of the Earth.

If you are looking for time from takeoff before you float you probably need to know that the Earths escape velocity is 11.2 km/s and an AU (distance between Earth and sun) is about 150 million kilometres. (149 598 000)

That should help get you started.