# Earth's gravitation question

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1. Nov 30, 2014

### gugicas

If we travel 100 km vertically from the surface of the earth, will we no longer be pulled by earths gravity and float into space? Same question as above yet with 1000 km. How far up vertically do we have to go to escape earths pull and how wide/long is the earths gravitational influence. Does an object stop being affected by earths gravity after it crosses the karman line if its mass is to small.
Im sorry for so much questions but if you could answer them all id be eternally grateful.

2. Nov 30, 2014

### DaveC426913

What do you think? And why?

Here's a starter: What keeps the Moon going around Earth every month?

Question: what is a karman line? I am not familiar with this term.

3. Nov 30, 2014

### jerromyjon

Another hurdle to strictly defining the boundary to space is the dynamic nature of Earth's atmosphere. For example, at an altitude of 1,000 km (620 mi), the atmosphere's density can vary by a factor of five, depending on the time of day, time of year, AP magnetic index, and recent solar flux.[citation needed]

The FAI uses the Kármán line to define the boundary between aeronautics and astronautics:[7]

4. Nov 30, 2014

### Danger

Technically, gravity is infinite. You feel gravity from every single thing in the "observable" universe. You'll certainly never notice almost all of it, but it's there. Since it propagates at light speed, anything beyond "observable" won't yet be felt. (But someday... brace yourself. :D)

5. Nov 30, 2014

### phinds

I think it would have been more helpful to the OP if you had waited for him to answer Dave's question, and thereby think about the issue himself, rather than spoon feeding him the answer yourself.

6. Nov 30, 2014

### Danger

I deliberately avoided that by making no mention of what constitutes a "gravitational well" which is what the question was about. Mine was a hint, not an answer.

7. Nov 30, 2014

### davenn

That's irrelevant when just dealing with the effects of gravity

Lets wait for the OP to answer DaveC's questions

8. Dec 1, 2014

### gugicas

Sorry for the late reply i posted this late at night. About
that question i think if you travel a 100 km up or even a 1000 km up you would fall back to earth since you are still in its hill sphere and still in under its dominant gravitational influence. But a teacher of mine said that if we travel a 100 km up(person only no spaceship) that we would float into space since earths gravity only affects objects with such a small mass under a 100 km radius.

9. Dec 1, 2014

### davenn

hi quqicas

OK now answer/comment on the second sentence in DaveC's post that you quoted

I don't think you worded that quite right ;)
try again

10. Dec 1, 2014

### gugicas

The Kármán line is the boundary between earths atmosphere and outer space. It lies at 100km(62mi) above sea level
Sorry for that xD. A professor at my highschool said:"If a person goes 100 km above sea level, he will float off into space because earths gravity only affects things with such a small weight up until 100 km line(Karman line). When he crosses that line he will float off into space because he wouldnt be affected by earths gravity". Edit: Forgot the apostrophe.

11. Dec 1, 2014

### davenn

The Karman has nothing to do with gravity and floating off into space
its to do with the thickness/density of the atmosphere its ability to be able to support aerodynamic lift

so lets get back to gravity

again I ask you to .......
cheers
Dave

12. Dec 1, 2014

### gugicas

The moon orbits around the earth because of earths gravity.

13. Dec 1, 2014

### phinds

But you just said that anything over 100km up would float off ... do you think the moon is closer than 100km?

14. Dec 1, 2014

### davenn

yes that's correct ... well partly ... the moon has gravity as well, so its a mutual gravitational attraction between the 2 of them

so maybe now you are starting to see the problems with your initial comments ;)

15. Dec 1, 2014

### A.T.

Have you even tried a web search for "earth gravity", before posting? The first hit is this:
http://en.wikipedia.org/wiki/Gravity_of_Earth

With this nice graph:

16. Dec 1, 2014

### gugicas

Well sorry for pestering you guys, but thanks for these answers. I got it now.

17. Dec 1, 2014

### phinds

Your questions were not pestering. That's what this forum is here for, to clear up this kind of misunderstanding.

18. Dec 1, 2014

### A.T.

Good. Then explain it to your teacher, if he/she really said this stuff.