Gravity -- Does gravity depends on atmosphere?

In summary, gravity depends on both mass and distance from the source. The greater the mass of an object, the greater its gravitational force. However, if the density of the object changes, the gravitational force may also change. Therefore, while Uranus is bigger than Earth and has a greater mass, its density is lower, resulting in a similar surface gravity to that of Earth.
  • #1
san D
Does gravity depends on atmosphere
 
Astronomy news on Phys.org
  • #3
Then on what factors it depends...??
 
  • #4
Mass and mass only.

(Now gravitational force, on the other hand, depends on mass and distance)
 
  • #5
The answer could be just as well 'yes'. It all depends on what you actually mean.

Why won't you try being a bit more descriptive? What exactly is it you want to find?
 
  • #6
My answer would be no, it's the other way around. The atmosphere depends on gravity. sanD, you don't seem to be putting much (ANY actually) research into finding this out on your own. This is not one of those forums where you ask trivial questions and someone tells you the answer, it's a forum where we try to help people figure out how to get answers on their own. The first thing to do on your own for a question like this is type the question into Google and see what pops up. If that doesn't quite give you want you want, come here with a more focused question.
 
  • #7
A body on a planetary surface will experience a different gravitational acceleration depending on what radius they are from the gravitational source's mass centre (core). This body will also likely be under atmospheric pressure, with a summed force in the same direction as the gravitational acceleration. Does this atmospheric force compound the gravitational force or will the atmospheric force have a net of zero?
 
  • #8
I'm going to take a guess at what the OP may be thinking about... which may be related to the different meanings of mass vs. weight...

When you "weigh" something in the conventional sense, in open air, you're actually not "weighing it" as much as you are determining how much "heavier" it is than air (or comparing the differences between the force on the atmosphere due to gravity and the force on the object due to gravity). It's a little easier to see what I'm getting at if you take the example of if we take a scale of infinite mass to the bottom of the ocean. If you placed a rock on a scale, you don't get the same "weight" as you do on land, even though gravity is (essentially) the same.

Like i said, I am just taking a guess of what the op may have had in mind when they asked the question...
 
  • #9
san D said:
Does gravity depends on atmosphere

no, but the opposite is true when it comes to a planet having an atmosphere.
Without significant mass, the planetary body won't have a strong enough gravity to retain an atmosphere
 
  • #10
davenn said:
no, but the opposite is true when it comes to a planet having an atmosphere.
Without significant mass, the planetary body won't have a strong enough gravity to retain an atmosphere
Read post #6. You're a day late :smile:
 
  • Like
Likes davenn
  • #11
phinds said:
Read post #6. You're a day late :)

LOL didn't even see that in your comment as I read through the thread ...
well at least I gave you good backup ;)

Dave
 
  • #12
Perhaps he wants to know if the effect of gravity feels stronger with greater atmospheric pressure. I'm not sure it works like that, I think a strong gravitational pull would crush you into the ground whereas a high atmospheric pressure would be more like an implosion. Or am I wrong?
 
  • #13
JLowe said:
Perhaps he wants to know if the effect of gravity feels stronger with greater atmospheric pressure. I'm not sure it works like that, I think a strong gravitational pull would crush you into the ground whereas a high atmospheric pressure would be more like an implosion. Or am I wrong?
You are right. Well, a crushing rather than an implosion but I see that you were thinking in the right direction.

In any case, it gets boring trying to figure out what some random posted comes and asks and then goes away and you never hear from them again. Maybe he'll come back to say what he really wants to know but don't hold your breath.
 
  • #14
Confused about this the gravity changes when we move out of the surface of Earth at the same time we can observe atmosphere also changes that's why i confused
 
  • #15
san D said:
Confused about this the gravity changes when we move out of the surface of Earth at the same time we can observe atmosphere also changes that's why i confused
Did you think the Earth's atmosphere just goes on forever into the universe? Of course it tapers off as you get higher, as does the force of gravity. What is confusing about that?
 
  • #16
Thank you
 
Last edited by a moderator:
  • #17
I will agree that gravity depends on mass only ...then the gravity of uranus must be greater than Earth's gravity because uranus is bigger than Earth but it's not why...?
 
Last edited by a moderator:
  • #18
san D said:
I will agree that gravity depends on mass only ...then the gravity of uranus must be greater than Earth's gravity bcz uranus is bigger than Earth but it's not why...?

That is probably surface gravity you're thinking about, which can be greater for a less massive object because the surface is farther away from the center of gravity in the massive object.
 
  • Like
Likes OmCheeto
  • #19
san D said:
I will agree that gravity depends on mass only ...then the gravity of uranus must be greater than Earth's gravity bcz uranus is bigger than Earth but it's not why...?
Gravity doesn't depend on mass only, but also on distance from the source. The gravitational force equation shows that clearly:
$$F=G\frac{Mm}{r^2}$$
(G is the only constant here)
Dividing both sides by m(test particle mass) you get the gravitational acceleration:
$$a=G\frac{M}{r^2}$$
As long as the two objects you're comparing have the same density, the larger an object is(greater r), the greater its gravity because as you increase radius the mass increases faster than the square of radius:
$$M=V\rho$$
where ρ is the density and V is the volume of a sphere
$$V=4/3 \pi r^3$$
Combining the above you get $$a=4/3G\pi r \rho$$

If you'll make one of the objects less dense, its surface gravity will fall down. As long as you make the density fall by the same fraction as you increase the radius, the surface gravity will stay the same.

With Uranus, its density is 4.3 times lower than Earth's while its radius is 4 times larger.
 
  • #20
Bandersnatch said:
Gravity doesn't depend on mass only, but also on distance from the source. The gravitational force equation shows that clearly:
As I said: gravity depends only on mass. The gravitational force experienced at some point depends additionally on its distance from the mass. A fine distinction perhaps, but a distinction nonetheless.
 
  • #21
DaveC426913 said:
As I said: gravity depends only on mass. The gravitational force experienced at some point depends additionally on its distance from the mass. A fine distinction perhaps, but a distinction nonetheless.
Could you clarify what you mean by gravity?
 
  • #22
JLowe said:
That is probably surface gravity you're thinking about, which can be greater for a less massive object because the surface is farther away from the center of gravity in the massive object.

Bandersnatch said:
The answer could be just as well 'yes'. It all depends on what you actually mean.
Why won't you try being a bit more descriptive? What exactly is it you want to find?

Bandersnatch said:
Could you clarify what you mean by gravity?

Fun thread.
I was thinking of Bandersnatch's alternate interpretation of the problem from the get go.
Just did the math.
It was very fun.

pf.2015.01.29.1152.gravity.png


Wait. What was the original question?

san D said:
Does gravity depends on atmosphere

Yes! As atmospheres have mass.

Duh.
 
  • #23
Bandersnatch said:
Could you clarify what you mean by gravity?
Gravity is an intrinsic property of anything with mass.
Gravitational force is an effect of gravity, modified by distance.

But now you're causing me to doubt my convictions... :s
 
  • #24
DaveC426913 said:
But now you're causing me to doubt my convictions... :s
With the caveat that you've just made me doubt mine...

How would that definition work? Isn't it just synonymous with mass?
 
  • #25
Bandersnatch said:
... Isn't it just synonymous with mass?

Noooooo! Don't say "MASS"! It'll attract those stress-energy-tensor fellows, with their "momentum warps space too" mumbo jumbo...
And then my head will explode, again.
 
  • Like
Likes phinds
  • #26
I got clear idea frnz gravity depends on density of the object Uranus is hav less density than earth
 
  • #27
Earth's gravity also varies with density w.r.t oceans,mountains etc..
 
  • #28
san D said:
I got clear idea frnz gravity depends on density of the object Uranus is hav less density than earth

Not entirely. The density of the Earth could change but it would have the exact same gravity as long as it's mass stayed the same.

It's better to discuss gravitational force at certain points, because what would change is the distance between the center and the surface.
 
  • #29
JLowe said:
Not entirely. The density of the Earth could change but it would have the exact same gravity as long as it's mass stayed the same.
This is only correct when talking about gravity(force or field) far away from the source. This whole discussion is about surface gravity, even though that might have not been clear when it started. For surface gravity that statement doesn't hold as you can't change density and keep mass constant without changing radius, so let's not confuse the OP needlessly.

OmCheeto said:
Noooooo! Don't say "MASS"! It'll attract those stress-energy-tensor fellows, with their "momentum warps space too" mumbo jumbo...
And then my head will explode, again.
Oh, you know what I meant, Om. We're all simple people here, talking about ye olde Newtonian ideas and none of that GR woo-woo.
 
  • Like
Likes OmCheeto
  • #30
Bandersnatch said:
This is only correct when talking about gravity(force or field) far away from the source. This whole discussion is about surface gravity, even though that might have not been clear when it started. For surface gravity that statement doesn't hold as you can't change density and keep mass constant without changing radius, so let's not confuse the OP needlessly.
He commented on the strength of Earth's gravity varying at different places. This is not really a density issue but a distance from the center issue. Otherwise, the strength of gravity would be weaker if you were in a boat then on land at sea level.

But yes I completely understand what you're saying.
 

1. How does gravity work in space?

Gravity still exists in space, but it is not as strong as on Earth due to the lack of atmosphere and other factors. Objects in space are still attracted to each other, but they may appear to float because they are constantly falling towards each other at the same rate.

2. Does gravity depend on the atmosphere?

Yes, gravity is affected by the atmosphere. The more mass an object has, the stronger its gravitational pull will be. The Earth's atmosphere also plays a role in the strength of gravity, as it helps to keep objects on the surface.

3. Can gravity be manipulated or controlled?

No, gravity cannot be manipulated or controlled. It is a fundamental force of nature that cannot be changed or turned off. However, the effects of gravity can be counteracted through the use of technology, such as rockets and spacecraft.

4. How does gravity affect the tides on Earth?

Gravity plays a major role in creating tides on Earth. The gravitational pull of the moon and sun on the Earth's oceans causes the water to bulge, creating high and low tides. The Earth's rotation also plays a role in the tides, as it creates a centrifugal force that counteracts the gravitational pull.

5. Can gravity exist without mass?

No, gravity cannot exist without mass. According to Einstein's theory of general relativity, mass and energy are equivalent, and both are necessary for gravity to exist. Without mass, there would be no gravitational pull between objects.

Similar threads

Replies
0
Views
282
  • Astronomy and Astrophysics
Replies
1
Views
804
  • Astronomy and Astrophysics
Replies
10
Views
339
Replies
3
Views
805
  • Astronomy and Astrophysics
Replies
4
Views
1K
Replies
2
Views
779
  • Astronomy and Astrophysics
Replies
14
Views
1K
  • Astronomy and Astrophysics
Replies
9
Views
1K
  • Astronomy and Astrophysics
Replies
2
Views
2K
  • Astronomy and Astrophysics
Replies
9
Views
1K
Back
Top