# The Naked Scientists Forum

### Author Topic: what if gravity was stronger than we think?  (Read 1893 times)

#### jeffreyH

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##### what if gravity was stronger than we think?
« on: 30/04/2016 14:10:14 »
This may be thrown into new theories and I anticipate that. To overcome inertia we required an input of energy proportional to the mass we wish to move. Gravity appears to distribute its force throughout a body. Should this action make it easier for gravity? Could it be the case that gravity acts to change the amount of inertia of an object over very small timescales?

This post has been edited to replace the word mass with body as per pmbphy's suggestion below
« Last Edit: 01/05/2016 11:21:50 by jeffreyH »

#### PmbPhy

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##### Re: what if gravity was stronger than we think?
« Reply #1 on: 30/04/2016 20:40:20 »
Quote from: jeffreyH
This may be thrown into new theories and I anticipate that.
Why? You're not proposing a new theory. You're asking a question about current theory. In this case you're asking about what would happen if gravity was stronger. That's too vague to answer properly because I'm not sure what it is that you want to know.

Quote from: jeffreyH
To overcome inertia we required an input of energy proportional to the mass we wish to move.
For those of you who don't know why this is true, its true because the amount of work required to change a particle's velocity from rest to v is W = mv^2/2 which shows that the work is linearly proportional to m and work is the energy needed to accelerate a body from v_initial to v_final.

Quote from: jeffreyH
Gravity appears to distribute its force throughout a mass.
People use the term "mass" when they really mean "body." It's an unfortunate use of the term since mass is a property of a body and does not refer to the body itself. I suggest avoiding using the term "mass" in this way.

Quote from: jeffreyH
Should this action make it easier for gravity?
No. In what you described you're referring to inertial mass. However the force of gravity relates to gravitational mass, the strength of which is determined solely by the gravitational constant, G, which does not appear in the expression for work and therefore work is independent of the strength of gravity.

#### jeffreyH

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##### Re: what if gravity was stronger than we think?
« Reply #2 on: 01/05/2016 01:16:17 »
Quote from: jeffreyH
This may be thrown into new theories and I anticipate that.
Why? You're not proposing a new theory. You're asking a question about current theory. In this case you're asking about what would happen if gravity was stronger. That's too vague to answer properly because I'm not sure what it is that you want to know.

Quote from: jeffreyH
To overcome inertia we required an input of energy proportional to the mass we wish to move.
For those of you who don't know why this is true, its true because the amount of work required to change a particle's velocity from rest to v is W = mv^2/2 which shows that the work is linearly proportional to m and work is the energy needed to accelerate a body from v_initial to v_final.

Quote from: jeffreyH
Gravity appears to distribute its force throughout a mass.
People use the term "mass" when they really mean "body." It's an unfortunate use of the term since mass is a property of a body and does not refer to the body itself. I suggest avoiding using the term "mass" in this way.

Quote from: jeffreyH
Should this action make it easier for gravity?
No. In what you described you're referring to inertial mass. However the force of gravity relates to gravitational mass, the strength of which is determined solely by the gravitational constant, G, which does not appear in the expression for work and therefore work is independent of the strength of gravity.

That has given me something to think about. I'm glad you are back. You keep me from veering off course.

#### Colin2B

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##### Re: what if gravity was stronger than we think?
« Reply #3 on: 01/05/2016 10:08:23 »
This may be thrown into new theories and I anticipate that.
No, as PmbPhy says it is a valid question about gravity and inertia.
However, silly posts will be moved and I've done that with one!!

#### jeffreyH

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##### Re: what if gravity was stronger than we think?
« Reply #4 on: 02/05/2016 14:45:42 »
In Newtonian terms we can state the following.

F = ma, Fg = mg

a = dv/dt, g = GM/r^2

dv/dt = GM/r^2

dv = GM dt dr^-2

So that for gravity the relationship between time and displacement is dependant upon the strength of the gravitational field. Whereas force (F=ma) depends upon the energy input into the system. If we were to mimic the acceleration due to gravity in the absence of a gravitational field of significant strength how would the graphs of the two situations compare?

#### alancalverd

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##### Re: what if gravity was stronger than we think?
« Reply #5 on: 02/05/2016 17:31:43 »
Gravity cannot be stronger than we think, because we only think what we observe. It would indeed be surprising if the real value of g was 34 rather than 32 ft/sec^2, but the laws of physics wouldn't change - after all, we have experienced all values of from -200 to + 200 from time to time and explored up to +/-60000  experimentally.

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#### evan_au

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##### Re: what if gravity was stronger than we think?
« Reply #6 on: 03/05/2016 03:51:36 »
Quote from: JeffreyH
If we were to mimic the acceleration due to gravity in the absence of a gravitational field of significant strength how would the graphs of the two situations compare?
• Gravity changes very slightly as you move up away from the Earth (about 90% of Earth's surface gravity at the height of the ISS). There is also some apparent "rotational" acceleration due to the rotation of the Earth, resulting in a Foucault pendulum changing direction through the day.
• If you were to mimic gravity by having a rocket accelerating in a straight line with an acceleration of g m/s2, then you would feel the same acceleration whether you moved "up" or "down"*. A Foucault pendulum would not change direction.
• If you were to mimic gravity by having a rotating spaceship (such as in "The Martian"), then you would feel the acceleration change rapidly as you moved "up" or "down". A Foucault pendulum would change direction over a period of a minute, rather than a day.

The Einstein equivalence principle says that you can't really tell the difference between the gravity of the Earth, and the acceleration due to a rocket - provided you are in a small laboratory, so you can't move "up" and "down".

*Of course, chemical rockets are a partially contained explosion, so they rattle your eyeballs; I don't think you could mistake a chemical rocket for standing on the surface of the Earth. It might be possible with a large ion drive.

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#### McQueen

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##### Re: what if gravity was stronger than we think?
« Reply #7 on: 03/05/2016 04:28:52 »
Could it be the case that gravity acts to change the amount of inertia of an object over very small timescales?

If two objects  of different materials and densities are held (in a vacuum) at a certain height and then dropped, they will both fall at the same rate and reach the ground at the same time. This is because while the gravity of the earth is attracting both objects towards the earth with a force proportional to their density, the gravity from other objects in space is attracting both objects  away from the earth with an equal force also dependent on their density. So while the less dense object will experience a lesser gravitational force away from the earth, the denser object will experience a greater gravitation force away from the earth. The net result is that both forces cancel out and the objects fall to the earth at the same time.  (This is a part of the Gestalt Aether Theory.)

#### jeffreyH

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##### Re: what if gravity was stronger than we think?
« Reply #8 on: 03/05/2016 07:57:40 »
Unfortunately for your theory, McQueen, there are just as many objects in space that will draw objects towards the earth as away. So the effects cancel. Unless you are suggesting that gravity can be shielded by the earth. You aren't suggesting THAT are you???

#### McQueen

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##### Re: what if gravity was stronger than we think?
« Reply #9 on: 03/05/2016 10:09:08 »
Unfortunately for your theory, McQueen, there are just as many objects in space that will draw objects towards the earth as away. So the effects cancel. Unless you are suggesting that gravity can be shielded by the earth. You aren't suggesting THAT are you???

I am sincerely sorry that all the new theories you are posting has left you a little unfocused, this is exactly what I had stated. A dense object will be pulled away from earth with a stronger force than a  less dense object and the same would hold true, only in the opposite direction, for the earths gravitational field. Thus the two forces cancel out and both objects fall to earth at the same time.

#### jeffreyH

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##### Re: what if gravity was stronger than we think?
« Reply #10 on: 03/05/2016 16:08:03 »
I have never ever posted a theory because I don't have one. Show me where I did so and I will apologise immediately.

#### McQueen

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##### Re: what if gravity was stronger than we think?
« Reply #11 on: 03/05/2016 16:24:23 »
I have never ever posted a theory because I don't have one. Show me where I did so and I will apologise immediately.