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Author Topic: How much mass is required for gravity?  (Read 9710 times)

@Linda_Khanyi

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How much mass is required for gravity?
« on: 05/04/2011 09:30:02 »
@Linda_Khanyi asked the Naked Scientists:
   
How much must an object weigh in order for it to have gravitational force?

What do you think?
« Last Edit: 05/04/2011 09:30:02 by _system »


 

Offline burning

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How much mass is required for gravity?
« Reply #1 on: 05/04/2011 14:46:53 »
Well under our current understanding any object with non-zero mass will exert a gravitational force.  The problem is that gravity is a very weak force, so it is very difficult to measure the force until you have a relatively large mass.
 

Offline Bill S

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How much mass is required for gravity?
« Reply #2 on: 05/04/2011 15:58:52 »
Hi, Linda.

I guess you already have the answer to your question, but here are a few thoughts from an amateur that may open up further discussion.

An object does not "weigh" anything unless it is influenced by the gravity of another (usually larger) object. 

More than one object is needed before gravity can be measured, unless there is some way of measuring the warping of spacetime without involving a second object.  Not including the measuring aparatus as the second object, of course.

If we are talking about gravitational attraction between two very small objects, the masses required for detection will depend on the sensitivity of the measuring instrument.  Having said that, although the masses of the objects may be too small for us to be able to detect gravitational interaction between them, that should not be taken to indicate that no such interaction exists.

If gravity was responsible for clumping in the early Universe, it must have started with very small particles. 
 

Offline syhprum

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How much mass is required for gravity?
« Reply #3 on: 05/04/2011 16:00:18 »
The amount of gravity you would experience would depend on which planet you landed on.
 
 

Offline yor_on

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How much mass is required for gravity?
« Reply #4 on: 06/04/2011 03:06:13 »
Linda, no object have a 'gravitational force' as such. What matter do is to distort the 'space' around it, but there is no 'force' involved in that. It's better to think of it as a ever changing 'topology' in three dimensions and time, as everything moves relative everything else.

Light bends to gravity and light has no mass at all. Under some circumstances it may even be possible for light to distort 'SpaceTime'  so much that it will 'attract'. As long as we don't have any proof for 'gravity' being 'particles' the idea of it as a 'force' seems misplaced to me. Quantum mechanics will work without gravity as 'force/particles' although they won't make everything into 'small scale interactions' with identifiable 'quanta' then.

Everything we use are 'tools' in a sense, if we can find better tools we will use them, but so far the best 'tool' for describing gravity is GR, not QM.
 

Offline Pritiblond

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How much mass is required for gravity?
« Reply #5 on: 06/04/2011 17:01:16 »
Better to ask "how much mass must an object have to gravitationally infuence another body".  Modern physics explain elementary particle using three quantities:  mass, spin, and charge.  None of these are really understood; they are only described by their physical effects.  What give rise to mass is totally unknown.  Some believe that the hypothetical "Higgs Field" may be responsible for mass. The giant accelerator in Cern is hoped to expose it.  Gravity is just as mysterious.  The warping of the space-time continuum is a mathematical way of describing gravity, but it is not truly comprehendible by anyone, including Einstein.  Perhaps there is a "particle" so small that it is unaffected by gravity (e.g., a string in string theory), but no one knows.
 

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How much mass is required for gravity?
« Reply #5 on: 06/04/2011 17:01:16 »

 

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