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Physics/Minimum Graviational Force/Influence


QUESTION: Is there a minimum gravitational Force/Influence?

For example:
If two objects of the smallest amount of rest or relativistic mass were separated by some extremely large distance ... does the gravitational force/influence eventually reach a cut off minimum level? ... ie go to actually ZERO, not just very tiny ... or does it have a truly infinite range , and can be arbitrarily small?

ANSWER: No measurement or experiment has concluded that it does go to zero so far.  It's not like radioactive decay, where eventually the last radioactive nucleus will decay, it's a force and spread through spacetime.  As far as we know, it's always there.

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QUESTION: Thanks Steve,
If it does have no minimum , and can be arbitrarily small ... Then I wonder ... Wouldn't any object of even the smallest mass create a black hole type effect at some large enough distance from it?

For example:
If the light redshifts as it climbs out of the gravitational slope , moving away from , or against the force/influence of gravity ... the Light photon no matter how energetic it was to start with ... is a finite value ... and over a infinite distance even a arbitrarily small/tiny gravitational force/influence would still be continuing to red shift the light ... it might take extremely long distances for very small masses ... but eventually it would happen ... only other stronger gravitational influences blue shifting the light would prevent the light from eventually being lost.

ANSWER: No, its reduction in strength over distance accounts for its behavior just fine.  And no, you need to have a certain mass density to create a black hole.  That's borne out by the mathematics.

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QUESTION: Thanks again Steve... :)

But I think I'm missing something about your last answer about the required mass density. It confuses me a bit.

I can see how a minimum mass density would be needed for it to happen within a certain distance of the originating mass.

But I don't understand why a smaller mass density would no longer be able to red shift light that is climbing up and out of the gravitational incline? ... it seems to me that it would just take a longer distance... no matter how small the originating mass.

For example:
There is still a gravitational incline light has to climb out of as it leave a star ... even one the size of our sun ... as light climbs out of that gravitational incline it red shifts ... Although the gravity from our sun is weaker by the distance of an object 1 light year away ... as long as gravity as no minimum ... then there is still a gravitational incline that the light would still have to climb out of ... even 1 light year away or 10 or a billion or infinity ... which should still cause a red shift ... even if the amount of red shift per light year continues to reduce as the distance continues to increase ... with no minimum gravity ... it would seem to be only a question of how far it takes to red shift that light into the back ground ... and thus effectively loosing the light completely.

Yes, you're missing something.  There will be a redshift, but the gravitational force decreases in proportion to 1/r^2.  This is the danger in thinking about physics but being unwilling to do the actual science and mathematics behind it, it leads to mistaken intuitive conclusions that don't match up with the science.  Your third statement is correct, but the decrease in gravitational detraction (which is tiny, by the way) from the energy of the photon is faster than the escape of the photon.  The energy will always decrease, but the gravitational force will always decrease faster.  

In short, you need to do the math and the physics.  The energy loss is linear, the gravitational decrease is quadratic.  Case closed.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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