Could Gravity Ever Be Negative?

[caters]

Now, I know that it is theoretically possible for negative mass to exist and for negative energy to exist. But any gravity would act on all objects and all energy, no matter if that mass and energy is positive or negative. So negative gravity would for example, pull a person upwards. Now yes, I realize that there already is a force that comes from the interaction of 2 masses that pulls everything away from 1 mass and towards the other mass. That is the tidal force. As an example, if a miniature black hole were in the core of a moon and the moon was somehow stable, as the moon's orbit gets closer to the planet, the tidal forces would become so strong that it overcomes the planet's gravity and everything gets pulled towards the moon.

That is basically like gravity being negative except that it is normally extremely small. And it isn't a true gravity but rather the force that arises from 2 gravitational fields interacting.

A true negative gravity would require just 1 source of gravity to achieve the same effects as the tidal force, pulling everything away from a mass. Negative gravity would mean that launching into space would require no more energy than the gravitational potential energy of the spacecraft . Of course, if gravity were negative the spacecraft couldn't be formed in the first place and any astronomical object would immediately be blown apart if there were negative gravity but is it at least hypothetically possible to have gravity be negative? Could dark energy be this negative gravity acting on the entire universe?

 

[jbriggs444]

Now, I know that it is theoretically possible for negative mass to exist and for negative energy to exist.

Reference, please.

 

[mathnerd21]

It really just depends on your reference point and how you look at it. On the other hand, if you have gravity going in the opposite direction it is supposed to, theoretically, you would just float up to space.

 

[sophiecentaur]

Reference, please.

And a small cup full too, if you could manage it. (Keep the lid on tight, though)

 

[Khashishi]

A white hole is a theoretical object that pushes things away from it. We haven't found any white holes or any objects with negative mass, so they might not exist.

Edit: A theoretical white hole still has positive mass and still appears to attract objects outside the white hole horizon, I think. But inside the horizon, everything is pushed to the outside.

I suppose you could also consider a theoretical negative mass object, but we haven't found any evidence for those.

 

[phinds]

I am a physicist and I don't even believe that mass increases as its speed approaches light speed

Well, I don't know. Right now, I AM moving at almost the speed of light (relative to a particle in the CERN accelerator) and I DO feel more massive. Of course, it could have been that heavy lunch I ate.

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

I know that it is theoretically possible for negative mass to exist and for negative energy to exist.

Please give a reference, as you have already been asked to do. Since the thread is closed for moderation, please PM me with the reference. Once we have it, the moderators will evaluate it and see if it is acceptable as a basis for a PF thread discussion.

 

[PeterDonis]

A theoretical white hole still has positive mass and still appears to attract objects outside the white hole horizon, I think.

This is correct.

But inside the horizon, everything is pushed to the outside.

This is not correct. Gravity is still attractive inside the white hole's horizon. But the horizon is moving inward at the speed of light, so even with attractive gravity, nothing can fall inward fast enough to catch the horizon, and things that are inside the horizon can't decelerate inward fast enough to stay inside it.