Gravity Disappears Universally?

[IndigoSensor]

My thoughts are going haywire right now lol

Thought provoking topic. I like it. =)

Haha, I can imagine! It's interesting. When you know a lot about one subject, you have a hard time throwing one piece of it out the window to do some interesting thought on the matter. It's because since you know so much you feel like it just wouldn't work because it effects everything else so an independent matter just isn't possible stand alone.

Like, if someone were to tell me "what would happen if electrons stopped moving". I would be like "wait, electrons can't do that, they... but...but but but!!! no! blarg! DOES NOT COMPUTE!" lol.

 

[Odyne]

Haha, I can imagine! It's interesting. When you know a lot about one subject, you have a hard time throwing one piece of it out the window to do some interesting thought on the matter. It's because since you know so much you feel like it just wouldn't work because it effects everything else so an independent matter just isn't possible stand alone.

Like, if someone were to tell me "what would happen if electrons stopped moving". I would be like "wait, electrons can't do that, they... but...but but but!!! no! blarg! DOES NOT COMPUTE!" lol.

loll!! pretty much my reaction too.

When you throw something as fundamental as gravity out the window, a lot of sciences, especially physics and astrophysics, will crumble and hold no value anymore. We'll need to redefine everything all over again. Which is an exciting challenge I find.

 

[bamf]

It isn't?

Don't we define the universe of how much mass we know exists, and how it interacts with itself?

Gravity is a force resulting from that interaction. So as long as there is mass, there should be gravity, however infinitesimal it is.

But again we define mass as the weight of matter. Which then needs gravity.

So gravity is defined by how much matter there is and how it interacts with other matter.

???

My thoughts are going haywire right now lol

Thought provoking topic. I like it. =)

Isn't mass a measurement of matter? And couldn't matter hypothetically exist without gravity, because of inertial mass?

But I honestly have no idea. I said centripetal force would fling us off the earth, when NV pointed out to me that centripetal force is what pulls things in, such as gravity. I very very well could be wrong on this one as well.

 

[TheLastMohican]

I think the earth would also stop rotating, so we'd be stuck in either an eternity of day or an eternity of night, even an eternity of a certain season. But then we would still need a sun for that to happen in the first place.

I think it would speed up slightly in its rotation. When the atmosphere dissipated (which it would do faster than anything else, being the most tenuous and least dense part of the Earth), the rest of the earth would be left with a lower moment of inertia, and would therefore spin faster.

Of course that would just barely happen, because at the same time, the earth would be crumbling and flinging off it's outer layers into space, while the inner layers would be expanding outward to release the enormous pressure. It would explode in a way, just more slowly than the sun would (since the internal pressures would not be nearly as great as the sun's, lacking the nuclear reactions and extreme heat).

Oh, also we can redefine mass and time in terms of light.
Mass: How matter interacts with light: absorbs it, reflects it, or deflects it.

There is little correlation between mass and interactions with light.

Don't we define the universe of how much mass we know exists, and how it interacts with itself?

No. We need to consider energy and the fundamental forces as well. Mass itself is not that well understood; with matter broken down into to so many different subatomic particles, and having anti-versions, and likely being a sort of illusion created by strings vibrating in 10 or more dimensions, we don't have a very clear idea of where mass even comes from. It might be possible to have matter with no mass, or mass with no matter. (Stay tuned for the Higgs Boson and other intriguing developments to come from the Hadron Accelerator.)

Also, it's pretty well established that we don't know the exact size or content of the universe. When we say "universe," we don't just mean the "visible universe," which is all we can observe and measure.

But again we define mass as the weight of matter. Which then needs gravity.

No, mass is better defined as a measure of the inertia of matter. Weight changes depending on which planet you're on, but mass does not.

 

[Ecton]

In a universe obeying generally relativity but with no gravity, there could be nothing with either energy or mass, because either would bend space-time and therefore create the effect we perceive as gravity.

Even particles with no rest mass, with kinetic energy, bend space time.

A gravity-less universe is an empty universe or a universe with no rest mass reduced to quantum foam near absolute zero (and that would answer questions about quantum gravity)

You can't have suns and planets 'fly apart' because by their very existence space time would continue to be bent. There 'flying apart' would in itself bend space time. A gravity less universe is essentially empty of most of what we can understand, instantaneously, the moment it is gravityless.

 

[TheLastMohican]

In a universe obeying generally relativity but with no gravity, there could be nothing with either energy or mass, because either would bend space-time and therefore create the effect we perceive as gravity.

The idea is to imagine what would happen if that relationship disappeared. What if mass no longer affected spacetime?

 

[enfp can be shy]

"DOES NOT COMPUTE" may turn out to be the mathematically correct answer. Essentially we set G=0, which we may not be able to do in a meaningful way, having already all the other constraints of the system.

Natural description of mathematical singularity is so appealing to reason about. Because... it's undetermined.

But don't fret, even in this case we could think about the different ways to approach G->0 near zero gravity, without ever reaching it. Hmmmm?

p.s. i realize the question is "almost" useless, but if anything at least it helps to comprehend the fundamental importance of gravity for any of our physical understanding.