The Center of the Earth and Black holes and Gravity

[PeterDonis]

Where would the effect of gravity be located?

An atom is not a single object--it has a nucleus and electrons. The nucleus and each electron all, in principle, are sources of gravity. Note that we are imagining the atom as like a miniature solar system here--in other words, we are ignoring quantum effects, which for a real atom are much, much larger than gravity. A better example might be the actual solar system: where is the gravity of the solar system located? There isn't a single source of gravity; the Sun is the biggest, but not the only one.

Would the effect of gravity be relevant to open spaces added up equally

I'm not sure what this means.

is there a particle or object responsible for it?

Anything that has mass or energy is a source of gravity. Of course, it takes a lot of mass or energy for the source to be significant.

 

[Firedog89]

Anything that has mass or energy is a source of gravity. Of course, it takes a lot of mass or energy for the source to be significant.

An atom has mass. I don't know about if energy is required to have gravity. Gravity is a source of potential energy. It is already energy. One of the 4 states of energy. While looking at the solar system you can recognize gravity. That doesn't mean that gravity cannot be looked in on smaller scales. For reasons unknown there should be a reason why gravity exist. Just like atoms have particles like gluons, guons, sluons (just naming random names), maybe one of these particles is responsible for the attraction of gravity. If I dig deeper, maybe it's not the particles themselves that exhibit gravity, maybe it's the open places between these particles that exhibit gravity.

While the nucleus can be responsible for gravity, I don't see how electrons can be. The attraction of the proton and electron is a source of electromagnetic energy. If an electron has mas that ma qualify it to contain gravity as well. Gravity is attractive so where would any mass be attracted to the electron? If we dig deeper into the electron, proton, or nucleus, where would the exhibition of gravity be located? Or is it just a force that is, completely gratified from the spaces in the particle. Which particle would be said to have no mass at all? Or even sub-particles tend to have mass as well?

 

[PeterDonis]

I don't know about if energy is required to have gravity.

I do; it is. General relativity is quite clear on this point, and its predictions in this regard have been verified by experiments.

Gravity is a source of potential energy. It is already energy.

No, it isn't. First, the concept of "gravitational potential energy" is problematic in GR, for reasons which are probably too involved to get into here. Second, again, GR is quite clear about drawing a distinction between "gravity"--more precisely, spacetime curvature--and its source, which includes, as I said, anything with mass or energy, but also includes momentum, pressure, and other stresses--the full source is expressed mathematically by an object called the "stress-energy tensor", and there is nothing representing gravity in the stress-energy tensor; everything about gravity (spacetime curvature) is contained in a different object called the Riemann curvature tensor.

One of the 4 states of energy.

I don't know what you mean by this.

While looking at the solar system you can recognize gravity. That doesn't mean that gravity cannot be looked in on smaller scales.

Of course not. But on smaller scales, with smaller objects acting as a source, gravity is a lot weaker, so it's harder to measure. We can measure the gravity of ordinary objects like lead weights by using sensitive devices. But we can't measure the gravity of individual atoms; they're too small and their gravity is too weak.

maybe one of these particles is responsible for the attraction of gravity.

Our best current belief is that there is such a particle; it's called the graviton, and it mediates the gravitational interaction in the same way as the photon mediates the electromagnetic interaction, gluons mediate the strong interaction, and the W and Z bosons mediate the weak interaction. However, all of this about particles mediating interactions comes from quantum field theory, and while we have directly measured the quantum nature of the other three interactions, we haven't done that with gravity. As far as we can tell, that is because gravity is so much weaker than the other interactions that we can't do experiments sensitive enough to reveal its quantum aspects.

If I dig deeper, maybe it's not the particles themselves that exhibit gravity, maybe it's the open places between these particles that exhibit gravity.

I'm not sure what you mean by this either, but it looks to me like pure speculation. I think you would be better off not engaging in such speculation until you know a lot more about what we already know about gravity and the other interactions.

While the nucleus can be responsible for gravity, I don't see how electrons can be.

I don't see why you don't see this. Electrons have mass just like the nucleus does; their mass has been measured very accurately. So, like anything else with mass, they produce gravity. Of course, as I said above, the gravity of an individual electron, just like the gravity of an individual nucleus, is far too weak for us to measure. But the electrons contained in the atoms in the Earth, for example, make up a small part of the mass of the Earth, so they contribute to the Earth's gravity.

If we dig deeper into the electron, proton, or nucleus, where would the exhibition of gravity be located?

I'm not sure what you mean by this either. Suppose we could do experiments that probed an electron or nucleus down to as small a distance scale as you like. What sort of experimental results would you be looking for to show you where "the exhibition of gravity" is located?

 

[Firedog89]

I don't know what you mean by this.

The 4 forces nature.

I'm not sure what you mean by this either. Suppose we could do experiments that probed an electron or nucleus down to as small a distance scale as you like. What sort of experimental results would you be looking for to show you where "the exhibition of gravity" is located?

Have we been able to single out the graviton? Or is the graviton just a theory?

I understand that the electron can produce gravity because it has mass. You are right, It is pure speculation. I know it would be weak on the molecular basis. Gravity just seems to come out of nowhere. It doesn't seem to form based on any interactions only increase and decrease by mass. It just seems to be a force that just is.

 

[PeterDonis]

The 4 forces nature.

Ok. "States of energy" does not seem like a good term for this; "fundamental interactions" would be a better one.

Have we been able to single out the graviton? Or is the graviton just a theory?

As I said, we are not able to do any experiments that probe the quantum aspects of gravity; we have no way of producing or accessing strong enough gravitational fields to do that.

However, I don't think that means the graviton is "just a theory" either; there are many good reasons to expect gravity to be fundamentally a quantum phenomenon, just like everything else. That's not to say it would be impossible to construct a theory in which gravity was purely classical (no quantum aspect, hence no graviton) and everything else was quantum; but I don't think anyone is seriously pursuing such a theory.

Gravity just seems to come out of nowhere.

If you just mean that we can't observe the graviton, so we can't experimentally verify that gravity arises from particle exchange, you should be aware that we can't observe gluons (the particles that mediate the strong interaction) directly either. In fact, we can't even observe quarks (the particles that make up mesons and nucleons) directly. We can only observe these particles indirectly, by experimenting on the properties of strongly interacting objects that we can directly observe, like mesons and nucleons. So "being able to directly observe the particle mediating the interaction" is not a good criterion to use.

If you mean that gravity only depends on mass, not on any other property of the object, I'm not sure why that's a problem, because every interaction only depends on one property of the object. For electromagnetism, it's electric charge; for the weak interaction, it's weak isospin; for the strong interaction, it's strong "color" charge. Mass (or more precisely stress-energy) is just the "charge" associated with gravity.

If you mean that, unlike the other interactions, there's no way to have an object that does not have the "charge" for gravity (mass-energy), that is indeed a feature unique to gravity. This feature actually helps us to determine what properties the graviton must have, if it exists, since only a particular kind of quantum particle can mediate an interaction with this property.