A gravitational field has energy, therefore mass.Will an object's mass also include the mass of its g- field ?

Question

You know, as Einstein said, all energy has an equivalent mass - E equals em cee squared and all that. So each object should carry, besides its own mass, the little bundle of mass equivalent to its gravitational energy.

Answer 1

Well, with lots of heavyweights saying nay, let me be a devil's advocate.

If I could magically turn off gravity, the gravitons conveying the force would disappear. Since they exist and therefore must have some energy content, this would seem to imply the total mass/energy concentration would decrease in their absence. That would seem to indicate they may make a contribution. Gravitons do feel the force themselves, so maybe they help contribute as well.

However, I believe the gravitons are virtual particles, so the situation is probably more complex than this. Maybe the rest of the virtual zoo magically shifts to take up the slack.


Edit:

Physics grad student did not seem to buy this little thought experiment. However, I must still challenge your learned reasoning.

You seem to be stating that because of the equivalence principle, turning off the gravitational field would not change the gravitational mass since it must remain equal to inertial mass. So therefore the field must not be contributing to gravitational mass. However it seems to me inertial mass would be expected to track down by the loss of this energy field as well, so no violation need occur.

Your first new point states the gravitational field does represent some storage of energy. Now, say I have two really beefy springs, and I compress one of them. The compressed spring becomes heavier due to the stored energy (a truly miniscule amount). So I would expect it to express both greater inertial mass to resist an accelerating force and greater gravitational mass to curve space-time.

This woud seem to be consistent with the increasing inertial mass associated with increasing velocities in relativity. I assume the equivalence principle is still in play here as well, so the increasing velocity/energy must be causing the gravitational mass to increase as well.

Perhaps you are implying that only rest mass curves space-time rather than the total mass/energy concentration?

Anyway, a fun question.

Answer 2

A massive object's gravitational field does contain energy called the binding energy of the gravitational field. It's equal to the amount of energy you'd need to separate the body into tiny particles and drag them away from each other to infinity. If I hadn't had so much to drink I could work it out for you. But ir rises as something like the square or cube of the object's mass, so it only becomes important for massive objects. The energy equivalent of a 1 kg mass =mc^2 which is very large, but the binding energy of its gravitational field is stuff all. If you had a 1 kg mass in outer space, it would take a negligible amount of energy to separate its particles against its weak gravitational field.

Answer 3

The gravitational Field of an object is a by-product of it`s mass ie, the more mass an object has the more gravity it has. Gravity is still a mystery to scientists as no scientist from Newton and Einstein to Hawking has ever properly defined what gravity actually is, it`s true that gravity has energy and imparts force on objects but it dosen`t obey the first law of thermodynamics which stipulates that a closed system can`t make new energy out of nothing there has to be an outside source of energy to balance the energy deficit, as you probably know gravity can keep exerting energy forever without needing a power source. For this reason it ts thought that gravity is an elementary force of the universe (the weakest in fact) rather than a peripheral force of the object it is associated to. I hope I have shed some light on the subject for you.

Answer 4

As far as I can guess there is no change in mass or gravity for difference in velocity, but the contrary could be quite true. As an object is accelerated to light speed, the matter of the object would leave behind it like a comet tail various energies because atomic structures can not endure the velocity as it increases to C, the universe and all its forces would change relative to the velocity (like one thing hitting another, the change is relative to their composit velocity expressed as power at the time contact). As subatomic particals fall behind, the atomic structures lose integrity and the disintegration excellerates as the velocity increases. Terrage accures as the thing travels through successive gravity and electromagnetic radiations (the energy fields of other things) and the relative effects increase as power is delivered into the propelled object. It is similar to carrying something up a hill and then dropping it over a cliff; all the force you used to get it there is expended when it hits the bottom of the cliff.

Answer 5

The gravitational field has energy which can be converted into mass or weight when some force is applied. This can be availed by putting a mechanical energy being converted into Electrical energy and when some mass is gained it should be immersed in water so that velocity decreases and osmostic action will be more. Hence g-field is included in a Object's mass.

Answer 6

Noooooooo.

OK, let me clarify a common misunderstanding: not all forms of energy are equivalent to mass. Mass is a form of energy just like kinetic or potential energies are forms of energy. If a ball has kinetic energy, not all that energy is in the mass.

Same thing for a massive particle in a gravitational field. It was once thought, and may still be thought, that the mass may increase slightly in a gravitational field proportional to the potential energy of the field (i.e., the potential energy goes to mass until it is converted to kinetic energy). I would strongly urge you not to take that too literally. It may or may not be the case. But physicists don't talk about it like that. They only consider the invariant mass.

Now, the gravitational field does NOT have mass. It is a field. It is carried by gravitons, which are massless particles. It curves spacetime. The field itseld doesn't have mass, though. Photons do not have mass either, but they have energy. Only certain particles (or fields if you understand Quantum Field Theory) have mass.

My point: mass is a very special property of some particles in nature. Not everything with energy has mass, but everything with mass has energy. The important property of a particle is not it's "relativistic mass" (an old-fashioned idea), but it's invariant mass (or rest mass). That's what E=mc^2 is dealing with: the rest mass.

I hope that helps.

EDIT:

1. The gravitational field does have energy just like an electric field has energy.

2. (Rest) Mass is an invariant. The mass of an object does NOT change when you cut off the gravitational field. To see this, let's examine the "Equivalence Principle" of General Relativity. One way of stating this principle (it can be stated in many different ways) is that the inertial mass of an object is exactly equal to the gravitational mass. Now I know that sounded like a "duuuuh" statement or else you're scratching your head wondering what am I talking about, so let me explain in classical terms.

In Newton's Second Law, we know that the acceleration of an
object is directly proportional to the force applied to the object. The constant of proportionality depends on how strong of a role Inertia plays on the object (Newton's First Law). We cal this constant the "Inertial Mass" or mass for short. So we define Inertial Mass as m_i=F/a, where the m_i stands for inertial mass. Now we know from Newton's Law of Gravity that a gravitational field is produced by a body. Nevermind what produces the field, we know it's produced, call the field g(r). The force this field applied on an object is given by F = m_g*g(r), where m_g is the gravitational mass, i.e, the constant of proportionality that describes the effects of gravity on an object. Since we know that this mass also causes the field, we could have defined the gravitational mass as the constant of proportionality that causes gravity. Either way, Einstein's equivalence principle states that m_g/m_i = 1.00000000000000.... (i.e. m_g = m_i). I stated it as a ratio because that's what can be measured in the lab. And as far as we can measure, they're equal.

Now, everyone reading this is probably wondering why I wasted space explaining something that you all know. Well, we don't know anything without measuring. Nature didn't HAVE to make those two "masses" equal. It's not a given. So I stated all that to explain this: say you can magically cut off gravity without changing the laws of physics (or, equivalently, move the particle far far away from all other matter so that gravity is negligible between the particle and another particle). The object must still obey the Laws of Inertia (as far as we know), and since inertial mass and gravitational mass is equivalent (we can't tell them apart in an experiment), the mass of the object must be invariant under changes in the gravitational field. Of course, if you're talking about relativistic mass, well see my above response. In technical jargon, we say: mass is invariant when boosting to an Inertial Frame of Reference (one in which Special Relativity works and GR is not needed) from a general frame of reference.

Answer 7

The falacy in your question is the presumption that a gravitational field has energy.
It does not.

You must raise a mass to give it potential energy, and this potential energy will exactly equal the kinetic energy used to raise the object.

As you can easily see, gravity supplies no "extra" energy.

When you free fall, there are no forces acting on you. If you were in a box, you would be weightless, again, with absolutely no forces acting on you.

The "force" you feel on your butt sitting at your keyboard is the earth's opposite reaction to your mass.

Answer 8

Yes, it will have a mass of its own, albeit very small. It takes an extraordinarily massive object to have a great deal of energy contained in the field itself.

Answer 9

Isnt it then vat you call as the weight...

Weight is infact the mass of a body under the gravitational force ...

Answer 10

Yes. But in ordinary objects it is much too small to measure. In principle, you could weigh a flashlight battery to see if it is good; in practice, it can't be done.