**Ask a monkey a physics question thread**

[MadMojoMonkey]

Do individual pieces of tnt have gravity?

Gravity isn't really a property that stuff has. Mass is a property that stuff has. Gravity is a consequence of what mass does to space-time.

To answer you, though, I guess a "yes" is in order. TNT is made of atoms, which are indeed stuff, and therefore have mass.

If you made a planet of tnt, would it have gravity?

Yes. See above.

If the planet then exploded, would the gravity (if any) change as the pieces exploded away from the center of the exploding tnt planet field?

As the mass density changes, the curvature of spacetime changes, and therefore the gravity changes.

The same total gravitational acceleration is expressed outside of the planet (sploded or not), since the total mass density inside a sphere of that radius was mostly empty space and one solid TNT body, and is still mostly empty space and the same amount of atoms, just in a wider spacing.

If you were in a place which was outside the planet before it sploded and inside the planet after it sploded (or inside and further inside), then you would experience a significant decrease in the acceleration you feel due to gravity. However, you would still need the same escape velocity to get "away" from the planet, because whatever lesser gravity you now feel, you have further "up" to go to get out of the planet. As you go up, you put more distance between you and the center, and therefore more stuff which was pulling you in all directions is now pulling you back to the center.

If the Earth were a hollow shell, there would be no gravity inside the shell, since there is no mass within that radius, and all of the gravitational pulls from the various bits of the shell cancel out.

In the same way, the Earth-moon system expresses it's gravity as though it's a single gravitational body, with all of its mass located at the gravitational center of the Earth-moon system. When we are close to the system, we begin to see and feel that it is not a single gravitational source. When we are "very close" to one of them, it's as though the other isn't even affecting us and the only gravitation we can discern is that of the closest source.

Did you see this question coming

Well, I was hoping, with a strong expectation.

and are you therefore psychic?

Nope. Physicist. Haven't you heard? We predict the future with math, rather than wild speculation.

In this case... people can be rather predictable when motivated in certain ways.