Avi Loeb

And that means that if I put it here in the middle of this room, it would float.

Gravity will not bring it down.

If Newton's apple was made of a negative mass, half of it negative mass, half of it positive mass, the apple would never fall on Newton's head.

And if I were to make it negative, in principle, next to a negative mass, you can produce repulsive gravity that would propel objects away.

Now, the point is this zero mass object, which with positive and negative, it's like a dipole,

that you can just give a nudge and it will escape the pull of the earth.

And just think how much energy we invest in lifting a payload away from the earth.

Most of the size of Starship, the rocket that Elon Musk is working on, the biggest rocket we ever produced, most of the mass of it is the fuel reservoir.

And getting rid of that and just taking the payload, putting next to it,

a payload of negative mass of the same volume, you can just nudge it.

A kid, it will just float like a balloon and escape the pull of the earth.

No investment of all these rocket fuel in lifting it out.

And such an object would be an ideal vehicle because you can accelerate or decelerate by...

uh pushing the the negative mass relative to the positive mass or or vice versa and uh so we just the only problem is we don't have access to negative mass we don't know how to produce it do we have to solve the supersymmetry problem the hierarchy problem first we have to understand how to unify quantum mechanics and gravity

And the most popular idea in this direction is string theory that we discussed, but at the moment they don't make any predictions, not to speak about engineering prospects for doing something with quantum gravity.

So we're sort of lost, but if we do detect,

an object manufactured by another civilization that maneuvers in ways that are very different than rocketry and accelerates to very high speeds.

And perhaps they mastered this technology.

So we cannot say that it's impossible.

By the way, if we had access to negative mass, we could build a time machine.