Imagine that I'm exactly in the middle of two identical masses. So that each of them exerts an identical acceleration on me and in the exact opposite direction. My question is Will these opposite accelerations cancel, or will they split me in half?
3 Answers
They will cancel in the middle of you, but one will be a bit stronger than the other on your left and vice versa. So your arms may get stretched. This is exactly the force that creates the sea tide due to the moon gravity. If the objects are normal planets, you wouldn't feel the tide forces, but if you get to be between a couple of close neutron stars, then sure, they would rip you apart.
It sounds like you're referring to being in between two planet-sized masses. If that were the case and they weren't catastrophically close to each other, I think it's safe to say you would just float in limbo right in the middle as long as you never moved from the exact center.
If you're talking about something as massive as a black hole and being less than an armspan away from both event horizons, you would be split in half without a doubt.
It all depends on the distance between you and the massive objects. And also the size of the massive objects.
The distance comes into play because of the inverse square law. As the distance from the (centre of the) object doubles. The gravitational force reduces by a factor of 4. No matter how massive the objects are. If you are even a few hundred miles away the tidal effect between your finger tips and the centre of your body will be negligible.
You would have to be almost within arm’s reach of the objects centre for the tidal effect to have enough difference along your body to generate a suitable force to tear you apart.
Then of course there is the mass of the objects. It doesn’t matter if you are arms length away of the objects are the mass of a tennis ball. I haven’t done the calculation but I’d put money on the fact that to be arms length away from the objects centre and for it to have enough mass to generate enough force. It would almost certainly be within its schwartzchild radius and so the objects would almost certainly be black holes.
Then comes the question of how do you keep these two black holes from collapsing into each other (and taking you with them) at such a small distance. Within the event horizon of the black holes even the particles that carry the strong nuclear force can not overcome the gravity so any structure holding the black holes apart for fall apart and be devoured by the black holes.
So, yes, technically you could create such a scenario on paper. But no, it would never be possible in the real world.