What would happen if you tied two helium balloons together with string long enough (assuming the weight of the sting had no effect) for each balloon to be on opposite hemispheres?

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What would happen if you tied two helium balloons together with string long enough (assuming the weight of the sting had no effect) for each balloon to be on opposite hemispheres?

In:

The balloons would fly up since their weight is less than the air around them. When going up they will expand because there is less pressure from the air above them. At a certain moment the material will they are made of will get a tear because of the imperfection of the material and the helium will escape. The material will fall back to the ground because of gravity.

The answer is that the two balloons will travel up and sidesway and end next to each other, and then will explode as they climb. If they are exactly at the opposite, and if the rope is exactly directed toward the earth where they attached to the balloon, this is an unstable equilibrium and so the slightest perturbation will break it.

If it’s not the case, or if the equilibrium is broken, the balloons will depend sideway toward each other in the same time they climb “up” and will end up next to each other.

In reality, as they will expend as they climb, they’ll probably explode way before that. But I’m not sure you care about the “in reality” with a weightless 20.000 km rope, tbh

If you have a magical string which has no weight and is always as long as it needs to be so that it doesn’t exert any tension, then the string may as well not exist. What would happen is the same thing as would happen if the string were not there.