# Why do other balloons explode when they reach a certain altitude?

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I just don’t understand what’s happening to them. Everything I’ve read says the lower external pressure causes the helium inside the balloon to expand. Does this just mean the pressure inside the balloon is rising as if I blew up a balloon to far till it bursts? Why does the balloon expand?

In: Physics

The balloon expands because the density of the air & pressure around the balloon decreases.

Similar how something is compressed the deeper you go in water.

As the ballon elevates the atmospheric pressure outside the balloon drops. Once the internal air pressure is higher if he outside it will break.

When you blow up a balloon, it reaches a point where the gas inside is pushing out the way, and the balloon itself and the air outside are pushing in the way.

When it gets higher up, the pressure outside drops. This doesn’t mean there’s more pressure inside, but the difference between the inside and outside is greater. So now it’s just the gas inside pushing out vs the balloon pulling in. So, it stretches more until the forces balance again.

When a balloon expands, the pressure inside it decreases. A balloon will continue to expand until the pressure inside the balloon is as low as the pressure outside (disregarding the elasticity of the balloon here). If the pressure outside goes even lower (when the balloon rises) the balloon will expand even more.

At some point, the balloon material will be stretched to its limit and the balloon pops.

If you blow something up, the only thing that determines when it will burst is the **differential** pressure, so the difference between the pressure on the outside and inside. This means you can cause something to burst _either_ by increasing the pressure inside _or_ by decreasing the pressure outside, because both increases the pressure difference.

As it rises the external pressure declines, so the gas withIN the envelope of the balloon expands as it basically meets less and less resistance. Assuming the balloon was inflated at sea level, The internal pressure would be approximately 14 pounds per square inch (I apologize for not going metric). The air pressure at 30,000 ft is about 4.3 psi. At 50,000 feet the air pressure is about 1.6 psi. At that altitude the balloon’s volume will expand by 14 divided by 1.6. So the balloon will be about 8.75 times larger than at launch. Hope this helps.

A balloon keeps its size because there is a balance between the pressure inside and the pressure outside. If the pressure inside is less than the pressure outside, the balloon shrinks until the gas inside is so compressed that its pressure is the same as outside (this happens if you put the balloon under water). Likewise if the pressure is greater inside than outside then it will expand until the two pressures match. Of course there’s a limit how much the elastic can stretch before it breaks amd bursts.

The reason why the balloon changes its size is not because it ‘wants to’ match the pressures of course. The prevailing explanation is that the gas in the balloon has energy which makes the gas particles vibrate and push against each other, making the body of gas expand. The gas outside the balloon also has energy and pushes against the balloon, keeping it from expanding indefinitely. Gravity squashes the air close to the ground more than the air higher up, resulting in less pressure higher up. You can reduce the energy of the gas inside a balloon by freezing it, making the gas lose energy and thus reducing its pressure and shrinking it.

Pressure air pressure outside the balloon gets considerably lower as you increase altitude, but the balloon has the same pressure as when it was inflated. So the pressure outside is less than the pressure inside and the balloon then expands until the pressure inside equals the pressure outside and the balloon will often burst before this hppens.

The balloon feels pressure from both sides.

The helium pushes outwards. The atmosphere presses inwards. When the air outside presses harder the balloon expands, and the pressure inside drops.

When the pressure inside matches the pressure outside the balloon stops expanding.

When the balloon rises, there is less air pressing down on it, and so the pressure drops outside. This means the gas inside the balloon win the pushing match, causing it to expand again until it presses out as hard as all the air outside is pressing in.

Rinse and repeat until the balloon stretches to fast, and it rips.