Sometimes I wonder, when a balloon pops, we say:

Oh the balloon exploded!

Instead of:

Oh the balloon imploded!

When a balloon pops, it becomes smaller. As I see it, the meaning of "imploded" is:

collapse or cause to collapse violently inwards.

Wouldn't it be more typical if we say "imploded"?

Maybe only I am thinking like that...

  • "When a balloon pops, it becomes smaller" --> U11-Forward, do you consider "it" to be the stretched out balloon material alone, or the sum of the material and the air inside it? – chux - Reinstate Monica Jan 2 at 3:32
  • U12 - If it were a balloon made from a plastic or paper bag and it was overfilled would the popping be described as an implosion. --- Explosion vs. implosion is direction of pressure vs direction of movement - if that helps you to improve your question and example. – Rob Jan 3 at 14:44

A balloon contains air under pressure. When it pops, the air expands.

Merriam-Webster defines "explode" as, among other things:

to burst forth with sudden violence or noise from internal energy, such as...to burst violently as a result of pressure from within

Referring to a balloon "exploding" refers to this sudden release of expanding gas (air) as a result of the pressure inside the balloon. The fact that the rubber shell that contained the gas ends up smaller in the end doesn't matter.

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    Yes, "explode" and "implode" have nothing to do with the size of the resulting debris field. "Implode" relates to things collapsing from excess external pressure; as a vacuum tube under ambient air pressure, or a submarine under great water pressure. A balloon burst is an internal pressure event: an explosion. – CCTO Dec 30 '20 at 21:01
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    @Mazura I'd argue that it is not colloquially useless since the question was asked based on incorrect definitions. Why do we say X instead of Y? The answer is simply because Y doesn't mean what you think it means. The answer chosen ignores that critical fact and instead runs with that incorrect definition by proceeding to talk about a bunch of irrelevant things. – DKNguyen Dec 30 '20 at 22:03
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    @applemonkey496 Stepping on the balloon does compress a small part of it it which reduces its overall volume, increasing internal pressure which is what actually ruptures it. But it is not the external foot pressure that is immediately causing the balloon to burst; It's the increase in internal pressure. Counter example: if you applied uniform inward pressure all around the balloon, it would not actually burst. It would just shrink a bit. Similarly, a pin prick causes an opening where the higher internal pressure escapes to the outside tearing it apart. The pin itself doesn't tear the balloon. – DKNguyen Dec 30 '20 at 22:43
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    @applemonkey496 a small pin causes a tiny hole which rapidly becomes bigger because all the air inside the balloon wants to escape. Much like an exit at a crowded theatre, everyone crams up at the exit. But in the balloons case the 'people' at the 'exit' have enough force to just blow the wall out, which rapidly destroys the balloon. Stepping on a balloon is a bit different, it increases the internal pressure to the point where the weak parts in the balloon wall can't withstand the outward pressure and give way. – eps Dec 31 '20 at 17:41
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    What's interesting is that if you make the hole big enough, the air molecules no longer have to crowd so much at the exit and instead can leave in a more orderly manner which doesn't destroy the balloon. In other words, the balloon will fly around the room as the air escapes -- it is functionally a rocket! Indeed, if you pack a bunch of explosives together and give them a hole to escape out you've made a rocket. If you contain them with nowhere to go you've made a bomb. – eps Dec 31 '20 at 17:44

I think there are many possible reasons for this; a single answer is not possible. Some suggestions:

  • Explode is a frequent word, whereas implode is less frequent, and somewhat limited to technical discussions. Therefore, it could simply be a case of the more frequent word covering a greater range of meanings / being used more vaguely.
  • Although balloons end up (looking) smaller after they pop, you can also conceive of the popping as causing material to radiate outwards. At the moment of popping, bits of balloon can fly outwards, at least momentarily. Also, the loud noise travels outwards from the location of popping. This may contribute to the impression of an explosion.
  • The popping of a balloon has things in common with prototypical explosions (such as bombs exploding)---notably, the loud noise. This may make people more inclined to use the word explosion.
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    I would say "The balloon burst" - I think of an explosion as involving chemicals or fire. – Kate Bunting Dec 30 '20 at 14:52
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    Yes, me too, actually (or popped)---was just going by what OP suggested, as I've certainly heard 'explode' used too. – legatrix Dec 30 '20 at 16:48
  • @Kate Bunting while most explosions involve "chemicals or fire" not all do. a nuclear explosion can be created by bringing sub-critical masses together with springs. When contained water freezes I would call the result an explosion. – David Siegel Dec 30 '20 at 17:00
  • @DavidSiegel Maybe a steam explosion would be a good example. No chemical (or nuclear ;)) reactions take place but they can be deadly powerful. Explosions are simply a matter of (sudden release of) pressure. – TypeIA Dec 30 '20 at 19:06
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    -1 because this answer entertains the OP's incorrect definition instead of just correcting it. This answer would only be valid in cases were people were referring to actual implosions as explosions (like building demolitions, perhaps?) – DKNguyen Dec 30 '20 at 22:12

An implosion is a region of low pressure collapsing because of the higher pressure surrounding it. That's clearly not what is happening when a balloon 'pops', as the sound that is produced is the high pressure air rushing into a lower pressure environment. Much like traditional explosives, when a balloon pops you have an area of concentrated matter expanding into the area of lower concentration.

Also, it is functionally the same thing as a car tire popping which clearly looks like an explosion: https://youtu.be/HANwJp8Z5mc?t=27


Comments in another answer made me realize the obvious connection between balloons, rockets, and bombs. If you fill up a balloon and let the air out the balloon will fly around the room like a rocket. Rockets don't explode because like the balloon they have a big hole to give the explosive material a way out.

If you instead fill up a balloon and prick it with a pin, the hole the air escapes from is much smaller. Much like people trying to quickly escape a building, this creates a crushing force at the exit, air molecules in a balloon do the same thing. Those air molecules have so much force that they can expand the hole in a destructive way which pops the balloon. This is what happens to rocket when the explosive material can't escape fast enough, it becomes a bomb!

So a balloon is essentially either a rocket or bomb depending on how exactly the air is escaping from it.

  • Rockets sure do explode when they are structurally unsound... :D – RonJohn Jan 1 at 20:19

The term "implosion" generally refers to the collapse of a vessel containing a vacuum, or at much lower pressure than its surroundings. Thus one can say that a submarine that went too deep imploded due to the pressure.

Back in the days before LCD screens televisions used Cathode Ray Tubes (CRTs); basically giant glass bottles with all the air removed from inside. If one of those imploded the flying glass could be a serious hazard.

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    CRTs aren't "basically" vacuum tubes; they are vacuum tubes. – RonJohn Jan 1 at 20:20

when a balloon pops, we say:

Oh the balloon exploded!

That's not restricted to balloons. If a grenade or a bomb explodes, the casing does not get bigger, only the contents.

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