[jojobas]

PSA: meteors have nothing to do with explosions. The shockwave comes from meteor's movement alone, the parts never move apart with any speed comparable to their common forward motion.

A breakup will increase surface area and therefore kinetic energy to shockwave transfer efficiency, still not an explosion.

[margalabargala]

PSA: The word "explosion" has multiple definitions, plenty of which are actually quite reasonable to apply to meteors! It can refer to the sound alone, for example. The people reporting an explosion in Massachusetts were not incorrect!

It would however, be incorrect to claim that the meteor had noting to do with explosions.

[jagged-chisel]

None of the definitions I found are concerned with only sound. One mentions sound as a result of an explosion.

PSA: expressing an opinion (incorrect or otherwise) is not actually a public service announcement

[jojobas]

No? There is no violent expansion or bursting, even if the sound is similar. It is as much an explosion as a supersonic jet passing by, and that is not much.

The term makes people think atmospheric heating causes an actual steam explosion and that's the source of shockwave, which can't be further from truth.

[bmelton]

Meteor Chelyabinsk suffered catastrophic fragmentation, a rapid, violent release of energy accompanied by a pressure wave with debris, which would satisfy the definition of an explosion (an in fact the energy released was equivalent to 400-500 kilotons of TNT.)

[jojobas]

If you could look at this catastrophic fragmentation you'd find it's about the same pace as dirt spreading on the ground as it gets tipped off a dump truck. The fragments outward speed is negligible compared with their forwards speed, and it's the forward speed that produces the shockwave, fragmented or not.

[sholladay]

Do you not consider Tunguska an explosion? It’s always described as such. IIRC, it never even hit the ground. Sure, a lot of the damage was caused by the air being compressed from above, but it created an air burst, which would have released a lot of energy in every direction.

[jojobas]

No, it's a misnomer as with any other meteor.

If you were to witness the breakup from the bolide's reference frame and without all the rushing air you'd never call it an explosion.

[margalabargala]

> and without all the rushing air

That's the exploding bit though. You don't need containment, you just need the the airburst. A hyper-heated pocket of air that then expands rapidly is itself an explosion.

[jojobas]

>then expands rapidly

Except it doesn't. The breakup has roughly the same dynamics as dirt spreading as it gets out of a tip truck. The shockwave is not produced by the outward motion, it barely has any speed.

[quuxplusone]

The Wikipedia article on "meteor air burst" has an explanation that basically matches yours, although they do use the word "explosion" to describe it. Which makes sense to me: whatever one chooses to call it, it's a nearly instantaneous spontaneous disassembly that is very bright, very hot, and very loud.

https://en.wikipedia.org/wiki/Meteor_air_burst

[jojobas]

The speed scale for disassembly is nowhere near the forward speed; you never get anywhere close to 45 degree debris divergence angle. It's also, again, not the disassembly that causes it to be bright, hot and loud. Wikipedians can also be wrong.

[adrian_b]

Some meteors do explode.

The meteors made only of iron alloy and/or silicate rocks do not explode, but they may fragment into many smaller bodies.

The meteors that contain great amounts of volatile substances (water, carbon compounds and sulfur compounds) may explode if the interior becomes hot enough to convert the volatiles into gases. When such a meteor rich in volatiles fragments, some of the fragments may explode, while others may reach the surface of the Earth intact.

[jojobas]

This fragmentation is not violent and it's not what produces the shockwave, the term "break up" is more appropriate.

[gruntled-worker]

We are not disassembling, we are assembling in another time direction.

[1970-01-01]

>The shockwave comes from meteor's movement alone, the parts never move apart with any speed comparable to their common forward motion..

PSA is false.

https://www.nasa.gov/blogs/watch-the-skies/2026/03/26/its-fi...

[dredmorbius]

jojobas and NASA's statements aren't contradictory.

NASA states: "the fragmentation of the fireball unleashes large amounts of energy, which also generates a pressure wave that can produce a very loud boom, even shaking houses."

Fragmentation of a fireball, whilst not explosive itself (the particles needn't diverge at a supersonic relative velocity) are nonetheless part of a supersonic / hypersonic particle field relative to the atmosphere they are passing through. Expanding the diameter of that particle field will increase the size of the resultant shockwave, whether the particle separation itself is "explosive" or not.

The "explosion" then is of the deceleration (aerobraking) shockwave, not the bolide separation. But the bolide separation increases the intensity of the shockwave, with more (and lighter) particles interacting with the atmosphere over a shorter distance than an intact, small-diameter bolide would.

Some of this depends on what definition of "explosion" one chooses, or whether people are intending an explosion specifically, or an explosive sound (sonic boom). That's confounded by bolide separation, the bright light emitted on entry, and sonic effects, all of which are semantically associated with other explosive events. Language is a consensus phenomenon.

I'd tend to call the event an explosion, though not in the expanding particle field sense.

[1970-01-01]

Your statement is not supported by, and is somewhat at odds with, physics. As described in this source, observed terminal brightening/"burst" of a bolide is tied to the body's material behavior (fragmentation, rapid lateral expansion, ablation), and not to a free-standing "deceleration shockwave" that exists independently of the body breaking up.

https://adsabs.harvard.edu/full/2001ESASP.495..491R

[adrian_b]

Some meteors really explode, because water and other volatile substances contained in them transform from solids into high temperature gases that expand quickly and cause the explosion of the body.

This is the same like how many kinds of water containing things, e.g. raw meat, eggs, fruits, can explode in a microwave oven if the microwave power is too high.

The meteor bodies belong to several classes of chemical compositions. Some of them contain very little volatiles, and they are made either of iron alloy or of silicate rocks or of a mixture of iron alloy and silicate rocks. These do not explode, at most they fragment into many smaller bodies.

Other classes contain great amounts of volatiles, e.g. water, organic compounds and sulfur compounds, and they frequently explode, depending on their size, shape and trajectory, i.e. if there is enough time for the interior to be heated to high temperatures, causing the phase change of the volatiles to gases.

[x______________]

Thank you for the clarity so far down in the responses.

Meteors and eggs do not normally explode, but under the right circumstances.. Boom!

[1970-01-01]

You forgot the fact it will hit something! Craters are not made silently! https://en.wikipedia.org/wiki/Meteor_Crater#Formation

[dredmorbius]

You're being excessively argumentative.

I didn't state that the shockwave is independent of whether or not the body breaks up, I wrote, emphasised, "Expanding the diameter of that particle field will increase the size of the resultant shockwave, whether the particle separation itself is "explosive" or not."

Which your article (partially read, sorry, incredibly shitty reader) largely substantiates, largely in the itemised list in section 2.2. Pancaking of a bolide through fragmentation increases frontal area, has multiple points of mass interacting with the atmosphere over a larger area and with less mass at each point, and the (undiscussed) light-emission mechanism which itself largely derives from compressive heating and ionisation of the atmosphere (rather than friction against the atmosphere or heating of bolide particles themselves). Increasing the number, and surface areas, of particles increases the region and intensity of this effect.

As your source discusses, most fragmentation is a result of mechanical rather than thermal forcing of the bolide.

[1970-01-01]

You wrote:

"jojobas and NASA's statements aren't contradictory."

jojobas wrote:

"PSA: meteors have nothing to do with explosions."

>You're being excessively argumentative.

You're defending idiocy. The PSA is false. There is science behind it. There is little nuance to salvage in any of it.

[gosub100]

Without disagreeing with you, what should the event be called?

Breakup, impact, fly-by? all those could be incorrect if all you know is a space object entered the atmosphere, made a sound, and flashed some light. What do you call that? Especially because you don't automatically know if it impacted the surface. At which point it becomes a meteorite, so even calling it a meteor is not fully correct. Or do you get ultra technical and say that when it made the sound and flash, it had not yet reached the ground, therefore it was a meteor at the time?

[Guestmodinfo]

You are correct in class 9 physics book in India we have a mention of supersonic planes producing a sonic "boom" so the suprsonic planes don't themselves explode but their fast movement makes the air produce the boom. So you were correct as far as I can tell. But meteors do get smaller and smaller due to extreme friction from air and they do break into several pieces so that can also add to the sound.

[Jblx2]

https://www.dictionary.com/browse/explosion