1970-01-01 5 hours ago

>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...

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dredmorbius 4 hours ago | parent [-]

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.

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1970-01-01 3 hours ago | parent [-]

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

	▲	dredmorbius 2 hours ago \| parent [-]
		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.