# Why were there no shock waves when the planes hit the Twin Towers?

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A 9/11 documentary showed up in my YouTube recommendations so I decided to watch it. As I was doing so, I realized that there were no shock waves when the planes hit the towers. You can hear the sound of the explosion travelling, but no massive window smashing/shattering like in the Oklahoma bombing or the Beirut explosion or even the [Black Tom explosion](https://en.wikipedia.org/wiki/Black_Tom_explosion#Explosion).

Why weren’t windows in New York blown out en masse that day? Was it due to the nature of the explosion? Thank you in advance!

In: Physics

ELI5 answer would be there wasn’t a shockwave similar to Beirut or Oklahoma City because the town tower hits were plane crashes not explosions.

An explosion and its shockwave come from a chemical reaction creating a rapidly INCREASING release of energy. 9/11 had plane crashes that would DECREASE their release of energy as the planes decelerated and broke apart dispersing that energy into the building.

You only get shockwaves from high explosives. The shockwaves is caused by the combustion front going faster then the speed of sound. But neither the force of the airplanes hitting the buildings or the burning of their fuels took place at speeds even close to the speed of sound. So there would not be any shockwave.

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This is the #1 argument I have when people say it was explosions that caused the towers to fall and not planes. Explosions have accelerating pressure causing shockwaves, something like a plane crashing decreases pressure.

Granted, the idiots who don’t think planes crashed into the towers also aren’t keen to understand logic and science.

Because it’s a crash. The fact there were no Shockwaves is another argument against the conspiracy nuts.

If I put a bomb in your fridge, there will be a shockwave.

If I hit your fridge with a bat, sword, or boomerang, or model plane, there won’t be a shockwave.

Explosions are different from impacts. They only become similar with big supersonic impacts like a meteors.

Explosions can be either subsonic (no shockwave) or supersonic (shockwave). Subsonic explosions are most commonly associated with slower reactions called deflagration. Gasoline igniting in an engine is an example of deflagration. Supersonic explosions are usually created through detonation, which are reactions that are so energetic they occur faster than the speed of sound, generating a shockwave.

The combustion of jet fuel would have been deflagration, creating a subsonic explosion, but no shockwave.

The planes hitting the towers didn’t cause an explosion in the strictest sense. Instead, the impact of the planes hitting the towers caused a lot of fuel to be vaporized and spread away from the plane, which *then* ignited and created a fireball. However, because the fuel was already dispersed, the fireball didn’t produce a rapid change in air pressure, and without such a pressure difference you won’t get a shockwave.

The breakup of the Space Shuttle Challenger is a similar situation; despite people typically referring to it as an “explosion,” it wasn’t actually an explosion in the strictest sense. The shuttle broke apart first, which produced a cloud of fuel, which in turn ignited and burned without resulting in a significant pressure change.

In both cases, the use of the word “explosion” is a bit of a misnomer; the average person thinks of an explosion as any big ball of fire that suddenly comes into existence, but from an engineering perspective we see a difference between a true explosion/detonation (which has a shockwave) vs. a rapid deflagration/really rapid combustion (which does *not* necessarily have a shockwave).