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Question #91400 posted on 06/05/2018 10:18 p.m.
Q:

Dear 100 Hour Board,

Is Superman faster than a speeding Avada Kedavra? Would Superman survive an Avada Kedavra?


-Stan

A:

Dear person,

My initial reaction (and Anne's, too) was that spells travel fairly slowly - perhaps 60 mph or so. However, I couldn't find the source on the internet that gives the exact speed. That means it's speculation time!

It's certain that the speed of spells is slower than the speed of sound because incantations are heard by their targets before they hit. If magic traveled at the speed of sound (1125 feet/second) and it takes about half a second for a person to speak a three-syllable word (e.g., stupefy, protego), then to block a spell with a three-syllable incantation I would have to be at least 562 feet away from the caster (assuming I didn't start casting shield charm before the caster was done saying the incantation). There's no way anyone could hear an incantation at that distance unless they were yelling.

It seems reasonable to assume that duellers frequently stand about 10 feet apart. It would take the sound of the finished incantation about .009 seconds to travel that distance. We need the spell to take at least 0.5 seconds to travel. So the spell needs to take a maximum of 20 feet/second to travel that far. Or about 13 miles per hour. That's too slow. 

Okay, that's not good. Let's assume duellers who have any sense of caution stand about 20 feet apart. That would double the speed it would take to cross that distance in .5 seconds to about 40 feet per/second or 26 mph. Also slow.

Okay, let's pretend they stand 30 feet apart. That brings the required speed up to 60 feet per second or 39 mph. Also still slower than Usain Bolt.

We made some big, not totally realistic assumptions conducive to spell slowness (i.e., that people being don't react before the incantation is over). I don't really see the number getting much higher than 50 or 60 mph (approximately 80 or 100 km/h). There. Final answer. 

If anyone would like to submit a correction because they have a link to the quote that Anne and I were thinking about or they noticed my math is terrible, please do so.

-Sheebs

posted on 06/06/2018 1:01 p.m.
Here's a slightly less speculative answer for you. Using this video as reference: (https://www.youtube.com/watch?v=BcJl2YjFcr0)

You can calculate how fast something is moving from a video if you know the framerate of the video and the distance that the object travels.

Movies are typically shot in 24 fps, and from what I could find, the HP movies are no exception.

In this video, it takes Voldy about 37 frames to SAY 'avada kedavra'. 37 frames at 24 fps is about 1.54 seconds.

It takes the spell exactly 8 frames to hit our protagonist straight in the chest. I counted it like 20 times. It's exactly 8 frames. 8 frames/24 fps is 0.333 seconds.

We all know that speed is distance over time, so now we need the distance. I used Radcliffe's height as a reference to get a good estimate of how far apart they are in the video. Luckily we've got a nice side view. Danny is 5'5", and using that, it seems like they are standing about 25 feet apart.

The Avada Kedavra spell travels 25 feet in .333 seconds, or 75 feet per second (75.075 if you wanna get technical) or 51.188 miles per hour.

(https://scifi.stackexchange.com/questions/80312/how-do-we-know-the-flash-is-faster-than-superman) that link says that superman can fly 7,200,000 mph... so... Yes, Superman can fly faster than the Avada Kedavra spell... by a longshot. Could he survive it? I don't know, and trying to cross the boundaries of alien abilities and magic gets a little tricky. I vote yes.

Yay for math!

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