Here's the original image. It was originally posted in 2017 and has been shared so many times it was difficult to find a good copy. I had to use wayback to get this copy.
this post was submitted on 15 Feb 2025
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thats one FAST car
And one fast head turn
Only as it's moving away.
eeeeeeeeeeeeeeeeeeeyowwwwwwwwwwww
I know just enough about the light spectrum and the red shift to understand why this is funny (thanks Prof. Brian Cox!), but it underlines how shallow my knowledge is. So much cosmology, so little time...
That car is speeding
I bet that guy feels like he gets where he's going in no time at all!
They'd only get a light sentence anyway.
Depending on the frequency of the offence
Might have community service periodically
Okay, just back of the envelope math. Assuming the car is truly 550nm, so the blue car is 400nm, and the red car is 700nm... How fast is the car going?
Napkin math says 0.27c.
Δλ=λ(V/c)
Now someone else can figure out the kinetic energy of the car and why the whole continent just exploded...
someone else can figure out the kinetic energy of the car and why the whole continent just exploded...
It's not on fire or melting the asphalt beneath it, so it must be really aerodynamic, and have really low rolling resistance tyres...
OK now how fast did old man's head move
Okay, napkin math... his nose is about 20cm long, and assuming it rotated about a perfect circle. The car moved say 10m. At the speed the car is moving, it covers that distance in ~120ns. So he has to move the end of his nose around a quarter circle of radius 20cm in 120ns. Let's say 30cm total movement, for easy math. 0.25cm/ns or 0.00025m/ns. The speed of light is 0.300m/ns, so we're talking about ~0.001c at the tip of his nose. Which is incidentally very close to the speed of sound in air.
So, probably not quite a sonic boom off the end of his nose. Assuming my math is correct. Very strong neck muscles. Also, he's been vapourized.
Ah this is so great. In the transonic regime (just below 1.0 Mach) the air moving over the surface of his nose will break the speed of sound as it gets out of the way.
I think you missed a factor of 1000 when comparing against the speed of sound in air. I think it should be almost 1000 times the speed of sound, so definitely sonic boom and definitely vaporised!
It's very possible. Napkins are notorious for stealing orders of magnitude.
What is a factor of 1000 between friends anyway? (Especially cosmologist friends)
Did you take into account that the car is not driving directly towards the viewer?
I ain't doing hyperbolic equations on my napkin ;)
So about 180 million MPH. I hope he doesn't get a ticket!
now calculate the Lorentz contraction
Instructions unclear, car stuck in dick.
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One shift
Two shift
Red shift
Blue shift
Damn, remember when Valve made half life games? It was a better time back then.
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Pretty sure the sonic boom of this car passing will kill this poor man
Well, when that finally happens the car will be fine, far away from Earth.
If that guy is keeping track of that car, his neck is def broken
Everything around the car would be broken too, including the car
what a beatiful green car
For some reason I can never remember which causes red or blue shift, but with this I might actually remember it
Blue has a smaller wavelength, so when something is approaching fast it "squishes" the light, making a smaller wavelength.
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You can either know the position of the car or the momentum, but not both.
But why is the car stretched? And why doesn't it appear rotated?
The poster you are replying to is pointing out the inaccuracies that this comic didn't consider relativistic effects.
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