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Turbulence and length compression are good evidence, but in theory not sufficient to infer the speed of the arrow: The arrow could have been squeezed and air turbulence induced some other way. These alone then would not make the arrow fly in the suspected direction.

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Hmm. If the arrow was actually travelling in a different direction, doesn't that imply that you'd need to be able to cancel the turbulence from that motion? Otherwise it'd appear in the snapshot as contradictory evidence.

Sure! I'm assuming if we have the means to fake the one turbulence, we can also cancel the other. Or the arrow is just not moving, thus no "natural" turbulance to cancel.

I'm not saying that air turbulence wasn't a very strong indicator for motion! And I am not sure the technology to fake them completely does exist. But I don't see why it shouldn't be possible, maybe with a very elaborate set of fans, air ducts and loudspeakers.

> I'm assuming if we have the means to fake the one turbulence, we can also cancel the other

That seems like a leap. There's a huge difference between generating some plausible-looking turbulence and generating one absolutely precise pattern of turbulence at one exact instant.

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