I know that astronomers observe jets that apparently move faster than light but really don't. I think I can simulate something that looks superluminal using just a bunch of x-mas lights and i am wondering if it is the same principle:

If I have, say, 1000 light bulbs each rigged to turn off and on at a specific time, then if by using a bunch of synchronized clocks, one for each bulb which send a signal like a billionth of a second after each other, then i could turn the first bulb on at time zero, the next bulb a billionth of a second later. an observe would see something that appeared to be a signal propagate so that the final bulb would turn on 1000 billionths of a second later (a micro second later) and if the thousand bulbs were a meter apart from its predecessor and successor, it would look like the signal crossed the kilometer in a millionth of a second, so a million kilometers per second or several times faster than light.

Now, no information is transmitted but how could the observer even know that a real signal was not transmitted over that kilometer? And is this simple demonstration basically what astronomers see but on a much smaller scale?

Note that one could simulate any speed in this way, the number of bulbs and distance crossed is completely arbitrary -- 1000 times light speed would also work although there is some speed at which the observer can actually see something happening and I think a human can't see anything that occurs in a micro second but around a millisecond humans can start to perceive things.


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Your setup is different from the "superluminal" astronomical jets.

The events in the astronomical jets that seem to be spacelike (faster-than-light) separated are actually timelike (slower-than-light) separated, and in fact are causally connected. They only seem to be spacelike separated if one mistakenly assumes that they're the same distance away.

In your setup, the events really are spacelike separated. That's only a paradox if one mistakenly assumes that one of them is causing the other.

The jets are covered in this Wikipedia article, and a classic thought experiment similar to yours is covered in this Stack Exchange question.


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