So, if you have a room that's got a dimension larger than 6 meters, and a fast oscilloscope, you can have a situation in which it is both easy and impossible?
I get in trouble regularly with my wife because I've been trained my whole life to think in a particular way, and that's not how other humans are wired:
if (a) {
b;
}
if (c) {
d;
}
versus
if (a) {
b;
}
else if (c) {
d;
}
She has mostly learned to put up with me by now, but the difference (how programmers think) still comes out sometimes.
Edited to explain: programmers don't think exactly like other humans.
Of course, in programming in the first case, "b" and "d" both happen when "a" and "c" are both true in many languages, unless "b" is something like "return e"
But, anyway, I was mostly joking -- its not like your meaning was at all unclear.
If the clocks are in the same room and you have a fast oscilloscope at hand, it's easy.
If the clocks are more than about 6 metres apart, it really is impossible.