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OT : Relativity Q

I'm in a spaceship travelling at 0.866c away from Earth. AIUI, that's a time dilation of 2, and my speedometer, which of course uses my on-board clock and a set of mile markers laid down by a previous expedition, indicates 2c.

Earth is beaming a laser in my direction and pulsing it once per Earth second. Clearly these pulses are going faster than me, and I have a handy pulse detector.

What frequency of pulse repetition will I measure with my on-board instrumentation?

And, Captain Slog-supplemental, what if the laser is instead at my destination planet?

Reply to
Clive Arthur
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Ignoring relativity, you'd see a new pulses originating from earth at the rate of one per second once every 7.5 seconds (Doppler effect) . Because of time dilation you'd think that there only 3.73 second between each new pulse.

You'd run into 7.5 pulses a second for a 1Hz pulse originating on your destination planet, and time dilation would made you think that it was pulsing at 14.9Hz.

So the Doppler effect is more dramatic than time dialation.

But why bother to ask the question? Darius the Dumb thinks that it is an off-topic question - why he should feel the need to point this out when you have marked it as off-topic in your subject line is a question worth asking, but Darius the Dumb is remarkably dumb.

Asking an off-topic question isn't actually proof positive that you are a troll. Most people who post here post off-topic question that they correctly imagine will still be of interest to the people who habitually post here, but that's a more complicated idea than Darius can get his head around.

Reply to
Bill Sloman

Thanks Bill, very helpful. That's what I'd worked out, but for some reason I'd convinced myself I was wrong.

I don't see his posts. I very rarely killfile, but life's too short to bother with sad attention-seekers.

Reply to
Clive Arthur

I'm no authority. There are a couple of people who post here who might give you a more reliable opinion.

<snipped a reference to Darius the Dumb>

He does waste a lot of bandwidth. He's even more inane than Skybuck Flying, and he posts a whole lot more.

Reply to
Bill Sloman

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