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If a camera was sent up in a satellite, put in orbit at close to light speed, and instructed to beam down images to earth, what would we see if we watched its video feed?

(Ignoring the fact that such an orbit speed is way above the escape velocity for Earth).

Would the video show Earth in slow motion? Or, would there another effect due to being in an accelerating frame?

Rupert
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2 Answers2

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This video gives a visual representation of special relativity when the speed of light is reduced. These are the effects the camera will witness.

Continuous
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Yeah the satellite wouldn't stay in orbit :) But ignoring that...

Time dilation comes into play at relativistic speeds. The faster you go, the slower time goes. As such an astronaut on the IIS will age a tiny bit slower than someone on Earth.

So for your example, time on the satellite will appear to slow down as observed by someone on Earth. This means that say for 1 second passing on a clock on the satellite, 2 seconds pass on a clock on Earth. Let's say the camera is recording at 30 FPS (satellite time) but that means it's only taking 15 frames for every second that passes on Earth. That means 2 seconds of Earth time are compressed into 1 on the satellites camera and it records things as if they are moving twice as fast.

Sending the signal back to Earth will cause some difficulties. Assuming a stationary position on Earth then the satellite will be whizzing towards you (at relativistic speeds) then past overhead and away. This will lead to some red/blue shift of the signal as well as the fact that the signal timing will be out but assuming we can correct for these effects then people on Earth will receive a video that appears much sped up.

Quantumplate
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  • I understand what you're saying, but you seem to be approaching this from the reference frame of someone on earth. However, the video is being taken from the satellite.

    If we were to assume that the satellite was an inertial reference frame (so not being accelerated around earth), then we would see earth moving at slower speed. Moving clocks tick slowly, and relative to the frame of the satellite, earth is moving very fast.

    My problem comes from trying to work out this problem given that the satellite is not an inertial frame of reference, but is being accelerated.

     – Rupert Feb 15 '15 at 10:09
  • Hi @Rupert, your question asks how someone on Earth would view the video so I've taken it from that perspective. Have a look at the answers on this question and this one for further info but essentially accelerated frames also experience time dilation in a similar fashion to inertial ones. – Quantumplate Feb 15 '15 at 23:36
  • There may also be a number of other effects on the recorded video due to their relativistic speed which I haven't mentioned, e.g. aberration and blue shifting of the light. Take a look at this link for further info. Again sorry this is for inertial frames but some of the effects will still apply for accelerated ones. – Quantumplate Feb 15 '15 at 23:43
  • The video will not run fast or slow. If it ran fast, you'd eventually see your own future (if the satellite stayed in orbit long enough). If it ran slow, you would have seen your own future at some point in the past (if the satellite had been in orbit for long enough). – benrg Oct 08 '20 at 03:46