Question about space time relativity and earth movements?

Question

Ok, so my brother has explained to me (probably very badly) the idea that the faster something is moving, the less time passes. So travelling at light speed, less time will pass than travelling slower. The idea that if you have two identical clocks and send one off at very high speeds for a while, eventually the clock travelling faster will show an time slower than the stationary clock. Is this right?

Also, what effect would this have on earth and other planets? So say there is a planet which revolves around its sun at a much faster rate. If you put an ordinary earth clock (I'm not talking physical day length) on that planet, would it run slower than its twin on the earth? Or would the gravity of the planet cancel out the effects of the planets speed? 

Thanks

oldprof · Accepted Answer

It's called time dilation and it's described in the special theory of relativity.

Suppose we have two reference points: the observed and the standard. The observer stands on the standard reference point and observes the observed reference point that's going V speed as measured by the observer. The speed of light, C, standard time dT, and observed time dt are all also measured by the observer on the standard RP (e.g., Earth).

Note I chose the term "standard RP" because everything, all the metrics, are measured relative to this reference point...it is the standard against which everything is measured. And this is a critical point to understanding time dilation. Everything in this case is measured relative to (relativity get it?) the designated standard reference point.

Here's what the observer sees (observes). The traveler's Rolex on the observed RP runs slower and slower as the observed RP rate of time goes from dT --> dt < dT. And at the same time the observer's Timex on the standard RP is still ticking at dT rate of time. And sure enough, as V --> C, that Rolex comes closer and closer to stopping altogether. Never quite does that as it's impossible for V = C and cause dt = 0.

And, yes, the rates of time are affected by the relative rates of the planets. If we could endure the heat and gravity, and intense radiation of the Sun, we could designate it as the standard and Earth as the observed RP. In which case, we'd see Earth's rate of time as dt < dT our own rate on the burning Sun.

Well...not quite. There is also another relativity effect and that's described by the general theory of relativity. The math is much more complex, but it says that the standard dT --> dt as the strength of the gravity field we're in increases over and above the strength of the gravity field on the observed RP. In plain English, the rate of time in the tremendous gravity force of the Sun would be slower than comparable rate of time back on Earth where the Sun's gravity field is considerably less.

In case you got lost on this, let's recap. The special theory says Earth's time would be slower than the Sun's due to the relative speed. But the general theory says the Sun's time would be slower than the Earth's due to the relative gravity pull. And, no, I've no clue which would dominate in this case.

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Question about space time relativity and earth movements?

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