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David H. Burns schrieb:
>> Well, then compare it with the perspective of a person actively
>> swimming: Despite obviously being inside the medium, from his point of
>> view water waves going in the same direction as he is appear to be
>> slower than those going in the opposite direction.
>
> Does he? Or does he just observe a frequency change, i.e. see the crests
> and
> troughs closer together or further apart, as with the doppler effect in
> sound and light?
Try it out, and you'll see that the crests and troughs will actually
apear to be moving at different speeds depending on direction - while
the distance between them will remain constant (which is /why/ they'll
appear to change their frequency).
> A curious result of this is that any mass measurements contain two
> components,
> the inertial mass (the mass that would be measured if the object were at
> rest with
> respect to the measurer) and the relativistic mass due to the relative
> velocity of the
> object with respect to the observer.
Yup. E = mc^2: From an outside observer's point of view, pumping energy
into some thing to speed it up to light speed also pumps up its mass.
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