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.

Post a reply to this message