Message-Id: <l03110714b24a90d1b6bd@[192.174.2.173]>
Date: Wed, 14 Oct 1998 09:34:06 -0800
To: pinhole@exploratorium.edu
From: Paul Doherty <pauld@exploratorium.edu>
Subject: re relativistic radio
Hi Steve
I just got a "white" LED with which you can change the color balance by
changing the voltage. Rather cool and expensive for now but I expect the
price to plummet soon. Expect to see some in TI activities.
The radio cannot go at the speed of light.
However let's talk about a radio transmitter going near the speed of light
travelling away from you.
The relativistic doppler shift has two parts, one the classic doppler
effect as for sound and a second part due to relativistic time dilation.
This doppler effect will change the frequency of the radio wave to lower
frequencies (longer wavelengths). The sound signal is carried as a
modulation on the carrier wave. The modulation frequency is also doppler
shifted so that when it is convverted into sound by the receiver the voice
is slowed down and shifted to lower frequencies.
Nice to hear from you
Paul D