Nintendo DS Wireless in Freefall
Nicholas Roussos writes "Wired reports about four skydivers who decided to give the Nintendo DS wireless capabilities a try while they were freefalling. 'The four sky divers proved that an ad hoc network set up using the wireless functions of a Nintendo DS works perfectly at distances of nearly 400 feet while falling 120 miles an hour,' states the article."
The skydivers experience is consistent with Galilean relativity, Einstein's special relativity wouldnt have much of an effect in this situation.
So I looked up the relativistic Doppler effect and plugged in some numbers.
.0017% of the total frequency range. Unfortunately, I don't know what the tolerances for 802.11b are, but I have difficulty believing that .0017% would cause much trouble.
For a relative velocity of 400mph you get an observed frequency of 2.39999856GHz.
Now, looking at the 802.11b spec available at the 802 working group site I see that it operates in the 2.4 - 2.4835GHz range.
So the Doppler effect at 400mph introduces a difference in frequency equal to
Now, backfiguring for a more common 5% tolerance, we get something like 500,000m/s or 1.1 million mph. So, yes, 802.11b probably won't work between passing spaceships. Aside from that, we're probably safe.