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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."
http://stashbox.fromtheshadows.tv/
or the actual torrent:
http://torrents.fromtheshadows.tv/fts_box1.0.avi.t orrent
I would just like to point out that the DS does *NOT* use ad hoc mode at all, but instead, uses infrastructure mode. The first DS into teh game acts as a wireless access point that the other units connect to.
Cell phones seem to work just fine at 100mph+
As radio communications with Apollo seemed to work just fine at relative speeds of about 25,000 mph. As others have noted EMR is really, really fast and doppler shift is relative to that speed.
In any case they have invented these things called "variable resistors" that can be used to make a simple circuit popularly refered to as a "tuner." They gone even further and created circuits that automatically seek and lock onto a signal, popularly known as "scanners." The radio in your car can probably serve as an example of one of these (FM signals can drift far more than you're ever going to see from a doppler shift on your wireless equipment).
Note that the radio in your car works just fine no matter how fast you go, but please, don't tell the officer about this post, K?
KFG
I hate to break it to you guys, but so long as the people are moving at the same velocity, there isn't any kind of problem. If all of them had been moving at .999 speed of light (in our point of view), there still wouldn't be a difference, because they are all in the same frame of reference, and they would all measure the speed of light from their point of view to be 3.0x10^8 ms^-1. No doppler effect of the radio waves would be created, and no greater time lag would ensue. It's as if they aren't moving, because according to each other, they aren't!
Not the theories of Relativity, the Principle. There is a difference. Einstein's theories of Relativity solved an increasingly important conflict between physicists beliefs that the Principle of Relativity was true (an intuitive belief) and their inability to put solid math around the way the Universe works.
The first chapter of this work should help. Basically, the principle of relativity is that physics is the same for all inertial reference frames; Einstien put that together with the fact that light appears to travel the same speed for all observers. Galilean relativity doesn't work with that; it has other contradictions inherent in it (it can't answer the Zeno paradox, again, see the linked work), but it takes longer to notice. There are other relativity theories that haven't panned out, either.
Pardon the pedantry, it's intended to be educational.
I have a question: If the skydivers were travelling near the speed of light, would this still have worked? (note: Ignore the detail that they'd punch a Wile E. Coyote-esque hole into the planet.)
Yes. Thats the whole point of relativity. Its just as valid to say that they're still and that the earth is moving near C towards them, in which case why wouldn't it work?
Why?
This is where relativity comes in. The RF signals are traveling at C relative to the transmitter. If the transmitters are moving at C - 5 MPH, then the radio waves are moving at 2C-5 MPH.
Wrong, actually.
Under Galilean Relativity, you would be correct. this isn't usually what people mean when they talk about relativity. The problem facing physics at the end of the 20th century was that we had two really great systems for describing reality - Newtonian mechanics with constant unchanging distances and a universal clock, and Maxwells equations that described electromagnetism. The problem was with light - Light always moves at C relative to you - regardless of your frame of reference. This totally fubars Galilean relativity, because of exactly this situation.
From the POV of the guys in the Air, obviously the radio signals are traveling away at C. However, according to Maxwell, this is also true for the guys on the ground. Einstein resolved this paradox by doing away with a universal clock, and for that matter universal distance and mass.
Why?
Electromagnetic radiation in a vacum travels at 1.8026175 × 10^12 furlongs per fortnight, always.
Time is not the same for everyone, and bends to make the above possible.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
No, it uses infrastructure mode. The reason it isnt tunneled is because it doesnt use TCP/IP at layer 3 and up of the OSI model.