Never mind - Wikipedia answered it of course…
299,792,458 m/s is the “defined” value to which the meter was adjusted. I guess the physicists don’t mind a little arithmetic.
My memory was different than yours, so I did some poking around. It turns out we’re both right.
She initially used her “nanosecond” for exactly the purpose you indicated, to explain satellite communication latencies. Later, she used them to explain why computers needed to be small to be fast, which is the version that I heard.
Actually, the big advantage of putting everything on one chip is not so much that things are closer together, but that you don’t get the big time hit of going through I/O buffers. Also, you traditionally couldn’t propagate signals on a board very quickly relative to what you can do on-chip, but serial I/O, (serdes) has made this much faster.
Omniscient, I guess I was focusing on the speed not the distance. Though at one point I was working on a chip so big that you needed a real estate license to sell it.
True, though the speed of light in a vacuum is a “constant” in a much more fundamental sense than is the speed of light through, say, glass. When one says that the speed of light through a particular sort of glass is 2*10[sup]8[/sup] m/s, that speed is measured relative to the frame of reference of the glass. But when one says that the speed of light in vacuum is 299,792,458 m/s, it doesn’t matter what you’re measuring it relative to: Light traveling through a vacuum has the exact same speed, no matter what you measure it relative to. This concept is the very heart and soul of Einstein’s theories of relativity.
That’s the precise value, and when we need to do a precise calculation, that’s the value we use. But there are a great many calculations in physics which don’t need that much precision, and calling it 3*10[sup]8[/sup] m/s is a darned good approximation (less than a tenth of a percent off), so we do, in fact, often use the less precise value.
>But there are a great many calculations in physics which don’t need that much precision, and calling it 3*108 m/s is a darned good approximation (less than a tenth of a percent off), so we do, in fact, often use the less precise value.
Heck, we’ll say Pi = 3 when we’re figuring how long it will take to walk around a big tank or something. People can judge absolute temperature to about 0.1% or 0.2%, if conditions are right and we try hard. And some of us more musically inclined can judge frequency to a percent or so. But nearly all the math that needs doing in this world can be done fairly well to a couple of significant digits.
Actually, this is another question I should have included, along with my inclusion of the medium in question :smack:.
The length (18,000 feet) is the typical distance limit for DSL signals. I was wondering what degree of speed increase there would be over that same 18,000 foot length using fiber optic line instead of copper wire (above and/or underground).
FiOS is employing FTTH (fiber to the home) in some if not all areas that FiOS is offered. I would assume that transmissions over fiber optic cable have a speed very close to c, and that signal degradation over copper would slow it down a little.
Given the responses here, it seems that the speed of data travel over the lines is only a part of the reason that fiber connections can deliver more, faster. I’m assuming that the device sending the signal is using a faster/more powerful system, and that the photo-electric (or whatever) receiver on the customer’s end can handle more data faster.
Maybe I should just start a “Why is FiOS faster than DSL” thread. I think I will, that will let anything going in this thread to continue.
Faster data is related to bandwidth and has little to do with the velocity of the electronic signal. Bandwidth is more typically a function of the frequency of the signal, not the speed. Fiber optics can provide faster data because it can handle higher frequencies (i.e. visible light).
We worry about how long it takes for signals to propagate in the cell phone business. We can control how much each phone interfere with another phone if we can ensure that the timing of the signals arriving at the cell tower are the same. This means that the phones farther away from the tower start transmitting a little bit earlier so that everything lines up at the tower.
OP- You fundamentally confuse speed and capacity in both this thread and the other.
Data rates are bits or bytes per second. Transmission speed is feet or meters per second. Two essentially unrelated things.
The former is how big a dump truck you’re driving. The latter is how fast you’re driving it.
You could theoretically run 1 gigabit/second over a taught string using mechanical vibrations. It’d propagate from one end ot the other at the speed of sound, figure 1000 feet per second.
So your 18,000 foot run would have 18 gigabits en route at any moment. When first started up, nothing would come out the other end for 18 seconds. But once it did start coming out, you’d be feeding a gigabit/sec in one end and getting a gigabit/sec out the other.
The converse is also possible.
ELF radio communications travel at the speed of light, but have a data rate of (IIRC) 3 - 10 bytes per second.
Overall, the physics level speed of the transmission medium has very little to do with the commercially saleable bandwidth of a data transmission device. A huge amount of engineering & other stuff stands between the two.
Minor nitpick: it would propagate at the speed of sound through the transmitting medium, which for a steel string would be roughly on the order of 16,000 fps.
What about two tin cans and a length of dime store twine?
Sorry, I lost you for a second. Some pidgeon sat on my string…
Carrier pigeon?
Just a regular B1-RD.
For the answer to that, I’m afraid you’ll have to delve into string theory.
To give an extreme example, the highest bandwidth information transfer technology is a 747 crammed full of DVDs. And, in fact, many scientific projects do use essentially this method, for very large datasets too large to transmit over any sort of network.
Latency can be an issue for some online applications, though, especially games. Many games have an option to show your your “lag”, which is generally the latency in milliseconds. If you have a satellite link, it’ll easily be in the hundreds or even thousands, which is quite slow enough to make many games unplayable.