[thayne]

> electron/light speed

Tangent, but changes in the electric field travel at the speed of light (in a copper wire, which is slightly slower than in a vacuum). The electrons themselves move much, much slower. The speed of light is what matters for speed of information transfer.

It is analogous to a pipe of water.

If you increase or decrease the pressure of the water at the input of the pipe, you can detect that difference in pressure at the other end long before the water molecules at the beginning of the pipe get at the time of the change get to the end of the pipe.

[arh68]

> changes in the electric field travel at the speed of light

Isn't it ~2/3 c thru copper? Roughly equivalent to light-thru-glass. I'm not quite sure who is running hollow-core fiber.

[Jakob]

TIL that signal speed in copper and in fiber is roughly similar, around 2/3 c. Thanks!

[thayne]

It depends on the properties of the wire, such as the diameter, the purity of the copper, type of insulation, etc. In a twisted pair wire the length the light travels is also longer than the external lenghth of the wire.

Cat5 is has about the same velocity factor as fiber: 2/3, but Cat7 is closer to 3/4. Coaxial can get even higher.

[thayne]

It depends on the properties of the wire, but it can be as high as over 0.99c.