Comment by mystified5016 | Hacker News Reader

Comment by mystified5016 | Hacker News Reader

Parent Full thread

The speed of light is actually the speed of causality. No matter, or more importantly information can go faster than that. This has some real consequences even on human scales.

For example, if you've ever opened an electronic device and seen squiggly traces everywhere, it's because of light speed[0]. When signals get fast enough, you have to make sure the traces have the same length to within a fraction of a millimeter. Otherwise, the signals on two traces arrive at different times and nothing works.

[0](electrons move at ~c, more or less)

There's a significant delay in satellite communications, on the order of milliseconds. It takes several seconds to reach the moon. 20 minutes to Mars, a few hours to Jupiter. Famously 8 minutes to the sun. The nearest galaxy is 1.5 million years away.

Consider how stupefyingly large our solar system is. Then consider how insanely huge the galaxy is: 90,000ly. It takes ninety thousand years for a photon to go from one edge of the galaxy to another. Then compared to the universe at large, our galaxy is essentially a single point.

Light is extremely slow and the universe is vast beyond our meat brain's ability to comprehend.

>[0](electrons move at ~c, more or less)

Pedantic: electrons (in a wire) move at relatively ordinary speeds. Wikipedia says this [0]:

>The drift velocity in a 2 mm diameter copper wire in 1 ampere current is approximately 8 cm per hour. AC voltages cause no net movement. The electrons oscillate back and forth in response to the alternating electric field

Think of it more like a long row of billiard balls. You hit the first one, it moves a little, then it hits the next one, that one moves a little etc. Except the "hit" is just getting closer to the next electron to make it move (like if they were magnets).

At least that's my understanding of it.

---

Maybe "hit" is the correct word? Isn't it the same forces at play that stop my hand from going through the table?

---

[0] https://en.wikipedia.org/wiki/Speed_of_electricity

You are correct, electrons (aka current) through a wire move at relatively low speeds at room temperature because of wire resistance. Changes of voltage however, like if you flip a data pin from 0V to 5V move at the speed of light.

So switching circuits need to take into account "transmission line" effects.

The this is only the drift velocity. Electrons are still orbiting the nuclei at relativistic speeds. Plenty of room at the bottom...

I don’t think you understood my point? Why did you type all of that, when it’s basically what everyone else has said. I know about max speed of information and causality and have for decades. I was talking that light in a vacuum speed is basically “fast” since nothing is fast, in both and absolute and a relative sense, at least in my take :)

Reply on news.ycombinator.com