This is a function of the permittivity of the material. A Vacuum is 1, the lowest possible. Air is 1.0006 so you won't see much difference.

Fiber optics of various types are usually on the order of 2 to 3 (closer to 2).

Distance is still a huge problem. The Starlink signal still needs to travel up to the satellites 500 KM up, and then another 500 KM back down. That should be around 2 ms (thanks user jobseeker990, corrected from previous 15ms) of added latency, so anything that is already below 4 ms of latency probably wouldn't be improved.

I think your math is way off. I'm getting less than 2 ms to go 500 km.

You're right, thanks. I was off by an order of magnitude. I've updated my comment

Light travels 1000km in under 4ms. What else are you adding to that time?

I have updated my comment above. I was off by about an order of magnitude.

That's true in vacuum. Light traveling through a medium has to reflect off of or absorb/re-emit from everything it bumps into, so it goes slower.

Would be fine with equivalency - that's a democratizing force. Will also spur more innovation in this area on behalf of HFT firms.

Lower latency across the globe is likely irrelevant to people that colocate in the same data centers as the exchanges to reduce latency.

Then again, maybe it's useful for arbitrage between different exchanges, where they would likely have equipment next to each exchange, and have a wide distance between them.

In case you didn’t know: there are several dedicated microwave links between Chicago and New York just for that reason.

IIRC this is how they plan to finance it.

You just made that up.

Why yes I make random shit up about how people plan to finance their low latency satellite constellations allla damn time. Ya got me. It's a fair cop guv.

If he was lying why would he say IIRC?

I doubt that, since I've also heard this claim several times.

Maybe he just doesn't recall correctly.

I don’t recall SpaceX explicitly stating who they expect their customers to be, but fans quickly dredged up currency and remote stock trading as one potential major source of funding (single customers with huge budgets, rather than hundreds of homes on the cheapest plan)