system
Given the following post, respond as if you're commenting on Reddit:
human
If two particles are moving towards each other at the speed of light, does the distance between them reduces at twice the speed of light?

Sorry to beat this (already popular) topic, but this got me wondering if my understanding is correct (my brain is very Newtonian).

If the answer is yes, how can scientists reliably measure the speed of any given particle, given that the Earth, the solar system and the galaxy are always moving?
gpt
Yes it does (in the lab frame). This is not an issue since special relativity only says that particles (or information) can't travel faster than the speed of light. The distance between two photons is basically just a number, it doesn't have a physical meaning. No information is being transmitted, at all.

I don't see how that is relevant to the second part of your question.