[arbitrage]

Tachyons aren't a thing. Tachyons are sci-fi nonsense.

Nothing in the universe can travel faster than the speed of light. This does not hold for the universe itself. It can and does expand faster than the speed of light, using specific reference frames (i.e., big enough).

So, space can increase FTL. Particles do not travel faster than light tho, that is nonsense.

[westurner]

If the universe is expanding faster than the speed of light, how are particles not traveling faster than the speed of light indeed with zero acceleration relative to the expansion?

If the Copenhagen interpretation is correct, particle states are correlated after a photonic beam splitter; if you measure entangled photons after a beam splitter, their states are still linked.

If virtual particle states are entangled with particle states in black holes or through ER=EPR bridges, is there effectively FTL?

There is FTL within dielectric antennae.

[cbolton]

Take a star in a region of the universe that recedes from us at 3c. In what sense is the star not traveling faster than the speed of light relative to us?

[westurner]

.

  v   - c < 0
  -3c + c = 2c
  +3c - c = 2c

[rthnbgrredf]

Well, we have (virtual) particles that can travel backwards in time, without breaking causality. There's no proof that Tachyons exist, they are purely hypothetical, but they are not outright nonsense.

[westurner]

From https://news.ycombinator.com/item?id=38045112#38047149 :

> from https://news.ycombinator.com/item?id=35877402#35886041 : "EM Wave Polarization Transductions" Lt. Col. T.E Bearden (1999) :

>> Physical observation (via the transverse photon interaction) is the process given by applying the operator ∂/∂t to (L^3)t, yielding an L3 output

[and "time-polarized photons"]