3 ms·
Yeah but good luck seeing them.
by paulddraper 2y ago
Yeah but good luck seeing them.
- thaumasiotes 2y agoWell, let's imagine an object that has some Platonic motion of 0.2c directly away from us, but it's so far away that spatial expansion boosts its velocity to 1.1c. At time 0 it emits a photon toward us. One year later, it's 1.1 light years farther away. The amount of newly-created distance between us is 0.9 light years. Some of that was created behind the photon, but I'll ignore that and just assume that all of the new space got in the photon's way. Over that one year, the photon has traveled 1 light year towards us, and only 0.9 light years of that distance was new. So it's gotten closer to us by (a little more than) 0.1 light years. This rate will accelerate over time. The object is still visible at the point where it emitted that photon, even though its velocity exceeds the speed of light. I think it will ultimately become invisible, though.