Hacker News Reader

Comment by singularity2001 | Hacker News Reader

singularity2001·

the radius of the visible universe is about 14.0 billion parsecs (about 45.7 billion light-years), while the age of the universe is 13.787 ± 0.020 billion years. I must have missed out on some caveats to the speed of light.

View on HN

You did - space-time can expand with unbounded speed, and that is what happened in the early universe. Remember that the big bang is not some point in space-time which we are moving away from, it is a point in space-time that has expanded to the size of the current universe (and keeps expanding).

The speed of light is only a limit on how fast matter/energy can move through space-time.

The speed of causation is also so unintuitive imo, but also a must to make anything make sense logically. After watching many hours of youtube i still cant wrap my head around it. Say you're accellerating 1g forever you never reach the speed of light for other observers.. Whats cool about gravity is that the spacetime 'train tracks' are tilted slightly into the earth so youre pulled down, but the earth is resisting tou going into it. Just waving your hands around is the same feel as playing with magnets

I think the most intuitive explanation I've seen for c is that in fact everything always moves at a fixed speed, c, in space-time - either through space or through time (from past to future). You can neither increase nor decrease your total speed, you can only change its direction - the larger the space-only component is, the smaller the time component is.

Additionally, mass deforms space-time such that a little bit of your motion towards the future is directed to the center of mass instead.

You just discovered the Big Bug theory.

Reply on news.ycombinator.com