5 ms·

From my understanding, if you travel at light speed, space is compacted to very tiny distances and time stops. If you take the math of relativity to its extreme

by mg631 7y ago

From my understanding, if you travel at light speed, space is compacted to very tiny distances and time stops. If you take the math of relativity to its extreme, time for you has stopped and your trip took no time. It actually takes no time because there is actually no distance between you and the black hole. But this is where paradoxes come in because the black hole, stationary from in its frame of reference, would still experience 26,000 years and not see you arrive until then. From my understanding, general relativity solves this paradox with de-acceleration causing the one who was traveling at the speed of light seeing the rest of the universe's clocks' speed up. So technically, your clock would have not moved 26,000 years forward, but other's would have.

wruza 7y ago
Not a physicist, but afaik you are right. If you go with the speed of light (or close enough), your travel time goes to zero. It is common misconception that to “reach the stars” you have to spend a couple of lives. In fact, you can get there before you finish your sandwich. This makes me think of lone sad CMB photons, who accidentally stop by hitting an atom and cannot even recognize a tiny bit of the universe they remembered since. A spark moment, and they lost everything to billions of years.
- candiodari 7y ago
  Does that also mean they would get hit by all the light energy that hit them on the way on the moment of "arriving" in that collision ? Or is it just the first collision ever that stops them and they just happen to miss every last particle in outer space for 13 billion years perhaps.
krastanov 7y ago
> But this is where paradoxes come in because the black hole, stationary from in its frame of reference, would still experience 26,000 years and not see you arrive until then. Special relativity solves this fine (there is no paradox in it for that particular thought experiment), no need to involve general relativity. There is nothing paradoxical about the observer near the center of the galaxy not seeing you until you are near, because you are traveling at speed almost as great as the speed of the information carrier (the light you emit if we are talking about space, or the sound you make if we are talking about something on Earth). So you actually do not even need relativity to explain the "they do not see us coming". You do need relativity to explain the fact that to you all of this took only a blink of an eye.
- mg631 7y ago
  My bad I meant to talk about the fact that there is no universal reference frame, so in your frame you would believe you aren't moving, but the black hole is moving towards you. In in a scenario where you are traveling at .99c, from your frame of reference you are not traveling at all and the black hole is traveling to you, so you see the black hole experiencing incredibly slow time passage. However, that is not what the black hole sees. Hence a paradox.

by mg631 7y ago

wruza 7y ago

Not a physicist, but afaik you are right. If you go with the speed of light (or close enough), your travel time goes to zero. It is common misconception that to “reach the stars” you have to spend a couple of lives. In fact, you can get there before you finish your sandwich. This makes me think of lone sad CMB photons, who accidentally stop by hitting an atom and cannot even recognize a tiny bit of the universe they remembered since. A spark moment, and they lost everything to billions of years.

candiodari 7y ago
Does that also mean they would get hit by all the light energy that hit them on the way on the moment of "arriving" in that collision ? Or is it just the first collision ever that stops them and they just happen to miss every last particle in outer space for 13 billion years perhaps.

krastanov 7y ago

> But this is where paradoxes come in because the black hole, stationary from in its frame of reference, would still experience 26,000 years and not see you arrive until then. Special relativity solves this fine (there is no paradox in it for that particular thought experiment), no need to involve general relativity. There is nothing paradoxical about the observer near the center of the galaxy not seeing you until you are near, because you are traveling at speed almost as great as the speed of the information carrier (the light you emit if we are talking about space, or the sound you make if we are talking about something on Earth). So you actually do not even need relativity to explain the "they do not see us coming". You do need relativity to explain the fact that to you all of this took only a blink of an eye.

mg631 7y ago
My bad I meant to talk about the fact that there is no universal reference frame, so in your frame you would believe you aren't moving, but the black hole is moving towards you. In in a scenario where you are traveling at .99c, from your frame of reference you are not traveling at all and the black hole is traveling to you, so you see the black hole experiencing incredibly slow time passage. However, that is not what the black hole sees. Hence a paradox.