6 ms·

In terms of comparisons to human lifespan, I think this one is interesting: If you can somehow accelerate/decelerate at a constant human-acceptable 1G, time di

by Terr_ 6d ago

In terms of comparisons to human lifespan, I think this one is interesting: If you can somehow accelerate/decelerate at a constant human-acceptable 1G, time dilation means almost anywhere is reachable in a human-lifetime. That coincidence(?) could easily become false if we are accustomed to lower accelerations or lesser lifespans.

thwarted 6d ago
This is a really interesting video that explores this topic, pointing out that at near light speeds, the entire universe becomes accessible in a single human lifetime. The Overview Effekt: Time Dilation Visualized https://youtu.be/8FT-oz9aZU4 https://youtu.be/8FT-oz9aZU4
sinuhe69 6d ago
Then I guess you will need millions tones of perfect mass to light converter like Astrophage just to get to the neighbor. The universe is simply too big to comprehend.
no_multitudes 6d ago
> If you can somehow accelerate/decelerate at a constant human-acceptable 1G Well, you also need clarketech heat dissipation and collision deflection technology, if you want to get there without vaporizing.
- Sohcahtoa82 6d ago
  Yeah, once you reach a certain speed, even colliding with a fleck of dust can obliterate a ship. Colliding with a single 0.3 mg grain of salt at 20% of the speed of light creates an impact with 560 MJ of energy, equivalent to 130 kg of TNT, over 8 times the nuclear bomb dropped on Hiroshima. Even a tiny speck of dust, half a microgram, is equivalent to a hand grenade when hit at 20% the speed of light. You wouldn't be able to even escape the solar system before your shields were devoured. If you accelerated at 1G constantly, you'd be going 3.5% of the speed of light by the time you reached Pluto's orbit. Space dust particles are already hitting you like nuclear bombs at that speed.
- dotancohen 5d ago
  Details, details. That's mearly an implementation issue.
ahazred8ta 6d ago
There's a diagram for how long it takes a 'light-hugger' ship to travel various distances at 1-G acceleration. Shiptime is on the left, earth time is on the right. https://en.wikipedia.org/wiki/File:Roundtriptimes.png https://en.wikipedia.org/wiki/File:Roundtriptimes.png http://www.zitterbug.net/future/future815.html http://www.zitterbug.net/future/future815.html What If Light Was Really Slow? https://www.youtube.com/watch?v=ge_j31Yx_yk https://www.youtube.com/watch?v=ge_j31Yx_yk -- https://duckduckgo.com/?q=slower+speed+of+light&ia=videos&iax=videos https://duckduckgo.com/?q=slower+speed+of+light&ia=videos&ia...
asnelt 6d ago
That's the premise of Tau Zero, a very good novel: https://en.wikipedia.org/wiki/Tau_Zero https://en.wikipedia.org/wiki/Tau_Zero
jtbayly 6d ago
I’m confused. Is it 11k years to the closest galaxy at the speed of light, or somehow accessible in a human lifetime?
- stouset 6d ago
  Relativity is weird. If you keep accelerating, at some point the objects stop accelerating toward you faster but the distances get shorter. To an outside observer, the trip might have taken you millions or billions of years while to you it was only ten or twenty. It’s helpful to think about the limit. To light, which travels at the speed of light, it arrives at your retina the exact moment it was created in the core of the sun. From our perspective, it took almost a million years (about a million years to make it from the core to the convective region, then another few minutes to travel from there to Earth).
  - digitalsushi 6d ago
    yeah but its statistical luck, a few photons keep winning the roulette wheel and pop out very quickly; and a few unlucky ones are still rattling around in there from year 1! it's more like winning a raffle than waiting in a queue
  - jtbayly 6d ago
    > “At 99.999% C, the traveler would take ~11,000 years to arrive to Andromeda.” So presumably this means 11k years from an earth point of view? But the traveler would still be alive and a very short time would have passed for him?
    - stouset 6d ago
      Nope! Far, far longer. I don’t know the specifics that the GP used but Andromeda is about 2,500,000ly away. An observer on Earth must perceive you as taking more than 2,500,000 years to get there, as you would have to have exceeded the speed of light to arrive any sooner. At 1g of constant acceleration you can reach Andromeda in just under 15 years of experienced time. An observer on Earth will perceive you as having taken a hair over 2,500,000 years to get there. You can get there arbitrarily quickly; at 10g it would take a 1 year 9 months. But an external observer on either planet will see you taking closer and closer to 2,500,000 years to make it the full distance.
andruby 6d ago
You're right, but not entirely. At 1G constant acceleration reaching Andromeda would take ~15 years, or ~29 years if we also need to decelerate at the same 1G rate to not just whoosh by. The furthest known galaxy is MoM-z14, which would take ~47 years to reach. But unlike Andromeda, MoM-z14 is accelerating away from us, or more precisely, the space between us and MoM-z14 is expanding. It's "receding" at 726,000 km/s (= 2.4 times the speed of light). And still accelerating. Because of these, even the magical constant 1G accelerating spaceship can never reach it, not even in 1 Billion years.
hebelehubele 6d ago
There was a bit in the series "The Expanse" about a what's called "Epstein Drive" where some guy invents a propulsion tech based on fusion and he losts control of his aircraft under an ever-increasing acceleration. After some minutes, his body gets crushed under its own weight before he could reach the controls and slow the spaceship down. https://www.youtube.com/watch?v=1lS_WxQ3zeU https://www.youtube.com/watch?v=1lS_WxQ3zeU
- Terr_ 6d ago
  Yeah, certainly a reason to have failsafe timers and dead-man switches when testing new things. While I did read The Expanse, when I think of that class of dangers, what pops to my mind is an old short story Neutron Star (1966) [0]. A financially desperate pilot is hired to discover what killed some researchers while leaving the indestructible starship hull intact... and the thrusters off. [0] https://en.wikipedia.org/wiki/Neutron_Star_(short_story) https://en.wikipedia.org/wiki/Neutron_Star_(short_story)
  - zem 6d ago
    there was an interesting retcon of that story in one of niven's later works, where it was pointed out that any spacefaring race would know instantly what killed him. it was just better PR to pretend that it was a huge mystery, and that their hull wasn't vulnerable to some stupidly obvious danger but rather to something no one could have foreseen.
  - dotancohen 5d ago
    > failsafe timers and dead-man switches when testing new things. Aircraft and spacecraft are more than anything, mass constrained. Such failsafes are welcome in software, but neither the bleeding-edge engineers not even the test pilots would support adding failsafe mass if it would affect the tests.
  - xelxebar 5d ago
    Thanks for the Niven reference. Neutron Star was a fun read. I'm currently working through a collection of 80s SF shorts[0]. It's an entertaining lens into the narratives mores of the time, and or own in contrast. [0]:https://ci.nii.ac.jp/ncid/BB07948947 https://ci.nii.ac.jp/ncid/BB07948947

by Terr_ 6d ago

thwarted 6d ago

This is a really interesting video that explores this topic, pointing out that at near light speeds, the entire universe becomes accessible in a single human lifetime. The Overview Effekt: Time Dilation Visualized https://youtu.be/8FT-oz9aZU4 https://youtu.be/8FT-oz9aZU4

sinuhe69 6d ago

Then I guess you will need millions tones of perfect mass to light converter like Astrophage just to get to the neighbor. The universe is simply too big to comprehend.

no_multitudes 6d ago

> If you can somehow accelerate/decelerate at a constant human-acceptable 1G Well, you also need clarketech heat dissipation and collision deflection technology, if you want to get there without vaporizing.

Sohcahtoa82 6d ago
Yeah, once you reach a certain speed, even colliding with a fleck of dust can obliterate a ship. Colliding with a single 0.3 mg grain of salt at 20% of the speed of light creates an impact with 560 MJ of energy, equivalent to 130 kg of TNT, over 8 times the nuclear bomb dropped on Hiroshima. Even a tiny speck of dust, half a microgram, is equivalent to a hand grenade when hit at 20% the speed of light. You wouldn't be able to even escape the solar system before your shields were devoured. If you accelerated at 1G constantly, you'd be going 3.5% of the speed of light by the time you reached Pluto's orbit. Space dust particles are already hitting you like nuclear bombs at that speed.
dotancohen 5d ago
Details, details. That's mearly an implementation issue.

ahazred8ta 6d ago

There's a diagram for how long it takes a 'light-hugger' ship to travel various distances at 1-G acceleration. Shiptime is on the left, earth time is on the right. https://en.wikipedia.org/wiki/File:Roundtriptimes.png https://en.wikipedia.org/wiki/File:Roundtriptimes.png http://www.zitterbug.net/future/future815.html http://www.zitterbug.net/future/future815.html What If Light Was Really Slow? https://www.youtube.com/watch?v=ge_j31Yx_yk https://www.youtube.com/watch?v=ge_j31Yx_yk -- https://duckduckgo.com/?q=slower+speed+of+light&ia=videos&iax=videos https://duckduckgo.com/?q=slower+speed+of+light&ia=videos&ia...

asnelt 6d ago

That's the premise of Tau Zero, a very good novel: https://en.wikipedia.org/wiki/Tau_Zero https://en.wikipedia.org/wiki/Tau_Zero

jtbayly 6d ago

I’m confused. Is it 11k years to the closest galaxy at the speed of light, or somehow accessible in a human lifetime?

stouset 6d ago
Relativity is weird. If you keep accelerating, at some point the objects stop accelerating toward you faster but the distances get shorter. To an outside observer, the trip might have taken you millions or billions of years while to you it was only ten or twenty. It’s helpful to think about the limit. To light, which travels at the speed of light, it arrives at your retina the exact moment it was created in the core of the sun. From our perspective, it took almost a million years (about a million years to make it from the core to the convective region, then another few minutes to travel from there to Earth).
- digitalsushi 6d ago
  yeah but its statistical luck, a few photons keep winning the roulette wheel and pop out very quickly; and a few unlucky ones are still rattling around in there from year 1! it's more like winning a raffle than waiting in a queue
- jtbayly 6d ago
  > “At 99.999% C, the traveler would take ~11,000 years to arrive to Andromeda.” So presumably this means 11k years from an earth point of view? But the traveler would still be alive and a very short time would have passed for him?
  - stouset 6d ago
    Nope! Far, far longer. I don’t know the specifics that the GP used but Andromeda is about 2,500,000ly away. An observer on Earth must perceive you as taking more than 2,500,000 years to get there, as you would have to have exceeded the speed of light to arrive any sooner. At 1g of constant acceleration you can reach Andromeda in just under 15 years of experienced time. An observer on Earth will perceive you as having taken a hair over 2,500,000 years to get there. You can get there arbitrarily quickly; at 10g it would take a 1 year 9 months. But an external observer on either planet will see you taking closer and closer to 2,500,000 years to make it the full distance.

andruby 6d ago

You're right, but not entirely. At 1G constant acceleration reaching Andromeda would take ~15 years, or ~29 years if we also need to decelerate at the same 1G rate to not just whoosh by. The furthest known galaxy is MoM-z14, which would take ~47 years to reach. But unlike Andromeda, MoM-z14 is accelerating away from us, or more precisely, the space between us and MoM-z14 is expanding. It's "receding" at 726,000 km/s (= 2.4 times the speed of light). And still accelerating. Because of these, even the magical constant 1G accelerating spaceship can never reach it, not even in 1 Billion years.

hebelehubele 6d ago

There was a bit in the series "The Expanse" about a what's called "Epstein Drive" where some guy invents a propulsion tech based on fusion and he losts control of his aircraft under an ever-increasing acceleration. After some minutes, his body gets crushed under its own weight before he could reach the controls and slow the spaceship down. https://www.youtube.com/watch?v=1lS_WxQ3zeU https://www.youtube.com/watch?v=1lS_WxQ3zeU

Terr_ 6d ago
Yeah, certainly a reason to have failsafe timers and dead-man switches when testing new things. While I did read The Expanse, when I think of that class of dangers, what pops to my mind is an old short story Neutron Star (1966) [0]. A financially desperate pilot is hired to discover what killed some researchers while leaving the indestructible starship hull intact... and the thrusters off. [0] https://en.wikipedia.org/wiki/Neutron_Star_(short_story) https://en.wikipedia.org/wiki/Neutron_Star_(short_story)
- zem 6d ago
  there was an interesting retcon of that story in one of niven's later works, where it was pointed out that any spacefaring race would know instantly what killed him. it was just better PR to pretend that it was a huge mystery, and that their hull wasn't vulnerable to some stupidly obvious danger but rather to something no one could have foreseen.
- dotancohen 5d ago
  > failsafe timers and dead-man switches when testing new things. Aircraft and spacecraft are more than anything, mass constrained. Such failsafes are welcome in software, but neither the bleeding-edge engineers not even the test pilots would support adding failsafe mass if it would affect the tests.
- xelxebar 5d ago
  Thanks for the Niven reference. Neutron Star was a fun read. I'm currently working through a collection of 80s SF shorts[0]. It's an entertaining lens into the narratives mores of the time, and or own in contrast. [0]:https://ci.nii.ac.jp/ncid/BB07948947 https://ci.nii.ac.jp/ncid/BB07948947