this post was submitted on 20 Jul 2023
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What if solving interstellar travel isn't about figuring out faster than light propulsion, but how to extend our own lives? (lemmy.world)
submitted 1 year ago by danhab99@lemmy.world to c/askscience@lemmy.world
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So I was day dreaming and I caught a thought. What if what we understand about physics is actually all there is to understand? What if you objectively cannot move faster than the speed of light because you can't do the time traveling things necessary. This would mean that the only way to travel amongst the stars would be to extend our lives so that a 5000 year trip at the speed of light would represent like 10% of our lifespans. Travel would be attainable but like the way it was when we were sailing ships to the new world.

That's just one practical solution I could think of to stellar travel. Does anyone else have a practical idea?

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[–] TauZero@mander.xyz 20 points 1 year ago (2 children)

You are behind the times on physics advancements buddy! Thanks to the recently discovered concept of relativistic time dilation, a 5000 light year trip at the speed of light will take literally 0 seconds of your lifespan. More practically, travelling in a starship that accelerates at 1G to the halfway point, turns around and decelerates to the destination, you can reach ridiculous distances within a single human lifetime:

shipboard time distance earth time
1 year .263 LY 1.05 Y
2 years 1.13 LY 2.37 Y
3 years 2.82 LY 4.35 Y
4 years 5.80 LY 7.50 Y
5 years 10.9 LY 12.7 Y
10 years 166 LY 168 Y
15 years 2199 LY 2201 Y
20 years 28.8 kLY 28.8 kY
25 years 380 kLY 380 kY
50 years 149 GLy 149 GY
100 years 22.8 ZLy 22.8 ZY

This is the formula to calculate the distance and time:

x(τ) = c**2/a [cosh(τ a/c) - 1]
t(τ) = c/a sinh(τ a/c)

a = 9.8 m/s
c = 3e8 m/s

The formula is hyperbolic, which is why travel distance is not a linear relation of travel time. E.g. given τ = 10 years:

x = 3e8**2/9.8 * (cosh(60*60*24*365*10/2 * 9.8/3e8) - 1) * 2 / (3e8 * 60*60*24*365)
  = 166 light years
t = 3e8/9.8 * sinh(60*60*24*365*10/2 * 9.8/3e8) * 2 / (60*60*24*365)
  = 168 years
[–] calhoon2005@aussie.zone 3 points 1 year ago (1 children)

But what about the bit about not hitting anything whilst travelling at that speed? Even a speck of space dust would do massive damage at those speeds, right?

[–] TauZero@mander.xyz 3 points 1 year ago

Oh yeah, it's like flying the wrong way down the tube of the Large Hadron Collider. The tougher challenge though is like @MuThyme@lemmy.world said maintaining 1G acceleration. Following the rocket equation, which is logarithmic, a 50 year multi-stage rocket will be bigger than the universe itself, even if you use some kind of nuclear propulsion 10000 times more efficient than our chemical rockets.

[–] danhab99@lemmy.world 3 points 1 year ago (3 children)

Wait so the only thing limiting our interstellar travel is money? That's awesome!!!

[–] Aux@lemmy.world 17 points 1 year ago

No, the only limit to everything in our lives and in the universe in general is... Energy! Energy is the real currency of the world.

[–] MuThyme@lemmy.world 10 points 1 year ago

Nah, it's actually super hard to maintain that acceleration. Not to mention all the fun of radiation, avoiding random obstacles and I assume the interstellar medium will become more dense to an accelerated observer.

We have idea on how to do it, but the engineering is far from it yet.

[–] spacedancer@lemmy.world 5 points 1 year ago

That, and figuring out how to travel even just a significant fraction of the speed of light.