# Perspective on “light years”

If Alpha Centauri (approx 4.5 light years) is our nearest star, at the highest possible speed for human spacecraft, how long would it take to travel there? People talk about interstellar travel. People do not realize the vastness and distances involved. Inhabiting alien planets or moons would have to therefore reside inside our solar system. Interstellar distances are simply too vast for this possibility.

• Not true thanks to relativity: math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html
– user7073
Oct 22 '18 at 2:07
• @SF, project Orion has a theoretical maximum $I_{sp}$ of 100000 seconds, according to wikipedia en.wikipedia.org/wiki/Nuclear_pulse_propulsion, corresponding to an exhaust velocity of about 1000 $km/s$. To get to alpha centauri in 100 years needs a velocity of $0.04 c$ about $13000 km/s$ so a delta-V of twice that. The mass ratio you would need is still ridiculous. Project Orion doesn't cut it. Oct 22 '18 at 15:52