Alpha Centauri Pictures

Alpha Centauri is the closest star to our sun at a distance of 4.4 light years. I once read an expert's estimate that if we poured resources into a project to get a probe to Alpha Centauri, comparable to what we did to get to the moon, in a decade we'd have a probe that could get there within a human lifetime, 40-50 years. Then of course, it'd take 4.4 years to get the first pictures back. Anyway, this got me thinking. How long, more specifically, would it take to get to Alpha Centauri, the closest star, at different percentages of light speed? How does this compare with speeds we are able to achieve with our current technology?

A few facts...

Distance to Alpha Centauri	4.4 Light Years
Speed of Light, in MPS	186,282.398
Seconds in One Year	31,536,000
One Light Year in Miles	5,874,601,690,713.6
Miles to Alpha Centauri	25,848,247,439,139.8

Here's what it's going to take!

Speed Record	% Light Speed	MPS	Travel in Years
	100	186,282.398	4.40
	90	167,654.158	4.89
	80	149,025.918	5.50
	70	130,397.678	6.29
	60	111,769.439	7.33
	50	93,141.199	8.80
	40	74,512.959	11.00
	30	55,884.719	14.67
	20	37,256.480	22.00
	10	18,628.240	44.00
	1	1,862.824	440.00
27.4 MPS is the speed of the the fastest man-made object, the Ulysses probe. This speed was achieved using multiple gravity assists from various planets to achieve a circumpolar orbit around the sun	0.0147089	27.400	29,913.96
10.278 MPS is 37,000 MPH, the approximate speed of the Voyager 1 and 2 probes	0.0055173	10.278	79,749.30
0.59 MPS is 2,124 MPH, over Mach 3, the unclassified speed record of the SR-71 Blackbird, set crossing the continental U.S. in 1990	0.0003167	0.590	1,389,224.66
0.375 MPS is 1,350 MPH, just over Mach 2, the cruising speed of the Concorde	0.0002013	0.375	2,185,713.47
0.066 MPS is 237.498 MPH, the Indianapolis 500 speed record, set by Arie Luyendyk in 1996	0.0000354	0.066	12,429,288.87
0.015 MPS is 55 MPH	0.0000082	0.015	53,649,330.51

Really puts it into perspective, doesn't it? Hmm, personally I don't have 53.6 million years to kill on a road trip...

Here's something else too. Lately I've been reading the book "The Physics of Star Trek" by Lawrence M. Krauss (fascinating stuff!), and I came across another thing relating to this subject. Suppose you had a starship capable of traveling at 50% light speed, and you've prepared yourself for the long trip to Alpha Centauri (eight years and nine 1/2 months), and you're all strapped in and ready to go, then Mr. Krauss points out:

"If I want to accelerate from rest to, say, 150,000 km/sec, or about half the speed of light, I have to do it gradually, so that my body will not be torn apart in the process. In order not to be pushed back into my seat with a force greater than 3 Gs [...] it would take some 5 million seconds, or about 2 1/2 months, to reach half light speed!"

Mr. Krauss goes on to say that spending 2 1/2 months accelerating to "half impulse" would make for an extremely dull Star Trek episode, and it certainly would! For us though, it just makes our 50% light speed trip to Alpha Centauri take 9 years and 2 1/2 months. However, there's another thing. Could the human body survive living at 3 gravities for 2 1/2 months? Fighter pilots and astronauts go through high G periods, but for seconds or minutes at most! Not for months! Perhaps it would be better to add a few more months to the trip and limit the acceleration to 1 G. I'd tell you how long the trip would take with a 1 G acceleration limit, but I don't know what calculations Mr. Krauss used to arrive at 2 1/2 months at 3 Gs to get to 50% light speed in the first place...

Woah! Just because I don't know, doesn't mean no one knows! Many thanks to Stuart Forbes, webmaster of the Space Exploration Discussion Page, who does know those calculations and sent me the following!