How fast would a spaceship have to travel to reach another solar system within the pilot's lifetime?

Question

Can any astronautical boffins give me a rough estimate of how fast you'd have to go to get to the nearest solar system/s to ours? Return journey, what's the point on going if you can't come back and tell people? Bonus points if the elpased time on earth can be worked out too.

Answer 1

Trick question. No such thing as "bonus points". You're not allowed to reward more points than the 'best answer' provides.

Answer 2

The current lack of knowledge regarding space travel, which would have to be, say, at the speed of "thought" (or something), and the severe restriction in our present upper age limits, which would have to be in the 100's and not the 10's as it is now, make it impossible to comprehend accurately and feasibly. However, the way technology is racing forward and each generation of people are living longer, I reckon that in another 500 to 1,000 years, we will have cracked most of the mysteries that confound us today, including space travel to other solar systems and galaxies, even though it's unbelievable now (like the dangers of travelling faster than walking pace on our first train and falling off the edge of the Earth, used to be).

Answer 3

Why don't the other answer give a straightforward answer?

To travel 20 light years, at 0.5 c, would feel like 34.6 years to the passengers. Meanwhile, 40 years have passed back on Earth. Total round-trip would be 69.2 years, with 80 years elapsed on Earth.

It would have to be a multi-generational trip -- start as a little kid, grow up, become part of the crew, have a full career, retire, then arrive back at Earth. Meanwhile, the other passengers and crew are also growing up, having families, etc.

Answer 4

Depending on factors..which destinational planet? The distance between here and there. The mode of transportation and its speed or velocity. If you travel at the speed exceeding light then it might be possible to reach planets outside our home range. Light travels from a planet to earth at a quasi-known speed, the time you get there would be in a classical sense, many generations later. 'Quasi' mainly because it is not actually and physically proved nor established as being true and as such needs to be taken into account.

Answer 5

Suppose the target is 4.3 light years away, so you need to go 8.6 light years. Call this d.

Suppose have 40 years to do it (you leave when you're 20 and want to be back by age 60). Call this tp, the proper time

According to special relativity

tp gamma = d / v

where gamma = 1 / sqrt (1-(v/c)^2)

(v * gamma)^2 = 1/ (1/v^2 - 1/c^2) = (d / tp)^2

c^2 v^2 / (c^2 - v^2) = (d / tp)^2

v^2 (c^2 + (d / tp)^2) = (cd / tp)^2

v = cd / (tp sqrt (c^2 + (d / tp)^2) )

So we know c, d, and tp. Plugnchug.

Then use v to calculate gamma.

Earth time = gamma * tp

Get out your calculator. Have fun.

And yeah, as Creole Geek said, this assumes you can get up to speed instantaneously. If you limit yourself to 1g of acceleration and deceleration, that slows you down more.

And we haven't even begun to discuss the amount of fuel you would need for this trip.

Or the shielding to protect yourself from cosmic rays (which are going to be very very intense at relativistic speeds).

Put all this together and you'll begin to understand why interstellar travel is many, many generations of technology away.

Answer 6

To reach the nearest "Earth-type" planet (only one is know to exist)) 20 light years away, within a lifetime and return:
Life expectancy = 78 years
Age at becoming an astronaut 25 years (very optimistic)
average speed = 40/(75 - 25) = 0.8c (allows 3 years retirement)
Under minimum constant acceleration the speed at turnover would be 1.6c with respect to Earth.

The elapsed time on Earth would be 50 years, just as it would be on the ship. The crew of the ship would have the privilege of seeing an entirely different universe than we see. Attempts to navigate by the stars we know would become futile.

Answer 7

To give you another example, like the other said, Alpha Centauri is 4.3 light year away from us. That means that at the speed of light (300,000km/sec) it will takes 4.3 years.

Supposed we are in Star Trek, maximum warp in Star Trek which is just a bit over Warp 9, represent approximatively 1000 times the the speed of light.

Even at that crazy speed it still takes 1.5 days to get there. Now imagine our galaxy is 100,000 light year wide, so even at maximum warp in star trek it will take them 100 years to cross it.

And our galaxy is just one of billions of other galaxies out there. Space is big, real big, even in a science fiction point of view.

Answer 8

Since Alpha Centauri is 4.3 light years away, you would have to travel at least 4.3 / 40 = .1075 times the speed of light to reach it in 40 years. That amounts to 20,000 miles per second. The fastest human beings have ever traveled in space is 7 miles per second.

Answer 9

4 years at the speed of light.

Answer 10

The speed is only part of the problem. If you wanted 1g of acceleration it would take 967 years just to reach the speed of light.

Answer 11

The speed of light.