The Final Frontier *insert Spock's 3rd ear joke here*

mrk

mrk

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How Far Could Astronauts Go?

How far could an astronaut travel in a lifetime? Billions of light years, it turns out. But they ought to be careful when to apply the brakes on the return trip.
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Ever since cosmologists discovered that the universe's expansion is accelerating, many have wondered just how much this will constrain what we could see with telescopes in the future. Distant regions of the universe will eventually be expanding so fast that light from any objects there can never reach us.

A nice little article I read over lunch today that I forgot to post, I especially like the terrifying conclusion at the end though meaning the space traveller that accepts the mission to sprawl the universe racing with expansion would only find nothing upon his return.

30-50yrs for the traveller = billions of years back in Earth time!
 

CBJ

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I take it this incredibly clever university scientist neglected the small matter of how you would power acceleration at 1G for that amount of time. I don't really fancy doing the maths, but I rather think that if you were using fuel then the amounts would be *ahem* astronomical, especially when trying to get going with a full fuel load at the start. OK, I know this was a thought experiment rather than anything terribly serious, but as usual it gets reported as though it were something more concrete. :rolleyes:
 
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I take it this incredibly clever university scientist neglected the small matter of how you would power acceleration at 1G for that amount of time. I don't really fancy doing the maths, but I rather think that if you were using fuel then the amounts would be *ahem* astronomical, especially when trying to get going with a full fuel load at the start. OK, I know this was a thought experiment rather than anything terribly serious, but as usual it gets reported as though it were something more concrete. :rolleyes:

Do you need constant thrust? Or would travelling in a vacuum only require one initial burst?
 

CBJ

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Constant thrust. You're accelerating at a rate equivalent to 1G.
 
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Going by 40 years equalling 70 billion on earth, couldn't you travel for .0000004 years (seconds) and when you come back 700 years will have passed?
 

CBJ

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Going by 40 years equalling 70 billion on earth, couldn't you travel for .0000004 years (seconds) and when you come back 700 years will have passed?
No. Travelling for that short a period of time, you'd never reach a speed at which relativistic effects would kick in. The reason for the time difference over 40 years is that you'd reach relativistic speeds after a certain amount of time; only then would the time dilation start kicking in.
 
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No. Travelling for that short a period of time, you'd never reach a speed at which relativistic effects would kick in. The reason for the time difference over 40 years is that you'd reach relativistic speeds after a certain amount of time; only then would the time dilation start kicking in.

How long does it take to reach relativistic speeds? ie How little time could you travel for before hundreds of earth years pass?
 

CBJ

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As I said, I can't be bothered to do the maths. With a little lazy Googling, however, I found this:

Grant Hutchison on some random forum somewhere said:
Trouble is, a constant 1g as measured aboard your spaceship will be a steadily decreasing acceleration as observed from outside: so your spaceship can never reach lightspeed. If β is the required velocity as a fraction of the speed of light, a is the constant acceleration aboard ship and c is the speed of light, then the time necessary to reach β as measured by a stationary observer is:

t = cβ/(a√[1-β²])

The corresponding time aboard ship is:

t' = c.arctanh(β)/a

Both of these climb towards infinity as β approaches 1.
Someone else rather more approximately suggested that you might reach a speed 0.99G after about a year. Without applying the formula I'm not sure whether this is correct but it doesn't sound totally unreasonable. That would mean a round trip of a little under 4 years should be plenty to create some seriously weird time effects. However the amount of fuel required would still be in the order of silly.
 
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v = at

So accelerating at a rate of 9.8m/s^2, you would reach .99C in about 354 days, however by filling body cavities with liquid much higher rates of acceleration can be achieved.
 

mrk

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Do you need constant thrust? Or would travelling in a vacuum only require one initial burst?

The article says that an Asteroid can in theory do it and an asteroid is hardly being powered by Shell VPower now :p

It also says that the return journey will be most challenging because if the brakes are applied a fraction out then you'll be billions of light years away from Earth!
 
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