A question about lightspeed travel

[mgwisni]

I have a question about lightspeed travel. I've heard if it were possible to travel at light speed or near it, time to those traveling that fast would go by much faster than the actually world around them. For example, if a man were traveling at near lightspeed and when he started he was 16. He travels 50 light years out. Supposedly it would feel like a few weeks to them, but it would be 50 years in regular time. Why is that?

[James R]

One word: relativity.

It turns out that time runs at different rates for different observers who are in motion relative to one another.

Einstein worked out the mathematics of this in his Special Theory of Relativity, which was published in 1905.

[mgwisni]

So does that mean that to ants, time goes faster than to humans?

[bigjnorman]

yeah, and sloths too.....

No, the reason it is hard to comprehend time delation is because humans never experience it. You would have to be traveling at a significant fraction of the speed of light in order to really experience the effects of relativity.

Jonathan

[mgwisni]

I still don't understand. If something was 50 lightyears away, wouldn't it take you 50 years to get there traveling the speed of light?

[Redrover]

To confuse you even more, according to relativity, if you were in that space ship going to close to the speed of light, it would feel as if you took less time to get there because it would feel as if your destination was much less farther away.

But before you actually feel any time dilatation, you have to go very fast. For example, the fastest speed ever inflicted upon a human is about 28 500 km/h. At that speed, your 50-light-year trip would take 376 years but at least it would only feel like a 372-years-and-a-half-trip.

[Janus58]

Originally posted by Redrover


But before you actually feel any time dilatation, you have to go very fast. For example, the fastest speed ever inflicted upon a human is about 28 500 km/h. At that speed, your 50-light-year trip would take 376 years but at least it would only feel like a 372-years-and-a-half-trip.

Um, at that speed, it would take 1894736 years to cross 50 ly. (But would only feel like 1894735 yrs, 364 days, 18 hrs, 13 mins and 15 secs.

[Redrover]

Sorry about that. I guess my brain conked out on that math bit.

[Greco]

If one travels at one G how long will it take to reach light speed?

How fast can somebody attain light speed without getting squished?

If you have a destination you got to slow down before you get there so that means at the half way mark you got to start breaking.

I suspect that even future travellers will travel at near light speeds for brief time periods.

[ElectricFetus]

If one travels at one G how long will it take to reach light speed?

about ~353 days: ((((299,000*1000)/9.8m)/60)/60)/24)

How fast can somebody attain light speed without getting squished

they never get squished only to a outside observer does it look like there getting flatter.

[Janus58]

Originally posted by WellCookedFetus
about ~353 days: ((((299,000*1000)/9.8m)/60)/60)/24)



they never get squished only to a outside observer does it look like there getting flatter.

I believe they were refering to how much acceleration one can withstand in attaining c.

Generally, the max G-force the human body can withstand is 9g-10g, but only for short periods of time (a few seconds). Such high gs cause the blood to pool in the in the body, which restricts circulation and causes oxygen starvation to the brain.

Even at 10g, it would take about 35 days to reach near light speed; much, much longer than the human body could withstand it.

Even two gs can cause some effects, (loss of peripheral vision, etc.), which leads one to assume that long term exposure may have permanent detrimental effects. No one really knows for sure, though, since we are not able to perform such long term tests.

We might be able to withstand a few percent over 1g for these long periods with ill effect, but we just don't know how few and for how long.

[ElectricFetus]

The human body could withstand far more if contained in an aqueous environment of equal density to the body. By the way how are you going to travel that fast and accelerate like that?

[Janus58]

Originally posted by WellCookedFetus
The human body could withstand far more if contained in an aqueous environment of equal density to the body. By the way how are you going to travel that fast and accelerate like that?

True, aqueous immersion can reduce the effects of g-force. Though I don't think even it would allow you withstand +10g forces for long periods of time. That still leaves you floating in a tank for 35 days.

You hit the nail on the head with the problem of actually maintaining these accelerations until you reach near light speed.

Oh, as a side note, the 353 day 1g acceleration time is as measured on ship. By Earth time it would be about 938 days. (to reach .99c)

[2inquisitive]

Something I don't understand. Isn't 1g the force we normally feel
standing on the face of the earth? Since this force would not be
felt by our bodies in the freefall of space (not accelerating), how would this affect the speed necessary to feel 1g (enertia?) while
accelarating in free space?

[ElectricFetus]

Experiment on salamanders demonstrated survival under 30-40g for several generations time period.

2inquisitive,

if your accelerating at 9.8m/s^2 or going 9.8meter per sec faster every second this would feel like earth gravity regardless of where you are… I’m not sure if I understand your question though?

[2inquisitive]

I posted that question without thinking. I feel like a moron. I guess
I was thinking that since we were feeling 1g on the earth and
0g in freefall BEFORE acceleration had begun, it might have an
effect on the speeds necessary to feel 1g. I realize now that
either way, we would still be feeling 0g due to acceleration and
the 1g due to gravity would have no effect. Sorry.

[Greco]

Originally posted by WellCookedFetus
The human body could withstand far more if contained in an aqueous environment of equal density to the body. By the way how are you going to travel that fast and accelerate like that?

I dont understand why one wouldnt feel the forces of accelaration if immersed in an aqueous environment it seems to me that the G forces would be equally distributed in the space cabin. A 10 G accelaration would put a 10 G pressure on your body. Maybe you can elaborate a little more on that thought.

I'm not a rocket scientist but speculating on fuels that can be used for such accelarations would be a. a fussion reactor/engine that would fuse hydrogen in a series of explosions b. matter antimatter reactions/explosions.

[eburacum45]

quote:
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If one travels at one G how long will it take to reach light speed?
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Originally posted by WellCookedFetus
about ~353 days: ((((299,000*1000)/9.8m)/60)/60)/24)

But if you consider the acceleration from the point of view of the traveller, you could accelerate for ever at 1 gee without ever reaching light speed.
Your mass would increase, time slow down, and your length contract as seen from a stationary viewpoint,

but from your viewpoint you would still feel one gee acceleration forever (until your fuel ran out).
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[2inquisitive]

Another dumb question from me. Would sitting in a rotatable seat,
attached to the inside of something simular to James R's avatar,
changing the body's orientation every few minutes, be enough
to keep the body's fluids from pooling? I guess the ship would
have to be on autopilot while accelerating, though.

[ElectricFetus]

Oh you would feel the Gs, the idea is that if your immersed in a fluid of equal density to your body, your body won’t get compressed or squished, though in reality your bones would.

Now come on stop nit picking you guys of course you can never achieve the speed of light.
Fusion propulsion at best could get you up to .15c or 15% the speed of light, and it accelerates like crap, antimatter and laser sails about .5c and they accelerate even worse.
http://www.islandone.org/APC/index.html

[eburacum45]

Absolutely, the fluid filled spacecraft is a much better idea for reducing the effects of acceleration; consider the whale, supported by water and it's own bouyancy- on land it cannot support its own weight and suffocates.

I would go further and fill the spacecraft with nanomachines, capable of actively carrying oxygen to the lungs and CO2 away, yet able to become rigid and supportive when required. Utility fog is an example of such an imaginary technology.
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[Greco]

[QUOTE]Originally posted by eburacum45
[B]Absolutely, the fluid filled spacecraft is a much better idea for reducing the effects of acceleration; consider the whale, supported by water and it's own bouyancy- on land it cannot support its own weight and suffocates.

Has anybody experimented with a centrifuge and a liquid filled cabin and the effects on living organisms?It seems to me that boyancy just muddles the waters.:D