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Physics/Relativity question


JerryK
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Why not ask it here? I already know my facebook friends can't help me.

It's simple really, here's the setup:

*You're going to a star 20 light years away - ROUND trip. 10 light-years each way.

*You're going at 90% the speed of light "C", with an estimated 30yr round trip time due to only going 90% of C.

*We all know that as you approach C, 'time runs more slowly'.

Questions:

I've told my kids you'd return from this trip 30 years older and due to the final statement, the earth might be 1000 years older.

But now I'm not so sure.

Perhaps the opposite happens? Perhaps 'time slowing down' means you'd think you're getting there in only a week, and you'd return in the pre-planned 30 earth-years? Put a little differently, as the astronaut approaches C, can his perception of time drop BELOW the established 20 light-years, or can that perception only drop toward a fixed lower limit of the 20-year measurement?

After all, 'Relativity' means relative to the observers, and your 90% of C velocity results from fuel/acceleration calculations that were done on Earth. 90%C IS your velocity as Earth sees it, and the star's distance is unchanging.

Many thanks for any nerds who can help clarify this.

Edited by JerryK
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Was able to get an answer...I'll pass it along for those dying to know :)

The term for this scenario is 'time dilation'.

Yes, the person traveling can experience far less actual time for the trip. .9999% of C could make vast distances nearly instant. (except your friends will be mummies when you return home)

Bonus, despite calculations of a 30yr round trip, you'd actually return in about 22, based on savings Relativity provides at that speed; savings that are not apparent in simple (velocity * time) calculations.

Live long and prosper.

Edited by JerryK
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Was able to get an answer...I'll pass it along for those dying to know :)

The term for this scenario is 'time dilation'.

Yes, the person traveling can experience far less actual time for the trip. .9999% of C could make vast distances nearly instant. (except your friends will be mummies when you return home)

Bonus, despite calculations of a 30yr round trip, you'd actually return in about 22, based on savings Relativity provides at that speed; savings that are not apparent in simple (velocity * time) calculations.

Live long and prosper.

And age only 18 months and find out the planet is ruled by Apes!

In all fairness this theory still has not been practically proved. Has it ?

If man landed on the moon and it took them say 7 days round trip did they come back in less amount of time than that ?

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And age only 18 months and find out the planet is ruled by Apes!

In all fairness this theory still has not been practically proved. Has it ?

If man landed on the moon and it took them say 7 days round trip did they come back in less amount of time than that ?

Here's a formula to determine the speed (as a fraction of c) that you would have to travel at to go any distance, d (in light-years), in any time, t (in years): v = 1 / √[1 + (t/d)²]

So to go halfway across the galaxy (est 25,000 light-years) in 1 month and join up with the rebellion, my son will need to go 0.99999999999444488888004628888933 of C.

He's going to need a faster bike. :)

Edited by JerryK
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Why not ask it here? I already know my facebook friends can't help me.

It's simple really, here's the setup:

*You're going to a star 20 light years away - ROUND trip. 10 light-years each way.

*You're going at 90% the speed of light "C", with an estimated 30yr round trip time due to only going 90% of C.

*We all know that as you approach C, 'time runs more slowly'.

Questions:

I've told my kids you'd return from this trip 30 years older and due to the final statement, the earth might be 1000 years older.

But now I'm not so sure.

Perhaps the opposite happens? Perhaps 'time slowing down' means you'd think you're getting there in only a week, and you'd return in the pre-planned 30 earth-years? Put a little differently, as the astronaut approaches C, can his perception of time drop BELOW the established 20 light-years, or can that perception only drop toward a fixed lower limit of the 20-year measurement?

After all, 'Relativity' means relative to the observers, and your 90% of C velocity results from fuel/acceleration calculations that were done on Earth. 90%C IS your velocity as Earth sees it, and the star's distance is unchanging.

Many thanks for any nerds who can help clarify this.

the former, you'd age 30 years and people on earth would have aged 70+.. moving near the speed of light allows time travel into the future.. to go backwards, you'd need a blackhole or massive amounts of gravity

look up twin paradox for more info

Edited by CTM
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And age only 18 months and find out the planet is ruled by Apes!

In all fairness this theory still has not been practically proved. Has it ?

If man landed on the moon and it took them say 7 days round trip did they come back in less amount of time than that ?

The speeds aren't close enough to the speed of light to have any real impact, but they have measured fractions of a second distortions in trips in fast jets

Edited by CTM
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JetsFanInDenver,

I think this test with atomic clocks on jets was intended to verify the 'time slowdown' of objects at high speed:

Hafele and Keating Experiment

"During October, 1971, four cesium atomic beam clocks were flown on regularly scheduled commercial jet flights around the world twice, once eastward and once westward, to test Einstein's theory of relativity with macroscopic clocks. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40+/-23 nanoseconds during the eastward trip and should have gained 275+/-21 nanoseconds during the westward trip ... Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59+/-10 nanoseconds during the eastward trip and gained 273+/-7 nanosecond during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks."

J.C. Hafele and R. E. Keating, Science 177, 166 (1972)

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JetsFanInDenver,

I think this test with atomic clocks on jets was intended to verify the 'time slowdown' of objects at high speed:

Hafele and Keating Experiment

"During October, 1971, four cesium atomic beam clocks were flown on regularly scheduled commercial jet flights around the world twice, once eastward and once westward, to test Einstein's theory of relativity with macroscopic clocks. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40+/-23 nanoseconds during the eastward trip and should have gained 275+/-21 nanoseconds during the westward trip ... Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59+/-10 nanoseconds during the eastward trip and gained 273+/-7 nanosecond during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks."

J.C. Hafele and R. E. Keating, Science 177, 166 (1972)

the former, you'd age 30 years and people on earth would have aged 70+.. moving near the speed of light allows time travel into the future.. to go backwards, you'd need a blackhole or massive amounts of gravity

look up twin paradox for more info

Interesting stuff guys.

On the other hand this thread makes me feel better about changing course towards computer science in school! :)

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the former, you'd age 30 years and people on earth would have aged 70+.. moving near the speed of light allows time travel into the future.. to go backwards, you'd need a blackhole or massive amounts of gravity

look up twin paradox for more info

CTM win

The speeds aren't close enough to the speed of light to have any real impact, but they have measured fractions of a second distortions in trips in fast jets

CTM win

Bullsh*t.

fluxcapacitor.jpg

Johnny Hector domination. LOL

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So to go halfway across the galaxy (est 25,000 light-years) in 1 month and join up with the rebellion, my son will need to go 0.99999999999444488888004628888933 of C.

He's going to need a faster bike. :)

He might also put on a lot of weight. Don't you start gaining infinite mass as you approach the speed of light, [C]?

Edited by kelticwizard
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Why not ask it here? I already know my facebook friends can't help me.

It's simple really, here's the setup:

*You're going to a star 20 light years away - ROUND trip. 10 light-years each way.

*You're going at 90% the speed of light "C", with an estimated 30yr round trip time due to only going 90% of C.

*We all know that as you approach C, 'time runs more slowly'.

Questions:

I've told my kids you'd return from this trip 30 years older and due to the final statement, the earth might be 1000 years older.

But now I'm not so sure.

Perhaps the opposite happens? Perhaps 'time slowing down' means you'd think you're getting there in only a week, and you'd return in the pre-planned 30 earth-years? Put a little differently, as the astronaut approaches C, can his perception of time drop BELOW the established 20 light-years, or can that perception only drop toward a fixed lower limit of the 20-year measurement?

After all, 'Relativity' means relative to the observers, and your 90% of C velocity results from fuel/acceleration calculations that were done on Earth. 90%C IS your velocity as Earth sees it, and the star's distance is unchanging.

Many thanks for any nerds who can help clarify this.

If I understand correctly the total round trip is 20 light years and you're going 90% the speed of light. You should be back in approx 22 years. As for the world probably being 1000 years older I've heard of theories like that but im not too familiar with it that info, however, light measured in light years is an earthly constant. If you're traveling at a speed based on earthly measurements then the travelers should return 22 years older and the people on earth should have aged the same amount of time given that we're dealing in a measurement relative to everyone, not specifically to the travelers or to the people left on earth.

I could be wrong here. Space is weirder than anyone's imagination.

Edited by villain_the_foe
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At c any journey is instantaneous to the traveler but the time passed from a stationary observer's perspective is 1 sec for each 186,000 miles traversed

time dilation equation returns an undefined solution when v is greater than c, hence the hypothesis by Einstein that c is the max velocity (not quite true depends on your frame of reference, which is what relativity means) and theories that if you could somehow exceed it you would go backwards in time.

Check out length contraction, another weird result of near c velocities

Edited by jgb
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jgb, very nice. I'm surprised you didn't end up in patent law.

I almost did, but after the lsat I decided I'm too old, and IP firms seemed stocked with people who are more like Gordon Gecko than Carl Sagan.

Haha - I was an astrophysics major in undergrad until I realized you couldn't bs your way through differential equations with a hangover. Hello polisci!

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You'd be in outer space most of the flight so once you escaped Earth's gravity it would be pretty smooth sailing. Problem is, as I understand it as you approach the speed of light you also begin to approach infinite mass, until when you hit the speed of light your mass is equal to that of the entire universe.

So it would be difficult imagining that happening.

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I'd need to see the curve of the mass increase vs speed to know if it's a problem to a traveler at 99.993%.

Is the increased mass really relevant at 99%? You won't get sucked into the floor because there's no earth under you, and everything around you is gaining at an equal rate. So wouldn't the gravities created by everything's increased mass be relatively equivalent?

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I'd need to see the curve of the mass increase vs speed to know if it's a problem to a traveler at 99.993%.

Is the increased mass really relevant at 99%? You won't get sucked into the floor because there's no earth under you, and everything around you is gaining at an equal rate. So wouldn't the gravities created by everything's increased mass be relatively equivalent?

Here's the chart. As you can see by the time you hit 97% or so of the speed of light, the curve for mass increase is virtually straight up. By the time you hit 99.993%, the mass must be absolutely staggering.

Chart was taken from the following site: http://www.lbl.gov/M.../massenergy.pdf

By the way, please don't get the idea that I figured this out from the relevant equations. Everything I know about this was from articles in Discover and similar magazines. The highlight of my mathematical ability is that I can tell you how many millimeters are in an inch without looking it up, (25.4).

post-8744-0-90441300-1315278328_thumb.jp

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