near lightspeed travel

[samtheflash82]

when you travel at speeds approaching that of light, is that not similar to traveling through time? i mean, lets say you leave earth on your near light speed journey and when you return, you will have experienced less time on the spaceship than people have on earth according to relativity. isn't that time travel? sorry if this is an obvious question but i have seen lots of people asking if "time travel" was possible.

[swansont]

It's time travel in the trivial way that we all travel through time.

[samtheflash82]

It's time travel in the trivial way that we all travel through time.

 

but people dont seem to realize this. many people (without a firm understanding of relativity perhaps?) seem to think that time travel is impossible, yet it clearly is not so.

[max.yevs]

There is an experiment where if two clocks are set to the same exact time, and one flown round trip across the world and back to where the second clock is would be a couple seconds behind the other one... i cant seem to wrap my head around how that works

 

http://www.pbs.org/wgbh/nova/einstein/hotsciencetwin/ (scroll down, i know this site is kind of made for kids)

 

it also has the example you're reffering to.

 

and it is sort of like time travel- in fact- the person on the spaceship would sort of be moving forward in time- but would the people on earth be moving backwards in time?

Edited March 25, 2009 by max.yevs

[iNow]

there is some experiment like if two clocks are set to exactly the same time, say in New York, and then one of them is taken on a jet around the world and back to New York, it will be like a couple seconds ahead or behind the other clock...

 

anybody know what i'm reffering to?

 

Yup. That's the Hafele-Keating experiment:

http://en.wikipedia.org/wiki/Hafele-Keating_experiment

 

 

gdRmCqylsME

 

 

It's also been done more recently using more modern clocks and techniques, and demonstrated to even greater accuracy since the above referenced experiment was run.

[cameron marical]

there is some experiment like if two clocks are set to exactly the same time, say in New York, and then one of them is taken on a jet around the world and back to New York, it will be like a couple seconds ahead or behind the other clock...

 

anybody know what i'm reffering to?

 

ya, its called the hafele-keating experiment. a couple atomic clocks and 2 commercial jet flights around the world twice. then compared with the u.s clocks naval observatorie. it worked too. like nanoseconds of pure relativity prediction.

 

dang it! you must have posted right before mine inow. blast.

[iNow]

dang it! you must have posted right before mine inow. blast.

 

No, I'm just traveling faster than you are.

[max.yevs]

how does that work? i mean you have two clocks, what importance is it how fast they're moving? sorry i just cant wrap my head around it

 

do both the planes get their watches behind? despite their direction?

[NowThatWeKnow]

but people dont seem to realize this. many people (without a firm understanding of relativity perhaps?) seem to think that time travel is impossible, yet it clearly is not so.

 

Gravity and speed (acceleration) cause clocks to to tick at different speeds so we are all traveling through time, but some at different rates. This could put you into someones future but not their past.

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do both the planes get their watches behind? despite their direction?

 

Yes, if the trips were the same as far as acceleration, speed and time.

[max.yevs]

intersting... i thought that if you move very fast, it will be as if everybody else is staying still, like in that movie... but this way, if everybody else is moving very fast they'll be staying still in relation to you?

 

P.S. i almost tipped over my monitor trying to get that bug.

[NowThatWeKnow]

Yup. That's the Hafele-Keating experiment:

http://en.wikipedia.org/wiki/Hafele-Keating_experiment

 

That video made it sound like only SR was considered and not GR because of altitude.

[swansont]

Yes, if the trips were the same as far as acceleration, speed and time.

 

Careful, though, because in the Hafele-Keating experiment, the two directions are not the same. The earth is not an inertial reference frame, so east- and westbound travelers are not going the same speed, even if their speed with respect to the earth's surface is the same. You have to do the comparison with respect to an inertial frame.

[NowThatWeKnow]

Careful, though, because in the Hafele-Keating experiment, the two directions are not the same. The earth is not an inertial reference frame, so east- and westbound travelers are not going the same speed, even if their speed with respect to the earth's surface is the same. You have to do the comparison with respect to an inertial frame.

 

Yes, everything would have to be equal relative to an inertial frame. After reading http://en.wikipedia.org/wiki/Hafele-Keating_experiment I see that GR was considered.

[asprung]

Clocks run slower molecules move slower but the progression of "now" does not.

[iNow]

asprung - Please don't hijack this thread with your metaphysical claims and your philosophical wanderings about the concept of now. We've covered that material in multiple threads already, and you've already conceded openly on more than one occasion that you cannot support your comments with evidence or citations, so please, mate... Stay interested, but also stay focused on where and what you post.

[cameron marical]

P.S. i almost tipped over my monitor trying to get that bug.

 

he. i was fooled by it myself.

 

Careful, though, because in the Hafele-Keating experiment, the two directions are not the same. The earth is not an inertial reference frame, so east- and westbound travelers are not going the same speed, even if their speed with respect to the earth's surface is the same. You have to do the comparison with respect to an inertial frame.

 

i got it all up to that, why wouldnt they be traveling at the same speeds no matter what direction they whent? how does east and west change their speeds? ya the guy going against the earths rotation would seem to go faster, but like you said, the earths not an inertial referance frame.{im not trying to challenge you, i know im wrong, i just dont know why.}

[iNow]

The earth rotates. If you fly with the rotation, you'll go faster than if you fly against it... relative to a reference frame off of/away from the earth.

 

Same idea as being on a treadmill (or, maybe a better example is one of those moving sidewalks like they have at many airports). If you walk with the moving strip, you go faster relative to an external point. If you walk against the moving strip, you go slower relative to an external point.

[cameron marical]

but not relative to your own. and besides, there off earth, and not connected with it at all, are they? so why would earth be included at all?

[Sisyphus]

but not relative to your own. and besides, there off earth, and not connected with it at all, are they? so why would earth be included at all?

 

Standing on a rotating body like the Earth means that you're continually accelerating as you move in a circle. So moving in two different directions with equal velocity relative to that spinning surface means you won't have equal accelerations over all.

[cameron marical]

but these planes werent standing on the earth. they were in the air, so they werent spinning with the earth at all, right?

[samtheflash82]

but these planes werent standing on the earth. they were in the air, so they werent spinning with the earth at all, right?

 

the earth was spinning under them.

[insane_alien]

the atmosphere spins with the earth. the only reason planes were used is that you can travel faster and in a straighter line than you can on the ground.

 

if the atmosphere didn't spin with the earth the equator would experience constant 1000+mph winds.

[virgo]

I have some questions about relativity (stupid lazy me not like to read books to get anwers)

 

Lets imagine a space with only 2 bodies that have mass (spaceships with people inside).

Both spaceships have same mass and stand still.

Now spaceship 2 accelerates to the 0,5c speed.

Who is getting older faster and why (SS1 pilot or SS2 pilot)?

How to define, who is accelerating and who standing still?

Lets imagine the SS2 accelerates to 0,5c, then brakes to 0c and then comes back same way

and it all takes one year for SS2.

Does it take 1 year for SS1 to wait for SS2 return? If not, why?

 

Now lets imagine Earth and spaceship the same way.

Earth standing still and SS accelerates.

People in SS see Earth accelerating.

SS goes to 0.5c, brakes to 0c and comes back the same way.

Are people in SS getting older slower? If yes, is this cause the mass?

Tell, me why not to think that Earth accelerates and people there getting older slower?

[swansont]

You can tell who accelerates. Their clock will run slow, if compared in the same frame of reference with the unaccelerated clock. The clock that doesn't accelerate can always be assumed to be at rest.

[swansont]

Please leave moderation to the staff

 

If you have a problem with a post, report it by clicking the triangle outlined in red. Vigilante posts attempting to enforce perceived or actual rules violations is inappropriate, IMO, and the sniping does not add anything to a discussion.