# Time comparison

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I have a question on Einstein's theory of special ralativity. They say that if two baby brother borned at the same day, but when one of them been put on a spaceship that travels at near the speed of light to another star. After earth's time of 10 years, he returns to earth, but his own borther who satyed on earth is 10 years oler than him. My questions is the brother stayed on earth growing for ten years, then wouldn't the brother in the sapceship also grows for ten years due to the metabolism?

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i would have thought , the metabolsim would have slowed down as well due to the time dilation ( from the point of view of the earthbound bro)

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It's due to the time on the brother at spaceship that travels near the light speed is faster than the time on the brother at the earth.

I would have tought, if we travels near the lightspeed, we looks other people as if they're stopped (It's caused we travels very fast), at the contrary, we can't look the people who travel near the lightspeed(It's caused we are very slow). If the brother at the spaceship that travels near the lightspeed during 10 years, the brother at the earth is still in one second.

--

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Time for the brother in the spaceship moves more slowly.

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It's due to the time on the brother at spaceship that travels near the light speed is faster than the time on the brother at the earth.

Sorry, that above is wrong, the right is :

']Time for the brother in the spaceship moves more slowly.

Due to the time for the brother in the spaceship more slowly, as if time is stopped.

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In relativity everything is relative.

The brother on earth Bob sees is twin Bill aging more slowly because Bill is going near the speed of light.

For Bill in the spaceship sees Bob on earth going away from him at near the speed of light so he see him aging more slowly.

That's the big paradox of relativity and I don't know it is resolved by the physicists.

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Of course the "big paradox" is resolved! Einstein presented it as a joke, as a koan, I've heard. Length contraction and time dilation are not the whole story of special relativity! There is also clock dissynchronicity to consider, and that element is essential to resolving any seeming paradox.

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heres what I dont understand, Im wearing a watch, and my watch is set to the exact same sime as a big clock, even the second hands are in synch.

now I move away from the big clock at light speed, the big clock will apear to have stopped, as Im traveling at the same rate as the photons that bounced off the clock face with the time data in them.

but I look down at my wrist watch and my watch is working normaly.

I travel at this rate for 20 mins and return back to the big clock.

Surely both would be back in perfect Synch again, telling the same time.

because both clock and watch were operating at the same rate, and the fact that it appeared to stop when moving was only a illusion created by seeing the same photons with the clock face information in them for 20 mins.

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That's the big paradox of relativity and I don't know it is resolved by the physicists.

That's not a paradox at all. The symmetry is broken because one has to accelerate to get back to the other.

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..because both clock and watch were operating at the same rate, and the fact that it appeared to stop when moving was only a illusion

You've got over 7300 posts here and you still think that time dilation is a mere illusion??? No, the time dilation effect occurs whether the movement is toward, away, or transverse to the observer. There goes your illusion, mister! Check out my website.

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Im uncertain where youre coming from here? if you consider my 7300+ posts as a qualification to my understanding of Physics, then YOU are Mistaken Mister

I tend to deal with Chem and Electronics as "my" area.

having gotten that cleared up, my point (probably badly worded) is closer too this.

somewhere in the Galaxy, from a stationary standpoint, you can listen to I Love Lucy from the original TV broadcasts in the 50s

if you travel BACK towards the source of the signal (Earth) the signal will be compressed and seem faster until such time as youve "caught up" with whats being broadcast NOW.

ok, inversely, if you travel AWAY and WITH the radio signal at the same speed, it will seem to "Freeze", the freq will slow down to a stop.

my point is that if you took the entire broadcast material with you and pressed "Play", to you all would be at the same rate as transmitted on Earth (to you).

when you arrive back, all should still be in synch.

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..if you consider my 7300+ posts as a qualification to my understanding of Physics, then YOU are Mistaken Mister I tend to deal with Chem and Electronics as "my" area.
My sincere apologies.

As for the remainder of your reply, I'd have to say you are confusing the Doppler effect with Einstein's Relativity, and they should rightly be dealt with separately.

Also, that's twice now that you've described a scenario of someone moving relatively at lightspeed, which you should well know is an impossible feat. 'Better to choose a different relative speed.

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My sincere apologies.

As for the remainder of your reply' date=' I'd have to say you are confusing the Doppler effect with Einstein's Relativity, and they should rightly be dealt with separately.

[/quote']

fair enough, on both counts.

the Doppler effect I can understand and visualise, why/How does this not apply to Light?

I was certain the "Red Shift" was not only interesting and a known phenomenon, but also used to detects relative speed of an object (celestial mostly).

Im wanting to know, WHY, if youre "Riding waves" does Time have to be affected in anyway, other than, the Appearance alone?

ie/ Listening to "I Love Lucy" on a planet 50 lightyears away.

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the Doppler effect I can understand and visualise, why/How does this not apply to Light? I was certain the "Red Shift" was not only interesting and a known phenomenon, but also used to detects relative speed of an object (celestial mostly).

Yes, the red shift is real and Doppler effect applies to light, but when you see a very very distant galaxy's radiations red-shifted, it is a compound effect -- some of it due to Doppler effect and some of it due to relativistic time dilation.

Im wanting to know, WHY, if youre "Riding waves" does ...
Sorry, but I don't do illicit drugs.
ie/ Listening to "I Love Lucy" on a planet 50 lightyears away.
I fail to see what distance has to do with our current discussion.

Check out my website.

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Distance has everything to do with it.

assuming Radio travels at C (and it does without nitpicking).

then listening to that would put you in A time frame of 50 years ago, just like the light from the Sun is about 8 mins old when WE see it on earth.

the closer we get to the Sun the less TIME elapses between solar event and our observation of it.

the fact that it takes 8 mins to reach us, is only a limitation of what we can see because light is of a finite speed.

an event that happens on the sun NOW happens NOW no matter where you are, it just takes the light a little time to Show you this, so that you can see it.

but NOW is NOW regardless

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.. but NOW is NOW regardless

Ah, alas, that's what poor Sir Isaac thought. Tsk, tsk, tsk. Never wrestle with a pig, my friend.

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Im unfamiliar with Newtons work other than the Apple tree and some basics (equal and opposite reaction and stuff) and a few bits to do with Rockets.

the time lag between event cause and event Observation, is only due to the finite speed of light or sound etc...

it doesnt mean the event DIDNT happen then, it only means it took a while for the sound or light to reach us.

otherwise how can we say it happened 8 mins ago?

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You call yourself "The Resourceful One", so find some good websites on Relativity and learn what it's all about. I personally favor explainrelativity.com, but that's just me... just me.

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Personal digs against me about trivia, reflect nothing more than an inability to explain or converse in a manor suitable for all, in other words a Limitation on YOUR part.

I admit my knowledge of Physics, quantum, relativistic etc... is limited, Common courtesy is not though!

and FYI, I have seen MANY of such sites, NON as of yet has presented an understandable explaination of WHY "NOW" isnt a constant.

it would appear that you cannot either!

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I don't know what "personal digs" you're referring to and SURE, I can explain why "NOW" is not a constant. But I don't think this forum is the logical venue in which to begin a 3000-word dissertation, which is about what would be required to indictrinate a total novice, which you readily admit that you are. THAT and ONLY that is why I instead -- politely -- referred you to other resources. [Harrumph!]

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heres what I dont understand' date=' Im wearing a watch, and my watch is set to the exact same sime as a big clock, even the second hands are in synch.

now I move away from the big clock at light speed, the big clock will apear to have stopped, as Im traveling at the same rate as the photons that bounced off the clock face with the time data in them.

but I look down at my wrist watch and my watch is working normaly.

I travel at this rate for 20 mins and return back to the big clock.

Surely both would be back in perfect Synch again, telling the same time.

because both clock and watch were operating at the same rate, and the fact that it appeared to stop when moving was only a illusion created by seeing the same photons with the clock face information in them for 20 mins.[/quote']

I'm not sure how much this will help but here we go...

Visualise two mirrors facing each other, travelling through space along parallel lines. There's a single photon of light bouncing between those mirrors.

When the mirrors are stationary the photon just bounces up and down.

When the mirrors start moving the photon doesn't just bounce up and down it has to travel forwards with the mirrors.

So as you trace the path of the photon viewing it from the side it's making an up/down "zig zag" line. So the photon's having to travel that extra distance compared to the mirrors.

Think of yourself walking along a quiet road, as you move along you bounce yourself off the kerbs to the other kerb (maybe you've been drinking, again ). It's going to take you longer to walk to the end of the road than it would going constantly straight forwards.

I'm not 100% clear on this next bit myself but..

So for moving objects travelling faster means they have to travel that extra diagonal distance too.

I don't know the quantum mechanics of it but I would assume that as electrons orbit the nucleas of the atom they have to travel that extra distance like the photon does.

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MadScientist, I was totaly with you in understanding until towards the end, other than that, its a good way to explain things like this to me, Im far from Stupid!, but I prefer mental images than formula and stuff, Most excellent effort!

now then, Lightsword.

it provides nothing of use as towards an answer of what "NOW" is, only an interpretation of it.

because and event doesnt effect you at this moment, it hasnt happened. is basicly what its trying to say (or convince you of).

I dont buy it mate, it really dont, not by a long shot!

if the sun blows up NOW, it blows up NOW, end of chat.

the fact we get the effects 8 mins later doesnt and should detract from the fact that it blew up when it did.

you hold a melon in your hand, Im 1km away with a a riffle and super-sonic round.

I shoot it, it explodes in your hands, a second or 2 later you hear the CRACK! from the gun.

WHEN did I pull the trigger?

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Before I say anything else, I'll say this: never, ever, do thought experiments involving anything but light (or the other massless particles) travelling at lightspeed. Many things take place (or not, as the case may be) at lightspeed that don't happen just under it.

Special Relativity doesn't replace the slowing down of the receiving of signals, it acts in addition to it. Time dilation is a result of the speed of light being constant for all observers.

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you hold a melon in your hand' date=' Im 1km away with a a riffle and super-sonic round.

I shoot it, it explodes in your hands, a second or 2 later you hear the CRACK! from the gun.

WHEN did I pull the trigger?[/quote']

It depends on who is doing the observing. About the only thing observers in moving rames of reference will agree on is that the bullet struck the melon after the trigger was pulled, since those are causally related.

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but surely theres no "frame of reference".

I agree that there1s no way it could have happened BEFORE I pulled the triggere as that would be absurd, so sure saying it occured a short while after would be correct cause/effect.

but if we use Sound as the "Frame of Ref" then its totaly out of synch, a melon exploding makes a "THUD SPLASH" sound, and then a sharp "CRACK" sound a second later, would be the observation

why, because sound travels slower than the projectile (you know all this anyway), pint being is that sound travels at a finite speed and the ref frame can cock up results.

Light travels at a finite speed also!

why is there any reason to beleive that Light is any different, and that the ref frame cant equaly cock up results?

esp when the trigger was pulled at a given time.

event cant preceed cause in ANY case Im aware of (I might be wrong, but I cant think of even a tiny case where this may happen, I`m no physicist).

and Cause occurs NOW, whether we can detect/see/hear/feel etc... is irrelevant surely?

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