# Special relativity... a westbound plane?

Discussion in 'Community Discussion' started by cleanup, Oct 14, 2010.

1. ### cleanup macrumors 68030

Joined:
Jun 26, 2005
Location:
Toronto
#1
So I've never studied physics before, but my friend showed me the results from the Hafele-Keating Experiment. It states that a plane-bound clock flying eastbound (with the earth's rotation) experiences time dilation and thus returns to us slower than a ground-based clock (and thus loses time). I get that. But it also shows that a plane-bound clock flying WESTBOUND (against the earth's rotation) experiences time contraction and returns to us FASTER than a ground-based clock (and thus gains time).

I honestly have no idea why the westbound clock is different. Isn't it still moving relative to the ground-based clock, regardless of its direction of motion? Doesn't it experience time dilation all the same? Why is it different?

Any physics buffs have any idea? I'm really at wits end with this... been thinking about it all week.

2. ### lewis82 macrumors 68000

Joined:
Aug 26, 2009
Location:
Totalitarian Republic of Northlandia
#2
The ground based clock moves at a speed of roughly 530 km/h (at the equator, being closer to the poles actually reduces the linear speed but not the angular speed). The eastbound-flying, which flies at about 800 km/h, has a total speed of about 1330 km/h. The westbound-flying plane, on the other hand, goes at about 270 km/h.

The time dilatation can be easily calculated, and is proportionnal to the speed. So there you go

3. ### ravenvii macrumors 604

Joined:
Mar 17, 2004
Location:
Melenkurion Skyweir
#3
So I'm growing slightly younger than everyone else every time I fly west?

4. ### CorvusCamenarum macrumors 65816

Joined:
Dec 16, 2004
Location:
Birmingham, AL
#4
Doesn't altitude have something to do with it as well? It's been a while, but I think I recall reading A Brief History of Time or some similar book where it was touched on, albeit briefly.

5. ### anjinha macrumors 604

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Oct 21, 2006
Location:
San Francisco, CA
6. ### flopticalcube macrumors G4

Joined:
Sep 7, 2006
Location:
In the velcro closure of America's Hat
#6
Yes. It's the effect of gravity on time. None of the time differences are significant to a humans lifespan, however.

http://en.wikipedia.org/wiki/Gravitational_time_dilation

7. ### redAPPLE macrumors 68030

Joined:
May 7, 2002
Location:
2 Much Infinite Loops
#7
this thread makes me think... somewhat interesting (for physics-type people)... but i find it boring. hey, maybe because i am not a physics-type person.

didn't a well known guy say 'time is relative'? in my dictionary, it means, time will have a different meaning for every person on this earth.

8. ### comictimes macrumors 6502a

Joined:
Jun 20, 2004
Location:
Berkeley, California
#8
True, but I should think that's basically inconsequential compared to the 66,660(ish) mph that both planes are moving at (due to the Earth going around the Sun). It's all relative to what point you consider fixed... after all, our entire galaxy is speeding away the point of the Big Bang at some even more crazy speed

9. ### Rodimus Prime macrumors G4

Joined:
Oct 9, 2006
#9
Relativity is one of those things that I found fun to calculated but always confused the hell out of me.

I hate physic II.

10. ### lewis82 macrumors 68000

Joined:
Aug 26, 2009
Location:
Totalitarian Republic of Northlandia
#10
The time dilatation depends on the observer. If the observer also moves at 66,660ish mph, the time dilatation due to the earth's orbit is the same for both, and will not affect the calculations.

The formula is:

where v is the relative velocity between the observer and the object.

11. ### Melrose Suspended

Joined:
Dec 12, 2007
#11
Jet lag is the body's way of preventing time travel. Imagine how sicker than hell you'd be if you travelled 100 years one way or another, rather than just a few hours?

I love physics.