space: evidence of length contraction (2 Viewers)

[Rahul]

i was doing a past paper and there was a question which asked to give recent evidence of time dilation and length contraction.

for the time dilation i used the muons example, but for the length contraction i used a car moving past you at high speeds...*cough* shit *cough*.

does anyone have any other evidence?

spaceship moving at high speed?

 

[...]

length contraction..u can still use muons..but if they were to ask u for 2...hmm...

 

[Rahul]

how can u use muons for length contraction??

they measure their lengths??!?! do explain.

if they ask for 2, and the muons can be used for LC, then i will use the atomic clocks for time dilation

 

[...]

muons are suppose to die out b4 they can be detected on the earth's surface...

however, with their speed very close to 'c', the distance they travelled was shorter...hence making it possible to be detected b4 they die...


m----------->detected

but due to high speed and length contraction

m---> detection


get what i mean?

 

[Rahul]

hmm...i think you're wrong...or i'm not understanding you well. is it anywhere in the texts?


m----------->detected

but due to high speed and length contraction

m---> detection

that is a total contradiction to time dilation.

the muon travellign at high speeds will be detected 'further' to the right.

 

[Dash]

That is so wrong!

Muons have a really short life span in their frame of reference. With this life span, they cannot reach the earth's surface, even though they have a speed very close to c. But! Because they travel at such high speeds, their lifetime is dilated to the stationary observer. So length contraction has nothing to do with it

 

[Dash]

I take that back dotty
Your idea was right, but your explaination was shotty.
Muons can be used to demonstrate length contraction
But, its not the muon that contracts in length
Rahul, refer to Physics In Context 2 (Page 109)
Its weird, read it, its interesting

 

[...]

yea, poor wording...pretty sick atm, so i dunno what i am typing..lol

yea, its not the muons that contracts, but rather the distance they travel...

 

[t-i-m-m-y]

particle accelerators- lenght contraction

 

[Dash]

Originally posted by ...
yea, its not the muons that contracts, but rather the distance they travel...

Yeh, that sums it up

 

[ND]

Umm can't you just say that because of teh equation c=d/t, and c is constant, if t varies so must d?

note: a different example for evidence of time dillation is the experiment where they synchronised 2 atomic clocks and flew one of them around the world.

 

[...]

Originally posted by ND
Umm can't you just say that because of teh equation c=d/t, and c is constant, if t varies so must d?

i was trying to put it that way..yea...

 

[Dash]

Originally posted by ND
Umm can't you just say that because of teh equation c=d/t, and c is constant, if t varies so must d?

I don't think that you can put it as simply as that. Cos thats dealing with normal velocities, and doesn't take into account the special relativity factor

 

[...]

umm..no actually..

cos speed = dist/time

and he is using that to relate the distance that the muon travelled and in the inertial frame of reference the distance muons travlled was shorter...

so if u travel this distance shorter, ur time will be shorter.

 

[Rahul]

Originally posted by Dash
Rahul, refer to Physics In Context 2 (Page 109)

aaargh! hate that book...

*reads*

ok...but cant this be due to time dilation?

thats one of the shittest piece of explanations i have read.....

it basically says, the muons last longer, so that shows length contraction???? i dont think its a valid explanation. they are relying on the fact that since time dilation occurs, so does length contraction.

 

[...]

umm...

*goes looking for his notes*

k..lets look it this way...

John is in a rocket to planet X that is 100ly away
Peter is on earth oberving

Peter looks at John:
v=L(o)/T(v) T(v)=time john takes to planet measured by peter

therefore:

v= L(o)/ { T(o)/ root[1- v^2/c^2]}

therefore:

v= {L(o)* root[1-v^2/c^2]} / T(o)

John looking himself

v= L(v) / T(o)

therefore:

= {L(o)* root[1-v^2/c^2]}/T(o)

according to Peter, John will reach planet at 100ly
but to john, it seems shorter

 

[Rahul]

YEP, thats time dilation. i know that... [i didnt get the point of you posting taht dotty ]
++++++++++++++++++++++++++++++++++++++++++++++++++

what is an evidence of length contraction?

 

[...]

err...muons

but like what ND and i've posted..

from the muon story

speed=distance/time

so if ur travelling at 0.99c

then time dilation...it will be shorter right??

therefore, the distance travel will also be shorter...because v=d/t

when ur travelling at close to 'c', the time it takes u to one place will be shorter than at normal...
so therefore, its concluded that the distance u've travelled is shorter...

 

[Rahul]

Originally posted by ...
from the muon story

speed=distance/time

so if ur travelling at 0.99c

then time dilation...it will be shorter right??

ooooooooh! i see it. that was the missing piece that the contexts2 didnt cover.

that links the distance and time for me

i would have still liked another example tho

 

[...]

hmm..muon is a popular one..and its very straight forward to be honest..

i asked my teacher about the atomic clock one, but he said its very hard to cover it right..so he didn't really explain it...

so can u tell me it rahul..plz

*looks hopeful*