• Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.


New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback


(propose a free ad)

Site Statistics

146 submissions , 123 unreviewed
3,961 questions , 1,408 unanswered
4,910 answers , 20,862 comments
1,470 users with positive rep
517 active unimported users
More ...

  muons and time dilation

+ 0 like - 2 dislike

Based on the observed behaviour of muons, assuming one comes into being at 10km and is travelling at 0.9997% lightspeed toward an observer on earth. Gamma for this speed is about 41. (I have seen various variations on the calculations but this doesn't really effect the question.)

In 0.75 microseconds the muon travels about 225 metres (300 metres per microsecond). With time dilation at this speed the observer will see the muon exist for 225*41=9225 metres (ok, not exactly 10km but near enough for the question)

My question is, from the muon's frame, and under the relativistic effects of 41 gamma, does it see time flow faster outside it's frame?

Baring in mind it hits earth's surface in 0.75 microseconds from it's frame, the earth must rotate to the same physical point that both it and the observer on earth see's it hit (an imaginary X on earth's surface)

If time flows more slowly outside the muon's frame, then in 0.75 microseconds it will miss the X and hit a different spot than the observer see's it hit, obviously this can't be right.

It makes sense to think time flows faster, and the muon would see the earth rotating 41 times faster, then it would hit the right spot

But I read that in relativity from the muon's frame a clock on earth would appear slower not faster.. 

So how does it manage to hit the right spot considering earth's rotation and difference in measured descent time between the two reference frames? 

Closed as per community consensus as the post is high-school/undergraduate level PhysicsForums.com would be a more appropriate home for this question.
asked Aug 29, 2015 in Closed Questions by anonymous [ no revision ]
closed Sep 4, 2015 as per community consensus

Note in muon's frame there's also length contraction. And yes in muon's frame the earth's time flow more slowly not more quickly. This isn't exactly a grad level question.

OP here, i see -2, no explanation why this might be, am i just supposed to 'believe' ?

It's just an indicator that this question is not suitable for the site, not that it's a bad question. Normally by now the moderators should've already initiated a "vote to close".

Voting to close as high-school level. The question might be more appropriate on PhysicsForums - PO is a graduate-level+ site.

@JiaYiyang Note that any user (with > 500 rep) may initiate a close vote.

@dimension10, let's be fair, this can be considered undergrad level.

@JiaYiyang Alright, I updated the close reason (although the general question here is not exclusive to GR).

user contributions licensed under cc by-sa 3.0 with attribution required

Your rights