Naked Science Forum

On the Lighter Side => New Theories => Topic started by: Fussball on 06/06/2019 11:49:10

Title: What is the aberration of light in the Michelson Morley experiment?
Post by: Fussball on 06/06/2019 11:49:10
Michelson writes about aberration in his apparatus:

"The ray sa is reflected along ab, fig. 2; the angle bab, being equal to the aberration =a, is returned along ba/, (aba/ =2a), and goes to the focus of the telescope, whose direction is unaltered. The transmitted ray goes along ac, is returned along ca/, and is reflected at a/, making ca/e equal 90a, and therefore still coinciding with the first ray. It may be remarked that the rays ba/ and ca/, do not now meet exactly in the same point a/, though the difference is of the second order;"

https://en.wikisource.org/wiki/On_the_Relative_Motion_of_the_Earth_and_the_Luminiferous_Ether

I made an animation depicting aberration as per the Michelson quote. Any one see any flaw in the animation? Here's the link to the animation:

Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: David Cooper on 06/06/2019 22:09:50
Your animation is incorrect - your telescope should not be tilted and the blue dot of light should not be following the path you make it move along. You have the light being emitted from the yellow thing which is moving to the right, then it bounces off the mirror (which is also moving to the right) and the light magically moves straight up the screen instead of moving to the right at the same speed as the rest of the apparatus. It should hit the middle of the top mirror and then go downwards to the telescope while still moving to the right at the same speed as the rest of the apparatus. The telescope should not be tilted because the light pulse will move to the right at the same speed as the telescope. To see it done properly, look at the interactive diagrams at the top of this page: http://magicschoolbook.com/science/relativity (you needn't read any of it, but just study the diagrams near the top), but use the second interactive diagram that shows length contraction rather than the first. If you click the direction button to run the action backwards, it will then show the light pulse go down into the laser in the same way as your blue dot should be going down into a vertically-aligned telescope.

Think carefully about how the light should reflect off the angled mirror when the mirror is moving to the right - the effective angle of the mirror is not 45 degrees because the mirror is moving. If you imagine waves hitting the mirror and draw a wave front heading for it, the bottom of that wave will hit the mirror first, and the top of the wave will hit the mirror later, but the mirror has moved between those two times of contact, so the effective angle of the moving mirror is shallower than 45 degrees. That is why the blue light pulse should retain a component of movement towards the right.

You may then be confused as to why a telescope would ever need to be tilted to point away from the star that you are looking at through it, but in the case of looking at a stationary star from a moving rocket, the telescope does need to be pointed away from the star because the star will not be seen in the sky in its actual location - it will be further back than it appears. If the star and telescope are co-moving, the light from the star will go straight down a telescope that is pointed straight at it and that moving star will be seen in its true location even though the light that's being detected from it is coming from where the star was earlier (at a different angle).
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Fussball on 07/06/2019 07:26:43
How do you account for the below statement in the animation?

"It may be remarked that the rays ba/ and ca/, do not now meet exactly in the same point a/, though the difference is of the second order;"
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Fussball on 07/06/2019 07:29:41
Also aberration means tilting of the telescope. Where does your animation depict that?
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Bored chemist on 07/06/2019 10:37:30
How do you account for the below statement in the animation?

"It may be remarked that the rays ba/ and ca/, do not now meet exactly in the same point a/, though the difference is of the second order;"
"below" is not an adjective.
Please don't use it as one.


It's your animation, so it's your job to account for things in it.
Also aberration means tilting of the telescope.
No it doesn't.
It means something unexpected or unusual.
There's none in the link posted above because light does what you expect it to.
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: alancalverd on 07/06/2019 17:20:06
The preposition in German can precede the subject, so it looks like an English adjective. Oddly, I come across "the above conditions" more often than "the below statement", and it seems acceptable at least to the legal profession.

Optical aberration is due to a lens not being the ideal shape (spherical aberration) or having wavelength dispersal (chromatic aberration). You can of course get rid of the latter by using a narrow spectrum (LED or laser) source but the former demands very careful optimisation of the lens profile: light entering offcenter or not parallel to the axis will not all be focussed to the same point or plane.   
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Bored chemist on 07/06/2019 18:17:40
I gather the same is true in Chinese.
Here's another interesting coincidence; we aren't speaking Chinese or German.
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: alancalverd on 08/06/2019 06:47:04
I suspect that anyone  called fussball probably speaks German at home, and the rest of us speak a language that was much closer to German within recorded history, but is less structurally rigid than modern German. One anomalous consequence of this fluidity is  that "the above conditions" is conventional but "the below statements" is not. Anomalies and inconsistencies in formal English interesting for me not are. Adequately gruntled in this moment am I, but you not. Chacun a son gout.
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: jeffreyH on 08/06/2019 12:40:17
OK Yoda. We get it.  ;D
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: alancalverd on 08/06/2019 12:51:14
So that's where they got the idea from - Hochdeutsch! Not all that surprising, knowing the source of much Hollywood talent. The resident genius in a best-forgotten sci-fi TV series was called Cho-chim, from the Yiddish chochim (pronounced hookhum)- a wise man!
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Fussball on 11/06/2019 06:43:01
It's your animation, so it's your job to account for things in it.

I already did. Michelson says, "the rays ba1 and ca1 don't meet at a1". And that's due to aberration. My animation shows that.
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Colin2B on 11/06/2019 07:29:12
As @David Cooper explained, you diagram is faulty.
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Bored chemist on 11/06/2019 07:30:29
Then the reason why it happens is  that you drew the animation so it happens.
You could also have drawn it turning into a pig with wings and flying away.
You can't use a cartoon as evidence of anything.
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Fussball on 12/06/2019 17:22:32
You could also have drawn it turning into a pig with wings and flying away.
You can't use a cartoon as evidence of anything.
It's your animation. It is your job to account for things in it.
Title: Re: What is the aberration of light in the Michelson Morley experiment?
Post by: Bored chemist on 12/06/2019 19:27:41
You could also have drawn it turning into a pig with wings and flying away.
You can't use a cartoon as evidence of anything.
It's your animation. It is your job to account for things in it.
It's really not my animation.
What did you mean?