Difficulty with imagine ( MM experiment)

In summary, the MM experiment is conducted by rotating an apparatus in order to create interference between two light beams. The experiment is repeated multiple times at different times of year to account for any effects of the Earth's rotation. The initial position of the apparatus is not important, only the orientation of the mirrors towards the Earth's motion.
  • #1
geneen
7
0
HI
I have difficulty with imagine why i must see the shift in the interference fringes when we rotate the apparatus 90 degrees !
what exactly happen to make me assuming see this shifting?( in michelson-morley experiment)

because when i finish from rotating, the same rays will be interference?! and i will see the same pattern!

and during the rotating the time difference between the two rays it will be constant because any decreasing time in one ray facing increasing time of the other ray ( of course this is when we take ether in account)like what was expect when did this experiment..

thanks in advance
 
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  • #2
What you are probably missing is that the transit time of the ray that moves perpendicular to the ether travels a longer path and thus is delayed.
 
  • #3
russ_watters said:
What you are probably missing is that the transit time of the ray that moves perpendicular to the ether travels a longer path and thus is delayed.
Huh? :confused:

Note however that while the orbital path of the Earth does not influence the MM measurements, the rotation around the Earth's axis does influence it.
 
  • #4
MeJennifer said:
Huh? :confused:

Note however that while the orbital path of the Earth does not influence the MM measurements, the rotation around the Earth's axis does influence it.
On the timescale of the experiment neither is really important, although the experiment is repeated multiple times at different times of year so that even if the apparatus happened to be at rest relative to the ether on one trial, it wouldn't be on all of them. But the idea is just that as long as the apparatus isn't at rest relative to the ether on a given trial, then if the arms are adjusted so there's purely constructive interference when the apparatus is oriented one way, then if the stone table the apparatus was sitting on was then rotated, they would expect to see some destructive interference as the orientation was changed. There's a good writeup of the how the experiment works on this page, it's a little different than what I had imagined based on more schematic descriptions I'd seen elsewhere (for example, there was no attempt to make sure that the lengths of the arms were identical, just that the positions of the mirrors were such that there was no destructive interference in the original orientation before the table was rotated).
 
  • #5
Hi again :0

first of all (russ, jennifer, jessem)thanks for the effort ..

What you are probably missing is that the transit time of the ray that moves perpendicular to the ether travels a longer path and thus is delayed.
yes , i know that (by the way I think you reversed the hypothesis.. perpendicular ray take less time than horizontal ray)

because when i finish from rotating, the same rays will be interference?! and i will see the same pattern!
and what I mean here was the properties of the rays when they are interference is the same ( i.e time different it will be the same because we just exchange the position of the rays but still one of them perpendicular and the other horizontal of the ether so we see the same pattern and we don't note the rotating )

because any decreasing time in one ray facing increasing time of the other ray
and here I mean the components of each ray according to the influence of the ether..

Note however that while the orbital path of the Earth does not influence the MM measurements, the rotation around the Earth's axis does influence it.
sorry I don't get your point here and how it is relating to my question ?

There's a good writeup of the how the experiment works on this page,
I looked to the page and it will be clear my confusing if I am sure about this point ( he Suppose that initially, the apparatus was arranged so that both paths were oriented 45 degrees away from the motion of the Earth through the ethe, then oriented by 90 degrees and see the different in the pattern)>>>>> i have no problem with this :)

but in four textbook i read it about ( MM experiment) they don't say that the initial position of apparatus was 45 degrees? they make you think that initial position was at zero degree then oriented by 90 degrees! >> and here was my difficulty in imagine

>>> by the way the reason behind this rotating is because in technical view point we cann't exactly make two lenghts L equal , so to make this small difference in length become unimportant , we rotate the apparatus>>> cause if we sure about the equality of the lingths we just need to check if the rays in phase or not !

the last thing I want to mention is the apparatus must be vacuumed from the air because if it isn't... why dosn't make the same influence like the ether??!

thanks ..and sorry for long respond :)
 
  • #6
Sorry, misread that the question was specifically about the rotation of the apparatus.
 
  • #7
geneen said:
sorry I don't get your point here and how it is relating to my question ?
Just a theoretical aside.
 
  • #8
geneen said:

yes , i know (by the way I think you reversed the hypothesis.. perpendicular ray take less time than horizontal ray)

and what I mean here was the properties of the rays when they are interference is the same ( i.e time different it will be the same because we just exchange the position of the rays but still one of them perpendicular and the other horizontal of the ether so we see the same pattern and we don't note the rotating )
Your analysis is correct, it is your visualization of how the interference pattern is formed that is incorrect.

Take two incoming beams A & B at right angles that will produce a interference pattern on a film plate marked with a center line. As you said the phase alignment of that pattern will not fit that center mark correctly since if the A path is slow the pattern will pulled to the A side of the film plate.
Can you measure that shift – NO it is small and you have no confirmed Reference Measurement to compare.
Solution assume A is the slow path; rotate 90° and B will be the slow path pulling the pattern toward B away from the center line. You still don’t have a center line standard to measure against but it must be out of phase with A side slow measurement since the pattern phase shifted in the other direction on the film. Remember the film turns with the experiment.

Any difference between the two paths must show up as a phase shift between the two film plate exposures as the experiment move though the ether – if not some new physics may be needed to resolve such a paradox i.e. SR.
 
  • #9
russ >>> no problem :wink:

MeJennifer >>> thanks :smile:

RandallB >>> big thanks for you :rofl: you find the wrong point in my imagination :cool:

is the apparatus must be vacuumed from the air because if it isn't... why dosn't make the same influence like the ether??!

I think the answer is we ignore the influence of the air because we are assumed that the air moving with the Earth so it is stationary relative to the Earth <<<< and I think there must be a little different between initial and second pattern(because air is a fluid) but it is not the scope of the study.

finally,thank you all for the cooperation :smile:



 

1. What is "Difficulty with imagine (MM experiment)"?

"Difficulty with imagine (MM experiment)" refers to a phenomenon observed in studies of mental imagery, specifically in the mental rotation task known as the Mental Maps (MM) experiment. In this experiment, participants are asked to mentally rotate an object and determine if it is the same as the original image or a mirror image. The difficulty with imagine refers to the challenges individuals may experience in visually manipulating and rotating images in their mind.

2. What causes difficulty with imagine in the MM experiment?

The exact causes of difficulty with imagine in the MM experiment are still being studied, but it is believed to be influenced by a combination of factors such as individual differences in spatial ability, working memory capacity, and the complexity of the mental rotation task. Other factors that may contribute to difficulty with imagine include fatigue, distractions, and lack of practice.

3. How is difficulty with imagine measured in the MM experiment?

In the MM experiment, difficulty with imagine is typically measured by the time it takes for participants to complete the task and the accuracy of their responses. Participants are usually given a set of images to mentally rotate and are timed to see how quickly they can complete the task. Their accuracy is measured by comparing their responses to the correct answers.

4. Can difficulty with imagine be improved?

Research has shown that difficulty with imagine can be improved with practice and training. Regular engagement in mental rotation tasks, as well as activities that involve spatial reasoning and visualization, can help improve one's ability to mentally manipulate and rotate objects. Additionally, techniques such as chunking and visualization strategies may also help individuals with difficulty with imagine in the MM experiment.

5. Are there any real-world implications of difficulty with imagine?

Yes, difficulty with imagine can have real-world implications, particularly in fields that require strong spatial ability and visual-spatial thinking, such as math, engineering, and architecture. Individuals with difficulty with imagine may struggle with tasks that involve mentally manipulating and rotating objects, which may impact their performance in these fields. However, with practice and training, individuals can improve their mental rotation abilities and potentially mitigate the impact of difficulty with imagine on their performance.

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