This explanation is bit incomplete. If you align the interferometer perfectly then it should not have any fringes, the fringes indicate that there is some angle between the light beams. If you get the interferometer aligned then the beam intensity varies as function of the difference of beam path lengths.
But yes :)
Wayback machine to the rescue:
https://web.archive.org/web/20260109203451/https://guille.si...
Very cool project!
Please do the delayed choice quantum eraser next and post it here!
and ha, that one requires a little more fancy equipment :)
(not a joke, I'd actually like to see that)
I would not actually use this for uhhh, repeatable measurements over any extended period of time!
(If that were the case, I'd recommend re-printing it in a slightly more stable material, or just CNC milling the mounts out of aluminum using some of the ~$1-2K aluminum desktop mills and using some aluminum extrusions as the base.)
I wonder if they have enough different metal choices that you could build a thermal expansion compensated version? https://patents.google.com/patent/US8292537B2/en
but at “get it done in JLCCNC” prices I think a thorlabs mount is probably in your future :)
(you can too, if you’d like, the CAD files are all online as .step files :)
alternatively one can use a more grazing sharper angle of incidence to bring it closer to 50/50 beam splitting, but then the internal reflections become stronger and the setup is no longer a nice orthogonal one (but how often is that really necessary for a task?)
> Ok, time to confess: I did cheat a little in calling it the “cheapest” Michelson interferometer, since technically even this beam splitter is like 16 USD, but it is very possible to use a microscope slide instead at the cost of some contrast, which will net out to < 20 cents, even at pretty expensive per-unit prices.
:)
Yes definitely a great extension would be to add a camera in the image plane (alternatively, defocusing the image slightly and using a photodiode would also be fun!)
xxx
Wish we worked on IMUs, I still need to get down quaternions
The Michelson–Morley experiment was indeed very important, but it has not proved in any way the non-existence of ether. It has just proved that the ether does not behave as it was previously supposed, i.e. like the materials with which humans are familiar.
It does not matter at all what names are used for it, one may choose to name it "ether", "vacuum", "electromagnetic field", "force field" or anything else, but all the modern physics, since James Clerk Maxwell and William Thomson, is built on the assumption that the space is not empty, but it is completely filled with something that mediates all the interactions between things.
Only before the middle of the 19th century, the dominant theories of physics assumed the existence of true vacuum. The existence of true vacuum is possible only in the theories based on action at a distance, like the Newtonian theory of gravity or the electromagnetic theory of Wilhelm Eduard Weber, but not in field-based theories, like the electromagnetic theory of Maxwell or the gravitational theory of Einstein.
It is rather shameful for physics that the main result of the Michelson-Morley experiment has been the replacement of the word "ether" by "vacuum", as if a change of name would change the thing to which the name is applied, instead of focusing on a better understanding of the properties of the thing for which the name is used.
That's kind of like saying that our failure to observe invisible pink unicorns does not prove the non-existence of invisible pink unicorns, it just proves that invisible pink unicorns don't behave the way you expect them to.
Luminiferous ether was a specific hypothesis about how light works. It made a prediction, which turned out to be wrong, which falsified the theory. Whether you want to attach the description "proves the ether does not exist" or "proves the ether does not have the properties ascribed to it by the theory" is completely irrelevant.
The obvious question to ask at this point is, "so ether is back on the table?".
Turns out the mistake is, as GP said, thinking MM proved space is empty; it only disproved a particular class of substances with particular properties. But that's not how they tell you about it in school.
That interpretation is also consistent with LIGO: we can detect those ether disturbances because the distortion of our motion on the apparatus doesn’t cancel the signal in the same way.
Or maybe an invisible pink unicorn is sneaking into the lab at night and tweaking things.
edit: not sure if you're referring to dark matter
yeah I gotta read your comment more thoroughly
No, the idea was that, in a space filled with the hypothetical ether, Earth's velocity through the ether should have been detectable by comparing light beams traveling in different directions.
The null result was very important -- it didn't prove the absence of an ether, it only showed that it wasn't a factor in light propagation.
1: https://www.thorlabs.com/michelson-interferometer-educationa...
It sort of depends on what your goal is; personally, I live to see something expensive on Thorlabs, and make a simplified, less accurate, and far cheaper alternative in my home lab. But that's rarely how folks in labs do it- instead, they will focus on getting people to be useful for performing state of the art research, which usually depends on applying hundreds of years of experience to make some tiny marginal improvement, which frequently depends on having extremely precise and accurate gear.
I think there's just such a huge middle ground that's missing (for funny historical reasons[1]) between "children's toy" and "lab-grade equipment" especially in optics, which is why I was excited to make this my first foray into making a fully 3d printed "useful-ish" thing that doesn't really exist otherwise.
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[1] This is because most lab equipment was made _in the lab_ back in the 60s or so, and having this technical ability was a huge advantage for many labs. Now, personnel cost/hours are much more expensive relative to equipment, so people will pretty much pay whatever to get lab-grade stuff.
I agree there is a huge middle ground- for example, I make hobby microscopes at home, and much of my work has been making accurate and precise 2D/3D stages. It's easy to buy great, simple (non-motorized) scopes with good optical quality, but as soon as you start adding motorized stages, or any sort of complicated illumination or filtering, it gets challenging quickly. My actual goal is to track microbes in real time using computer vision, but the professional hardware to do so is out of my price range.
I have spent literally thousands of hours fiddling with one part or another Today, I'm working on a high speed flash illuminator that is coupled to the camera, and it's one problem after another. Reality has a fractal level of detail.
Since I haven't been able to look at your project yet, I don't know if you worked on this area, but I found it really useful to clone the Thorlabs cage system components: https://www.thorlabs.com/optical-cage-systems and specifically https://www.thorlabs.com/item/CXY2A (you can download their 3D model and see that the mechanism isn't that complex).
Another thing I've ended up doing is prototyping in plastic and then having it machined at a place like JLCPCB out of aluminum. PLA is just flexible enough (especially under load) that it can make the results very frustrating.
Yes this is very cool (hope you make it open source :) but have you taken a peek at the openflexure project? They make a fully motorized 3-axis microscope that is 3d printed and relatively inexpensive (parts+motors+electronics - PLA net out to USD 250?)
it’s very cool! maybe you can also take some ideas from there :)
It's pretty close to the Thorlabs Cerna, https://www.thorlabs.com/cerna-r-series-modular-microscopy-s... although I just do low-magnification light microscopy.
The current system I am building is mainly optimized around scanning large areas quickly; I have already demonstrated that I can create accurate stitches by moving, stopping, taking photo, repeat, but it's slow (due to the stopping) so I am working on an approach that keeps the stage moving constantly, but triggers a bright flash that freezes intermediate exposures. This gives a good 10X speedup over the simpler model of move/stop/photo/repeat but brings in a number of other challenges.
good luck! are you posting updates anywhere?
so yes, we _also_ (back in my phd lab) built equipment in that sense, but there was a pretty good foundation of Fairly Fancy stuff already sitting around !
I mean, it's practically the most basic optical experiment that you can perform. Nobody needs to pay $3K to learn how an interferometer works. It's not a MoT or something exotic like that, it's a beam splitter and a couple of mirrors.
Put another way, it's the difference between building a Heathkit and putting a bunch of parts together that you salvaged from other stuff, for those who are old enough to grasp that analogy.
If you are putting together some more advanced educational or experimental apparatus, they are pretty much a no-brainer supplier, as you say. But their level of quality, support, and system integration just isn't necessary for something like this.
There's a balance that has to be struck between: 1) Equipment that's so perfect that students learn nothing about the effort to get an experiment working. 2) Or so crappy that it's an obstacle to learning anything at all.
Also, the crappy-ness is multiplied by 30 for the number of setups needed for a class of 60 students, assuming they work in pairs.
Oh, the crappy oscilloscopes. They were cheap "student scopes" and their controls were worn out, so they behaved erratically. Since then I've met other people who took freshman physics lab, and they remember the "oscilloscope lab" with disgust.
that one has uhh substantially less drift for what it's worth, but reprinting in more stable material would help that a ton (and still be quite cheap!)
I think M3 standard thread pitch is 0.5mm, so to a first approximation that almost 1000 wavelengths (if I have the SI units right in my head, and I'm not 3 orders of magnitude out?). I suspect the left/right and up/down adjustments have as fairly high lever ratio, but I can't imagine you could successfully adjust the in/out distance with any precision (not in the 690nm sense anyway)? Is the in/out distance not important so long as the beams are aligned?
Dunno if you've seen it, but there's a great youtube video explaining how the actuators to align the James Webb mirrors work: https://m.youtube.com/watch?v=5MxH1sfJLBQ including a 3D printable version of them: https://www.thingiverse.com/thing:5232214 "This is a replica of JWST's mirror actuators. Six of these actuators are paired into a hexapod / stewart platform arrangement and used to control 6 degrees of freedom of each mirror segment (tip, tilt, roll, x, y, z translation)."
Very interesting re: JWT, I will definitely take a peek, thanks !
It's important to say the original interferometer was much less elegant -- there were no lasers in 1887. But it did have a solid stone "boat" floating in a little lake of mercury. Not making this up.