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 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.
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!)
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.
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.
edit: not sure if you're referring to dark matter
yeah I gotta read your comment more thoroughly
(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
xxx
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!
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)."
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 :)
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!)
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.
