Electron band structure in germanium, my ass (2001)
(pages.cs.wisc.edu)897 points by tux3 3 days ago
897 points by tux3 3 days ago
More jabs available at https://pages.cs.wisc.edu/~kovar/bio.html and https://pages.cs.wisc.edu/~kovar in general.
Taken down since you posted the links it seems. I wonder why?
Why is it a jab at physics? It's honest and beautiful -- I imagine this is exactly what an experience on the cutting edge of experiment is like! :D
Making this measurement (an ancient discovery) with latest equipment is easy, but imagine what it might have been like for the people who actually discovered this property of germanium. Our tools/probes cannot advance much faster than our understanding of a (related) subject -- we are constantly inventing/improvising tools using cutting edge scientific knowledge from a related field.
I mean if you didn't already know how to solder to Germanium crystals you would have had to spend months experimenting with the material before you could get leads to stick.
Google said (AI result):
Soldering a lead to a germanium crystal typically involves using a gold-germanium solder alloy (like 88% gold, 12% germanium) due to its compatibility and good bonding properties
Plus you'd need to decide how to get a good thermal connection to set the temperature of the crystal - maybe via one big lead?
Being in the future makes some things simpler?
The little experience I've had with lab physicists showed they needed a good ability to build, debug and maintain their own equipment. You can't always rely on technicians.
I'm an industrial physicist, and the post put a smile on my face. And indeed, it's not fiction. It's a blast. You will go through times like this, I guarantee it.
I've been wrestling with a cantankerous experiment for a couple of weeks. It produces reproducible results, but they don't make sense, and the work is not in a domain where discovering new physics by accident is likely.
I understood and appreciated it, and I’m not special
(2000)
(at most: https://web.archive.org/web/20001031193257/http://www.cs.wis...)
https://pages.cs.wisc.edu/~kovar/cv.html
Looks like he went on get a PhD in CS and is now a staff SWE at Google, according to his LinkedIn. Guess he's rolling in cash after all.
You're right, I looked up and he seems to work at Google as a SWE: https://www.linkedin.com/in/lucas-kovar-185a3531
Happy he made the leap and at least get's paid well now (I hope).
> (2000)
It was probably actually written sometime prior to June 1999, because that's when the author got his Physics BS at Stanford (https://pages.cs.wisc.edu/~kovar/cv.html).
I kinda want to know more of the backstory around this. What grade did he get? Or was this a private venting exercise he later put up on his webpage, once he was well clear of the course?
The author did eventually go into CS, I wonder if this project was his actual breaking point.
Looks like the article is 404 for some reason.
https://web.archive.org/web/20250311184956/https://pages.cs....
Summary:
``` The author sets out to investigate the temperature-dependent resistivity of germanium, a classic topic in solid-state physics. However, they quickly become disillusioned with both the theory (which they find overly abstract and nonsensical) and the practice (plagued by faulty equipment, uncooperative materials, and lack of support). Their experimental setup involves a precariously mounted crystal, unreliable tools, and a leaking thermos of liquid nitrogen.
Despite their intense effort, the data collected fails to demonstrate the expected exponential relationship. In frustration, the author draws a curve "through the noise" hoping it will look convincing enough to pass. Ultimately, they conclude the project—and their choice to study physics—was a total waste of time and regret not choosing computer science instead, where at least they'd be making money, if still unlucky in love. ```
This reminds me of how the Fahrenheit scale came about.
For all its flaws, Fahrenheit was based on some good ideas and firmly grounded in what you could easily measure in the 1720s. A brine solution and body heat are two things you can measure without risking burning or freezing the observer. Even the gradations were intentional: in the original scale, the reference temperatures mapped to 32 and 96, and since those are 64 units apart, you could mark the rest of the thermometer with a bit of string and some halving geometry. Marking a Celsius scale from 0 to 100 accurately? Hope you have a good pair of calipers to divide a range into five evenly-spaced divisions...
Nowadays, we have machines capable of doing proper calibration of such mundane temperature ranges to far higher accuracy than the needle or alcohol-mix can even show, but back then, when scientists had to craft their own thermometers? Ease of manufacture mattered a lot.
They say two points but it was really three. The ammoniac mixture at 0F, water freezing at 32F and body temperature at 96F.
Also Celsius, for whatever reason, originally put boiling at 0 and freezing at 100. Maybe Sweden is just that cold.
Jame's Burke's "Connections" series covered this in series 3 episode 10. Here's that clip:
100 + 28 degrees are not harder to mark than 64, and then aim 0 and 100 properly. :-/
What would be the process to do that? To aim 0 and 100 properly, you'd need a tool to calculate a 100:28 (25:7) ratio on an arbitrary distance, wouldn't you?
One can build such a tool, but it's not a doubled-over piece of string.
Make marks on the thermometer at 0 and 100 degrees C, then project light from a candle to a wall to see these marks with say 5x magnification. Now project marks from the 128 mark ruler to the same wall and align marks from both, then place marks on the thermometer with 5x better accuracy.
Surely you can simply use a ruler and rotate it away from the parallel to achieve any arbitrary scale, right?
A classic I will never not upvote.
Maybe the frustrations of undergrad lab work would be easier to swallow if they were better situated in historical context. This kind of result should give the experimenter some sympathy for the folks who originally made these discoveries, with less knowledge and worse equipment. But I don't think it's usually explained that way.
For those who are actually interested in this field, the proper way to measure this would be with a four point probe. You do need a constant current source and a high-impedence voltage meter, though.
Also, you don't need to solder wires to the sample. But if you want to measure the hall resistance of a thin film of a semiconductor, you can solder a glob of indium on to four corners of a 1 cm x 1 cm wafer, put it in a magnetic field, and then do basically the same measurement as four point probe, except not inline.
Very much my undergrad lab education experience...
I currently write my master's thesis in experimental quantum computing - the platform is similar to what Google published in December, just with less qubits. A lot of it just comes down to how much money the lab can spend to get the best equipment and how good your fabrication is.
You can have the best minds in experimental physics, but without the right equipment the grad students are just busy trying to make things work somehow and waste months if not years away.
Oh, BTW, the whole "Friction is directly proportional to the normal force": My Ass!
I could never reproduce it well in the lab, because it's really not true. Take a heavy cube the shape of a book. Orient it so that the spine is on the floor. It's a lot more friction to move it in one direction than in the transverse direction. Yet the normal force is the same. Any kid knows this, and I feel dumb it never occurred to me till someone pointed it out to me.
Friction is proportional to the normal force, more specifically, it is the normal force times the coefficient of friction.
What you are describing (if the normal force is actually the same) is a contact situation where the coefficient of friction is different in different directions (anisotropic friction.)
When you define a new concept called "coefficient of friction" to be the friction force divided by the normal force, then yes, the friction force is the normal force times the coefficient of friction.
We can do this with any pair of values, such as current and voltage, but it's useful when the graph between current and voltage is close enough to linear, which means the corresponding coefficient is approximately constant. Well, is it? You have to show that with experiment. Once your data shows a line then you can calculate the slope of the line. If your data shows a parabola, you can calculate the quadratic equivalent of slope - don't calculate the actual slope and then declare that to be the result.
Sometimes you see people trying to measure the resistance of diodes, or worse, incorporating the resistance of diodes into calculations. What's the voltage across the diode? The current times the resistance, of course...
The “proportionality constant” is doing a lot of work in that claim. A lot of “constant” parameters are swept under the rug. If you fix enough stuff that claim is indeed correct, although I agree a bit simplistic
I was about to say exactly this.
Applying force directly to the center of gravity with one finger is hard.
You end up applying torque plus adjustments in response to that torque. And that is heavily dependent on your moment of inertia, unlike the normal force.
But I do agree that explanations of friction are right up there with “how do airfoils work” where poor instructors are liable to get long past the edge of their knowledge and just make shit up.
> ignoring all the actual data points
Well that's your problem.
The line is the predicted, not actual. How would you derive that line from plot of noise?
>> I drew an exponential through my noise.
The issue is that there was supposed to be a curve according to his reading, but the actual had no measurable trend. It's possible that the data was measured on the wrong scale. If you zoom out, those noise plots become a line segment. Then again, the predictable line is on the same scale (and we're assuming that it's correct according to his reading or the best he could fit) so zooming out would probably be a different form of lying with statistics via overfitting.
I once wrote A* in LabVIEW for a robot.
It was a competition sponsored by National Instruments, so the code was supposed to be in LabVIEW. Another person wanted to write it as a C plugin, but I thought that was cheating.
There's A* built into LabVIEW, but it's for completely generic graphs so it takes a lot longer to run. The rewrite brought it from about 10 seconds to compute a path, down to about 0.5 seconds.
Lmao my entire undergraduate physics program is still entirely labview instruments.
The main lesson I was taught by undergrad chemistry and statistics is that the point of science is to lie and massage your terrible incorrect results until they look realistic, claim any remaining error was due to the shitty inprecice equipment you're saddeled with, and turn it in, because you don't have enough time or money to try again.
hahaa, I love it! That's right there is engineering and true work and dedication. Can hear the frustration and it's 100% warranted.
I wish universities were better equipped for what you pay. Where is all that money going anyways? Leaking like free electrons?
The 2023 education and general fund budget for Penn State allocated 5.7% to equipment and maintenance and repairs of approx $2.5 billion in use. I assume that would include thing other than just lab equipment.
Overwhelmingly, most education fund use goes to salary, benefits and student aid (~$2 billion, 81%).
Interestingly the amount of money raised by tuition and fees almost exactly matches the amount spent on salaries, benefits and student aid. So one way of viewing it is that things like lab equipment are basically funded by grants, gifts, and state appropriations.
I assume this would be similar at Wisconsin in the late 90s, I doubt universities have changed much.
Maybe research budgets offer more flexibility and better equipment but I doubt the undergrads get to touch that stuff.
Source: budgetandfinance.psu.edu
> money is indeed being pocketed
No. What amount (if any) is being pocketed is not apparent from such data. Perhaps contrary to your expectation, it's basically impossible to pocket money allocated for salaries (people would complain they don't get what they're owed). It's much easier to pocket equipment. In any case, the referenced data is quite independent of that.
Instead, it shows that the universities do not allocate money on equipment (because that's what grants are for). Of course, spending grant money on lab equipment for undergrads directly competes with equipment for research, which puts a group at a competitive disadvantage in their field of research.
> Sorry! The URL you requested was not found on our server.
404 error now, perhaps some admins took it down due to traffic?
The user's directory is still linked from the listing [0] though.
I've seen this reposted many times, many places, and I always wonder ... maybe this person was just not very good at soldering. I had professors order me to do things they didn't know how to do themselves many times. Working with zero competency and support is the norm in academia. Soldering is a bit of an art. I'm a natural, soldering, brazing, and welding are really, really easy for me, but some people never get it and never improve. I did a four-month welding course and there were some people who were no better at the end than they were at the beginning.
A thing of beauty is a joy forever - John Keats
Honestly, physics is so full of pretension and hero worship. Even among seasoned lecturers there's a tendency to mythologise the progress of the art by making it sound like all the great results we rely on were birthed fully-formed by the giants who kindly lend us their divine shoulders.
Ironically there's a kind of Gell-Mann amnesia here, working scientists know that must of your work will consist of stumbling down blind alleys in the dark and looking for needles under lampposts that aren't even near the haystack.
I'm reminded of an anecdote which I can't currently source, but as I remember it Hilbert was trying to derive the Einstein Field Equations by a variational method. He correctly took the Ricci curvature R as the Lagrangian, but then neglected to multiply by the tensor density, sqrt(-g). This is kind of a rookie mistake, but made by one of the history's greatest mathematical physicists.
Anyway I love this article, it's a breath of fresh air and rightly beloved by undergrads.
(edit: for a counterpoint to this work please see another classic: "The physics is the life" -http://i.imgur.com/eQuqp.png )
Just physics is like this? Hero worship like this is pretty endemic.
It’s weird because on one hand it promotes this disempowering mythology that all progress comes from a vanishingly tiny fraction of humanity, but on the other hand people find it inspiring because if heroes exist then it means people (and maybe you!) can do amazing things. It’s a weird double edged sword.
Fwiw I certainly didn't mean to say this is unique to physics, I'm just not qualified to comment on other fields. Furthermore you make a good point, the hero worship is fruitful. Anecdotally I'd say a full third of my undergrad cohort cited Feynman's auto-hagiography as part of their decision to study physics.
(I also note that any double-edged polyhedral sword is necessarily degenerate.)
There seems to be a bit of confusion about the Hilbert-Einstein controversy [1], and I believe consensus is that Hilbert derived the equations a few days before Einstein, but did not claim ownership of the research. But this is the first time I'm hearing that Hilbert made a mistake. (I mean, maybe he did, but he got the right result eventually.)
[1] https://physics.stackexchange.com/questions/56892/did-hilber...
I was about to link you what I thought was best coverage of the priority I knew about, https://www.science.org/doi/10.1126/science.278.5341.1270 but now I see that's in the second edit of the accepted answer at your link.
(I certainly count myself among the confused, but I don't think there's any real dispute to answer.)
See also: this work alleging some foul play in the historical record - https://www.degruyter.com/document/doi/10.1515/zna-2004-1016...
On the contrary, what is presented by the OP is one of the many reasons that worship of science's heroes, unfashionable for decades, a whiggish pablum, is justified. If great results were birthed fully-formed -- a view I've frankly never heard anyone profess who has bothered to consider such things even briefly -- they would hardly be any heroes. Even little children who reflexively chomp on every superhero film aeroplaned towards their face understand this.
For me, it wasn't the subpar equipment, it was the subpar instruction. I will never forget trying to explain to the graduate TA leading my circuits 1 lab, that, no, you can not use a multimeter to measure impedance of an element in a circuit while the circuit is live, and that that is dumb for multiple layers of reasons.
He got pissed off at me for questioning his authority, I told the class "Uh, guys, why don't we all wait until [GTA's name] and I talk this out to proceeded, unless ya'll want to be replacing fuses in the multimeters" that REALLY pissed him off.
He was yelling. He told me I needed to talk to him in the hallway. I informed him that if I was wrong, this would be a great lesson for the class, and that, no, I will not being going somewhere to be yelled at in private, anything he had to say could be said there. That really did it. He yelled more. I was laughing at his tantrum. He took me up to the lab lead (not the prof overseeing the class - not 100% sure of how this person fit into the the hierarchy), intending to get me kicked out of the class for disrespect. He goes on to this guy about how I'm the worst, and I just stand there, smiling.
Finally, lab lead guy has gotten tired of the second hand yelling, and asks for my side - He wasn't oblivious to the fact that I'm sitting there fiddling with my 12AX7 necklace while leaning on my longboard I burnt with high voltage. I oozed the hardware hacker ethos very visibly - and I respond simply "He told the class to measure impedance, with an ohmmeter, while the circuit was live"
It was at that moment I learned it was this lab lead's role to repair equipment (or at least replace fuses) when things like this happen.
Watching that GTA have to tell the class "I was wrong" after he was yelling at me in front of everyone had to be the best.
---
Fast forward a year, and I got to deal with even more mind numbing stupidity: https://opguides.info/posts/whydidipay/#8---senior-spring-20
We went to school together :) I would agree with Prof Sayood's "Signals and Systems" was a great class. I would agree that many TAs, including myself when I was a TA, were confused and/or overwhelmed.
Archive link, since the original seems to have disappeared completely: https://archive.is/1s9Jd
But that so-called best fit line is not an exponential. Exponential functions are convex, that line is concave.
I’m afraid you’ll have to repeat the experiment.
Wayback Machine Link: https://web.archive.org/web/20250311184956/https://pages.cs....
I'll repeat the same comment I made to the same article when it posted here about a year ago:
As an odd coincidence, I did the same experiment on a shoestring budget with substandard equipment also. I too used a fancy computer algorithm to get a best fit. Except that I managed to get four significant decimal places in the result — an improvement over the (also outdated) textbook.
The author of the angry rant had a life-defining experience of overwhelming frustration.
The same scenario resulted in a positive life-defining experience for me
It’s funny how unpredictably things pan out even in identical circumstances…
I was excited at first because I thought he had found Electron band structure both in germanium, and his ass, but I was woefully mistaken.
I felt that, I felt that deeply
One of the most devious analytic chemistry labs I had was the one where the spectroscope was ancient, its tray was less transparent and more milky white, and the fluid to analyze was some sort of expired flavored water. The attempt vs result chart looked exactly like that figure.
A really eye-opening experience in many ways.
This is about the material, not the size. If the solder just doesn't stick, it doesn't matter how big it is.
Common solder is, of course, designed to stick really well to copper. Which it does. To solder more exotic things, you probably need a completely different alloy.
Try faking your data next time, dude! You will be famous for some time. Do you even know how hard it is to make data points that seem natural but follow some clear pattern you want it to follow? I spent a good half of a day looking for that proper inverse formula.
Looks like he didn't measure the temp correctly, who knows what the real temp was inside the crystal.
This should be a reminder that more than you would expect, "the results didn't replicate" is really a statement of how difficult science is to do well.
maybe related?
Cracks in the Nuclear Model: Surprising Evidence for Structure
Have anyone tried to recreate this experiment since 2001?
Soldering to germanium? Personally I wouldn't have even tried such a method - rather pin the crystal between two spung gold contacts.
Before we had silicon based semiconductord we had germanium based semiconductors. I wonder if we can build chips using germanium. If yes, how would they compare with silicon made chips?
I also regret studying physics, lol, although in my case I thought fiddling with algebra would be the best job ever, until I got bored of using my mind as a compiler.
It takes a special kind of mind to appreciate this short post, not as fiction, but as truth and also as a jab at the physics sciences in general.