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Home-Built Scanning Tunneling Microscope (2015)

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Re: Home-Built Scanning Tunneling Microscope (2015)

#51

Post by feralimal2 »

adge wrote: post #46
feralimal wrote: post #25

Yes, look at all that squashed DNA, lol. Seriously though, how do we know that is DNA? It just looks like wiggly worms. And the DNA pic is black and white, but the picture of graphite is in colour. How is it in colour? Is it 'enhanced' with photoshop or something?

You can't actually "see" DNA itself because it is smaller than the wavelength of light. Those groves are 50nm and the wavelength of blue light is about 480nm. So how then are the images generated? It uses a technique called Fluorescence Microscopy: https://en.wikipedia.org/wiki/Fluorescence_microscope You essentially stick some special molecules on the DNA that absorb light in one frequency and then they emit light i…

This is a useful explanation - thanks!

What does this mean to the value of what we are "seeing"?

The example used before - that it is equivalent to a deaf man seeing a music visualisation - is apt. It is some sort of model, but not particularly close. It might still be useful, of course.

Re: Home-Built Scanning Tunneling Microscope (2015)

#52

Post by feralimal2 »

jacquesm wrote: post #49
crispyambulance wrote: post #48

Earlier quoted context omitted.

> But its not showing things directly, is it? I don't understand the downvotes. That's an honest fundamental question. It's not "showing things directly" because it can't. The limit of what you can see with light is proportional to the wavelength of the light (this is called the diffraction limit). For visible light and lens-based optics that's around 1/2 micron. The distance between the atoms in that graphite is ~3…

> I don't understand the downvotes. Because the comment is factually wrong. Because it tries to argue something in bad faith. > That's an honest fundamental question. But it wasn't a question, it was a statement, and a faulty one at that. Best case interpretation would require substituting 'current' for 'frequency' and even then it would be inaccurate because the current is a proxy for the Z-distance to the tip which…

The reason for the downvotes.... won't be popular to hear, but here it is.

This forum apparently values the scientific outlook, which is purported to be a skeptical one. Do not commit to accepting whatever-it-is without evidence, right?

But that unpopular, question opinions are so downvoted (which has the effect that replies cannot be posted until the next day when no one is watching) speaks volumes about how skeptical people really are. How much application of the scientific method do people actually use in their lives?

What we really have in science, and society in general, is an echo chamber where lots of lip service is given to the scientific method but no one actually implements it personally. Then when someone like me comes along and critically reviews the presentation, it leaves people feeling uncomfortable as they realise just how much they have taken on trust.

So, the answer is to downvote. Its not pretty but everyone can get back into the comfortable echo chamber. And in preventing unpopular skeptical opinions (ie maintaining the echo chamber) is what HN is here to facilitate.

Re: Home-Built Scanning Tunneling Microscope (2015)

#53

Post by argvargc »

jacquesm wrote: post #49
crispyambulance wrote: post #48

Earlier quoted context omitted.

> But its not showing things directly, is it? I don't understand the downvotes. That's an honest fundamental question. It's not "showing things directly" because it can't. The limit of what you can see with light is proportional to the wavelength of the light (this is called the diffraction limit). For visible light and lens-based optics that's around 1/2 micron. The distance between the atoms in that graphite is ~3…

> I don't understand the downvotes. Because the comment is factually wrong. Because it tries to argue something in bad faith. > That's an honest fundamental question. But it wasn't a question, it was a statement, and a faulty one at that. Best case interpretation would require substituting 'current' for 'frequency' and even then it would be inaccurate because the current is a proxy for the Z-distance to the tip which…

The GP's "statement" contained three relevant sentences, two ending with question-marks. I learned from both your answer and its parent, furthering conversation, for me at least.

Re: Home-Built Scanning Tunneling Microscope (2015)

#54

Post by [deleted] »

feralimal2 wrote: post #52
jacquesm wrote: post #49

Earlier quoted context omitted.

> I don't understand the downvotes. Because the comment is factually wrong. Because it tries to argue something in bad faith. > That's an honest fundamental question. But it wasn't a question, it was a statement, and a faulty one at that. Best case interpretation would require substituting 'current' for 'frequency' and even then it would be inaccurate because the current is a proxy for the Z-distance to the tip which…

The reason for the downvotes.... won't be popular to hear, but here it is. This forum apparently values the scientific outlook, which is purported to be a skeptical one. Do not commit to accepting whatever-it-is without evidence, right? But that unpopular, question opinions are so downvoted (which has the effect that replies cannot be posted until the next day when no one is watching) speaks volumes about how skeptic…

[deleted]

Re: Home-Built Scanning Tunneling Microscope (2015)

#56

Post by hintymad »

The geek culture in the US is simply amazing. People build all kinds of miraculous machineries at home, many of which have become world-class products. Some products even changed the history of mankind.

What's even more amazing is that the US somehow keeps this culture despite decades of mockery and bullying from the pop culture and from school, and despite that generations of Americans thought that the biggest events had to be the football games in their neighborhood high schools and the coolest people were queen bees and sports jockeys.

Re: Home-Built Scanning Tunneling Microscope (2015)

#57

Post by jacquesm »

argvargc wrote: post #53
jacquesm wrote: post #49

Earlier quoted context omitted.

> I don't understand the downvotes. Because the comment is factually wrong. Because it tries to argue something in bad faith. > That's an honest fundamental question. But it wasn't a question, it was a statement, and a faulty one at that. Best case interpretation would require substituting 'current' for 'frequency' and even then it would be inaccurate because the current is a proxy for the Z-distance to the tip which…

The GP's "statement" contained three relevant sentences, two ending with question-marks. I learned from both your answer and its parent, furthering conversation, for me at least.

Read the rest of their comments and see if you still feel that way. As well as the novelty account made for the express purpose of further derailing the conversation.

Re: Home-Built Scanning Tunneling Microscope (2015)

#58

Post by anitil »

ahartmetz wrote: post #50

I worked with a simple STM in a lab exercise. At the beginning, we created a new, clean tip. Guess how we did that?... We cut a piece of ordinary steel wire diagonally with an ordinary wire cutter. Somehow we did it right - the first one worked. It was all somewhat fiddly and sometimes the image was noisy. But we did get images of atoms.

This reminded me of a Thunderf00t video where he created tiny jets for ammonia. I expected it would be some expensive procedure, but he just heated up some glass, stretched it and cracked it. Not every one worked, but it was surprising how mundane some super precise tooling can be

Re: Home-Built Scanning Tunneling Microscope (2015)

#59

Post by adammunich »

hintymad wrote: post #56

The geek culture in the US is simply amazing. People build all kinds of miraculous machineries at home, many of which have become world-class products. Some products even changed the history of mankind. What's even more amazing is that the US somehow keeps this culture despite decades of mockery and bullying from the pop culture and from school, and despite that generations of Americans thought that the biggest event…

The football people quickly burn out when nerds are just getting started.

Re: Home-Built Scanning Tunneling Microscope (2015)

#60

Post by oasisbob »

ahartmetz wrote: post #50

I worked with a simple STM in a lab exercise. At the beginning, we created a new, clean tip. Guess how we did that?... We cut a piece of ordinary steel wire diagonally with an ordinary wire cutter. Somehow we did it right - the first one worked. It was all somewhat fiddly and sometimes the image was noisy. But we did get images of atoms.

I haven't thought about tips in a while... definitely part of the "magic" of STM. Cutting a wire under tension sounds like it was a pretty common technique, it's the one my lab was using too.

If the imaging just wasn't happening, it was common to goose the bias voltage (10x) for a split second in hopes of perturbing the tip enough to get things to go.

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