Some quick napkin math (please let me know if I'm way off base here): in the second pic, the electrodes are ~74 pixels apart and the strontium atom is ~2 pixels wide.
The electrodes are ~0.078 inches apart, so these 2 pixels represent ~0.0021 inches (or ~0.05334 mm).
Google tells me that the Van der Waals radius of a single strontium atom is 255 pm.
So the diameter of the actual atom is something like 10,000x smaller than the space represented by these pixels. Crazy!
I guess it's basically a point source compared to the camera resolution, so what you're seeing as the "atom size" is the diffraction limit of the camera lens.
I was just thinking that the atom has to be letting off (reflecting) some serious quantity of light in order for just one to appear with off the shelf camera equipment.
Edit: based on seeing it in actual size, I would say it would be hard to see it with the naked eye, that said as pointed out in other comments, I suppose not impossible if a human eye can detect a single photon.
The article did mention that the photo was long exposure, so it may not be possible to see it easily with the naked eye. A single photon emitted occassionally would be pretty hard to see, even though the human eye can detect a single photon.
Photographer here. The amount of attention this has received has caught me a bit off guard – this is really just a somewhat pretty picture of what is a standard technique in physics by now.
I'm putting together a short post with answers to some of the most commonly asked questions, but in the meantime, check out this great comment by a well-informed Redditor:
Why does the atom look so big in the bicture?
Atomic radius of Strontium is 219 pm, so that small spec there in the picture should be about 438 pm across.
I'm assuming the two ball-pen nib shaped structures on both sides of the spec in the picture are "two metal electrodes placed about 2mm (0.078in) apart". So, the space between the left tip of the electrode and left edge of the spec is about 1 mm. Based on some "visual calculation" (zooming in the picture and doing some approximation), the spec seems to be closer to about 0.03 mm across, which is orders of magnitude larger than 438 pm that it should be. What gives?
The atom can't be directly imaged by bouncing light off it, it's far too small to do that (with visible light).
Instead they're shining a laser at it, which excites some of its valence electrons to higher orbitals. When those electrons drop back to their ground states they emit (visible) light, some of which reaches the camera.
The atom is effectively acting as an isotropic radiator (radiating equally in all directions). The camera lens is much larger than the atom.
There are thus multiple paths from the atom to the lens and the sensor behind. Less light will reach the camera from greater angles, so the light that goes straight towards the lens or nearly straight will impact the sensor most, and that area will appear brightest. (This is my somewhat mangled attempt to explain abberation in optics...)
Even if the light were perfectly collimated in a beam the size of the atom it would still be unable to make a dot in the final image smaller than a single pixel of the sensor. If film were used instead of a digital sensor it would expose at least one pigment grain, again much larger than the atom itself.
The apparent size is an artifact of the imaging process.
You're not looking directly at the atom itself (which is impossible... atoms are smaller than light's wavelength).
You're looking at the photons emitted by an excited atom, as collected over an extremely long exposure by the camera's sensor. Which will resolve to ~1px in size... the smallest unit the camera can image.
Implying a pale, yellowish white dot depicting the Sun is next. (Or a pale red dot of a Tesla, more likely, given that negatives are probably already being post processed. You have to imagine that astronomy as a discipline took the last few nights off from science.)
How is this possible? For an atom to stand out, are all the atoms around the area cleared out using electricity so it’s pure, empty space? Is that possible? Also, as other people mentioned, I imagined atoms to be MUCH smaller in scale than anything like what seems to be visible here.
Could someone explain to me how a DSLR camera can capture an image of a single atop? I thought atoms were very very small, like so small only an electron microscope could "see" them. Maybe this device has been misrepresented and it is holding a small amount of atoms rather than a single one?
In exactly the same way that a camera can take a photograph of a star, which (for all but the Sun) is an infinitesimally small point of light. As long as the light intensity is higher than the background noise, it will render as a smeared out blob[1] due to diffraction.
> When illuminated by a laser of the right blue-violet color, the atom absorbs and re-emits light particles sufficiently quickly for an ordinary camera to capture it in a long exposure photograph.
Years ago, someone created a similar picture with a single atomic nucleus. I'd like to find it again.
Normally, nuclear transitions are invisibly-high energies. X-ray and gamma. But a couple of nuclei have multi-step spin isomer decays (or was it shape isomer?). One step of which is visible. So someone trapped and fully stripped a nucleus, and bombarded it to visibility. Naked-eye visibility. And took a picture. Of vacuum vessel window, with a green(?) fluorescence dot.
I saw that picture years ago. Likely a cover photo on something.
I would very much like to find it again. For use in educational content. A lot of time has been spent looking for it, both by myself, and a couple of MIT science librarians. If anyone has a clue, I'd very much appreciate it. Here is a mockup[1] I gimped for user testing.
Why use it in education? To make the concept of atoms more concrete. Atomic electrons are too small (and slow and fragile) to see with your naked eye. But (a couple of) nuclei you can (under hard-to-contrive conditions). Absent concrete, students build their understanding of materials on muddy misconceptions. For example, one failure-mode in teaching high-school stoichiometry, is students not thinking of atoms as real physical objects.
And to preempt a common response... one professor complained "you aren't really seeing the nucleus - it's only a diffraction dot"... right before they headed out to a star party, to apparently "not see" stars. ;)
The laser light is absorbed by the atom and is released at a different wavelength. While the radius of the atom is 200 x 10^-12 meters, the wavelength of the light being emitted is in the visible spectrum, so between 380-500 x 10^-9 M which is why it is visible at the scales you can see.
A scanning electron microscope, or an x-ray crystallography based machine, uses items with much smaller wavelengths, .01 - 10 nm in the case of x-rays and so they're able to peer inside an atomic structure.
I'm imaging that the process of "magnifying" objects through photography has to degrade the true representation of the object. Kind of like expanding 1 pixel to cover a 500x500px space. In that sense I wonder how clearly we can ever hope to see an atom.
Obviously the technology and intent is impressive, but will we ever be able to see an atom more clearly or is it simply too small to be seen without Photoshopping in the details?
The internal structure of an atom is vastly different from the impression that most science books give you with their illustrations to the point that the question of us being able to clearly seeing an atom is almost nonsensical/doesn't make sense.
Atoms are much more nebulous than the concept of small indivisible balls of matter.
Machines like the scanning electron microscope or an x-ray crystallography machine allows us to peer inside atomic structures to some extent.
The problem is that of scale: visible light has a wavelength of 380-750 nm (10^-9 meters) while the atomic radius of even large atoms are still in the ~200 pm (10^-12m) which means that visible light still has a wavelength 1000 times that of an atomic radius. To peer more closely at an atom, you would need to be able to use something moving at a much smaller wavelength, like an x-ray or a focused beam of electrons.
I don't think that is completely true... if you are using lenses to magnify, you aren't doing the same thing as expanding 1 pixel to 500x500. The light 'resolution' is already present, you are just spreading it out so you can see each bit more clearly.
For the folks wondering how a single atom is showing up on a DSLR CMOS, try taking a photograph of a head of a metal pin with a very bright light shining on it. You'll see lots of glint and reflection, and it'll look larger on the camera - basically a single point reflecting light into multiple pixels of the camera sensor.
I followed ion and atom trapping a long time ago, when it was still fairly new. (i.e., a couple decades ago) That was a valid question from the git-go, and there were a number of techniques. One way is that the trap is less stable when there are multiple atoms, so the extra atoms will eventually evaporate away, and you can measure the diminishing intensity of the scattered laser light. A paired atom will also interact with the light differently, for instance having a different spectral signature.
How does this not violate Heisenberg's uncertainty principle? Unless the explanation is that the atom moves around a lot in that tiny space, so we haven't actually determined its exact position and momentum.
[+] [-] arunc|8 years ago|reply
[1] http://klickverbot.at/
[2] https://github.com/ldc-developers/ldc
[+] [-] dgritsko|8 years ago|reply
Some quick napkin math (please let me know if I'm way off base here): in the second pic, the electrodes are ~74 pixels apart and the strontium atom is ~2 pixels wide.
The electrodes are ~0.078 inches apart, so these 2 pixels represent ~0.0021 inches (or ~0.05334 mm).
Google tells me that the Van der Waals radius of a single strontium atom is 255 pm.
So the diameter of the actual atom is something like 10,000x smaller than the space represented by these pixels. Crazy!
[+] [-] semi-extrinsic|8 years ago|reply
[+] [-] ars|8 years ago|reply
[+] [-] theandrewbailey|8 years ago|reply
[+] [-] granto|8 years ago|reply
Edit: based on seeing it in actual size, I would say it would be hard to see it with the naked eye, that said as pointed out in other comments, I suppose not impossible if a human eye can detect a single photon.
[+] [-] craftyguy|8 years ago|reply
[+] [-] lighttower|8 years ago|reply
[+] [-] klickverbot|8 years ago|reply
I'm putting together a short post with answers to some of the most commonly asked questions, but in the meantime, check out this great comment by a well-informed Redditor:
https://www.reddit.com/r/interestingasfuck/comments/7x4o27/p...
[+] [-] 4mitkumar|8 years ago|reply
I'm assuming the two ball-pen nib shaped structures on both sides of the spec in the picture are "two metal electrodes placed about 2mm (0.078in) apart". So, the space between the left tip of the electrode and left edge of the spec is about 1 mm. Based on some "visual calculation" (zooming in the picture and doing some approximation), the spec seems to be closer to about 0.03 mm across, which is orders of magnitude larger than 438 pm that it should be. What gives?
[+] [-] SAI_Peregrinus|8 years ago|reply
Instead they're shining a laser at it, which excites some of its valence electrons to higher orbitals. When those electrons drop back to their ground states they emit (visible) light, some of which reaches the camera.
The atom is effectively acting as an isotropic radiator (radiating equally in all directions). The camera lens is much larger than the atom.
There are thus multiple paths from the atom to the lens and the sensor behind. Less light will reach the camera from greater angles, so the light that goes straight towards the lens or nearly straight will impact the sensor most, and that area will appear brightest. (This is my somewhat mangled attempt to explain abberation in optics...)
Even if the light were perfectly collimated in a beam the size of the atom it would still be unable to make a dot in the final image smaller than a single pixel of the sensor. If film were used instead of a digital sensor it would expose at least one pigment grain, again much larger than the atom itself.
The apparent size is an artifact of the imaging process.
[+] [-] tjohns|8 years ago|reply
You're looking at the photons emitted by an excited atom, as collected over an extremely long exposure by the camera's sensor. Which will resolve to ~1px in size... the smallest unit the camera can image.
[+] [-] ammon|8 years ago|reply
I find the parallel awesome.
[+] [-] mwest|8 years ago|reply
Ref: https://en.wikipedia.org/wiki/Pale_Blue_Dot
[+] [-] jsmthrowaway|8 years ago|reply
[+] [-] alborzmassah|8 years ago|reply
[+] [-] Nec28|8 years ago|reply
[+] [-] VohuMana|8 years ago|reply
Could someone explain to me how a DSLR camera can capture an image of a single atop? I thought atoms were very very small, like so small only an electron microscope could "see" them. Maybe this device has been misrepresented and it is holding a small amount of atoms rather than a single one?
[+] [-] matthewmcg|8 years ago|reply
[1] an Airy disk: https://en.wikipedia.org/wiki/Airy_disk
[+] [-] dgritsko|8 years ago|reply
> When illuminated by a laser of the right blue-violet color, the atom absorbs and re-emits light particles sufficiently quickly for an ordinary camera to capture it in a long exposure photograph.
[+] [-] dharmon|8 years ago|reply
[+] [-] vanderZwan|8 years ago|reply
[+] [-] mncharity|8 years ago|reply
Normally, nuclear transitions are invisibly-high energies. X-ray and gamma. But a couple of nuclei have multi-step spin isomer decays (or was it shape isomer?). One step of which is visible. So someone trapped and fully stripped a nucleus, and bombarded it to visibility. Naked-eye visibility. And took a picture. Of vacuum vessel window, with a green(?) fluorescence dot.
I saw that picture years ago. Likely a cover photo on something.
I would very much like to find it again. For use in educational content. A lot of time has been spent looking for it, both by myself, and a couple of MIT science librarians. If anyone has a clue, I'd very much appreciate it. Here is a mockup[1] I gimped for user testing.
Why use it in education? To make the concept of atoms more concrete. Atomic electrons are too small (and slow and fragile) to see with your naked eye. But (a couple of) nuclei you can (under hard-to-contrive conditions). Absent concrete, students build their understanding of materials on muddy misconceptions. For example, one failure-mode in teaching high-school stoichiometry, is students not thinking of atoms as real physical objects.
And to preempt a common response... one professor complained "you aren't really seeing the nucleus - it's only a diffraction dot"... right before they headed out to a star party, to apparently "not see" stars. ;)
[1] http://www.clarifyscience.info/assets/2017-Atoms/assets0/wk/...
[+] [-] cantrevealname|8 years ago|reply
People can sense single photons: Experiment suggests that humans are capable of perceiving even the feeblest flash of light [1][2]
[1] http://www.nature.com/news/people-can-sense-single-photons-1...
[2] https://news.ycombinator.com/item?id=12163109
[+] [-] joshdance|8 years ago|reply
[+] [-] nikdaheratik|8 years ago|reply
A scanning electron microscope, or an x-ray crystallography based machine, uses items with much smaller wavelengths, .01 - 10 nm in the case of x-rays and so they're able to peer inside an atomic structure.
[+] [-] everdev|8 years ago|reply
Obviously the technology and intent is impressive, but will we ever be able to see an atom more clearly or is it simply too small to be seen without Photoshopping in the details?
[+] [-] Tsarbomb|8 years ago|reply
Atoms are much more nebulous than the concept of small indivisible balls of matter.
[+] [-] nikdaheratik|8 years ago|reply
The problem is that of scale: visible light has a wavelength of 380-750 nm (10^-9 meters) while the atomic radius of even large atoms are still in the ~200 pm (10^-12m) which means that visible light still has a wavelength 1000 times that of an atomic radius. To peer more closely at an atom, you would need to be able to use something moving at a much smaller wavelength, like an x-ray or a focused beam of electrons.
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[+] [-] PhantomGremlin|8 years ago|reply
https://upload.wikimedia.org/wikipedia/commons/2/22/Hubble_E... https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field#Hubble...