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Picture of a Single Atom Wins Science Photo Contest

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Re: Picture of a Single Atom Wins Science Photo Contest

#71

Post by dingo_bat »

ars wrote: post #59
albedoa wrote: post #47

Earlier quoted context omitted.

> No, that's not it. That has to be at least partially it for the rest of your comment to be right (which it is!). To say the atom was "held nearly motionless" is to say it moved a little during the exposure. It sent the light toward the sensor from all of its positions.

> That has to be at least partially it No, not at all. The wavelength of the light is about 1,500 times larger than the atom emitting it. So the atom would need to move at least 1,500 diameters to make any difference in the light. It doesn't move that much.

> It doesn't move that much.

Source?

Re: Picture of a Single Atom Wins Science Photo Contest

#72

Post by teekert »

excalibur wrote: post #9
dgritsko wrote: post #6

Earlier quoted context omitted.

From the article: > 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.

That explanation doesn't really satisfy. Perhaps, based on a large body of experimental evidence, it is known that the number of atoms present can be determined by the apparent brightness. Perhaps it's something totally different. Regardless, it would be helpful if the author/photographer/somebody explained the rationale that makes them confident that this is only a single atom.

When blasting light in every direction, does it really matter how small the source is? As long as those photons hit your eye, you can see the object.

Re: Picture of a Single Atom Wins Science Photo Contest

#73

Post by alborzmassah »

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.

Re: Picture of a Single Atom Wins Science Photo Contest

#74

Post by sudhirj »

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.

Re: Picture of a Single Atom Wins Science Photo Contest

#75

Post by Nec28 »

alborzmassah wrote: post #73

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.

My guess is they made that atom very, very, very bright, among other things...But I'm no scientist

Re: Picture of a Single Atom Wins Science Photo Contest

#76

Post by StavrosK »

tjohns wrote: post #61
4mitkumar wrote: post #60

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 "vis…

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.

It doesn't really mean anything to day "you aren't looking at it, you're looking at the reflected photons". You're always looking at reflected photons of everything.

Re: Picture of a Single Atom Wins Science Photo Contest

#77

Post by PhantomGremlin »

gigatexal wrote: post #31

this takes the cake for great desktop backgrounds.

For a while I used the "opposite" of a single atom for my desktop background. Quite a few atoms in that picture! 5500 galaxies worth.

https://upload.wikimedia.org/wikipedia/commons/2/22/Hubble_E... https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field#Hubble...

Re: Picture of a Single Atom Wins Science Photo Contest

#78

Post by BuildTheRobots »

ars wrote: post #58
BuildTheRobots wrote: post #44

Earlier quoted context omitted.

If we're seeing the single photon emitted by a single atom, then how much larger is the spot of light in the image compared to the atom that emitted it? Why isn't there a ruler somewhere in the picture? My brain is absolutely failing to make sense of the scales and sizes in this image.

> then how much larger is the spot of light in the image compared to the atom that emitted it? The atom is about 255 picometers, the light is around 400 nanometers. That makes the light around 1500 times larger than the atom. (Which also helps explain why visible light can not distinguish atoms placed close together - it's so much larger than them.) > Why isn't there a ruler somewhere in the picture? My brain is abso…

Thank you so much; that was exactly the explanation I needed =)

Re: Picture of a Single Atom Wins Science Photo Contest

#79

Post by SAI_Peregrinus »

4mitkumar wrote: post #60

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 "vis…

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.

Re: Picture of a Single Atom Wins Science Photo Contest

#80

Post by ars »

dingo_bat wrote: post #71
ars wrote: post #59

Earlier quoted context omitted.

> That has to be at least partially it No, not at all. The wavelength of the light is about 1,500 times larger than the atom emitting it. So the atom would need to move at least 1,500 diameters to make any difference in the light. It doesn't move that much.

> It doesn't move that much. Source?

Here: https://en.wikipedia.org/wiki/Laser_cooling
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