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Can a Human See a Single Photon? (1996)

math.ucr.edu

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Re: Can a Human See a Single Photon? (1996)

#111

Post by Luc »

thesimonlee wrote: post #99
eternauta3k wrote: post #90

Earlier quoted context omitted.

Does an infrared photon have enough energy to stimulate a rod?

Definitely. 20 years ago when homes were not littered with LEDs all over, I would wake in the night to total blackness. I could still find my way around the house just able to see based on what is I suppose a noise floor of ambient temperature. Go into the kitchen & behold the stove top emitting 'bright' white light, from I suppose a temperature of around 30degC /90F. Obviously everything is a blackbody, but those ph…

Did you consider you were seeing (very low amounts of) visible light? Temperature had nothing to do with it.

Re: Can a Human See a Single Photon? (1996)

#112

Post by [deleted] »

thesimonlee wrote: post #99
eternauta3k wrote: post #90

Earlier quoted context omitted.

Does an infrared photon have enough energy to stimulate a rod?

Definitely. 20 years ago when homes were not littered with LEDs all over, I would wake in the night to total blackness. I could still find my way around the house just able to see based on what is I suppose a noise floor of ambient temperature. Go into the kitchen & behold the stove top emitting 'bright' white light, from I suppose a temperature of around 30degC /90F. Obviously everything is a blackbody, but those ph…

[deleted]

Re: Can a Human See a Single Photon? (1996)

#113

Post by stainablesteel »

its an interesting space to try and inspire engineering from biology, a quick search says eagles have the best eyesight

i just saw a video about a dog's nose being used for particle detection in crime scenes, i'm wondering if there's already been, or when there will be work on recreating the basis of an eye as a detector

or if maybe this has already been subverted by lens manufacturing

Re: Can a Human See a Single Photon? (1996)

#114

Post by Sharlin »

devindotcom wrote: post #93
Sharlin wrote: post #71

Earlier quoted context omitted.

A bit more than just “some” luck needed for one of those photons to be emitted straight into the other person’s pupil! The angular diameter of a human pupil (~5 mm) at a distance of ~2 m is about 0.2 degrees, taking the small angle approximation. So the area of the pupil is maybe 0.04 square degrees, or around one millionth of a full solid angle (~41,000 square degrees). Assuming a spherical isotropically radiating h…

>Assuming a spherical isotropically radiating human ...in a vacuum, of course!

Of course.

Re: Can a Human See a Single Photon? (1996)

#115

Post by 323 »

xhrpost wrote: post #106
lebubule wrote: post #15

Recent experiments have put the claim to test Overview https://www.nature.com/articles/nature.2016.20282 The actual work https://www.nature.com/articles/ncomms12172 > Here we report that humans can detect a single-photon incident on the cornea with a probability significantly above chance.

> To optimize this ratio in practice, we used the multi-pixel sensor of an electron multiplying charge-coupled device (EMCCD) camera as our idler detector (Fig. 1a). As the EMCCD can detect multiple photons simultaneously, it allowed us to identify and reject, that is, post-select, all events other than those where a single-photon pair was generated with a higher efficiency than with more traditional single-photon av…

> How is it possible to both detect a photon and then allow it to travel to the human eye?

Leonard Susskind explained it like this in one of his lectures (they are on YouTube, he's an excellent explainer):

From the moment the photon is emitted, to the moment it's detected, the photon exists in entanglement with all the intermediary things it "touched". Only at the final location it's "absorbed" (with a probability). At the intermediary locations the probability ended on the low side so it passed through.

Re: Can a Human See a Single Photon? (1996)

#116

Post by 323 »

mensetmanusman wrote: post #38
lebubule wrote: post #15

Recent experiments have put the claim to test Overview https://www.nature.com/articles/nature.2016.20282 The actual work https://www.nature.com/articles/ncomms12172 > Here we report that humans can detect a single-photon incident on the cornea with a probability significantly above chance.

Would be fun to see if it’s possible to set up the experiment as a double slit. Would humans sense an interference pattern? Is the back of an eye a sufficient observer? :)

When you look at the flickering pattern a laser pointer makes on a rough surface, that flickering pattern is similar in nature to the double slit interference, and you are seeing it with your eyes.

Don't forget that the interference pattern is a statistical one, you need to average over a number of photons to "see" it emerge.

Re: Can a Human See a Single Photon? (1996)

#117

Post by Derbasti »

tlhunter wrote: post #92

This reminds me; if I look at a red LED in the dark, my eyes seem to add a purple shape around it, kinda like an infinity symbol. Does this happen to anyone else?

I thought that's astigmatism, which distorts different wavelengths differently. Some LEDs have very few, widely separated wavelengths, and your astigmatism separates them.

Re: Can a Human See a Single Photon? (1996)

#118

Post by maxbond »

gameshot911 wrote: post #80

Another cool fact is that the human eye can see individual cells! [1] In this example it's a white blood cell, but the eye can also see human ovums as well. I was convinced this was the case as a kid, but no one ever believed me! [1] https://www.wikiwand.com/en/Blue_field_entoptic_phenomenon

One time a fellow intern and I were isolating single colonies of spirulina (many bright green algae* cells in a spiral [1], which is roughly 50 micron wide and maybe 15 micron tall, if memory serves), and I got one colony on it's own in a drop of water under a microscope (using a special pipette & the wick effect for suction).

I took my eyes off of the eyepiece, and looked at the drop of water. I could see a bright green dot in the middle, right where I'd left my spirulina.

I asked the other intern if they saw it too; they did. It was a magical moment.

I had a similar experience when I was doing something with H. pluvalis (an algae that turns bright red and forms a film under stress [2], you've likely seen it in a birdbath or shallow puddle) and I put this film under the microscope, looked at it, and saw it was 1 cell thick. I'm confident if I had gotten a single one of those cells on it's own, I could've seen it. Can't confidently remember how big they were, but large on the scale of cells you find in a drop of water (maybe 25 micron in diameter?), but smaller than most animal cells.

* Technically a cyanobacteria and not an algae, but if a lay person looked at a pond of it they'd say to themselves, "that's a bunch of algae"

[1] https://images.fineartamerica.com/images-medium-large/1-spir...

[2] https://images.squarespace-cdn.com/content/51511761e4b0323b0...

Re: Can a Human See a Single Photon? (1996)

#119

Post by beefield »

As a layman in modern physics, I struggle to understand the shape and size of a photon as a wave. As far as I understand, e.g double slit experiment would implicate that the size of a single photon wave would be clearly macroscopic in nature. Is there any text available that would discuss this without a need of Ph.D in physics?

Re: Can a Human See a Single Photon? (1996)

#120

Post by brummm »

beefield wrote: post #119

As a layman in modern physics, I struggle to understand the shape and size of a photon as a wave. As far as I understand, e.g double slit experiment would implicate that the size of a single photon wave would be clearly macroscopic in nature. Is there any text available that would discuss this without a need of Ph.D in physics?

So I think one conceptual issue that makes this so hard to understand is that we tend to imagine a physical reality where light is a wave or a stream of particles. However, that is absolutely wrong. Both the wave and the particle concept are mental models we have constructed to explain light as a phenomenon and to calculate things. And in their respective realms, they work exceptionally well.

However, where things start to get complicated is when the models give different results. However, this doesn't mean something is wrong, it just means the mental model we use to make sense of nature is stretched beyond where it's applicable.

So to preface, light is neither a stream of particles or some sort of wave like the ones on the surface of water. Light is the excitation of the electromagnetic field and is described by a quantum field theory called the standard model. So. photons are 0-dimensional (so no size) excitations of this field and they interact with matter like our eyes, surfaces, sensors in an experiment and produce physical effects.

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