YouTube Description:
What would you see if you were drifting through space, looking back at the sun? Well its light intensity would decrease as the inverse square of distance from the sun. And you would imagine the intensity would decrease smoothly, asymptotically approaching zero.
But this is not what happens.
If you had sensitive enough eyes, like frogs' eyes, you would find that at some point the sun would start to flicker. You would see flashes of light separated by complete darkness. And as you drift further from the sun, what's strange is that these flashes do not decrease in brightness, but they do become less frequent. That's because light comes in lumps, called quanta or photons, which are indivisible. So if you try to spread light out very thinly, you reach a point where there are only single bits of light reaching an observer's eye at any given time.
I should acknowledge the book "The Fabric of Reality" by David Deutsch, which contains a similar story about a frog and a torch. It inspired me to make this film. Thanks also to MinutePhysics for reviewing earlier drafts and suggesting I make it more ridiculous.
7 Comments
oritteropo*related=http://videosift.com/video/Minutephysics-The-Origin-of-Quantum-Mechanics
I'm surprised he didn't manage to fit in the light bulb research, although I guess that has been done.
siftbotMinutephysics -- The Origin of Quantum Mechanics has been added as a related post - related requested by oritteropo.
ZawashTo see this for yourself - just have a look at distant stars - preferably from orbit, outside the atmosphere.
rich_magnetSo if a single photon from a distant star passes through the slit-like pupils of the frog's eye the question is: which slit does it pass through? And what retina does it impinge on?
This is actually a trick question, easily answered by the experimental results of the famous double-slit experiment.
Also, I'm disappointed. I was hoping to learn about the optical/visual system of frogs.
oritteropoHmm... now you've made me curious too. I have found a few interesting pages, but nothing specifically about frog vision apart from mentions that it's sensitive.
I'm not quite as sure about the single photon claim. I found a Physicsworld.com article from September 2012 talking about using a single rod cell from a frog eye being used as an extremely sensitive detector which is able to detect a single photon, but according to the original Usenet Physics FAQ (I cite an updated version hosted at math.ucr.edu) human retinas can also respond to a single photon, but have a neural filter to block the signal unless 5 to 9 photons arrive within less than 100 ms.
References
Julie Schnapf, "How Photoreceptors Respond to Light", Scientific American, April 1987
S. Hecht, S. Schlaer and M.H. Pirenne, "Energy, Quanta and vision." Journal of the Optical Society of America, 38, 196-208 (1942)
D.A. Baylor, T.D. Lamb, K.W. Yau, "Response of retinal rods to single photons." Journal of Physiology, Lond. 288, 613-634 (1979)
Also, I'm disappointed. I was hoping to learn about the optical/visual system of frogs.
oritteropoI have found an article on frog and toad eyes and optic systems, hosted on David Olmsted's neurocomputing.org.
It still doesn't directly address the claim that they can detect single photons in the way this video suggests.
deathcow> block the signal unless 5 to 9 photons arrive within less than 100 ms
This is true. My own system (as new) was 8 photons at 80ms. I installed the tweaking kit from NewEye and have been running around set to 3 photons and 200ms lately and.. it's a trip. Anything beyond the Selsky border of 3 photons and 150ms will show you aura (around healthy people anyway) so I am seeing aura almost every time at 3/200. I have to scale back when driving.
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