# Light The pin cushion experiment

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Thanks for all your really informative answers to does light accelerate I have another more interesting question.

For this consider the following crude analogy: Consider a perfectly spherical pin cushion about the size of a golf ball, it filled full of pins tightly packed together so much so that you can no longer see the pin cushion only the pins. Imagine this perfectly spherical pin cushion is suspended in the centre of a balloon , which itself is suspended inside a spherical hot air balloon, which is suspended is a sphere the size of the moon, which is suspended inside a sphere the size or earth , next the size of sun. Now extrapolate the pin lines outward until they touch the inner surface of each of the aforementioned. Because the do not expand as cone shaped but simply straight  lines you end up with a very spikey pin cushion and as the pins get further away from the cushion the distance between the pins expands. In between the pins there is space with no pins.

Now consider a light source about the size of the pin cushion, we can calculate the amount of light emitted right (yes). So if each of the photons/stream of photons/light waves leaves the perfect spherical surface as they travel outward they will become more distant from each other.  Ahaa I hear you cry but you must take into account the fact the light will leave the sphere at a multitude of angles. I have considered this and still think you would need an infinite number of photons (streams, waves) leaving at an infinite number of angles if you were to end up with a wall of light a trillion miles away . Where am I going wrong??

Thanks

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19 minutes ago, timharvey027 said:

Where am I going wrong??

I think in your (implicit) assumption that there will still be a continuous "wall" (wavefront?) of light at a great distance.

If you look at something sufficiently far away then you will receive very few photons: some might go just above you head, some to your right and, every now and again, one might enter your eye (or telescope). Some images of very distant objects are taken over very long periods because it takes hours or days to catch enough photons to make an image.

But your model does explain why the intensity falls off with the square of the distance: the photons are spread out over the surface of a sphere whose area is proportional to radius squared.

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48 minutes ago, timharvey027 said:

Thanks for all your really informative answers to does light accelerate I have another more interesting question.

Hopefully you noted my point about the difference between streams of particles (photons), waves and light rays ?

49 minutes ago, timharvey027 said:

For this consider the following crude analogy: Consider a perfectly spherical pin cushion about the size of a golf ball, it filled full of pins tightly packed together so much so that you can no longer see the pin cushion only the pins. Imagine this perfectly spherical pin cushion is suspended in the centre of a balloon , which itself is suspended inside a spherical hot air balloon, which is suspended is a sphere the size of the moon, which is suspended inside a sphere the size or earth , next the size of sun. Now extrapolate the pin lines outward until they touch the inner surface of each of the aforementioned. Because the do not expand as cone shaped but simply straight  lines you end up with a very spikey pin cushion and as the pins get further away from the cushion the distance between the pins expands. In between the pins there is space with no pins.

Now consider a light source about the size of the pin cushion, we can calculate the amount of light emitted right (yes). So if each of the photons/stream of photons/light waves leaves the perfect spherical surface as they travel outward they will become more distant from each other.  Ahaa I hear you cry but you must take into account the fact the light will leave the sphere at a multitude of angles. I have considered this and still think you would need an infinite number of photons (streams, waves) leaving at an infinite number of angles if you were to end up with a wall of light a trillion miles away . Where am I going wrong??

Thanks

This is still about light rays not waves or particles.

However Strange does make a very good point about the inverse square law. +1

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8 minutes ago, studiot said:

This is still about light rays not waves or particles.

Good pint. Treating light as rays is very useful for many purposes form optics to computer graphics, but it doesn't really correspond to what light "is", just how it behaves.

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3 minutes ago, Strange said:

Good pint.

Greene King is my favourite.

4 minutes ago, Strange said:

Treating light as rays is very useful for many purposes form optics to computer graphics, but it doesn't really correspond to what light "is", just how it behaves.

The point is that a streams of particles model does not allow the light to spread out into the space between the streams.

But because the stream is made of particles, there are necessarily gaps along the stream between the particles as well as side to side  between the streams.

Rays are at least continuous along their length.

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And, of course, none of these descriptions are what light "is"; they all just model its behaviour.

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10 minutes ago, Strange said:

And, of course, none of these descriptions are what light "is"; they all just model its behaviour.

√   A large tick here. (just to show off how much I enjoy using Charmap.exe)

Edited by studiot

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