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my thought is light reflects off what ever it comes in contact with. it is the light you see not actually the object it self. so no matter how far the light travels the imprint of that item is in that beam of light as well as anything else that same beam of light reflected off of. sort of like those picture mosaics you see where they take a thousand pics of varying colors and shades of light and dark and make a larger pic of something. yet when you magnify it only then do you notice all of the other pics in it. Would that then make that light a time recorder?

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    $\begingroup$ What do you mean by "memory" or "time recorder"? You can certainly use a wavefront of light to 'look back in time' (think stars - the light coming from Alpha Centauri has been traveling a couple years to reach us), but the only 'memory' light has is that it maintains its polarisaton and frequency when propagating in vacuum. $\endgroup$ – catalogue_number Apr 25 '17 at 1:36
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    $\begingroup$ In the light's frame of reference distances have contracted to zero. As far as the light is concerned it's everywhere at the same time. Not much need for a "memory". $\endgroup$ – M. Enns Apr 25 '17 at 2:13
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No, light does not have memory. All the processes of light propogation are the same backward and forward, there is no 'arrow of time' in the way light behaves. The example of light changing color is an interaction with matter, probably generating heat: the matter is doing that, and it's irreversible.

The light alone cannot learn, and cannot turn to heat, because both those processes are asymmetric to time reversal, and light is symmetric.

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Actually, almost the exact opposite is true. Color is a byproduct of what wavelengths the object in question is able to absorb. A red table appears red because it reflects red light. Similarly, the atmosphere scatters blue light (or light at a wavelength that we understand as "blue"), and therefore appears blue.

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  • $\begingroup$ I will not downvote this answer John but I think you need to expand it a bit. Colour does not come simply from absorption or emission. Colour ultimately is derived from perception (chiefly through how our eyes pick up the wavelengths and how our brain ultimately interprets them). For example, there is no purple wavelength but we do have a purple colour. $\endgroup$ – Apoorv Khurasia Apr 27 '17 at 10:35
  • $\begingroup$ I agree. The perception of color is a byproduct of the biological systems that have evolved over time to better help us survive. $\endgroup$ – john morrison Apr 29 '17 at 7:39
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Does light have memory?

Light, as a collection of zillions of photons of various frequencies can be considered to have memory. Holograms are a proof.

Holograms need coherent radiation, i.e the phases of the electromagnetic waves involved are fixed, not random, and that allows the recording in the light/electromagnetic radiation the signal of the objects projected as images.

An even simpler "memory" for the small time interval between focus and screen are lense images, the light carries information and reproduces it on the screen.

my thought is light reflects off what ever it comes in contact with. it is the light you see not actually the object it self. so no matter how far the light travels the imprint of that item is in that beam of light as well as anything else that same beam of light reflected off of.

Ordinary incoherent light , like the light ambient in a room, which has reflected from all surfaces has lost all phase information of the frequencies it is composed of, so the "memory" cannot be unscrambled. If you see a red reflection, you can guess it came from something red, some memory, but the dimensions and angles that define objects will be lost due to incoherence of phases.

Light from astronomical objects does carry memory, as spectra of atoms and frequency of the radiation, an imprint of the whole history. Also cosmic microwave background radiation carries information in the intensity of the light arriving at our detectors, i.e. whether there is absorption on the way or not, as shadows do. In general not in the form you imagined.

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Proof of 'Light having a memory' might be best proved by the path it takes through the Universe. Consider the line of sight of the light emitting . from a source, say sixty million light years away. Without obstruction, it is a direct observation. However, if that light encounters a black hole, say located thirty million light years away, that light is bent around the object and continues on to us for observation. I have often wondered the following. (A) the Black hole is an object that is so massive that all light is captured and it reflects none. (B) The path of light is refracted at one hundred and eighty degrees around the object, so it appears to have 'passed through' that black hole and continued on it's original path toward us to see. Without that memory, the gravitational effects of a black hole should randomly throw that light in every conceivable degree of the available three hundred sixty degrees of arc. Someone needs to explain why the beam of light travels on at the same path it even with the gravitational encounter.

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Light can be one of the best ways to record something. Not only can we see things that happened billions of years ago but most likely after Earth and this solar system have died some distant world will be able to see us in the distant future when our light finally reaches them.

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I concur with Apoorv Khurasia.

Ultimately it’s all in the mind of perception. In radiobiology physics the universe is described as an invisible field of electromagnetic vibrations oscillating at different frequencies, therefore light has no color until our eyes refract it as such, and our brains reflect it so.

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