# Nature of light

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The Bible tells us that the next step after creating the heaven and the un-formed earth, God said, "Let there be light" and there was light. (Genesis 1:3) [My speculation: That is when God fired up the sun.]

But for all of recorded history, we human beings have wanted to know more about light than that.

We have known that the lights that appear in the sky are way, W - A - Y far away, and that the light has to travel to get here.

Maybe that's all that was known until modern times when some enterprising scientists whose names I have forgotten made a rather successful attempt to discover the order of magnitude of the speed of light.

Now that we know to several decimal places "HOW FAST?" we come to the question "HOW?".

I speculated that it was somewhat like a rope-wave. The energy is transmitted along the physical rope and one can see the waves. (Only there is no rope. There is no medium. There is no "Aether".)

The roof fell in on me. Not because I suggested the rope-wave analogy. But because I speculated it in somebody else's Thread -- "hijacking". MigL suggested I ask the questions on my own Thread.

[An ancient folk-tale from India depicts a magician doing astounding tricks -- and for a grand finale, he causes a rope to stand vertically. He climbs the rope until he is clear up out of sight, and then pulls the rope up after himself. A cynic is depicted as saying, "Very good. Now do it without the rope."]

The rope analogy is not really much good for the transmission of light -- because light does it without the rope.

For those who have not done it, tie one end of a rope to a post, and pull the other end so that the whole rope is clear of the ground. Now move your hand. You can see a wave move along the rope. The energy of your hand is transmitted the whole length of the rope. At each point, the movement of each short length of the rope is transmitted to the next short length. If you move your hand up and down, you produce vertical waves. If you move your hand in a circle, you make circular waves.

Light is like that -- only faster -- and without the rope. Hmmmmm?

Fifty or sixty years ago our Physics Professor took apart the "Aether" explanation with an account of a careful experiment that involved the speed of star light six months apart. This not only had the observation points on the earth 2 AU apart, but going in the opposite direction. The light from that same star arrived at the same velocity. Some of us opined that some of the Aether was scooting right around with the earth. He very carefully demolished that speculation, too.

So (for me) it remains a mystery.

Is light little particles called Photons -- that travel at c?

Is light some kind of waves called Photons -- that travel at c?

Is light something ELSE -- called Photons -- that travel at c?

If light has no mass, how can it make the black and white vanes in those trick light-bulb (radiometer?) thingies revolve?

If light has no mass how does it force electrons to move when it hits a solar panel?

Edited by frankglennjacobs@gmail.com

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In my opinion, saying that light ''moves like waves on a rope but without the rope'' is like saying ''the sea is yellow but without the yellow color''. It doesn't mean anything. Esentially, it means that photons have a wavelike behavior, which has been known for a long time. So, if there was a speculation there, it doesn't represent anything.

The answer to your first three questions is yes, and your last two questions are actually good. I would drop the speculations and let them be answered, then take in that knowledge.

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The roof fell in on me.

I agree, I thought the general response rather heavy handed at the time.

I also feel offended if religious preaching is presented as pseudo science and some may have thought this was the case.

However the question you ask "what is light" is a vital one in science and has been the subject of a fascinating investigation stretching back at least 400 years in our civilisation alone.

When we investigate something in science we abstract observations and then try to construct a model within our known theoretical structure that matches and replicates the observations and provides predictions for us to make new observations to stengthen that model.

Nature does not always play ball with our models and sometimes we find that we have to make new models to suit new information.

This has happened during development of several models of light.

It should be said that even today we do not have a single model that explains everything.

In some circumstances light behaves like one model and in other circumstances it behaves like quite a different model, even to possessing apparantly contradictory characteristics.

That is what makes it so challenging.

So in the modern era the first theory was due to Newton and called the corpuscular theory which regarded light as a purely mechanical stream of bullets that we now identify with 'photons'.

Young offered an alternative wave explanation, still mechanical, but with some properties concerning refraction mutually exclusive to the corpuscular theory.

Tests over the next century favoured the wave theory and your question about waves received much discussion.

It was discovered that light could not be like sound waves because it is a purely transverse wave.

That is the vibrations occur at right angles to the direction of propagation.

Sound waves are longitudinal - the vibrations occur along the line of propagation.

This was discovered because it is only possible to polarise a transverse wave. A longitudibnal wave has only one vibration direction available, a transvers one has many and polarisation is the process of selecting one of these.

The following century was completely occupied with the issue of the medium.

Up to that time the only known waves were all mechanical and all required a mechancial medium of propagation.

But light can transit a vacuum.

So the ether ( in fact several ethers) was proposed and much work went on to investigate the properties of the ether.

The most famous of these was the Lumeniferous Aether of Lorenz.

No such Aether or ether has been discovered but light was shown to be a version of the electromagnetic waves predicted by Maxwellian models and wave theory consolidated.

Towards the end of that century two new observations came about.

The photoelectric effect and the stability of the electron in the atom.

These were incompatitible with wave theory and led to the quantum theory which allows that light has some characteristics (but not all) of waves and some characteristics of (again but not all) corpuscles or particles.

And that is basically where we are today.

Dos this help?

Edited by studiot

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So (for me) it remains a mystery.

Is light little particles called Photons -- that travel at c?

Is light some kind of waves called Photons -- that travel at c?

Is light something ELSE -- called Photons -- that travel at c?

Light is a wave in the electromagnetic field. The field is quantised so there is a smallest "size" of disturbance, for any given frequency. That "quantum" of the filed is called a photon in the case of the electromagnetic field (and called an electron, in the case of the electron field, etc).

If light has no mass, how can it make the black and white vanes in those trick light-bulb (radiometer?) thingies revolve?

Light has momentum and that is transferred when a photon is absorbed. (Strictly speaking, the Crooke's Radiometer doesn't actually work like that, but the principle applies.)

If light has no mass how does it force electrons to move when it hits a solar panel?

Light has energy and that energy can be transferred to an electron, bumping it up to a different energy level.

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Just a small point, I did not identify modern quantum theory with classical particulate one, I merely pointed out that new information brought about a reintroduction of some particulate properties.

Here is a thought about QFT.

Imagine an electron in some block of substance.

Do it create a field; is it a field ?

If so How far does that field extend?

As far as my eye?

If so why does it not interact with my eye?

Now Fred comes along and heats the block with a blowtorch so the electron emits a photon.

You say blythely that this photon is a 'disturbance in the field'

So what happens after the photon has entered my eye and been absorbed by my? cones.

Does the field still exist?

If the field exists when there are no photons is that not in effect a non corporeal ether?

Does a QFT field ether not posses the ehter like propertiy of pervading all matter?

To return to my original comment that we now teach that from the quantum point of view light has some properties of a wave, but not all and some properties of a particle, but not all.

Some find this a very disturbing concept, but as a generalist I observe that such symbiosis is very common in natural processes.

Even in waves, not all waves have all wave properties, as I have already noted with polarisation.

But thin of plasticity.

This offers some of the characteristics of a fluid and some of the charactistics of a solid.

So is it solid or liquid?

Why the either or?

Edited by studiot

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Light is a wave in the electromagnetic field. The field is quantised so there is a smallest "size" of disturbance, for any given frequency. That "quantum" of the filed is called a photon in the case of the electromagnetic field (and called an electron, in the case of the electron field, etc).

Light has momentum and that is transferred when a photon is absorbed. (Strictly speaking, the Crooke's Radiometer doesn't actually work like that, but the principle applies.)

Light has energy and that energy can be transferred to an electron, bumping it up to a different energy level.

In the beginning there was light, may be more correct than people think. Except for one thing, for there to be light there had to be space, for light to exist in. Unless of course light is made of space, in which case the bible is correct, on this point.

Light can be described by mathematical equations or in words or pictures.

Light is a polarized vibration of space, travelling at light speed with reference to the space around it.

Light has momentum but no mass. Space has momentum but no mass. The double slit experiment shows space has a memory of what has passed or momentum.

It is well known the double slit experiment can be carried out firing single photons, producing a wave effect, the path of photons is affected by vibrations or waves already existing in space. The single slit experiment shows divergence or fringing. These experiments cast light on the nature of light and of space light travels through.

Space on a cosmological scale is not stationery, it is expanding, and contracting. There is absolutely no reason why this cant be happening on a quantum scale also, creating waves.

The speed of light is c, wrt space around it. Galaxies are regressing away from us at 3c at the edge of the visible universe, space with in those galaxies, is moving with those galaxies in a difference reference frame to our solar system.

A photon of light can create a gravitational effect around it, showing that it can effect space around it.

Wave particle duality is confusing. If we state all things are waves in space of one form or another, things are easier to visualize.

Photons are polarized waves with inertia, that have energy = hf. This energy wave can be transferred to atoms to raise electrons to higher energy levels, or when an electron decays to a lower energy level a photon is given off.

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The double slit experiment shows space has a memory of what has passed or momentum.

The speed of light is c, wrt space around it.

You can't measure speed relative to space, only relative to another thing.

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After all the recent discussion on modern physics being about models not absolutes I think there are too many absolute statements in post#7, many of them may have some truth in them but may also be false in some circumstances.

eg

Photons are polarised waves with inertia.

One very useful modern model of photons is the solitary wave or soliton model.

Much of soliton maths also fits well with QFT maths.

But like every model it works well where it works but does not answer every question.

https://en.wikipedia.org/wiki/Soliton

Edited by studiot

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Space has momentum but no mass. The double slit experiment shows space has a memory of what has passed or momentum.

!

Moderator Note

Responses, even in speculations, are to be mainstream science, not more speculation

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So, the only thing the rope-wave exercise is good for is to visualize a wave in action -- and to make little boys ask questions.

I am trying to visualize a light wave going thru the void. Somehow it forms its OWN aether. It jiggles itself. The rope at point A jiggles the rope at point B. The wave at point A jiggles the wave at point B.

No. Let that one rest. Maybe in a month or two it will come more clearly to me.

Thank you, gentlemen. I will study your answers more than once because there is wisdom in them.

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So, the only thing the rope-wave exercise is good for is to visualize a wave in action -- and to make little boys ask questions.

I am trying to visualize a light wave going thru the void. Somehow it forms its OWN aether. It jiggles itself. The rope at point A jiggles the rope at point B. The wave at point A jiggles the wave at point B.

No. Let that one rest. Maybe in a month or two it will come more clearly to me.

Thank you, gentlemen. I will study your answers more than once because there is wisdom in them.

Here is the fundamental problem with seeking heuristic simplified explanations.

They tend to be based on analogies, in the attempt to explain complex subjects in terms readily understood. However they are just analogies. As such any heuristic explanation should only be treated as an analogy.

Edited by Mordred

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The Bible tells us that the next step after creating the heaven and the un-formed earth, God said, "Let there be light" and there was light. (Genesis 1:3) [My speculation: That is when God fired up the sun.]

If it would be written like

"light is photon, with energy E=h*f, momentum p=E/c, where h=6.62607004*10^-34 J*s, f- frequency in Hz = 1/T = c/wavelength, c=299792458 m/s,wavelength in meters,

but photon energy is not constant, it depends on who/what is detecting photon, in which FoR (Frame of Reference he/she/it is),

so one can perceive photon redshifted (Relativistic Doppler Shift) f=f0 sqrt(1-v/1+v) and other one can perceive photon blueshifted f=f0 sqrt(1+v/1-v),

photon has polarization"

and so on, so on,

nobody at the time, would understand any tiny bit of it...

As they didn't know math, nor physics, nor quantum physics..

Explanation of nuclear fusion in the Sun (or any star), and how light-photons are created by the Sun.... would open even more questions than about properties of photons..

Go to any city/village and ask random people what they know about protons, electrons, photons, what is mass of electron, charge of electron, mass of proton, charge of proton, what is speed of light, and so on, so on,

and you will notice nothing but unbearable incompetence..

Edited by Sensei

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After all the recent discussion on modern physics being about models not absolutes I think there are too many absolute statements in post#7, many of them may have some truth in them but may also be false in some circumstances.

eg

Photons are polarised waves with inertia.

One very useful modern model of photons is the solitary wave or soliton model.

Much of soliton maths also fits well with QFT maths.

But like every model it works well where it works but does not answer every question.

https://en.wikipedia.org/wiki/Soliton

Thanks for that very useful answer.

One final paradoxical question ref light if I may, we know photons are absorbed by atoms moving electrons to higher energy levels.

Gravity can be viewed as the contraction of space, could it also be viewed as being absorbed by atoms.

Or is gravity better described as being a disturbance in space which gives the appearance of stretching space.

Einstein Strangely stated "god does not play dice with the universe" It is interesting to try to picture exactly how a photon moves through space, and how space is distorted around it, causing it to ripple and cause a gravity effect, as all moving waves must do. The ripples of which will affect the waves around them, which in turn will be seen in the various slit experiments as waves, etc All things being waves of one kind of another is very easy to visualise, and leads a little towards string theory, however I do not believe in any theory should be believed like a religion, and never questioned. I do not for instance believe in the graviton.

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Gravity can be viewed as the contraction of space, could it also be viewed as being absorbed by atoms.

Or is gravity better described as being a disturbance in space which gives the appearance of stretching space.

It s probably better viewed as the curvature of space-time. It is mainly the curvature of the time dimension that causes gravity.

I do not believe in any theory should be believed like a religion, and never questioned.

No one does.

I do not for instance believe in the graviton.

Belief shouldn't come into it. There is no evidence, currently, for gravitons.

Edited by Strange

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The Bible tells us that the next step after creating the heaven and the un-formed earth, God said, "Let there be light" and there was light. (Genesis 1:3) [My speculation: That is when God fired up the sun.]

A well known book says otherwise

Genesis 1:16

"God made the two great lights, the greater light to govern the day, and the lesser light to govern the night; He made the stars also."

An interesting point; how very human of God to start- as we would- by switching on the light.

Why?

Was He worried about not knowing where He was?

Did He think He might bump into something?

Is this the first bit of the Bible that gives strong evidence that it was actually written by people

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A well known book says otherwise

Genesis 1:16

"God made the two great lights, the greater light to govern the day, and the lesser light to govern the night; He made the stars also."

An interesting point; how very human of God to start- as we would- by switching on the light.

Why?

Was He worried about not knowing where He was?

Did He think He might bump into something?

Is this the first bit of the Bible that gives strong evidence that it was actually written by people

+1

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One final paradoxical question ref light if I may, we know photons are absorbed by atoms moving electrons to higher energy levels.

Gravity can be viewed as the contraction of space, could it also be viewed as being absorbed by atoms.

Or is gravity better described as being a disturbance in space which gives the appearance of stretching space.

Einstein Strangely stated "god does not play dice with the universe" It is interesting to try to picture exactly how a photon moves through space, and how space is distorted around it, causing it to ripple and cause a gravity effect, as all moving waves must do. The ripples of which will affect the waves around them, which in turn will be seen in the various slit experiments as waves, etc All things being waves of one kind of another is very easy to visualise, and leads a little towards string theory, however I do not believe in any theory should be believed like a religion, and never questioned. I do not for instance believe in the graviton.

!

Moderator Note

I refer you to my previous modnote, which you apparently ignored. Keep your pet theories out of other peoples' threads.

If you aren't sure what mainstream physics says, don't make it up as you go along.

Do not respond to this modnote in the thread.

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Einstein Strangely stated "god does not play dice with the universe"

You misinterpret this quote entirely..

Einstein was thinking from point of view of absolute determinism,

while in Born's point of view, everything is result of probability.

One could say that Einstein rejected free will, while Born was supporting it..

It s probably better viewed and the curvature of space-time. It is mainly the curvature of the time dimension that causes gravity.

Somebody jumps from 1m and nothing happens (at worst case broken bones),

somebody else jumps from 10m and is dead..

Curvature and geometry will decide whether you're dead or alive.. ?

Curvature/geometry will decide whether glass will break apart, or remain solid piece.. ?

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So this is where this thread went...

Apparently Sensei, if you're moving along a geodesic, minding your own business, and someone puts a world in your way, then YES, some broken bones may result, or even death.

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lol though you would find yourself on a different geodesic though not in your favor. 😲

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AH! There IS humor among scientists! (". . . someone puts world in your way . . .")

As to God turning on the lights, I am sure He didn't need light, but He knew that many of His living creatures would need it.

And Moses was writing to a world full of goat-herders and pocket-miners. (But that's MY level, anyway.)

Never mind for now. I have to go study your many answers until they shake down in my mind to make sense to me.

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Studiot,

Yes, it helps.

It helps when you say yes.

It helps when you say yes, but . . .

It helps when you say no.

The kind words help.

The explanations help.

Thank you.

Lord Anteres,

I disagree. Having done the rope-waves thing has given me a starting point to understanding the propagation of waves. It is a kindergarten-level exercise, but I had to start somewhere. "Now do it without the rope," is a step up.

Strange,

Quantum? The littlest pieces of energy? I will have to follow your thread elsewhere. It sounds interesting.

Handy Andy,

You are beyond me. I have no idea what you mean. I am at kindergarten level. Maybe in a few years. You talk about creating space, for example. I will have to come back to that later.

Sensei,

You speak truth, but the "insufferable incompetence" is ignorance about these high-level subjects. Ask those same people about fishing or logging or laying brick, and you will find them quite competent.

Mordred,

Of course that is right. The transmission of light is NOT like a rope wave -- or like anything else.

We are not able to jump from complete ignorance to full knowledge. So, light is "like a wave" and "like a handful of gravel". "Only, without the rope."

Edited by frankglennjacobs@gmail.com

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All right now, back to the rope: I see that the wave reflects off the tie-point and comes back to my hand.

Sound waves cannot be seen (I think) but the rope waves can.

If I slap two boards together, they make a sound wave that echoes off each house all the way down the street. I can understand from the echoes that my sound wave has gotten to the red house and come back; to the yellow house and come back, etc.

Going outside at night with one of those expensive trick "tactical" flashlights, it can make a light wave and I can see that it gets to the next house and the next and so on, and back to me -- as far as I can tell, instantly.

Not instantly. Sometimes on the telephone, there is an echo and I hear my own voice coming back from space just a fraction of a second later. They tell me the space satellite is 23,000 mile away. So the electromagnetic pulse goes 46,000 miles in that time.

People who know about that sort of thing tell me radio goes as fast as light.

Now we're getting somewhere.

But I am beginning to see why light is not like a rope-wave. It is totally different. It cannot be explained with rope waves. It cannot be explained with water waves nor sound waves. It is like trying to explain an internal-combustion engine with a candle.

I cannot even explain it by way of radio waves -- because I don't know what they are nor how they travel.

Gentlemen, I thank all of you for carrying me around on a silken cushion.

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I cannot even explain it by way of radio waves -- because I don't know what they are nor how they travel.

Radio waves are the same thing as light waves, just a different frequency.