Speed of Light ?

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Offline unstman

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Speed of Light ?
« on: 23/08/2006 01:14:04 »
What actually causes a ' light photon ', to travel at the speed of light????

David
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Offline ukmicky

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Re: Speed of Light ?
« Reply #1 on: 23/08/2006 02:42:19 »
If you mean why does a photon travel at 186,000 miles a second then thats just our man made measure of its speed .

but as to why it at always travels at the speed it does in a vacuum and never any faster or slower then nobody knows



Michael
« Last Edit: 23/08/2006 02:45:22 by ukmicky »

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Offline lightarrow

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Re: Speed of Light ?
« Reply #2 on: 23/08/2006 08:24:30 »
quote:
Originally posted by unstman

What actually causes a ' light photon ', to travel at the speed of light???

Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?"

Solving the wave equations we can find exactly the propagation speed.
For what concerns light, solving the electromagnetic wave equation in the void, we see that the waves propagates with the speed v = 1/square[mu(0)*epsilon(0)], where mu(0) is the magnetic permeability of void and epsilon(0) is the electric permeability of void.

Given the values of these two constants (we can calculate them from electric and magnetic strenght) we can compute the speed v, that we call c: 299,792,458 m/s

Said in a more simple way: when you move an electric charge here, you produce a variable electric field there. A variable electric field there, produces a (variable) megnetic field, which in turns, produces a (variable) electric field and so on. So you have a variable electromagnetic field moving in the void.
You don't have to accelerate particles having a mass, so the speed can be very high, without limit, actually. Infact, the speed of light is actually infinite, but I don't want to explain this now.
« Last Edit: 03/09/2006 10:42:13 by lightarrow »

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Offline unstman

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Re: Speed of Light ?
« Reply #3 on: 23/08/2006 11:24:46 »
quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ???

David
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Offline lightarrow

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Re: Speed of Light ?
« Reply #4 on: 23/08/2006 11:51:04 »
quote:
Originally posted by unstman

quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ??

Did you read my post? You have the answers there.
Light doesn't need a medium of matter to travel, as electric force doesn't need a medium of matter to act between charges, as gravitational force doesn't need a medium of matter to act between the earth and the sun...ecc. As I explained, light is a variation in the electromagnetic field, that is, a variation of electromagnetic force. Since electric, magnetic, electromagnetic, gravitational, ecc forces, act through the void space, it's not so difficult to imagine that their variations act through the void as well!

If you see light as made of particles, I have explained you that these particles are massless, so they can be accelerated to very high speed without the need of a high force. If you shoot a fast bullet through the void space, it doesn't stop, it keeps going forever at the same speed! At least, until it hits something or is captured from an object's gravitational field.

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Offline Soul Surfer

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Re: Speed of Light ?
« Reply #5 on: 23/08/2006 16:45:21 »
Empty space may contain nothing but it does posess properties and the important features in this question are the ability of a changing electric field to polarise it and cause current to flow which crerates a changing magnetic field which in its turn polarises space create a changing electric and so on field the valiues of this polarisablity determine the velocity of light.  These properties of spave were measured and understood long before quantum mechanics was known about and the existence of electromagnetic waves was predicted by physicists before it was understood that light was in fact an electromagnetic wave.

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Offline Solvay_1927

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Re: Speed of Light ?
« Reply #6 on: 24/08/2006 01:48:23 »
quote:
Originally posted by unstman

... what medium is there for a photon to travel at such a high speed, and still sustain itself ... for such vast distances ???


Why does it need to "sustain itself" to keep moving?

Newton's 1st Law applies: Every object continues in its inertial state (i.e. either at rest or in a state of uniform linear motion) unless acted upon by an external force.  (Or, as lightarrow said, "If you shoot a fast bullet through the void space, it doesn't stop, it keeps going forever at the same speed!")
 

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Offline syhprum

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Re: Speed of Light ?
« Reply #7 on: 24/08/2006 12:36:27 »
When we speak of light (photons) travelling in a vacuum what we are in fact observing is photons travelling through the dark matter with which our galaxy in enveloped.
Has any attempt been made to measure the speed between galaxies away from the dark matter.
Not to mention the sea of quantum particles/anti-particles neutrinos, Gravitons, and the 2.7K CBR that fills space

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Offline ukmicky

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Re: Speed of Light ?
« Reply #8 on: 23/08/2006 02:42:19 »
If you mean why does a photon travel at 186,000 miles a second then thats just our man made measure of its speed .

but as to why it at always travels at the speed it does in a vacuum and never any faster or slower then nobody knows



Michael
« Last Edit: 23/08/2006 02:45:22 by ukmicky »

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Offline lightarrow

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Re: Speed of Light ?
« Reply #9 on: 23/08/2006 08:24:30 »
quote:
Originally posted by unstman

What actually causes a ' light photon ', to travel at the speed of light???

Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?"

Solving the wave equations we can find exactly the propagation speed.
For what concerns light, solving the electromagnetic wave equation in the void, we see that the waves propagates with the speed v = 1/square[mu(0)*epsilon(0)], where mu(0) is the magnetic permeability of void and epsilon(0) is the electric permeability of void.

Given the values of these two constants (we can calculate them from electric and magnetic strenght) we can compute the speed v, that we call c: 299,792,458 m/s

Said in a more simple way: when you move an electric charge here, you produce a variable electric field there. A variable electric field there, produces a (variable) megnetic field, which in turns, produces a (variable) electric field and so on. So you have a variable electromagnetic field moving in the void.
You don't have to accelerate particles having a mass, so the speed can be very high, without limit, actually. Infact, the speed of light is actually infinite, but I don't want to explain this now.
« Last Edit: 03/09/2006 10:42:13 by lightarrow »

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Offline unstman

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Re: Speed of Light ?
« Reply #10 on: 23/08/2006 11:24:46 »
quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ???

David
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Offline lightarrow

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Re: Speed of Light ?
« Reply #11 on: 23/08/2006 11:51:04 »
quote:
Originally posted by unstman

quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ??

Did you read my post? You have the answers there.
Light doesn't need a medium of matter to travel, as electric force doesn't need a medium of matter to act between charges, as gravitational force doesn't need a medium of matter to act between the earth and the sun...ecc. As I explained, light is a variation in the electromagnetic field, that is, a variation of electromagnetic force. Since electric, magnetic, electromagnetic, gravitational, ecc forces, act through the void space, it's not so difficult to imagine that their variations act through the void as well!

If you see light as made of particles, I have explained you that these particles are massless, so they can be accelerated to very high speed without the need of a high force. If you shoot a fast bullet through the void space, it doesn't stop, it keeps going forever at the same speed! At least, until it hits something or is captured from an object's gravitational field.

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Offline Soul Surfer

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Re: Speed of Light ?
« Reply #12 on: 23/08/2006 16:45:21 »
Empty space may contain nothing but it does posess properties and the important features in this question are the ability of a changing electric field to polarise it and cause current to flow which crerates a changing magnetic field which in its turn polarises space create a changing electric and so on field the valiues of this polarisablity determine the velocity of light.  These properties of spave were measured and understood long before quantum mechanics was known about and the existence of electromagnetic waves was predicted by physicists before it was understood that light was in fact an electromagnetic wave.

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Offline ukmicky

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Re: Speed of Light ?
« Reply #13 on: 23/08/2006 02:42:19 »
If you mean why does a photon travel at 186,000 miles a second then thats just our man made measure of its speed .

but as to why it at always travels at the speed it does in a vacuum and never any faster or slower then nobody knows



Michael
« Last Edit: 23/08/2006 02:45:22 by ukmicky »

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Offline lightarrow

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Re: Speed of Light ?
« Reply #14 on: 23/08/2006 08:24:30 »
quote:
Originally posted by unstman

What actually causes a ' light photon ', to travel at the speed of light???

Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?"

Solving the wave equations we can find exactly the propagation speed.
For what concerns light, solving the electromagnetic wave equation in the void, we see that the waves propagates with the speed v = 1/square[mu(0)*epsilon(0)], where mu(0) is the magnetic permeability of void and epsilon(0) is the electric permeability of void.

Given the values of these two constants (we can calculate them from electric and magnetic strenght) we can compute the speed v, that we call c: 299,792,458 m/s

Said in a more simple way: when you move an electric charge here, you produce a variable electric field there. A variable electric field there, produces a (variable) megnetic field, which in turns, produces a (variable) electric field and so on. So you have a variable electromagnetic field moving in the void.
You don't have to accelerate particles having a mass, so the speed can be very high, without limit, actually. Infact, the speed of light is actually infinite, but I don't want to explain this now.
« Last Edit: 03/09/2006 10:42:13 by lightarrow »

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Offline unstman

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Re: Speed of Light ?
« Reply #15 on: 23/08/2006 11:24:46 »
quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ???

David
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Offline lightarrow

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Re: Speed of Light ?
« Reply #16 on: 23/08/2006 11:51:04 »
quote:
Originally posted by unstman

quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ??

Did you read my post? You have the answers there.
Light doesn't need a medium of matter to travel, as electric force doesn't need a medium of matter to act between charges, as gravitational force doesn't need a medium of matter to act between the earth and the sun...ecc. As I explained, light is a variation in the electromagnetic field, that is, a variation of electromagnetic force. Since electric, magnetic, electromagnetic, gravitational, ecc forces, act through the void space, it's not so difficult to imagine that their variations act through the void as well!

If you see light as made of particles, I have explained you that these particles are massless, so they can be accelerated to very high speed without the need of a high force. If you shoot a fast bullet through the void space, it doesn't stop, it keeps going forever at the same speed! At least, until it hits something or is captured from an object's gravitational field.

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Offline Soul Surfer

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Re: Speed of Light ?
« Reply #17 on: 23/08/2006 16:45:21 »
Empty space may contain nothing but it does posess properties and the important features in this question are the ability of a changing electric field to polarise it and cause current to flow which crerates a changing magnetic field which in its turn polarises space create a changing electric and so on field the valiues of this polarisablity determine the velocity of light.  These properties of spave were measured and understood long before quantum mechanics was known about and the existence of electromagnetic waves was predicted by physicists before it was understood that light was in fact an electromagnetic wave.

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Offline Solvay_1927

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Re: Speed of Light ?
« Reply #18 on: 24/08/2006 01:48:23 »
quote:
Originally posted by unstman

... what medium is there for a photon to travel at such a high speed, and still sustain itself ... for such vast distances ???


Why does it need to "sustain itself" to keep moving?

Newton's 1st Law applies: Every object continues in its inertial state (i.e. either at rest or in a state of uniform linear motion) unless acted upon by an external force.  (Or, as lightarrow said, "If you shoot a fast bullet through the void space, it doesn't stop, it keeps going forever at the same speed!")
 

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Offline syhprum

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Re: Speed of Light ?
« Reply #19 on: 24/08/2006 12:36:27 »
When we speak of light (photons) travelling in a vacuum what we are in fact observing is photons travelling through the dark matter with which our galaxy in enveloped.
Has any attempt been made to measure the speed between galaxies away from the dark matter.
Not to mention the sea of quantum particles/anti-particles neutrinos, Gravitons, and the 2.7K CBR that fills space

syhprum
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Offline lightarrow

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Re: Speed of Light ?
« Reply #20 on: 23/08/2006 08:24:30 »
quote:
Originally posted by unstman

What actually causes a ' light photon ', to travel at the speed of light???

Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?"

Solving the wave equations we can find exactly the propagation speed.
For what concerns light, solving the electromagnetic wave equation in the void, we see that the waves propagates with the speed v = 1/square[mu(0)*epsilon(0)], where mu(0) is the magnetic permeability of void and epsilon(0) is the electric permeability of void.

Given the values of these two constants (we can calculate them from electric and magnetic strenght) we can compute the speed v, that we call c: 299,792,458 m/s

Said in a more simple way: when you move an electric charge here, you produce a variable electric field there. A variable electric field there, produces a (variable) megnetic field, which in turns, produces a (variable) electric field and so on. So you have a variable electromagnetic field moving in the void.
You don't have to accelerate particles having a mass, so the speed can be very high, without limit, actually. Infact, the speed of light is actually infinite, but I don't want to explain this now.
« Last Edit: 03/09/2006 10:42:13 by lightarrow »

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Offline unstman

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Re: Speed of Light ?
« Reply #21 on: 23/08/2006 11:24:46 »
quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ???

David
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Offline lightarrow

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Re: Speed of Light ?
« Reply #22 on: 23/08/2006 11:51:04 »
quote:
Originally posted by unstman

quote posted by : lightarrow - 'Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?" '

I thought light was a wave and/or particle ? (I may have put this wrongly lol). I see your point regarding the travelling of a sound wave and this of a wave...both have the medium of matter to transfer one energy to another. However, in the vaccum of space, what medium is there for a photon to travel at such a high speed, and still sustain itself (in terms of energy (if it is a form of energy)), for such vast distances ??

Did you read my post? You have the answers there.
Light doesn't need a medium of matter to travel, as electric force doesn't need a medium of matter to act between charges, as gravitational force doesn't need a medium of matter to act between the earth and the sun...ecc. As I explained, light is a variation in the electromagnetic field, that is, a variation of electromagnetic force. Since electric, magnetic, electromagnetic, gravitational, ecc forces, act through the void space, it's not so difficult to imagine that their variations act through the void as well!

If you see light as made of particles, I have explained you that these particles are massless, so they can be accelerated to very high speed without the need of a high force. If you shoot a fast bullet through the void space, it doesn't stop, it keeps going forever at the same speed! At least, until it hits something or is captured from an object's gravitational field.

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Offline Soul Surfer

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Re: Speed of Light ?
« Reply #23 on: 23/08/2006 16:45:21 »
Empty space may contain nothing but it does posess properties and the important features in this question are the ability of a changing electric field to polarise it and cause current to flow which crerates a changing magnetic field which in its turn polarises space create a changing electric and so on field the valiues of this polarisablity determine the velocity of light.  These properties of spave were measured and understood long before quantum mechanics was known about and the existence of electromagnetic waves was predicted by physicists before it was understood that light was in fact an electromagnetic wave.

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Offline Solvay_1927

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Re: Speed of Light ?
« Reply #24 on: 24/08/2006 01:48:23 »
quote:
Originally posted by unstman

... what medium is there for a photon to travel at such a high speed, and still sustain itself ... for such vast distances ???


Why does it need to "sustain itself" to keep moving?

Newton's 1st Law applies: Every object continues in its inertial state (i.e. either at rest or in a state of uniform linear motion) unless acted upon by an external force.  (Or, as lightarrow said, "If you shoot a fast bullet through the void space, it doesn't stop, it keeps going forever at the same speed!")
 

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Offline syhprum

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Re: Speed of Light ?
« Reply #25 on: 24/08/2006 12:36:27 »
When we speak of light (photons) travelling in a vacuum what we are in fact observing is photons travelling through the dark matter with which our galaxy in enveloped.
Has any attempt been made to measure the speed between galaxies away from the dark matter.
Not to mention the sea of quantum particles/anti-particles neutrinos, Gravitons, and the 2.7K CBR that fills space

syhprum
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Offline Soul Surfer

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Re: Speed of Light ?
« Reply #26 on: 29/08/2006 09:26:00 »
An interesting and highly relevant thought syhprum, dark matter (the major constituent of the universe)does cause light to be deflected by its gravitational attraction.  hence the effects of "gravitational lensing"  that are well known and observed but it is only a very tiny amount  (seconds of arc) unless you are very close to an extremely dense object like a neutron star or a black hole.

However because of the relatavistic equations this deflection is not seen as being a speed change (like the refraction of likght though a glass lens) but a slight distortion in the fabric of the universe.

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Offline lightarrow

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Re: Speed of Light ?
« Reply #27 on: 29/08/2006 10:31:35 »
quote:
Originally posted by Soul Surfer


However because of the relatavistic equations this deflection is not seen as being a speed change (like the refraction of likght though a glass lens) but a slight distortion in the fabric of the universe.
Yes, because matter --> gravitational field, doesn't change the speed of light, it simply bends it.
« Last Edit: 29/08/2006 10:33:09 by lightarrow »

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Offline syhprum

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Re: Speed of Light ?
« Reply #28 on: 29/08/2006 17:50:51 »
Our mesurements of the speed of light are those made in our galaxy enveloped in dark matter,
is there any evidence as to its speed outside this clump of dark matter as I understand that dark matter is not spread uniformly throughout space

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Offline Soul Surfer

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Re: Speed of Light ?
« Reply #29 on: 30/08/2006 08:07:26 »
There is plenty of evidence that the observed variations in the density of dark matter do not distort light any more than that caused by the observed variations due to gravitational deviation.  A singnificant variation in the velocity of light would cause severe distortion of our image of the universe



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Offline Soul Surfer

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Re: Speed of Light ?
« Reply #30 on: 30/08/2006 08:07:26 »
There is plenty of evidence that the observed variations in the density of dark matter do not distort light any more than that caused by the observed variations due to gravitational deviation.  A singnificant variation in the velocity of light would cause severe distortion of our image of the universe



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Offline lightarrow

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Re: Speed of Light ?
« Reply #31 on: 03/09/2006 10:51:07 »
About the speed of light, if I have understood correctly, (please let me know if I'm saying something wrong), we perceive a change in it, only if we look at the space as if it were euclidean, but, actually, it's not, near massive objects.

So, considering the real geometry of space-time, light always move along a geodesic, which is the analogue of the straight line in an euclidean space, and in that geometry we don't see any change of light's speed.
« Last Edit: 03/09/2006 10:52:08 by lightarrow »