# The Naked Scientists Forum

### Author Topic: Speed of Light ?  (Read 10013 times)

#### unstman

• Jr. Member
• Posts: 11
##### Speed of Light ?
« on: 23/08/2006 01:14:04 »
What actually causes a ' light photon ', to travel at the speed of light????

David

#### ukmicky

• Moderator
• Neilep Level Member
• Posts: 3011
##### 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 »

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 »

#### unstman

• Jr. Member
• Posts: 11
##### 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

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 ??

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.

#### Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
##### 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.

Learn, create, test and tell
evolution rules in all things
God says so!

#### Solvay_1927

• Sr. Member
• Posts: 383
##### 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!")

#### syhprum

• Neilep Level Member
• Posts: 3823
• Thanked: 19 times
##### 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 2.7°K CBR that fills space

syhprum

#### ukmicky

• Moderator
• Neilep Level Member
• Posts: 3011
##### 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 »

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 »

#### unstman

• Jr. Member
• Posts: 11
##### 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

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 ??

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.

#### Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
##### 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.

Learn, create, test and tell
evolution rules in all things
God says so!

#### ukmicky

• Moderator
• Neilep Level Member
• Posts: 3011
##### 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 »

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 »

#### unstman

• Jr. Member
• Posts: 11
##### 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

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 ??

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.

#### Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
##### 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.

Learn, create, test and tell
evolution rules in all things
God says so!

#### Solvay_1927

• Sr. Member
• Posts: 383
##### 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!")

#### syhprum

• Neilep Level Member
• Posts: 3823
• Thanked: 19 times
##### 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 2.7°K CBR that fills space

syhprum

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 »

#### unstman

• Jr. Member
• Posts: 11
##### 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

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### 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 ??

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.

#### Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
##### 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.

Learn, create, test and tell
evolution rules in all things
God says so!

#### Solvay_1927

• Sr. Member
• Posts: 383
##### 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!")

#### The Naked Scientists Forum

##### Re: Speed of Light ?
« Reply #24 on: 24/08/2006 01:48:23 »