How does light travel Through a vacuum

[DennisN]

How does this all, get a photon from point A to point B in a vacuum if there is no "ether" with which a photon can travel within?

My reply may not be satisfactory, but it is intended to make you ask yourself why you think an ether is needed at all (I've heard this em/etherargument many times before).

If you throw a ball out into empty space, the ball will travel forever in uniform motion (unless it's disturbed) - this is Newton's First Law.

My point is: We don't demand an ether for a ball to travel from point A to point B. So why should we demand it for a photon? (this is not a perfect argument - it is intended to make you think about your question).

In modern physics, there is no ether; there is no universal (or preferred) frame of reference. There are fields, e.g. the electromagnetic field, extending throughout space.

 

[davenn]

[Quote by mikeph]

[Quote by Darrenmackenz]

Is there already an electromagnetic field present before light is even introduced?[/quote]

Yes. [/quote]

This response will be misleading if not properly understood. Any radio transmitted which is electrically neutral can emit an EM wave. It’s quite possible for an electrically neutral atom that is in an excited state to transition to a state of lower energy by emitting of a photon. You can also have a charged particle located inside a charged sphere where the total charge is zero. Set the charge inside oscillating and it will emit an EM wave. Look at your uncharged hand. If you see it then it’s emitting light and there is no electric field present. There are any number of examples of this. What mike is thinking of is the fact that at subatomic level there are fields which don’t cancel – I just wanted to be crystal clear on this point.

thanks for that popper, I would need mikeph to give some good back up to his response
cuz I would have responded like you did. ... for a transmitter be it RF or say light ... how can there be a pre-existing EM field when the unit hasnt even been turned on ?

There cannot be any pre-existing EM field

Dave

 

[lss1]

I don't know much about this, but here's what I do know:

Light is created by one of two things (possibly more, but I don't know of them): a changing magnetic field or a changing electric field. Basically, if you move a magnet, you will produce a changing electric field, which will produce a changing magnetic field, which will produce a changing electric field, and so on until something absorbs the energy. You can do the same thing if you turn a current in a wire on and off again and again.
You can prove this in a thought experiment. Have a bunch of neutral particles, each composed of one positive and one negative charge, in a plane. Then, introduce an electric field. The definition of an electric field is the direction a positively charged particle (or constituency) will take in the presence of said field. Therefore, if you introduce an electric field into this plane, all of the positive charges in the particles will line up facing the same way in each particle as will the negative charges (in the opposite way, of course). Once they all line up, the positive charges will be facing the negative charges, which means they will attract. This then creates a magnetic field. I'm not sure how a changing magnetic field creates a changing electric field, but trust that it does, by a relation of reciprocity.
Here is where my knowledge fails me. I looked through my notes, and they say that the medium for electromagnetic waves is the changing magnetic field. However, when I tried to look it up on the Internet, it says that electromagnetic waves do NOT need a medium to propagate. This is very disturbing to me, so I encourage you to look it up and share the results. I will stick with my magnetic field idea but will stand corrected if need be.

I hope I have been of some help to you, or to anybody else.