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Q & A: electromagnetism everywhere

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Most recent answer: 04/16/2017
Q:
My question is based on two assumptions: 1. Light oscillates electromagnetism 2. Light can travel in any region of space (supposing their are no objects in space) If light is basically electromagnetic waves, and it can travel trough any region of empty space, then that means that electromagnetism must be in every region of empty space. Electromagnetism can't just "be there". There must be some source (I know that we are supposing that no objects are in space, but disregard that for this particular point) that is sustaining it. How can electromagnetism be everywhere?
- Luke Langlois (age 15)
Walker, Loisiana, U.S.A.
A:

It's not clear why you think electromagnetism can't be everywhere in space. Electromagnetic waves are one of the basic ingredients of the universe. Sure the waves that are around now have sources, in that there was some last interaction with other matter. The universe is filled with electromagnetic radiation that last interacted strongly with matter some 13.8 billion years ago. The main thing that has happened to that radiation since then is that it has gotten to be more dilute and lower frequency as the space it's in has stretched out.

Mike W.


(published on 04/13/2017)

Follow-Up #1: history of light

Q:
Thank you for that answer, I appreciate it. However, if what you say is true, a couple of things must also be true. I have several questions. Firstly, if there is electromagnetic radiating, that was produced 'long ago', then that means, 1. Light can't travel in some regions of space (not all regions can be affected by radiation) 2. Radiation is slowly (or quickly) deteriorating, which means at some point in time light will not be able to flow. However you said that, "Electromagnetic waves are on of the basic ingredients of the universe". How can electromagnetic waves be one of the ingredients of the universe if it is a side-effect of the universe? (Universe, then source interact with electromagnetism- radiation). Basically, electromagnetism is not uniform throughout the universe?
- Luke Langlois (age 15)
Walker, Louisiana, U.S.A.
A:

I don't understand the reasoning that leads to your points (1) and (2).

This question I understand: "How can electromagnetic waves be one of the ingredients of the universe if it is a side-effect of the universe?" It raises an important philosophical issue.

The distinction between ingredients and side effects is pretty much arbitrary. Two photons can collide and turn into an electron and a positron. In the early seconds, that happened a lot. Then an electron and a positron can collide and make two photons. That also happened a lot. Which (photons or electron/positrons) is the basic stuff and which is the side effect? Does nature have any idea what those words mean?

The distinction between ingredients and other things is a bit more meaningful. For example, we say that sound waves (phonons) are not a basic ingredient because we understand them as one of the ways things like air or steel can behave. You can't have phonons with some sort of medium like that. Photons are a basic ingredient because they can exist in a vacuum without any underlying medium, as least so far as we currently understand the world. Maybe someday what we now call a vacuum will be thought of in terms of some deeper structure, in which case we'd have to revisit this question.

Mike W.


(published on 04/16/2017)

Follow-up on this answer.