Q: If accelerating charges radiate, and everything is full of charges, then why don’t I radiate every time I move?

The original question was: From what I understand, an accelerating charged object will emit radiation (such as an accelerating electron). However, considering that our bodies consist almost entirely of charged particles, why is it not that we are constantly emitting electromagnetic radiation. Every time I move, say while typing this email, every electron in my arm is being accelerated. So, why am I not emitting a constant stream of radiation while doing so?

Physicist: There are a couple reasons; firstly, your charges are in balance, and secondly, a human can only move so fast.

Very nearly every electron in your body is right next to a positively charged nucleus. Every movement of a negative charge that would create a wave in one direction is coupled to an opposite wave created by a nearby positive charge.

Moving a charge makes a wave. Moving an opposite charge makes exactly the same wave, just oppositely. If the charges are right next to each other, these two waves cancel each other almost completely.

Since the charges are merely very close to each other, and not in exactly the same place, there are some very slight “near field” effects.  But that’s not radiation (radiation is sometimes called the “far field“).  Also, even if you built up a huge static charge (so that not every charge was balanced) the acceleration it would take to radiate a noticeable amount of energy would not be survivable.  The electrons in a radio tower regularly experience accelerations in excess of tens of million G’s.

This entry was posted in -- By the Physicist, Physics. Bookmark the permalink.

8 Responses to Q: If accelerating charges radiate, and everything is full of charges, then why don’t I radiate every time I move?

  1. David says:

    Isn’t the short answer really, YOU DO!!!! After all, according DeBroglie’s formula, all matter is oscillating at some frequency, but for large objects this happens so fast that we cannot perceive these vibrations. So depending upon the type and character of the radiation to which the question refers, we definitely radiate E-M waves at some frequency that is imperceptible. There is also the problem of wave cancellation that occurs and the fact that billions of random momenta always equate collectively to zero.

  2. The Physicist Physicist says:

    I read the question as “do I radiate as a direct result of my conscious movement?”. That answer is “no” or more precisely “really, barely at all”.
    We do however radiate EM radiate all the time, simply because of our body heat. But that’s due to the thermal movement of our atoms (and charges).
    If particles could radiate merely by virtue of their wave nature they would radiate forever (they’re always going to be waves). But that’s no good (conservation of energy).

  3. Neal says:

    Same reason you can’t “make light” by shaking a magnet really fast, yeah?

  4. The Physicist The Physicist says:

    Pretty much! You just can’t move that fast.
    Also, (to complete the comparison) the magnet wouldn’t be magnetized.

  5. Miki says:

    Of course you radiate. But in non visible spectrum. Mostly it is infrared radiation (aka “heat”)

  6. bescientist says:

    There is a site which is also related to science and math. Don’t forget to check (http://www.bescientist.info)

  7. Jake says:

    I need simple explanation on how accelerated charges radiate energy

  8. Sheldon says:

    …This made me wonder; what if you ionized the person moving?

Leave a Reply

Your email address will not be published. Required fields are marked *