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Why light is not matter?
Question Date: 2013-05-11
Answer 1:

Thanks for your great question! Light is a very interesting and unique thing that we all experience every day. You are right to think that light has no mass, and light also does not have a volume in the same way that "normal" objects (like a pencil, cup or person) do.

Light is a form of (electromagnetic) radiation, which is a way of saying that light does belong in a class of its own! Radiation also includes other "things" that we experience every day like radio waves, microwaves, and x-ray waves. All of these things have a couple of characteristics in common:

• Radiation (like light) has no mass, but still exists!
• Radiation carries energy (that's why sunlight warms you up when you stand in it, or microwaves cook food) In some ways it is appropriate to think of radiation as "made" of energy.
• Radiation travels at light speed in a vacuum (like outer space). Nothing can travel faster than light speed. I know that light can be kind of tricky to think about - many scientists (myself included) certainly think so! - but I hope that I have been able to answer some of your questions. Please send along any other questions you have in mind!

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