It sounds like a joke but I just want to know if shadows have mass, since shadows are formed when there is blocking of light. It forms a black pattern with no energy therefore it has no mass.

  • 4
    $\begingroup$ Only Peter Pan's shadow. $\endgroup$
    – docscience
    May 23 '15 at 14:37
  • $\begingroup$ Here's a Vsauce episode, where Michael asks a similar question: youtube.com/watch?v=Do1lm9IevYE $\endgroup$
    – SU3
    May 23 '15 at 21:00

A shadow is a lack of light. Therefore, a shadow has no mass, for a shadow is not an object or energy. Shadows can go faster than light in certain cases because they are not objects. In the same way, a vacuum has no mass.

  • $\begingroup$ Can you explain in what cases shadows can go faster than light? $\endgroup$
    – Prahar
    May 23 '15 at 21:41
  • $\begingroup$ @Prahar physics.stackexchange.com/q/63434 and youtube.com/watch?v=JTvcpdfGUtQ $\endgroup$
    – Jimmy360
    May 23 '15 at 22:33
  • $\begingroup$ @prahar I have read this stuff as if it is a violation of GR(although Jimmy has given a good justification on the stuff), in Michio Kaku's book - physicis of impossible $\endgroup$
    – David
    Nov 20 '20 at 13:19

Shadow is not a matter; so it does not have mass. The simple characteristics of matter are: They have mass and take up space.


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