I finally understood why photons have energy but no mass! (My mind is blown)

Video Description

To try everything Brilliant has to offer—free—for a full 30 days, visit https://brilliant.org/FloatHeadPhysics/. The first 200 of you will get 20% off Brilliant’s annual premium subscription. Chapters: 00:00 Why photons have no mass (vague "explanations") 01:19 What is mass, exactly? 04:33 Understanding E = mc2 05:50 Does kinetic energy add more mass? 07:35 Total energy 09:15 Finding mass of light 10:05 Sponsor shoutout 1107 Photons have no rest frame (hence no mass) 12:32 Relativistic mass? 14:05 Why we don't use relativistic mass anymore 17:48 Speed of causality and massive photons? 20:45 Summarising in 2 lines Photons have energy. According to Einstein's E = mc^2, they should have mass too. But, photon's are massless. Why? Why E = mc^2 doesn't apply to photons? Why massless particles always travel at the speed of 'c'? This videos hopes to connect all the pieces together to provide a much more profound understanding of this topic. By the end of the video, you should have clear idea why we say light (or photons) are massless and why any massless particles should always travel at c. We will also see that c is actually the speed of causality. This video was sponsored by Brilliant ================================================ Follow me at Linkedin: https://www.linkedin.com/in/maheshshenoyteaches/ ================================================ Support me and learn more physics at the same time by enrolling in my Udemy course https://www.udemy.com/course/become1dkinematicsmaster/ https://www.udemy.com/course/becomeakinematics2dmaster/ ================================================