Where Does Light Actually Get Its Speed From (Its Impossible!)

Where Does Light Actually Get Its Speed From (Its Impossible!) Light always travels at about 300,000 kilometres per second, never faster and never slower in empty space. It doesn’t speed up, it doesn’t need to accelerate, and nothing pushes it. So where does light actually get its speed from? In this video, we dig into one of the deepest questions in physics and discover that the answer has less to do with light itself and more to do with the nature of space and time. We start with James Clerk Maxwell, who discovered in the 1860s that the speed of light falls straight out of the equations for electricity and magnetism, using nothing but two basic properties of empty space. Then we follow the search for the mysterious “ether” light was thought to travel through, the Michelson–Morley experiment that failed to find it, and Einstein’s realisation that the speed of light is the same for everyone. We explain why anything without mass, like a photon, must always move at this exact speed, why it’s really the speed limit of cause and effect in the universe, and why light seems to slow down in glass and water without actually changing its true speed. Finally, we look at the question physicists still can’t answer: why this speed has the value it does. In this video: Light never accelerates Maxwell’s discovery The hunt for the ether Einstein and the constant speed of light Why massless particles must move at light speed The speed of cause and effect Why light “slows down” in glass Why this exact speed? If this blew your mind, like the video, subscribe for more physics explained simply, and tell us in the comments which physics question we should tackle next.