Brian Greene gives a bite-sized daily equation – a simple formula that makes you think twice. | World Science Festival

If you race toward a beam of light, why doesn't the light approach you faster than the speed of light? If you race away from it, why doesn't the light approach you slower than the speed of light? In today's Daily Equation, Brian Greene describes the relativistic velocity combination law to provide an answer. | World Science Festival

Brian Greene talks time travel. Not the kind of time travel you encounter in sci-fi, but real time travel – the kind that's written into the laws of physics and understood using the time dilation equation. Watch to learn more about how and why our perceptions of space and time are not fixed, but relative. | World Science Festival