Everyone loves Ted Ed. And everyone loves time travel. So what happens when you put them together?
Now, aside from the wonderful wonderful fact that the TARDIS makes a few appearances (making a certain Whovian very happy) as well as the DeLorean, what's actually going on? How does it relate to "time travel"?
Well, the velociraptor is here to explain this to you. The only constant in the entire universe that is consistently constant (yes that's a sentence) is the speed of light in a vacuum (about 3e8 m/s). Therefore, if someone is moving whilst holding a flashlight, the velocities don't add up or subtract like they usually would. Instead, it is time that is warped. The greater the velocity of the mass, the more time is dilated for it. Essentially, if it was possible to have enough energy to accelerate an object to close to the speed of light (let's say 99.99%), relative to the inertial frame of say, the earth, the object could pass what was 10 years to itself and travel thousands of years into the future of the earth.
Einstein explains this better than me. But there's some Theory of Special Relativity for ya