Two people moving at the same velocity will each agree their measures of distance and time match. As one person changes speed, however, they will see the other's measure of time and distance change, even as their own stays the same.

Without any reason to prioritize one perspective of time o...

similarly, the space-contorting volume beyond the horizon of a black hole also distorts perspectives of time.

in our universe, we have freedom of space and can move around as we like, but we're forced to march along time's arrow in a linear direction.

Calculations show that crossing o...

Models of space-time can describe measurements of time and space varying from one point to the next, but they don't explain much about time's stubborn adherence to a sequence of events.

Under these descriptions of time, our Universe is a single block of space-time. There's sort of a beginni...

Time is a measure of non-stop, consistent change in our surroundings, usually from a specific viewpoint.

While the concept of time is self-evident and intuitive – the steady passing of events before our eyes; the orbit of the Moon around our planet – describing its fundamental nature is muc...