Spacetime: Geometry of Universe | 15 Jan 2024

Spacetime is a mathematical model that combines the three dimensions of space and the dimension of time into a single entity.

The universe at the largest scale looked different from the scale of human experience due to the universe’s geometry.
- At the human scale, spacetime appears to be flat: a beam of light from a laser will travel in a straight line.
- But at the largest scale, our spacetime may actually occupy a spherical space.
- If you shine a powerful laser in front of you and wait for an incredibly long time, light from the laser could technically circle back to you.
Albert Einstein’s special theory of relativity posited that if there are two observers A and B, each with a clock, such that A is moving (but not accelerating) faster than B, A’s clock will measure less time as having passed than B’s clock.