Flat spacetime

Empty space

The blue net on the screen is a picture of space, which we normally cannot see. Einstein thought of space and time as one single thing, called spacetime. With nothing around, the net is flat. The clock here is the reference for every other clock in this story.

Why?Space is invisible, so we draw it as a net or a rubber sheet. It is not a photo of the real shape. It is a rough picture that helps us think.

Learn moreThe big text at the top shows how much slower the clock we are watching runs than this empty-space clock, per year, per day or per hour. The small number below it is the clock rate: how many seconds that clock ticks while the empty-space clock ticks one second.

Clock we are watching

A clock far away in empty space

How much slower

Not slowed at all

Clock rate

1

seconds this clock ticks while a clock far away in empty space ticks one second · calculated with the formulas of relativity