A century ago our understanding of space and time changed forever.

In our everyday experience we would likely agree with Galileo and Newton that space and time are absolute. Clocks seem to run at the same speed wherever they are and regardless of how fast they are moving, and a meter stick always seem to be a meter long whether it is at rest or in motion (along its length.)

Careful measurements show that time and space are not absolute, moving clocks run slow and moving meter sticks shorten. However, the speed of light* is always the same no matter how the source or detector of the light move.

In 1905 Einstein formulated the special theory of relativity in which absolute space and time are combined into spacetime. In spacetime the speed of light* is absolute and constant while time and space are not.

The physics of high speed motion seems strange to us because at even the fastest speeds tthat humans have ever travelled the effects are very small.

We live our lives at slow speeds, compared to the speed of light so these differences in clocks and meter sticks are not obvious.


Join us as we explore space-time in an Exploratorium way.

We'll look at experiments, do thought experiments, play with spacetime and even get a chance to "do the math" to get a feel for what's going on.

But first let's go to a party!

(Story of a party on a planet around Epsilon Eridani 10 light years away.

The party will be in 20 years use our online relativistic trip planner to plan your trip.)

Relativitistic Road Rally

The two fundamental ideas of relativity.

You can't tell if you are moving at a constant speed by doing any experiment in a closed room.

The speed of light is always the same.

On the trip planner page there are links to the following:

On every page there could be links to other topics as on the spaceweather explorer:











electric meter, gas pump

Move this to the trip planner page.

Explore Time, moving clocks run slow.

Explore Space moving objects are shorter in their direction of motion

Explore Mass objects increase in mass when their speed increases

Energy can be converted to Mass, E = mc^2

Explore Speed no massive object can ever reach the speed of light,

the cost of speed, fuel calculation

Exploring Spacetime what remains the same, invariants

prove it

play with it

do the math

mind games

Table of data



* the speed of light in a vacuum

Scientific Explorations with Paul Doherty

© 2005

8 May 2005