Space and Time
We exist in space and time. These concepts are so familiar that we
don't realize that the nature of space and time lies at the the heart
of some of the deepest mysteries of physics.
Take a concept like position. You learn in kindergarten how to measure
position with a ruler. Later on, you learn to say where something is
in space by giving coordinates--- numbers like street addresses. You
say where something is in time by giving, well, the time. What could
be mysterious about that?
The Very Small
Physicists have found that when you study very small things, they
behave in highly unexpected ways, not at all like everyday
objects. For one thing, everything is made of particles, tiny,
discrete packets of energy that can't be divided up. For another
thing, you can't actually pin down exactly where the particles are in
space, or how exactly how they move. In fact, they act in many ways
like waves--- a kind of sloshing around of energy that doesn't happen
at just one place, but is spread around in space, and even in time.
This dual, particle/wave character applies to all forms of ``stuff'',
like atoms and light--- everything whatever.
What we haven't found out is whether it also applies to space and
time. Could it be that space and time are also made of waves and
particles? Could there be ``particles of time''? What does that even
You can see that things get mysterious pretty fast.
The Fermilab Holometer is machine designed to study the properties of
space and time at the very smallest scales. We shine light in
different directions, through tubes 40 meters long, to measure whether
space and time stand still, or whether they slosh around a tiny
bit. The experiment is designed not to be affected by normal sloshing
of particles. It can detect a sloshing of spacetime by a tiny
amount--- a billionth of a billionth of a meter, almost a billion times
smaller than an atom, in about a millionth of a second. That
corresponds to an extremely slow motion, about ten times slower than
If we find the motion we are looking for--- sometimes called
``holographic noise'', because it resembles the blurring in a
hologram--- it will help us understand the nature of reality at the
Last modified: 03/26/2012