Time is a strange beast. As far as we know it always appears to go forward although strange things start to occur in the presence of gravity. Indeed if you synchronized two atomic clocks together then took one of them on a trip around the world with you by the time you got back they’d be wildly out of sync, more than they ever could be through normal drift. This is part of Einstein’s theory of general relativity where time appears to speed up or slow down due to the differing effects of gravity on the two objects which results in time dilation. This effect, whilst so vanishingly small as to be inconsequential in day to day life, becomes a real problem when you want to tell super accurate time, to the point where a new atomic clock might be worthless for telling the time.
Most atomic clocks in the world use a caesium atom to tell time as they transition between two states with an exact and measurable frequency. This allows them to keep time with incredible precision, to the point of not losing even a second of time over the course of hundreds of millions of years. Such accurate time keeping is what has allowed us to develop things like GPS where accurate time keeping allows us to pinpoint locations with amazing accuracy (well, when it’s not fuzzed). However a new type of atomic clock takes accuracy to a whole new level, being able to keep time on the scale of billions of years with pinpoint precision.
The Strontium Optical Atomic Clock comes from researchers working at the University of Colorado and can hold perfect time for 5 billion years. It works by suspending strontium atoms in a framework of lasers and then giving them a slight jolt, sending the atoms oscillating at a highly predictable rate. This allows the researchers to keep time to an incredibly precise level, so precise in fact that minor perturbations in gravity fields have a profound impact on how fast it ticks. As it turns out Earth is somewhat of a gravitational minefield thanks to the tectonic plates under its surface.
You see the further away you are from the Earth’s core the weaker its gravitational pull is and thus time passes just a little bit faster the further away you get. For us humans the difference is imperceptible, fractions of a fraction second that would barely register even if you found yourself floating billions of kilometres away in almost true 0g. However for a time instrument as sensitive as the one the researchers created minor changes in the Earth’s makeup greatly influence its tick rate, making accurate time keeping an incredibly difficult job. Indeed the researchers say that these clocks are likely to only be able to truly useful once we put one in space, far beyond the heavy gravitic influences that are found here on Earth.
It’s amazing that we have the ability to create something like this which throws all our understanding and perceptions around such a common and supposedly well understood phenomenon into question. That, for me, is the true heart of science, uncovering just how much we don’t know about something and then hunting down answers wherever they may lie. Sure, often we’ll end up having more questions when we come out of the end of it but that’s just a function of the vastness of the universe we live in, one that’s filled with ceaseless wonders that we’re yet to discover.