Atomic clocks are the most accurate timekeeping instruments we have. A new study proposes a way to use the instruments’ mind-blowing level of precision to detect the tiniest of energy fluctuations, potentially giving scientists a way to observe some types of dark matter.
Dark matter continues to prove elusive: though we haven’t observed it directly, we can see its effects on the Universe. Frustratingly, there is nothing in our current models of physics to explain what we see.
Here, researchers from the University of Sussex and the National Physical Laboratory in the UK have suggested using atomic clocks to detect certain low-mass particles theorized to potentially make up this mysterious material.
The thinking is that these particles interact with regular matter particles, but very weakly. Atomic clocks rely on almost imperceptible oscillations of atoms as they move between energy states to tell time, so any slight knock to these oscillations – from an ultra-light dark matter particle, for example – could be spotted.
First, the researchers proposed some theoretical models for how variations in atomic clock timings could be measured. After that, they then took readings from existing atomic clocks to help prove the viability of the approach.
The next step would be to set up an experiment where two atomic clocks could be compared: one that was slightly more susceptible to variations in what are known as fundamental constants, or the constant values that the laws of the Universe are based on.
In this particular study, two fundamental constants were looked at: the fine-structure constant, which describes how strongly electrons are attracted to protons in an atom, and the electron-to-proton mass ratio, which indicates the ‘heaviness’ of atoms.
Both constants could be disrupted by interactions with certain ultralight particles theorized to be responsible for dark matter’s effects, such as the hypothetical axion. This study sets limits on the magnitude of variations that would perhaps indicate the particles’ presence.
Clearly there’s a lot of theory here, and we’re dealing with a lot of assumptions and predictions – albeit very smart ones. Ultimately though, minute changes in the ticking of an atomic clock could have profound implications for physics.
Atomic clocks are hugely useful to scientists beyond being able to keep time with unparalleled accuracy across billions of years. They’ve been used to measure gravitational redshift for example, the way that gravity can interfere with time.
They’re also important in quantum physics too, and have opened up areas of research to ways that quantum information could be transmitted or stored. Now it seems they could be dark matter detectors too.
These findings don’t rely on any pre-existing theories, the researchers say, and the models produced have a lot of flexibility – potentially enough to apply beyond the realm of dark matter and into other unexplained phenomena.
The research has been published in the New Journal of Physics.