“We are entering the second half of the 2020s, and it is an incredibly exciting time for dark matter research…”
SACKMESTERKE/SCIENTIFIC PHOTO LIBRARY
It's a surreal time to be a dark matter researcher. Even as governments around the world cut back on research funding, dark matter remains one of the biggest and most interesting open problems in all of physics—all of science, to be honest. Most of the matter in the Universe appears to be invisible: for every kilogram of visible matter, there are apparently 5 kilograms of dark matter. We know this only because we have seen the influence of dark matter on the structure of the visible elements of the Universe.
Galaxy clusters are best explained when the suspected component is dark matter. Observations of the distribution of the earliest free-flying light in the Universe only match our theoretical predictions if dark matter is part of the model. Many other observations confirm the same thing: there is a lot of dark matter that is invisible to us unless we look at how it forms visible matter.
We are entering the second half of the 2020s and it is an incredibly exciting time for dark matter research. The work of the European Space Agency's Euclid Space Telescope will lead to a better understanding of the structure of galaxies. In tandem Vera S. Rubin The observatory is just beginning a 10-year study of the sky that will almost certainly change our knowledge of the satellite galaxies that orbit larger satellites. These dynamics will help us determine in more detail how dark matter controls visible matter.
To study something that we know exists but cannot see directly is to push the boundaries of our creativity as scientists. Among the questions we must ask and try to answer creatively are: How do we look for it? Can we catch a dark matter particle in the laboratory? How can we study its properties if we cannot?
The only way out is to pass. We must start with what we know and try to expand our knowledge from there. We are fairly confident that dark matter is matter-like, assuming we can use the same mathematical tools to study it that we use to study ordinary particles, such as quantum field theory (QFT).
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We are now increasingly looking for evidence that dark matter is scattered by electrons rather than simply hitting its target.
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QFT sounds complicated – and it is – but a layman can still feel it. It is perhaps our most fundamental theory of physics because it combines special relativity and quantum mechanics (but not general relativity). The idea behind this is that throughout the entire Universe, at every point, there is the possibility of creating a particle due to the presence of a field associated with that type of particle.
Think of strawberry fields. Strawberry only appears in some places and not others. This is due to the special properties of these points in space-time – these are places where suitable conditions exist for a strawberry flower to bloom. Potential for strawberries is everywhere in the strawberry field, but only in some places will it actually appear. In much the same way, QFT tells us that particles come into being.
QFT is a complex topic that even experts spend many years mastering. And even if we think it's reasonable to apply QFT to dark matter to make some reasonable guesses about it, the question arises of how we could write equations to describe something whose properties largely elude us.
From a sociological perspective, it is quite interesting to see the many ways in which scientists have answered this question. Over the last decade or so, one popular approach to describing what we don't know has been the development of “effective field theory” (EFT). EFT is a convenient way of writing a generalized set of equations with characteristics that can be tuned based on observations.
EFTs can also be designed to suit a specific experimental design. For example, one important way to understand dark matter is through direct detection experiments. We hope that through this some kind of interaction between dark matter and visible matter will lead to an effect that can be observed in a ground-based experiment. Direct detection approaches have matured and proliferated over the years. Instead of simply looking for evidence of dark matter hitting a target, we are increasingly looking for signs of dark matter being scattered by electrons. This experimental shift means that EFT must evolve with it.
IN preprint In a paper published this month, researchers Pierce Giffin, Benjamin Lillard, Pankaj Moonbod and Tien-Tien Yu propose a feasibility study that can better explain these scattering interactions. Although the article has not yet been peer-reviewed, it caught my attention because it is an excellent example of work that may never make the front page, but is nonetheless the very thing that drives research forward. Science requires patience, and I hope our leaders remember that.
Chanda Prescod-Weinstein is an assistant professor of physics and astronomy at the University of New Hampshire. She is the author Disordered space and future book The Edge of Spacetime: Particles, Poetry, and the Boogie of Cosmic Dreams
What am I reading
I just finished the stunning debut novel by Eddie E. Sitchens. Dominion.
What am I watching
I recently watched the summer episodes Emmerdale and HOLY SMOKE!
What am I working on
My colleagues and I have some interesting new research ideas about dark matter scenarios.
Spend a weekend with some of science's brightest minds as you explore the mysteries of the universe on an exciting program that includes a tour to see the famous Lovell Telescope. Topics:
Secrets of the Universe: Cheshire, England
