Sneetches are Sneetches
This is the story about the search for dark matter, but really it’s about the scientists who study the largest things and the scientists who study the smallest things finding common ground. Crazy stuff.
Cosmologists are astronomers who study the evolution and space-time relations of the universe. Since the universe, by definition, is everything, it also is the largest thing. Particle physicists are scientists who study fundamental subatomic particles and the forces that constitute matter and radiation. This goes all the way down to quarks, which (depending on the argument) either have zero size or are too small to be measured with current technology.¹
That brings us to dark matter. First proposed by Fritz Zwicky in 1933, it gained credibility when cosmologists measured that galaxies were rotating at a speed too fast to be explained only by their gravity. Something we can’t detect directly was giving galaxies extra force to stay intact. This led to the theory that the void of space contained dark matter, something that had mass but didn’t absorb, reflect, or emit light – and therefore it was not visible to us or dark. This extra (unseen) mass gives galaxies the extra gravitational force to rotate at faster speeds. Estimates vary but cosmologists think that over 25% of the universe is comprised of dark matter. (there is also a similar theory about something called dark energy as a way to explain how the universe is moving at an accelerated rate but that’s a conversation for another day).
Now the universe is an ideal palette for cosmologists to develop theories. These theories may be discarded as and when more information becomes available. For instance, the new James Webb Space Telescope extends the visible universe (the part of the universe we can see/detect) and may someday alter the thinking around dark matter.
While the universe is ideal for theories, it’s hell on experiments. One can’t reach out and tweak a galaxy and measure the changes. Remember, the light from other galaxies took billions of light years to reach us and is showing us what that galaxy looked like billions of years ago. Looking into the night sky is like looking into the past (even the light from our sun takes over eight minutes to get here – you’re looking at the sun from eight minutes ago!).
However, if you imagine and interpolate … if dark matter exists in space, wouldn’t it also exist here on earth? And if it exists on earth, wouldn’t it also exist at the subatomic level? If not that would imply a point in space where it ceases to exist, which at the very least would be counter intuitive. (Um, is dark matter in the room with us now? YES!) Enter the particle physicists.
Here cosmologists hand the baton off to particle physicists to track down dark matter. This brings us to the Large Hadron Collider in Geneva, Switzerland. Particle physicists gather information by accelerating two subatomic particles in opposite directions around a huge ring until they reach nearly the speed of light and then smashing them into each other. They then analyze the debris. How’s that for a cool job? It was this approach that found the Higgs Boson – very possibly the connection that gives matter its mass (and therefore it’s energy – remember Einstein’s E=MC² formula tells us that mass <=> energy).
A lecture about searching for dark matter using the large hadron collider is available on YouTube (https://www.youtube.com/watch?v=yDSrnL7Dw4M). It’s well beyond me but I admire the speaker’s enthusiasm. TL;DR – still looking.
But, truthfully, it’s not solution that matters². To me it’s the story rather than how the story ends. It’s how two groups working on vastly different stuff can find common ground. Maybe the lesson is differences don’t make us different; instead, they emphasize our similarities.
¹ If you’re like me, it’s possible your understanding of subatomic particles begins and ends with protons, neutrons, and electrons. But au contraire! That is so yesterday. The current thinking is referred to as the Standard Model of Particle Physics, and involves even smaller subatomic particles.
² Unwrapping the mystery around dark matter / dark energy could help solve the two biggest riddles puzzling scientists today:
- Finding common ground between Einstein’s Theory of General Relativity (which explains much of what cosmologists have unearthed) and Max Planck’s Quantum Theory (which explains much of what particle physicists have unearthed). This is the Theory of Everything that Steven Hawking worked on. You might know the book / movie.
- What the heck is gravity anyway? The standard model would be so much more elegant if there was only one force instead of the four forces that are generally accepted now.
