“Cantankerous” isn’t usually a word frequently used to describe cosmologists, but in the case of Fritz Zwicky, pictured below, it has been used more than once.
Zwicky was a visionary and a brilliant nonconformist. His eccentricities were legendary, but his ideas about the nature of our universe shaped modern astronomy.
Zwicky spoke abut “the useless trash in the bulging astronomical journals,” and said, “Astronomers are spherical bastards. No matter how you look at them they are just bastards.” Is it any wonder few people have heard of him?
While these frank assessments certainly didn't win him many friends in the scientific community, I have to admit that they add a certain panache to his legacy. And: what a legacy it is.
Today, I’ve brought in
, who writes Arkinfo Notes, to talk about Zwicky’s enduring legacy. Mir writes very accessible descriptions of physics and other complex things, translating them into easy to understand pieces. Here’s Mir:When you observe the galaxies closely, you begin to notice that their behavior is rather odd. Fritz Zwicky, in the 1930s, was one of the first to hint at something amiss.
What Zwicky noticed in 1933 was that a cluster of galaxies called the Coma Cluster was moving too fast. It turns out that the observed mass simply couldn't account for the speed at which the cluster was revolving.
Using the mathematics of the time, the only explanation was that there was more mass—mass that was invisible to telescopes and thus, unaccounted for. With a boldness characteristic of him, Zwicky posited the existence of a mysterious and unseen form of matter called "dark matter."
Dark Clouds
Here’s Mir again:
Although unseen, Dark matter plays an indispensable role in explaining the workings of the cosmos. It's theorised as the gravitational glue holding galaxies together. Without it, our 200 billion-galaxy universe wouldn't look the way it does. It also provides explanations for minute temperature fluctuations in the Cosmic Microwave Background (CMB) and the phenomenon of gravitational lensing, where space bends under the influence of mass.
It also makes up around six times as much of the universe as does “normal” matter, the stuff we can see. Up until Zwicky’s groundbreaking insights, the general consensus was that stars composed the bulk of the universe's mass.
Zwicky’s viewpoint was further refined in the 1970s by Vera Rubin, another trailblazing astronomer, who provided additional compelling evidence for the existence of dark matter.
But what was this stuff?
WIMPs, MACHOs, and Weird Stuff
Mir kicks us off again:
The heart of the dark matter discourse beats around its nature. Is it made up of WIMPs (Weakly Interacting Massive Particles) or MACHOs (Massive Astrophysical Compact Halo Objects)? WIMPs are elusive, rarely interacting with other matter, making their detection a profound challenge. MACHOs, considered to be ordinary entities like brown dwarfs, lurk in the halos of galaxies.
Think about this: there are either ultra-tiny particles that we can't see, which collectively make up six or seven times more mass than the stuff we can see out there (WIMPs), or… well, it gets weirder and wilder from here.
Those WIMPs are so hard to detect that they haven’t been detected yet.
That, or they don’t exist. Scientists have gone to extraordinary lengths just to catch a glimpse of them, setting up deep underground labs where radiation from space can’t interfere, hopefully increasing their chances of detecting a WIMP if it interacts with ordinary matter. It's starting to seem like searching for a needle in a cosmic haystack.
Meanwhile, team MACHO isn’t quite dead yet. Could there be really big objects we just can’t see out there? Are there planet-sized things and dying stars (brown dwarfs) that are just somewhere we can’t see them?
Finally, there’s the idea that we might have our idea about gravity all wrong. All of the evidence for this “missing mass” comes from gravity, after all.
At its inception, MOND challenged our comprehension of gravity, suggesting that our foundational understanding might be incomplete.
MOND (Modified Newtonian Dynamics) questioned the necessity of dark matter by offering adjustments to Newton's laws, especially at very low accelerations. While most of the scientific community has swung back to the dark matter explanation, thanks to compelling evidence from the Cosmic Microwave Background Radiation (CMBR), MOND serves as a sobering reminder of the ever-evolving nature of science.
The story of dark matter is reminiscent of the 19th-century discovery of Neptune, an unseen planet whose existence was deduced from its gravitational effects. Today, dark matter is our 'Neptune', its presence felt but not seen. The hunt to decode its mysteries is akin to a cosmic detective story, uniting history, science, and profound curiosity.
From Zwicky's initial bold claims to today's labyrinthine web of theories, the quest for understanding dark matter remains one of science's greatest open-ended questions. Whether made up of WIMPs, MACHOs, or some form of matter or force yet to be discovered, this cosmic detective story is far from reaching its final chapter. And as long as the mysteries persist, so will our insatiable curiosity to solve them.
Today, I wanted to give you a “toe in the water” on a complex subject, so maybe you’ll become more curious about dark matter and want to learn more, or maybe you’ll get some value out of a quick overview. I wanted to include Mir today since he does a good job of breaking down complex topics like this, and I’ve wanted to write about dark matter for a while now.
Don’t forget to check out Arkfino Notes if you’re interested in checking out some simple descriptions of complex things.
Thank you for indulging me today! Let me know if you learned about any of this for the first time today, or if you’ve been thinking about the make-up of the cosmos for a long time like me. Either way, I’m glad to have you as a part of this conversation.
Can we take a moment to appreciate how awesome of a name Fritz Zwicky is? It kind of says it all. Also I personally believe that most of what we think we know about just about everything is, at the very least, incomplete. I think it’s arrogant to think we have something fully figured out. That doesn’t mean the accrued knowledge is meaningless, but we should always leave room for exceptions and variations.
And again, Fritz Zwicky is fun to say. Maybe I should write another AI song about him. “Fritz the Zwick. He’s Zwicky-quicky-quick. He’ll burst your bubble and make brains tick.” I dunno. I may need some help from one of the apps.
My favorite line: “It's starting to seem like searching for a needle in a cosmic haystack.”