Wednesday, January 11, 2023

Dark Side of the Universe is Way More Mysterious Than the Light Side

In “Star Wars” lore, the dark side and the light side of the Force are always at odds with each other. Fans argue for hours about which team is better. 

Even though these arguments seem pointless because they are about a made-up world, there is something similar in real life.

Even in our universe, there are both light and dark parts. On the one hand, there’s the light side, which is everything that can be seen and interacts with radiation, like stars, quasars, planets, etc. On the other hand, there is a dark side that is made up of things like dark matter and dark energy that are only thought to exist.


Of course, we know a lot more about the good side. But observations of the light side give us clues about what the dark is like, and the more we learn about this mysterious realm, the more we realize that it won’t be easy to figure out what it’s like.


The fact that our observations of the Hubble constant, which is the rate at which our universe is expanding, are getting more and more different shows that there may be more to the dark side than meets the eye. Different ways we have to measure how fast something is growing don’t seem to agree.


For example, if we look directly at how fast faraway objects like supernova are moving away from us, we get a rate of about 73.2 kilometers per second per megaparsec. (A “megaparsec” is a distance unit equal to 3.26 million light-years.) But if we try to figure out the rate of expansion by looking at the most detailed map of the early universe ever made, which is the so-called “cosmic background radiation” that can be found everywhere in the universe, we get a number between 67 and 68 kilometers per second per megaparsec.


That difference might not seem like much, but on the scale of the universe, it’s huge. If scientists can’t figure out how to make these different measurements match up, it could mean that some of our most important ideas about the universe need to be thrown out the window and started over.


Is there something missing?


One of these reboots would make the dark side of the universe much bigger. Lloyd Knox, a cosmologist at the University of California, Davis, is interested in this idea. He recently talked to Scientific American about his work.


“Potentially where this is leading us is to a new ingredient in the ‘dark sector,’” he said.


Knox likes to call this mysterious new dark ingredient “dark turbo.” This is a good name for a force that speeds up the expansion of the universe in certain situations, like when the universe was a big ball of plasma right after the Big Bang. If the rate of expansion of the universe hasn’t always been the same, this new measurement could make all of our other math work.

It’s also possible that Knox’s dark turbo is just another type of dark energy. Scientists use the term “dark energy” to describe how the universe is expanding faster and faster. This would mean that dark energy is much more complicated than we thought before, but that wouldn’t be a surprise. Knox says that the light side of the universe has many different types of particles and forces and then asks, “Why couldn’t the dark side also have complex parts?”


It’s likely complicated, of course. After all, this is where everything is. Scientists tend to ask more questions than they do to give answers. That’s just how the game works.




“It’s much more interesting if it turns out to be fundamental new physics — but it’s not up to us wanting it to be one way or another,” exclaimed Wendy Freedman of the University of Chicago, who has been laboring away on the Hubble constant problem for more than three decades. “The universe doesn’t care what we think!”

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