Is the Universe a fractal?
💥 Almost, but not quite. Here’s why.
with Ethan Siegel • January 4, 2025
Greetings readers,
Welcome to 2025 and happy new year! There's so much that lies ahead and so much to learn and share — including some things that are brand new as well as others that were old but are now new again — that I'm excited to get this new year started off right: with science stories to delight and inform you the way nothing else will.
Have you ever wondered about the Universe's structure, and whether it's fractal-like or not? It turns out that appearances can be deceiving. What appears to be "repeating patterns" of structure breaks down very thoroughly, indicating that our Universe isn't a fractal at all. On the other hand, some have recently argued (to great success in popular media) that dark energy may not exist and that it may solely be an artifact of the fact that the Universe isn't perfectly uniform. But it turns out that isn't quite right either. I should know: I was one of the people who did the pioneering work that first showed this 20 years ago!
We've also got a fantastic one-page calendar as an alternative to a traditional "12-month" calendar, a truly weird and unexpected JWST trick that does indeed reveal dark matter, and the shocking quantum reason behind why the Sun shines — all for you on this new, 2025-edition of Starts With A Bang!
All the best,
Ethan
COSMIC SCALES
Is the Universe actually a fractal?
On larger and larger scales, many of the same structures we see at small ones repeat themselves. Is it possible that we live in a fractal Universe and that this continues all the way up and all the way down?
ORGANIZING TIME
The one-page calendar that changes how you view the year
Rather than having to change your calendar every month, this one-page calendar works for the entire year to give you all the information you need, practically immediately. Even better: if you understand how it works, you’ll never need to buy another calendar again, as simply switching a few “boxes” around can renew it for every year to come.
ASK ETHAN
Ask Ethan: Can a lumpy Universe explain dark energy?
The most compelling evidence shows that dark energy may be what is causing this expansion and acceleration of our Universe. However, one recent study has claimed a “lumpy” Universe is actually the cause, and dark energy doesn’t exist. Does this wild claim ring true? Let’s explore.
If you have a burning question about the Universe, send me an email.
QUANTUM PHENOMENA
The quantum reason that explains why the Sun shines
Despite the Sun’s high core temperatures, atomic nuclei repel each other too strongly to fuse together. That’s where the rules of quantum mechanics come in, allowing these particles to quantum tunnel into a more stable state and enabling the fusion reactions that power our Sun.
JAMES WEBB SPACE TELESCOPE
This weird JWST trick lets us “see” dark matter
It’s not only the gravity from galaxies in a cluster that reveals dark matter, but the ejected, intracluster stars as well. When stars are ejected or form in the space between galaxies within a cluster, they go where the dark matter is, and measuring that intracluster light shows us dark matter as never before.
Ethan Siegel, Ph.D., is an award-winning theoretical astrophysicist who's been writing Starts With a Bang since 2008. You can follow him on Twitter @StartsWithABang.