0:00 The Dark Energy Spectroscopic Instrument just found a 3.1 sigma statistical preference for dark energy not being constant, but evolving over time.0:10 Now, on our last episode, Admin, we debated infinite universes you can't see.0:15 This week, we're talking about the ninety-five percent of OUR own universe we can't see.0:21 So my question is...0:22 are we discovering new physics, or just finding new cracks in the old model?0:28 That’s a great way to frame it.0:30 But I think that DESI result is a perfect example of how science is SUPPOSED to work.0:36 We observe an effect—the universe’s accelerating expansion, which started about five billion years ago—and we work to understand its cause.0:45 We call that cause dark energy.0:47 Seeing it evolve?0:49 That's not a crack, that's a clue.0:51 I hear you, but calling it "dark energy" or "dark matter" feels like putting a label on a mystery box.0:58 It doesn't tell us what's inside.1:00 You know, we've been doing this since Fritz Zwicky in 1933.1:04 We see something we can't explain, and we invent an invisible substance to fill the gap.1:10 It's not inventing something!1:12 It's inferring its existence from overwhelming evidence.1:16 Vera Rubin's work in the 1970s showed that galaxies are spinning so fast they should fly apart.1:23 They don't.1:24 Why?1:24 There has to be some extra mass, some "invisible glue" providing the gravity to hold them together.1:31 That’s dark matter.1:32 Okay, but that assumes our understanding of gravity—general relativity—is the final word on the subject.1:39 What if the law of gravity itself changes on cosmic scales?1:43 Instead of inventing invisible glue, maybe we just need a better theory of adhesion.1:49 That's the whole idea behind Modified Newtonian Dynamics, or MOND.1:54 Um, MOND is a classic example of a theory that explains one thing well and fails at everything else.2:01 It works okay for some galaxy rotation curves, I'll grant you that.2:05 But it completely falls apart when you look at galaxy clusters, or the large-scale structure of the universe, or the cosmic microwave background.2:15 The standard model, ΛCDM, with dark matter and dark energy...2:19 it's the ONLY model that consistently explains all of it.2:23 It explains it by positing that ninety-five percent of reality is made of stuff we can't see, touch, or detect in any direct way!2:32 That's not an explanation, that's a fudge factor.2:36 A massive one.2:37 We can't detect it directly, yet.2:39 But we see its effects everywhere!2:41 Gravitational lensing, where the gravity of invisible matter bends the light from distant galaxies—we see that.2:49 The entire web-like structure of the cosmos—simulations only reproduce that if you include dark matter.2:56 It's not a fudge factor, it's the foundation.2:59 Okay, but let's talk about the biggest problem, the one that I think sinks the whole ship.3:05 The cosmological constant problem.3:08 Quantum theory predicts a certain amount of energy in empty space—vacuum energy.3:13 And its prediction is wrong by a factor of 10 to the power of 120.3:18 That is the single most incorrect prediction in the entire history of physics.3:23 Alright, I'll give you that one.3:25 The cosmological constant problem is a monumental gap in our understanding.3:31 No one denies that.3:32 It is a genuine crisis at the intersection of quantum mechanics and general relativity.3:38 Exactly!3:38 So how can you be so confident in dark energy when the theory underpinning it has a hole that big?3:45 Because that's a problem with the theory, not the observation.3:50 The observation—confirmed again by new analyses just this June—is that the universe's expansion is accelerating.3:57 That is a hard fact.3:59 Dark energy is simply the name for whatever is causing that fact.4:03 The theoretical mess doesn't make the observation go away.4:07 So we're left with a phenomenon that our best theory can't predict, explained by a substance that makes up sixty-eight percent of the universe, but whose nature is a complete mystery.4:20 It just feels like we're papering over the cracks.4:23 Or...4:24 or we're standing at the edge of a profound discovery.4:27 Look, everything we've ever known, every star we've seen, every person who has ever lived...4:34 all of that is in the five percent of the universe that's normal, baryonic matter.4:39 Maybe the problem isn't the theory, but our own bias that the universe should be simple and intuitive for us.4:47 I'm not asking for simple, just consistent.4:50 A theory that doesn't require me to believe the universe is run by invisible magic.4:56 It's not magic, it's just physics we haven't finished discovering.5:00 That's the whole point.5:02 So, what do you think is more likely?5:04 I think the real question is this: what's the bigger leap of faith?5:09 Believing in an invisible universe that makes our current equations work, or believing those equations themselves are due for a revolution?
