I unlock my office door and there’s Vinnie in the client chair flipping a coin from hand to hand. If my building ever switches to digital locks he’d take it as a challenge. “Morning, Vinnie.”

“Morning, Sy. Been reading your multiverse series and something you said bothered me.”

“What’s that?”

“Back when you wrote up your anti-Universe idea that some other group had come up with first—”

“Don’t remind me.”

“—you mentioned how time going backwards makes for negative energy, like that’s obvious. It ain’t obvious to me.”

“Okay … Ah. What word keeps coming up in our black hole discussions?”

“Geez, frames again? Universes ain’t black holes.”

“Don’t be so sure. Suppose there’s a black hole Event Horizon that encloses our entire Observable Universe. An Event Horizon’s diameter depends on how much mass it has inside. Astronomy’s given us an estimate of how much normal matter our Observable Universe contains. I adjusted that number upward to account for the expected quantity of dark matter plus dark energy’s equivalent mass. When I plugged that grand total into Schwarzchild’s formula for the diameter of an Event Horizon, the result was about seven times wider than what we can observe. We could be inside a huge black hole but we’ll never know either way.”

“Whoa! Wouldn’t we notice a drift towards the singularity at its middle?”

“Not if we’re reasonably far out or if the drift rate is tiny compared to the slow chaos of intergalactic space. Mind you, it took us centuries to develop the technology that told us we’re inside the Milky Way and two‑thirds of the way out from the core.”

“We used frames for thinking about going really fast or being outside a black hole. Now we’re inside one or maybe not. How’s frames gonna help us with that?”

“Well, not the inertial frames where we compared relativistic observers, but the idea is similar. A traveler in an intense gravity field experiences slower time in its inertial frame than a distant partner does in theirs. Clocks appear to run weirdly if they’re compared between separate frames whose relative velocities are near lightspeed.”

“Yeah, that’s what we said.”

“Now picture two observational frames, one here in our Universe and one in the anti‑Universe if there is one. Time in the two frames flows in opposite directions away from the Big Bang between them. The two‑frames notion is a convenient way to think about consequences. Negative energy is one.”

“Now we’re getting somewhere. So give.”

“Well, what does energy do?”

“It makes things happen.”

“Negative energy does, too, considered from inside its frame. Looking from our frame, though, negative energy makes things unhappen. This spoon on our table has gravitational potential energy relative to the floor, right?”

“Yeah, you push it over the edge it’ll fall down.”

“But looking from our frame at a similar situation in the anti‑Universe running on anti‑time, an anti‑spoon on its floor has negative gravitational potential energy. We’d see it fall up to its table. Make sense?”

“Gimme a minute.” <pause> “Kinda hard to visualize but I’m starting to get there.” <longer pause> “Alright, you know I hate equations but even I know about Einstein’s E=mc². That c² is a square so it’s always positive so if E is negative then the mass gotta be negative, too.”

“From our frame all mass in the anti‑Universe looks negative. Negative mass would attract negative mass just like positive mass attracts positive mass here. Gravity in the anti‑Universe would work exactly the same way as our gravity does, so where’s the problem?”

“Gimme another minute.” <more pausing> “Suppose that spoon was an anti‑egg. You’re sayin’ when it goes splat over there, we’re gonna see it unsplat? Unsplatting uses up entropy. How about the ‘Entropy always increases‘ rule?”

“Right on the unsplat, wrong on the other. The full statement of Thermodynamics’ Second Law says that entropy never decreases in an isolated system. You can’t get much more isolated than being a separate Universe — no inputs of energy or matter from our Universe or anywhere else, right? From our frame, it looks like the anti‑Universe flipped the Second Law but that’s only because we’re using the wrong clock.”

~~ Rich Olcott