“Sure?”

Bounce bounce bounce bounce BOUNCE. Lev is SO EXCITED.

"Okay so. Imagine that the universes consists only of me and you. No Earth, no Sun, no trees, just the two of us and endless empty darkness. And let's say we are drifting apart. How could you tell which of us is moving?"

“I... don’t... know?” 

"Yeah! Exactly! Good job!" Lev kisses him. "You can't. From my perspective, I'm still and you're moving, and from your perspective, you're still and I'm moving. And this seems like-- stoned dorm-room philosophizing bullshit-- but it's important because that's how it actually is in the actual universe. When we say 'the Earth goes around the Sun' what we mean is 'if we model the Sun as the stationary thing and the Earth as the thing that moves, the math is much simpler than if we do it the other way around.'"

“Huh. That’s... weird, to think about. Like, I guess?? But... how would the other planets be moving, then?”

"That's also a really good question! Every object exerts a gravitational force on every other object, no matter what you decide to think of as stationary. Heavy objects exert way more gravitational force though, so we can ignore most objects when we do our calculations. The Sun is the heaviest thing in the Solar System so it would be the most important object to think about when calculating the orbits of everything, even if you decided the Earth was stationary actually. That is why the math would be so complicated if we did it that way. --You do have to think about the gravitational effects planets have on each other sometimes though. Neptune was predicted before it was discovered, because Uranus moved differently than the way we predicted just thinking about the Sun, so there had to be some other planet exerting a lot of gravitational force on it."

“You’re really smart. —What does this have to do with magic not making the ocean colder?”

Lev finds a piece of paper and a pencil. "Back to our two-person universe. We're going to add a third thing. It's an electron. --Electrons can't be created or destroyed." He draws two stick figures and labels them 'Lev' and 'Martin,' and draws a dot for the electron. "So let's say from my perspective I'm stationary and you're moving towards the electron. And you're moving very very very fast, at like half the speed of light. And this electron suddenly disappears and then at this very same instant, from my perspective, it reappears over here." He adds a second dot on the other side and labels it New Electron. "The electron is not created or destroyed. But what do you see?"

“...it disappears?”

"But does the electron disappear and reappear at exactly the same time for you?"

The good thing about true/false questions is that he always has a 50% chance of being right. “...N..o...?”

"Do you know why?" Martin should have Lev on top of him for motivational purposes.

“Because... I’m... moving... very... fast?”

"...you know it is better to say when you're confused than to guess randomly unless you are taking a multiple-choice test with no penalty for guessing." Lev kisses him. "You're moving very fast! And when you move towards something, you get closer to it. And light takes time to travel over space. So what do you see?"

“...I don’t... know?”

Kisses. "Good job. Light is traveling a shorter distance from the Old Electron to you than from the New Electron to you. So you see the Old Electron disappear before the New Electron appears. So from your perspective the conservation law was violated-- for a while an electron was destroyed."

“That’s... Weird to think about, but I think I get it?”

"And it would all be fine if you were definitely moving, right?" Lev says. "Because they happened at the same time, you just saw the light at different times. But like I said before we can't tell which of us is moving. So electrons cannot poof out of existence and reappear somewhere else. So if magic is paying attention to conservation of energy by making the oceans colder, then it has to be true that there's something in the universe which is objectively stationary."

“Oh.” 

"Where did I lose you?"

“All... of... it...? I’m sorry, I am trying, I just...”

"...I'm not mad at you."

“...Oh. Sorry.” Pause. “Right, I know I just apologized again when I probably shouldn’t have and that if I apologize for that it’ll only make it worse, but I’m not sure what to say to make it better? I’m, um. Glad you’re not mad at me, I guess? I didn’t really think you were, though, you were just, I dunno, excited? And I wasn’t able to keep up.”

"You don't have to make it better, if I get excited and suck at explaining things then it is my fault. I'm the one who's trying to explain things. --I'm not going to get mad at you if you can't get things. I mean, I think you can or I wouldn't have tried to explain it? Or at least you can when you aren't using up all your energy panicking about it. But if I'm wrong about that I'm not going to be upset with you or think any less of you."

(He has a gentle voice and a kind of protectively pissed off face.)

“Oh.” Martin tentatively reaches down to comb his fingers through Lev’s hair. “I like it when you’re excited? You’re really cute when you’re excited. But then you ask questions and you look so— so hopeful, like you’re so sure I can get it, and you’re so excited for me to get it, it’s... I dunno, I don’t know if any of that made any sense, but... I guess I just wish I could give that to you?“