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  • Hello Internet.

  • While working on a future video, I offhandedly wrote, “Venus, the closest planet to Earth.”

  • But later, while editing, I thought, “You know, let me check that.”

  • Which led to me to this video by Dr. Stockman explaining how, no, Venus is not the closest.

  • This blew my mind and I contacted the author to adapt his video into the one you probably just watched.

  • It blew my mind, not just because it was surprising,

  • but also because I taught physics for years and probably said

  • Venus is the closest planetdozens of times without ever thinking about it.

  • How does that happen?

  • First, asking the precisely right question is vital.

  • "Which planet is closest?" is *not* the precisely right question.

  • Because it’s really made of four parts:

  • Which planet ever gets the closest?

  • Which planet is the closest for the longest time?

  • Which planet has the shortest average distance to Earth?

  • Which planet takes the least amount of time to travel to?

  • The answer to the first one is Venus.

  • The second two? Mercury.

  • The last? It's complicated, get a physics degree.

  • Literal rocket scientists think mostly about that last question

  • and the rest of us are probably vaguely asking about the first when we say

  • "Which is the closest?" because we're not thinking about the planets in motion.

  • If we were, we'd ask something closer to questions two and three,

  • which is what the main video is about.

  • Mercury, on average, has the shortest distance to all the other planets,

  • and for the inner planets, it’s also the closest planet most of the time.

  • But to get an answer that precise requires a precise question.

  • Unlike the way things are done in school, where questions yield knowledge,

  • it's knowledge that yields questions, which yield knowledge.

  • Now, it's hard to think about the raw knowledge of everything all at once,

  • so we condense down part of what we know into a model to help us think,

  • like with the line of the planets.

  • But, as with fuzzy questions, models can trick us too:

  • Which planet is the closest?” looks like a simple and easy question

  • when the solar system is shown this way.

  • Like even when you know that isn't *really* how the Solar System looks.

  • Can't possibly be.

  • In my old video about Pluto

  • (where I sound like a completely different person)

  • I covered this exact point as I've often done in class:

  • (past Grey) "If we take this diagram

  • and adjust for the correct sizes of the planets, it looks like this.

  • Think about it.

  • If Jupiter was this close to Earth, it wouldn’t look like a dot in the night sky,

  • but would be rather overwhelming. So it must be really far away.“

  • (present-day Grey) Still, the model gets into your head in ways you don't notice

  • and lets you ask imprecise questions, easily, but insufficiently answered.

  • The result is something that's retroactively obvious can hide for a long time.

  • The fact about Mercury being the closest on average feels like something Newton could have noticed.

  • But it wasn't published until *this year*.

  • Which is crazy. It's a property of concentric circles.

  • (Something Pythagoras, were he not so obsessed with triangles, might have noticed.)

  • So, I love this fact about Mercury being the closest planet,

  • (depending on exactly what you mean by closest)

  • because it’s a fantastic example of how if you can get rid of old or incorrect models

  • from you head and think clearly in a way to ask a precise question,

  • the universe awaits with new knowledge for you to find.

  • Isn't that great?

  • [soft ambient music]

Hello Internet.

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