Re: Which Planet is the Closest?

Re: Which Planet is the Closest?


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 planet” dozens 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]

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    Metal Bat

    It makes sense since all planets orbit the sun and Mercury is the closest planet to the sun. Doesn't this mean by the same logic that the sun is closer to any planet than any planet is to any other planet?

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    Andrew Zebic

    Alright, time to figure out who Grey is: first he's white and American, so that reduces the population pool to about 200 Million people. Second he's a teacher/lecturer so that reduces that number to 2 Million (assuming 1/100 people are educators). He did physics which probably reduces this to about 100,000 (assuming 1 in 20 educators are doing physics).
    I also know that Mathematicians basically say that a problem in Ramsey theory is pretty much solved since they know it's between 12 and Graham's number. Because I've done this reduction, I have established his identity. Grey is a guy who does physics at uni. QED

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    Robert H

    I always though that "wich planet is closest?" implied distance to the orbital radius and i dont think thats a failed assumption to make. If people want to be more specific they can just explain further AND people that assume things can just be open to the fact that several interpretations is possible.

    Nobody talks hyperspecific anyway in their normal life.

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    Matthew Lui

    Venus can get the closest, therefore closest.

    CGP Grey: No, we have to make things complicated and say Venus isn't the closest planet so I can make 2 videos in a row.

    Reality: It depends.

    For a physicist (as you said so), it is totally unforgivable just to assume something that CAN be interpreted in another way to BE the correct way to interpret. You can't just come out and say 'I got another answer, therefore the first one is wrong' without considering it is a question interpreted in different ways.

    Saying Venus is the closest planet is not wrong, but it is not absolutely correct either. If someone asks, just tell them in what basis you are determining that Venus is the closest planet. No one can argue that Venus can get closest to Earth… yet.

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    Kram1032

    The sun is closer to Earth than Mercury.

    Honestly I find this take on closeness fairly useless. The closest in terms of travel time, and perhaps of that the average, probably given some reasonable acceleration profile, would definitely be more interesting. But yeah, just from that extra dependency it should become clear that it is indeed a tough question to answer. Also, what do you want to actually do? Fly by? actually land? Include a trip back to Earth? All of those would likely get vastly different answers and are really time-critical. Like, if the solar system aligns accordingly, you can neatly use gravity assisted maneuvers to change your trajectory in a number of interesting ways. It's an ever changing problem.
    It's like if the streets in your city were ever shifting around and so whether the street you want to take next even exists critically depends on how long it takes you to get to the end of your current street.
    Heck, it's actually more like, if you go at a different speed, you are automatically on a different street! On top of how they already change anyway due to planetary movement.

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    kordell curl

    That’s only use today’s definition of a planet. What if you were to use the old geocentric definition? Then the moon would be the closest.

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    theIcyToad

    Followup: I'm sure the underlying models have taken this into consideration and that what we were shown was made for illustrative purposes. But, just as the planets aren't in a single line next to each other, they (presumably) aren't orbiting the sun in the same 2-dimensional alignment. Whether those orbits shift on a 3-dimensional plane or not is obviously going to have to be factored in, but what I'm really curious about is how much of a difference there is between the 2-dimensional alignment model and a more accurate 3-dimensional calculation in terms of average distance/top proximity frequency?

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    youmongrel

    This whole subject seems so pedantic. The question, when asked, is certainly meant to imply which planet's ORBIT is closest. Venus.

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    Crenshaw Yeo

    That moon inflatable. I saw it in person. Its incredible. you can't capture how cool that thing is in a video. I tried.

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    Tom Fluxus

    Our moon is too large be considered a regular moon, some may even classify it as a tiny planet. So there, I win :p https://www.google.com/amp/s/phys.org/news/2017-02-reclassify-moon-planetreopening-centuries-old-debate.amp

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    Bob Joe

    This is because schools don't teach in this way, hence why most people or school teachers without a degree in physics, teach the way they do.

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    Mark Hutsell

    The Moon is a planet sharing Earth's orbit—looking as if our moon is one of the many natural satellites in the system. There, I said it. The Earth's moon gets no respect.

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    A Voice Over IP

    I think you're not quite correct with your 4 questions; I think most of us are thinking about *orbits*, rather than *planets*, when we ask this question.

    Despite how fascinating it is on the face of it, "mercury is the closest planet to Earth" is true in the same way as "molecules don't make contact, so even when you pick something up you're not really touching it" is; technically by some definitions true, and even important in some contexts, but utterly useless to most people. The sort of factoid that some self-proclaimed genius will bust out at a party to prove how they're smarter than everyone else. I enjoyed the video at first but once it was over I had this feeling like, great, now for the rest of my life every time I say "X is the closest planet to Y" and am generally understood to be meaning X's orbit comes closest to Y's orbit, someone is going to interrupt me to say "Well *actually*.."

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    theextremeviking

    earth is flat. there are no planets. we get photoshopped bullshit from nasa. we are just looking at lights in the sky. retards.

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    Melvin Klein

    There is also a 5th question: Which planets orbit is closest to that of the earths orbit. Which is what I think when I hea r which planet is closest

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    Cindy Castillo

    Two questions: 1. Where is he? and 2. Do they have heavy security that will unable someone to take that big beautiful moon to put it in her/his room?

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    DatPiano Dude

    This is what I want when I ask which planet is closest: Draw out the path of the orbits of all the planets. Which orbit line is the closest on average to the earth's line?

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    Perryman1138

    When people ask “what planet is closest” perhaps they are actually thinking about “what planet’s orbital path is closest”? I think that is the notion likely presupposed by most.

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    just a pear

    Grey walking into the international space station: "guys can I just grab a quick look at mercury"
    The astronauts: "wtf"

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    VelleVette

    It is great! I'm so happy to learn more about the solar system, even if it means I was thinking about it wrong before 🙂

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    Steve Smith

    How has "what is the order of the average center-to-center distance from each planet to the sun, and what non-Earth planet has the value with the smallest absolute difference to Earth's" not come up?

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    Karl Smallphones

    The closest planet to Earth is the planet clackertio its where all the UFOs come from
    It's hard to see and can only be seen at night but the problem is the Planets surface is black with spots of light so it looks like space and stars
    Only intelligent people are told about it if you don't know about it it's because you're one of the stupid ones

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    Mike234

    People with physics degrees: Venus is the closest planet to Earth.

    Me, an intellectual without a physics degree, but a thousand hours in Kerbal Space Program: Are you sure about that?

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    Wizard Tim

    We assumed aether was a thing for thousands of years until someone decided to prove it and found out they couldn't.

    It's confirmation bias. We received information from what we believed to be credible sources (Aristotle was the source of many falsities), and just accepted it as fact without further thought.

    The sun is yellow (actually white)

    Nights grow longer in the winter (the longest night cycle is the first day of winter)

    Etc.

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