17 thoughts on “Space Is Really Really Empty”

  1. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.

  2. I disagree. Space isn’t empty at all. Thinking of stars, planets, and asteroids as the only things that fill up space is wrong but even if you do include asteroids, I am not sure how you get to empty.

  3. Wodun, look up the average distance between asteroids in the main belt.

    Depending on what criteria you use (eg the minimum size for what counts as an asteroid, the boundaries of the main belt, etc) you’ll find estimates ranging from 600,000 miles (already two and half times the distance from Earth to the Moon) to two million miles or even more. That’s pretty empty, but of course, that’s the main belt where asteroids are more densely located.

    Look up the average distance between comets in the Oort cloud!

    And then, jumping a few categories of emptiness, there’s always intergalactic supervoids to contemplate.

    1. And look at how many strike Earth on any given day. Space isn’t empty. Thinking of space as a void with periodic planets and asteroids is the wrong way to view it. It is like looking out over the ocean and thinking how empty it is because all you see are waves and the horizon.

      Do you really think there is nothing between asteroids in the asteroid belt?

      1. Most meteors weigh less than 2 grams (source: http://www.amsmeteors.org/meteor-showers/meteor-faq/#3)

        Your attitude toward small things seems like an avenue to happiness!

        Wodun’s friend: “Oh my God! You’ve been robbed!
        Wodunn: “Yes, the car appears to be missing. Well, it isn’t all bad. You see an empty garage, but I see a garage chock full of air and dust.”

        1. The difference between a garage and an universe is a garage is suppose to have a car in it.. Our solar system and galaxy is pretty full when you consider the effects of gravity and time.

          Or in the space of our solar system what would it be like if there was 10 or 100 times more “things”. So 10 times the number of planets, and 10 times the amount of space rocks.

          1. Bob-1, based on a short look at the image of our solar system compared to the others, I don’t know that I draw the same conclusion that our solar system is anomalous.

            I don’t know much about Kepler, but it seems to me that the other explanation for that image is that Kepler is designed to be able to find tightly-packed systems more easily than wide-flung systems, based on the amount of perturbation to the star’s orbit by its closer planetary neighbors.

            Obviously I need to read more about Kepler, though.

          2. You’re right — there illustration only illustrates what I’m talking about but not the statistical argument that must be made, taking Kepler’s biases into account as well as the sheer number of stars that have been examined. I’ll look for a reference.

          3. It appears that Kepler is designed to determine planetary existence by way of the transit method, and an object must transit its star three times before it can be confirmed by Kepler. Part of the reasoning behind this is because the mission is designed for finding planets in the “Goldilocks Zone”, and part of it is because it is trying to find planets approximately the size of Earth (rather than large planets that have been found earlier).

            Given the length of the Kepler mission to date, and its mission parameters, it’s not too surprising that it’s found so many systems whose planets orbit within a similar distance to their star as we are to ours.

            It seems that it’s a good way to help fill in the gaps of other extrasolar planetary searches, for sure. Looking at the images of the search cone for the program, I can’t help but be reminded of how vast our own galaxy is, and about how little of it we have any significant detail. And I really want to go out there and see it all for myself some day, but that’s beside the point.

  4. I saw that linked at Ace of Spades about a week ago. I just clicked on the link, and it has been greatly improved since I first saw it.

    That is one of the best sites ever. Previously, you could have book illustrations and wall charts showing the Sun and planets to scale in size OR distance, but never until now was it possible to show them to scale in both size AND distance.

  5. Wow! That’s impressive. I had no idea.

    I did make it to Saturn (barely), but had no patience to try for the outer planets.

  6. Excellent!

    I remember years ago seeing Carl Sagan on the Tonight Show addressing the same subject. Carson asked him “Space is mostly empty isn’t it?” and Sagan replied in his patented cadence “Yes….that’s why we call it space.”

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