Space is really, really big

In his book The Hitchhiker’s Guide to the Galaxy, Douglas Adams wrote that the Guide says that: “Space … is big. Really big. You just won’t believe how vastly hugely mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to space.”

Although I am aware that space is big, evidence of its vastness still continues to surprise me. Just yesterday, I was listening to a news report about the launching of a rocket to study three of the moons of Jupiter. I was startled when they said that it will take eight years for it to get there. Somehow, the fact that Jupiter is part of the same planetary system as the Earth made it seem like a nearby neighbor, farther than the Moon but not by that much. But if the distance to Jupiter is so much greater than what I intuitively felt, you can understand why interstellar distances seem almost inconceivable.

It is hard to comprehend things that are outside our human scale: the vary small, the very fast, deep time, and deep space. We have developed methods to get some idea of what things are like under those conditions but they are still not intuitive.


  1. Canadian Steve says

    I once had middle school science students create a scale diagram of the solar system. It is fascinating to see them realize just how big the spaces between the planets are, how small the earth is relative to the giants, and how much further the planets beyond earth are from the sun than they would expect. They had to get long rolls of paper to make it reasonable. It made an excellent impression.

  2. beholder says

    JUICE is going in circles multiple times before it gets there. It’s doing two flybys of Earth and one of Venus to use gravity assists instead of wasting fuel going straight to Jupiter.

    It will be interesting to see what’s going on with Ganymede. Maybe it still has a few unexpected things going on that will be worth taking a close look at.

  3. beholder says

    For comparison, Galileo took 6 years to get to Jupiter and Juno took 5 years, with 86% and 56% of the launch mass as propulsion, respectively. JUICE has 59% of its launch mass as propulsion, but the payload is significantly larger than Juno’s, and far more massive than Galileo.

  4. sonofrojblake says

    One of the best ways I know to get some sort of grip of the scale of space is to play Elite Dangerous.

    Annoyingly, access to the Sol system is barred to anyone who hasn’t got Elite status, which means you either have to get really good at combat, spend a good deal of time trading (and know what to trade where for profit), or spend a LOT of time exploring aka just jumping from system to system, all the way to the centre/opposite site of the galaxy and back. Travel from one star system to another is carried out using “Frame Shift Drive”, which is essentially a short lightshow while the system loads up/procedurally generate the target solar system. A single jump always takes about the same length of time, from memory about thirty or forty seconds, and depending on how tricked out your ship might cover ten or thirty light years or more. There’s no control or interaction while jumping via FSD.

    In system you fly around like more or less any ship in any space game, except distances, sizes and positions of bodies are realistic. Travel speeds, though, still go up to several multiples of lightspeed to allow you to get from one planet to another in less than months.

    Once you do get to Elite level you get access to the Sol system, and a beautiful reproduction of the actual positions, appearances and relative sizes of the planets, moons, dwarf planets and so on. The FTL drive means you get from Earth to Mars in minutes. A trip out to Pluto is a bit longer, and out as far as Persephone (the big planet MUCH further out “discovered” some time in the future from our perspective) takes quite some time.

    Even with the FTL drive, the system still feels big, and the planets within it tiny and insignficant. And even with FSD, reaching something as relatively “close” as the Orion nebula can take hours and hours. One on level, it makes for a game some would call meditative, and others “boring”. I’d not argue with either of those characterisations.

    Check it out if you haven’t already.

  5. Rob Grigjanis says

    Sun to inner planets; light minutes.
    Sun to outer planets; light hours, possibly light days for distance travelled by probes.
    Sun to nearby stars; light years.

    After that, it gets silly.

  6. says

    Scaling objects is something I used to use in my freshman intro engineering course. Good ones were scaling earth/moon or earth/sun to locations on campus. In my intro electrical circuits course, I used to use the reverse: a scaling for hydrogen, namely the size of an electron versus the average distance to the proton. If I remember correctly, it worked out that if the electron was the size of a golf ball, the proton would be at a popular pizza place some distance from campus. The point I used to stress was that even solid objects are mostly nothing (empty space). These exercises are useful because these students are going to be dealing with very large and very small numbers, and getting them proficient in scientific and engineering notation is a must.

    But it’s not just for college students. A buddy of mine who taught middle school science had the kids map out the distances to the planets along a walking path that ran along the school grounds. You actually need that sort of distance (a sizable chunk of a mile) if you want to make the scaled inner planets even visible to the naked eye.

    Of course, sometimes knowledge of these things can ruin films, TV shows, etc. I was watching a sci-fi movie the other day and it said that the space ship had left Earth and was now some 750 million miles away, moving from star to star. My immediate thought was, “But at that distance, it hasn’t even left our solar system”. I guess it’s too much trouble for the average screen writer to look up what constitutes an “interstellar distance”. But “750 million miles” seems like so much, right? Heck, even if they had upped it to 750 billion miles, the ship still wouldn’t be halfway to Alpha Centauri, let alone going from star to star to star.

    Oh, and then there’s the popular misconception of an “asteroid belt”. No, it’s not a huge field of giant boulders that are constantly smashing into each other like bumper cars at a carnival ride. Do you have any idea of how much mass that would entail?

  7. Rob Grigjanis says

    Of course this stuff is beyond our intuition. The human brain has a hard time grasping the notion of “a thousand times bigger” or “one thousandth the size of”. So a sequence like person-mountain-planet-interplanetary distance-interstellar distance-galactic size, etc is ridiculously beyond us. As is person-cell-molecule-nucleon.

  8. says

    Once you do get to Elite level you get access to the Sol system, and a beautiful reproduction of the actual positions, appearances and relative sizes of the planets, moons, dwarf planets and so on. The FTL drive means you get from Earth to Mars in minutes. A trip out to Pluto is a bit longer, and out as far as Persephone (the big planet MUCH further out “discovered” some time in the future from our perspective) takes quite some time.

    True fun Elite Dangerous fact: if you go on the correct course, far enough, you can find the voyager probe.

  9. Pierce R. Butler says

    A local astronomy club, decades ago, took advantage of a city road with an uninterrupted mile of frontage along a preserved wetland area to erect a series of obelisks & data plaques representing the sun & planets (including Pluto at the time), placed (but not sized) proportionately (plus a couple of smaller markers showing the perihelion and aphelion of Halley’s Comet).

    I’ve hiked and driven along it many times, but only the former really demonstrates how many AU it takes to get to the gas giants. So far I have yet to receive a second to my motion that the city demolish several houses on the “outer” end to add heaps of gravel, dust, and gauze representing the Kuiper Belt, Oort Cloud, and heliopause.

  10. sonofrojblake says

    Not sorta-fun fact about Elite Dangerous: BOTH Voyagers are out there, although not, as far as I can remember, the Pioneers. I found one.
    When I first started playing, there were Reddit posts about that would tell you in some detail where you’d have to be and in which direction to point and how long you’d have to fly to find them. I gave it a go a couple of times, but as I believe has been noted -- space is BIG. Any tiny mistake in the bearing you take while in Earth orbit multiplys by squares as you travel outwards.
    Then there was an update to the game… which included a kind of system-wide scanner, which made locating them trivially easy. Which made it possible for me to find them, but almost completely removed the kick for having done so.

  11. sonofrojblake says

    Aside: access to the Sol system is clearly a motivating reward for achieving Elite status.

    However, I think it’s past time Frontier Developments made JUST the Sol system available as a separate, standalone playable thing. Give you one ship, no Frame Shift Drive and no way to get one, so no jumping out of system. Some space stations to dock with, some other artifacts to find/explore, maybe even some in-system missions to give you something to do, but mainly an accurate representation of the solar system with Elite-style in-system FTL to allow you to explore and understand the scale and layout of the system. I think it’d be great, and would likely sell a few more copies of the full game at this late stage of its development. I think it would be a superb educational tool.

  12. birgerjohansson says

    There is a reason why the Total Perspective Vortex completely destroyed minds.

  13. sonofrojblake says

    Indeed. E:D is very good at covering the scale of the galaxy. It’s a reasonably accurate model in size, shape and star population. At thirty seconds per jump, and thirty light years per jump, it’s can take you a whole evening or more just to cross human occupied space… Then you look at the map and make out the whole bubble as a barely visible dot.

    It’s great.

  14. seachange says

    The Silk Road from took two years there and back again. I’m presuming this is a best-time estimate. Here in Los Angeles even though we’re raddled by freeways *time to get there* is the distance-unit we use. The Silk Road had bandits and repeated taxation. Los Angeles has traffic jams, so a car which is the accumulation of thousands of years of knowledge, it is not necessarily any faster than a bicycle…or a camel.

    The trips out to Jupiter are even faster than a camel or a car. They’re not done by commercial enterprises in which time is money. They are governmental actions subject to rules and regulations and budgets which are political. So yes, #2 beholder is correct. But that’s not the end of it.

    I dunno if I’m being cynical or optimistic here. To me eight years seems very reasonable. The facts that these missions aim to learn will still be true eight years from now, they won’t go away, so sure go around in circles. Humanity may still be alive eight years from now to receive those signals, wow!

  15. KG says

    JUICE will, if successful, make two passes of Europa (apparently it’s limited in how long it can stay near Europa because of the latter’s proximity to Jupiter, which produces copious radiation), and 31 of Callisto, and go into orbit around Ganymede -- the first spacecraft to orbit a moon other than Earth’s. I guess it needs to save as much fuel as possible for those manoeuvres, hence the complicated gravity-assisted trajectory. NASA’s Europa Clipper, due to launch later this year, will reach its destination before JUICE.

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