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Comment by aetherson | Hacker News Reader

I've been interested in scale models of the solar system (or other astronomical systems like say the moon system of Jupiter) for a while, partly to try to teach my kids stuff and partly just because I think they're cool.

My opinion is that this solar system model is too big to be useful. If you're trying to teach people about the scales of space, I think you need something humanly navigable, ideally something where you can see with a single sight-line back to the previous object in the model, or, failing that, where at least you can walk between elements of the model in a short enough time that you can kind of keep yourself on-task and thinking about the model for the whole walk.

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There's one north of Boston [1] that I accidentally found walking one time. Turns out I remembered it from a HN posting some years ago. I'd already walked some 3 mi or so by the time I walked across Neptune, so couldn't go all the way to Topsfield and back. I thought it gave a really good sense of how big space is. It's about 1 mi from Neptune to Uranus and another mile or so to Saturn (as far as I got). On my return I walked directly at a fast walking pace, so it took some 20 minutes to from Saturn to Uranus and another 20 minutes to Neptune. (Distances and times are approximate.) At the time I think I calculated my walking speed to be four times the speed of light. It's pretty awesome, in the original sense, that going 4x light speed it still takes a long time to get from one outer planet to the next.

Wikipedia has quite a list of other models [2], although it doesn't seem to include Topsfield, MA.

[1] https://www.wickedlocal.com/story/chronicle-transcript/2021/...

[2] https://en.wikipedia.org/wiki/Solar_System_model

I dunno... Earth is 4.7 mi from the sun. That's walkable.

I like that this actually gives you a sense of real meaningful distance and size. This is a sun that's still big compared to humans, and a distance to the earth that isn't negligible.

And then a real lesson about how insanely larger the solar system is when you try to get out to Jupiter and beyond.

It's walkable, but you can't see the "sun" from the "earth," and it's walkable in well more than an hour, at which point I don't think that you're really keeping the scale in mind.

We can always look at images or whatever if we want to get an intellectual sense of the scale of things. I think the advantage of a model is that you feel immersed in it, and I don't think you do at this scale.

It's challenging! It's hard to find a location and a scale which gives you this human sense of the sizes involved. At most scales, you have to make the planets pinpricks in size. But, especially for the inner system, you can make it work.

EDIT: Here's I think something that works.

https://www.youtube.com/watch?v=zR3Igc3Rhfg

For a better perspective on scale, they should do a model where in 1 place you have the sun, its planets, asteroid belts etc, and (to scale!) in a 2nd place you have a model representing the nearest star system (Alpha Centauri).

Oh... and of course put in where Voyager, Pioneer & New Horizons probes are these days - after 40+ years of travel at ~15km/s.

I think this is near-impossible. The diameter of earth is about 12,700 km. So if the distance between the Sun and Alpha Centauri were "the maximum distance available on Earth," then the scale is 3.25 billion to 1.

The sun's radius is about 696,000 km, so 7x10^6 meters, so at 3.25 x 10^9:1 scale, it's about 2mm across. The planets would all be specks. You could see orbits, though they'd be small. And that's if you place your alpha centauri model literally "on the other side of the world" from your sol model.

I think you can do very slightly better by using great circle distances rather than straight lines cutting through the earth. After all, I think that's what this model is doing.

Sure, it could be half the circumference of the earth instead of the diameter. The circumference is pi times the diameter, so half the circumference is a little over 1.5x the diameter -- the sun could be 3mm across instead of 2mm.

> humanly navigable

This is Sweden; I would bet that there are hiking trails connecting everything on that map, although maybe not a single one for all the planets. Roslagsleden (13 day hikes) + the first 9 etapper of Vikingaleden bring you from (close to) Mars to Uranus. And these are some nice hikes:

https://www.roslagen.se/roslagsleden

https://www.roslagen.se/vandra-vikingaleden

> If you're trying to teach people about the scales of space, I think you need something humanly navigable

The Somerset Space Walk [1] seems to be a very nice candidate for your requirements.

[1] https://en.wikipedia.org/wiki/Somerset_Space_Walk

Is it an actual linear scale?

The Sweden one? Seems like yes to me.

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