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Comment by ggreer | Hacker News Reader

Just FYI the sizes of the planets, stars, and their orbits are not to scale at all. To get an idea of how empty space is, there are 63,360 inches in a mile, and 63,239 astronomical units in a light-year. So if you scaled everything down such that Earth was 1 inch from the Sun, Neptune would be 30 inches away and Alpha Centauri would be 4 miles away.

If you were using a 4k display and had the Sun and Alpha Centauri visible at opposite sides of the display, the orbit of Neptune would be in the same pixel as the Sun.

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FYI we have a up to scale model of the solar system in Sweden https://en.wikipedia.org/wiki/Sweden_Solar_System

Come visit!

Wow. Such an awesome idea! Thank you, you made my day

That is awesome!

That looks really cool! I've visited scale models of the solar system in Eugene, Oregon[1] and Norwich, Vermont[2], but neither one is anywhere near that size.

[1] https://eugenesciencecenter.org/exhibits/eugene-solar-system...

[2] https://montshire.org/exhibit/exhibits/outdoor-discovery-tra...

Here in Australia we have earths largest scale model of our solar system.

https://www.nsw.gov.au/visiting-and-exploring-nsw/locations-...

No, the one in Sweden is bigger. See:

https://en.wikipedia.org/wiki/Solar_System_model#Permanent_t...

There is one in Corpus Christi (Texas) that I've seen.

https://www.visitcorpuschristi.com/blog/post/things-to-do-on...

There is also one in Palo Alto, California! https://www.paloaltozoo.org/Exhibits/Solar-System-Model

There is also one in Zagreb, Croatia https://en.wikipedia.org/wiki/Nine_Views

Traverse City, MI has one on their bike trail system: https://traversetrails.org/solar-system/

We have one in Munich as well. Quite nice walk along the river

https://www.deutsches-museum.de/museumsinsel/programm/progra...

It is old, hence Pluto is still part of it

There is a Wikipedia List (German) [1] of quite a few of those (in Germany and in other countries). I stumbled upon it, while trying to find a link to the one in my home town I have wandered quite a few times, as I lived between Neptun and Pluto (it was built before Pluto was demoted), very close to Pluto. It ran the street I grew up in and was built to scale (1:4 bln scale) by a teacher who was a full blown astro nerd and in his free time taught quite a few of the local youth about space, planets, the science behind it, but also built rockets with us and let them fly.

I so fondly remember him, as he was one of those people being a massive inspiration to my life.

[1] https://de.wikipedia.org/wiki/Planetenweg

Edit: Added scale.

You are technically correct, the best kind of correct. However! That would be a terrible UX/UI experience. While showing distances on a linear scale is accurate, it fails to capture all the information a person in an interstellar ship may wish to see.

Something like logarithmic distances would better capture information like "Am I about to crash into the star or enter a nice orbit" while still showing the full picture of where you are in relation to where you're going and where you came from.

No idea of that's what happened here, just a thought, I'm not an expert in starship computer interface design.

Mercury is orbiting partially inside the Sun, and Jupiter is nearly as wide as the Sun when it should be 1/10 as much, so the planet nodes should be scaled down 10x relative to the Sun.

Also, I did a top-down pixel measurement, where I could see the distance to Tau Ceti as well as the orbit of Neptune. The radius of Neptune's orbit was 32px, while the distance to Tau Ceti was 1152px, for a ratio of 36, when in reality, Tau Ceti is 11.9 ly away, while Neptune has an orbit radius of 30 AU, which means Tau Ceti is around 25,000 Neptune orbits away, so the planet orbit scale is too big (or distance to other stars too small) by a factor of ~694 (25000/36)

Edit: Since this was top-down, the vertical displacement didn't factor into the distance, which also contributed to Tau Ceti appearing too close on screen, so the error is slightly better than that, maybe a factor of 600.

Edit 2: Tau Ceti is rendered at 3.652 pc × 3 world units/pc = 10.956 world units

Neptune’s orbit radius is rendered as 30.05 AU × 0.0065 world units/AU = 0.195325 world units

The rendered ratio is 10.956 / 0.195325 = 56.09 Neptune-orbit radii

The real ratio should be 25,067.5 Neptune-orbit radii

The scale error = 25,067.5 / 56.09 = 446.9×

Also, since we're nit-picking, the positions of the planets are not being updated in real time. For example, I know that Venus and Jupiter are currently approaching conjunction: there are spectacular views of them both at sunset right now here in the Southern Hemisphere!

Thanks: All your math checks out.

Sure, but why does this need to be to scale. Isn't the point more to get the humans a way of understanding where things are relatively? Navigating the map makes it interesting in being able to interactively see where some of the stars are relative to each other. Seeing Regulus and Castor/Pollux from this perspective is much different than on terra firma.

It can't do that if it's not to scale! And who knows where the errors are? Neptune's orbit is way too big compared to Alpha Centauri. Are other stars also way too close compared to that? I can't stand these intentionally misleading education images of stuff. You have to work at undoing the artistic license of the author before it's useful.

We seem to be conflating the actual navigation computer with a display to show the humans information. If it were to scale, it would effectively be useless to the human as the scale of space is just too damn big to fit in some sort of navigation display. However, the actual navigation computer can be as accurate as necessary to not become Lost in Space. That's an entirely different franchise

I suspect this lack of scale on the planets was intentional from a usability perspective, because otherwise the planets be bits of dark dust that would be really hard to find. Jupiter has 11x more diameter than Earth and the Sun is 109x larger. When you consider the size of the solar system (including the Oort cloud) the Sun itself is bit a spec of tiny dust.

Another comparison: if you count the "solar system" as ending at Neptune's orbit (obviously it extends much further, but just for the sake of comparison), then you could fit ~4465 "solar systems" in between our sun and the closest star, Proxima Centauri.

As I understand it, there is no consensus on the size of our solar system. We can measure the orbits of the planets, but it is much harder to measure where the Kuiper Belt or the Oort cloud ends. Estimates on both of those vary greatly.

Even sci-fi writers that try to get this right have a hard time wrapping their heads around it.

"It's called space for a reason."

When I saw the series adaptation of The Expanse, it was really obvious they played a lot of artistic license to make it exciting. A real space battle would be dots firing invisible dots at each other. "Close quarter battle" would be within something like 2000 kilometers, maybe more. That is close.

> When I saw the series adaptation of The Expanse, it was really obvious they played a lot of artistic license to make it exciting. A real space battle would be dots firing invisible dots at each other. "Close quarter battle" would be within something like 2000 kilometers, maybe more. That is close.

This is noteworthy because The Expanse tried to get this better than other scifi, say Star Trek, Battlestar Galactica, or Star Wars (ok, space opera), where engagements take place at absurdly short ranges. In The Expanse you see the spaceships are really far apart, mostly dots to each other, and the engagements are (mostly) at really long torpedo ranges, with the exception of those cool scenes using PDCs. You get all those awesome shots where one spaceship sees the other as a tiny dot, then the camera zooms in dramatically to the other point of view. Cool!

And still, engagements are far too close range. But they "feel" long range in The Expanse, I think they got that visually right. I cannot blame them because I haven't seen anything any space combat in shows or movies that is even half as exciting and well done.

The Expanse also was (for me) the first to introduce the concept of a braking burn. Star Wars ships just stop without turning around - can’t unsee it. I think the way X-wing fighters “fly” also wouldn’t work at all, I don’t see any reaction mass coming out the sides.

Babylon 5 was the only show in the 90s that actually had any sort of physics based space combat (as opposed to Star Wars-style "they're really just airplanes but we're pretending it's space").

I really missed on watching Babylon 5 (it was during my time, but I unfortunately dismissed it as just another Star Trek wannabe, and only learned later this was unfair). I wish I had given it a chance. I cannot watch it now because of several reasons, and I'm not sure it would stand the test of time anyway, after having watched The Expanse.

I was in a kind of similar situation. Didn't watch it when it was originally airing, though I could have. I eventually watched it decades later and absolutely loved it. That said, it was pre-The Expanse. But I still think it holds up pretty well, even if the special effects aren't as good.

Babylon 5 is at the beginning of the uncanny valley of computer graphics so it looks funny (I think they used Amigas) but if you pretend that those effects are of current cinema quality, everything else is good. They travel with hyperspace portals (maybe you saw Cowboy Bebop) so they don't have to perform many unphysical motions in normal space. It's still a great show. Less of a space opera compared to the Expanse, more like a Star Trek DS9 with ETs way more powerful than earthlings.

I personally think B5 is a better show than The Expanse, but I don't mind the dated visuals or the occasional bit of campy acting or whatever. The storytelling is absolutely first-rate.

Biggest thing they all still get wrong for reasons of drama is showing humans wrestling with controls and flying like a fighter pilot. Real spaceships do not and will not have humans in the control loop except to specify a destination or target.

>Real spaceships do not and will not have humans in the control loop except to specify a destination or target.

Jim Lovell would like a word.

Present and future tense, not past tense.

As would Neil Armstrong.

After the accident, Apollo 13 had 4 burns.

The DPS-1 burn which restored the free return trajectory was done using the Apollo guidance computer.

The PC+2 burn which sped up the return from earth was done using the Apollo guidance computer.

The MCC-5 mid-course correction burn was done by hand.

The MCC-7 mid-course correction burn was done by hand, but used the Apollo guidance computer to integrate the accelerometer to let everyone know when the burn was done.

(All the burns on Apollo 8 were computer controlled. I'd assume Gemini 7 and 12 were hand flown, though I don't know for sure.)

Would dead-reckoning work or using some galactic sextant?

Maybe?

Ultima (Proxima Book 2) by Stephen Baxter:

    “Oh, come on. This is just great. An imperial Roman starship! . . . We know they lack sophisticated electronics, computers. I wonder how the hell they navigate that thing.”

    “The drive isn’t always on,” said Titus.

    Stef realized that a more precise translation of his words might have been, *The vulcans do not always vomit fire.*

    “Every month they shut it down, and turn the ship.” He mimed this with his one good hand, like aligning a cannon. “The surveyors take sightings from the stars. Then they swivel the ship to make sure we’re on the right track, and fire up the drive again. It’s like laying a road, on the march. You lay a stretch, and at the end of the day the surveyors take their sightings to make sure you’re heading straight and true where you’re supposed to go, and the next day off you go. Works like a dream. Why, I remember once on campaign—”

    “Navigation by dead reckoning,” said the ColU. “Taking sightings from the stars—simply pointing the craft at the destination. They have no computers here, Colonel Kalinski, nothing more complex than an abacus. And they have astrolabes, planispheres, orreries, sextants, and very fine clocks—all mechanical, mechanical, and remarkably sophisticated. But, Colonel, this starship is piloted using clockwork! However, if you have the brute energy of the kernels available, you don’t need subtlety, you don’t need fine control. You need only aim and fire.”

Ha!

Yeah. Though they do have some nods towards realism, like how most combat systems are fully automated. PDCs fire automatically (at most they need a designated target, and for point defense they just fire), and even torpedos are assigned to targets using some touch screen and that's it, they are not fired using a joystick or similar nonsense.

Star Trek (TNG onwards) gets this right.

That's how The Expanse generally worked, except when they needed to do things outside of normal circumstances.

I seem to remember there was a scene where a human piloted Rocinante through a space station, using what looks like joystick controls and a large viewscreen in front of him.

https://www.youtube.com/watch?v=_c9W-icdTmg&list=PL66J-Gd5vt...

Yeah, exceptional circumstance.

That’s actually how the cons work in Star Trek (and many other SciFi shows too).

What officers do at the con once the ship is in motion is monitor ships systems and check for any external changes to the environment (such as other ships coming in for interception).

Yes sure I'd say that's the exception, can't think of many others.

Yes, even today it’s rare. Docking with the ISS or initiating the trans lunar burn on the most recent mission were all completely automated. The pilot arms the engine and authorizes it to proceed. I can imagine it being possible to grab the controls but it’s only done in exceptional or unusual cases.

Of course astronauts are trained for it in simulators in case computers fail.

If there are ever real space battles, that’s actually the most ridiculous time to have humans flying. Human reflexes and ability to mentally model 3D space under microgravity and orbital mechanics are just categorically inferior to what any machine can do. We are too slow and too imprecise.

If there are pilots at all it’ll be at a higher level, like the piloting equivalent of a programmer commanding AI bots. The computer will present the pilot with a digested real time tactical and strategic abstraction and the pilot would make decisions at that level.

A computer or avionics failure in a space battle would probably just be fatal. Which would mean EMP weapons against computers might factor in heavily.

Lucas wanted to make a swords and sorcery epic in space, and that’s what he did. And he wanted to make space battles look like WWII dogfights, so he did that too. There’s no point trying to compare Star Wars with any sort of realism.

The books are more realistic than the show. The show takes liberties to look cool, I think, which is okay. Not only does it mess with scale a lot but it also adds a lot of sound and visual effects that would not be there.

> also adds a lot of sound and visual effects that would not be there.

Nah, they'll have regulations forcing them to add artificial sound generators like today's EVs

> Star Trek, Battlestar Galactica, or Star Wars (ok, space opera), where engagements take place at absurdly short ranges.

I think that is we could maneuver spaceships like cars and get from place to place in seconds then we would engage at close distance. The only reason for keeping far away would be to have time to react to missile launches and attempt to intercept them. But that's not different than what ships do at sea.

>The only reason for keeping far away would be to have time to react to missile launches and attempt to intercept them. But that's not different than what ships do at sea.

Yes, that's why you would do it in space, too. The only reason sci-fi media doesn't do it is that it would look boring onscreen. You're just sitting there in the dark then all of a sudden a tungsten rod moving at some fraction of c vaporizes your hull, or a cloud of goo attaches to your hull and you bake to death slowly because you can't evaporate heat well enough. And of course actual lasers in a vaccuum are invisible.

Everything in space is so big, spaceships have to be so fast to get anywhere in a TV-friendly amount of time. I feel like spending an appreciable amount of time inside visual range would be like 2 enemy fighter jets pulling up next to each other so the pilots could sword fight. It really needs the deliberate cooperation of both parties. If anybody even breathes on their control stick they'll drop out of range instantaneously. Not that I'm complaining lol, I like to be able to see things in my TV shows.

Hitting debris at these velocities would be instant death. Debris comes from other vehicles (generally). You’d never want to be going where other people are, for safety.

Assuming identical weapons.

But if your weapons outrange your enemy you will want to keep the range long. And if your weapons suffer less range penalty than theirs do you will want to keep the range long. The flip side being that if you're on the other side of either of these scenarios you want to keep the range short. And that's before you consider the effects of shielding--most universes with shields make them more effective against weaker attacks. This would mean that if you're facing lighter weapons than your own you keep the range open, if you're facing heavier ones you close.

There was one particularly egregious scene in The Mandalorian. The protagonist had to fly from Planet A to Planet B without hyperspace for reasons, and he was waylaid by some kind of space patrol, and then he just "turns the steering wheel sideways," and bam, he's landing on a different planet!

Even by Star Wars standard that was absurd. What is this, a highway chase scene?

I recently read The Mote in God's Eye and its (much later) sequel The Gripping Hand, which had very interesting long-distance space combat scenes with high powered lasers - which only move at the speed of light. There's a very real "fog of war" element where you might be VERY out of date with what's happening just due to radio transmission speeds / direct observation.

I don't think the Expanse authors were going for "hard sci-fi." There's, you know, fiction elements -- gates, aliens, magic. And the TV series is itself an adaptation of the books for a visual medium. Showing almost nothing would make for kind of boring TV combat.

Agreed. It's not "rock-hard sci-fi." It's "medium-hard sci-fi."

The background world building was pretty good from a hard SF point of view. Fusion rockets are possible and the high performance ones in the series are at the edge of physical plausibility but possible. Some of the details, like spinning up asteroids, don't work, but the basic physics of humanity's solar system build-out is mostly sound.

The rest of it gets increasingly soft and fantastic. Which is fine, it's fun space opera.

The biggest issue is that with the energy economy of the drives as shown, none of the actual conflicts would ever happen.

Earth, the belt, etc. would have infinite clean water, for example, and plenty of energy to grow food via hydroponics.

No one would have any issues refining metals or other materals, due to all the available energy. Etc. etc.

The issue is, and I believe the authors talk about this, is that the fusion torches they use are absolutely plausible, the problem is that theres no way those ships hold enough fuel for those trips, ripping the engines back out of plausibility again.

Right, they hand-wave this away with the "Epstein Drive"[0] (a name which I suppose has not aged well), which appears to somehow run on orders of magnitude less propellent than seems realistically possible.

[0] https://expanse.fandom.com/wiki/Epstein_Drive

> There's, you know, fiction elements -- gates, aliens, magic.

Setting aside magic, fictional science and technology aren't incompatible with hard sci-fi; in fact I'd argue that exploring those on "serious" terms is the entire point of the genre.

At some point I started seeing people advance this weird idea online that hard sci-fi means essentially nonfiction but that's not correct (or even sensible if you stop and think about it since at that point you're just writing a traditional character or political drama or whatever). It simply means taking a simulation style approach to various technological elements of the story. The deeper the simulation goes (ie the more nested levels of "okay and why does that work that way and what are the practical impacts on society") the "harder" the work is.

Magic is an interesting case. In theory it could be compatible with science but in practice the sort of phenomena that people usually mean by that term necessarily imply the intervention of some higher power.

All of those authors usually have to resort to the idea of "shipping lanes" so if the heroes are stranded between two planets eventually someone else will pass close to them on the way from one of those planets to the other one. This is wrong in a number of ways (first of all, they keep going anyway) but without that and without magically powerful fuels plots would be "they launched from Mars to Neptune, forget about them for the next three seasons, they'll be there at the beginning of the fourth one".

I thought orbital mechanics would still create those "shipping lanes" as the most efficient way to go from A to B. Of course with enough fuel you can go anywhere, but shipping specifically will love those reduced costs.

The problem is that the planets aren't standing still.

You want to do an optimum burn for Earth -> Mars? Compute an ellipse such that one end touches Earth's orbit, one end touches Mars' orbit. Oops, Mars isn't going to be there, you wait. Once every 26 months you will find that half an orbit later Mars will be there, then you burn. We call this a launch window.

26 months later they will line up again, but neither Earth nor Mars are where they were before. A spacecraft in this second window will never pass anywhere near a crippled spacecraft that flew in the first window. Nor could they do anything but send a report if it did happen--if you're doing efficient burns you don't have the fuel to go to somebody's aid.

Hitchhiker's Guide to the Galaxy:

   “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."

That’s quite true. But even leaving that aside, most space battles are poorly written too. One of the best that I know of is the battle for Proxima from Babylon 5 (<https://www.youtube.com/watch?v=bE7lZv6LmrM>). This one is really good because we know why the battle is important, why the battle is going to happen here and not somewhere else, but most importantly we learn who the _people_ are (or at least the captains). They become characters, not just anonymous chits on a map.

Although the Expanse did well in some areas, it had no battles that were as well written or as memorable as this one.

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