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Comment by t-writescode | Hacker News Reader

When trying to describe sizes and scale, having a reference that one of their readers would be able to go "oh, ... that size, huh?" is useful. There's a meme about "Americans will use anything but the metric system" when describing buildings as "100 school buses back to back" or "3 football fields"; but it's to make numbers real and relatable.

If the article said "500km", someone in the comments would go "that's about as wide as Germany!" or similar.

And, since it was km -> "state size", it was almost certainly for the American audience, since they would have used something like the size of Germany for a European, or "twice the size of South Korea" or something.

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For science education, I am strongly for using the units directly to describe everything at first, with these looser comparisons in brackets, rather than inline prose. So I would've instead said, 'is 500 km in diameter (roughly the size of Ohio, or Germany from East to West)'. For extremely large or small values I would use scientific notation only, and expect my audience to understand it, because I'd expect their education to be up to mark.

You said these comparisons are made to make things real or relatable; I personally would expect more out of my audience and give them the magnitude and units directly. I'm not writing for a tabloid; having a strong grounding in units understanding without needing to relate to daily phenomena is in my view critical to not making apparently trivial mistakes that can potentially lead to horrible disasters.

When has there ever been a horrible disaster in space exploration because of units? ;)

https://everydayastronaut.com/mars-climate-orbiter/

Although, as it turns out, "orbiter" was a poor choice of name.

Yeah, that was the joke, but a link is good for people who are unaware!

> they would have used something like the size of Germany for a European, or "twice the size of South Korea" or something

I don't have a concrete proof, just a gut feeling, but I think that this kind of comparisons are much more common in texts written by Americans and for Americans than in any other culture, that's why:

> There's a meme about "Americans will use anything but the metric system" when describing buildings as "100 school buses back to back" or "3 football fields"

>I don't have a concrete proof, just a gut feeling, but I think that this kind of comparisons are much more common in texts written by Americans and for Americans than in any other culture, that's why:

Those filthy new worlders and their propensity to make technical writing parsable by the unwashed masses. If the masses want to understand science they should just go to Oxford or whatever.

Just an observation, I didn't mean to say that it is bad. It's a bit grating, if you are not used to it, but there are no real harm to it, when an actual number is just one Wikipedia search or one Google search or, sigh, one chatbot prompt away.

There is much to be said about the irony in said New Worlders refusing to get with the programme, and instead obstinately clinging to an ancient, Babylonian-Roman-Anglo-Saxon-Viking hodge-podge of units instead of something modern and universal.

> make technical writing parsable by the unwashed masses

> If the masses want to understand science they should just go to Oxford

This is a bad strawman. I learnt scientific notation in secondary school. I expect most educated people to understand what is meant by '1.5 × 10^8 km' in an instant. If they don't, then honestly, skill issue, and it is a big indictment of their parent country's education system.

The correct compromise would be "500km diameter, about the size of Ohio"

This is moderately misleading in some ways, but illustrative enough and also technically valid if somebody wants to model it accurately.

> This is moderately misleading in some ways

I think that this is more than moderately misleading, because it is ambiguous:

- if they meant "diameter is similar to Ohio dimensions", they are a little bit off, because Ohio is about 355*355 km and Enceladus diameter is around 500km

- if they meant surface area, then they are very off, because Ohio is 116,096 km^2 while Enceladus is about 800,000 km^2. In this case it would be more accurate to say that it is bigger then Texas, but smaller than Alaska (if we want to use US states for comparison)

> - if they meant "diameter is similar to Ohio dimensions", they are a little bit off, because Ohio is about 355*355 km and Enceladus diameter is around 500km

I think they used the diagonal of a hypothetical square Ohio: sqrt(355^2 + 355^2) ≈ 502 km.

The classical definition of diameter of a set is "the largest possible distance between two points". So in this sense your square Ohio has a diameter of 502 km.

(It is still misleading to compare it to the diameter of an almost-spherical object, I agree. Especially because moving on the surface of a sphere it takes much longer than 502 km to walk from one point to the antipodal one.)

If so, they passed up the opportunity to make another dumb Ohio joke:

"Ohio isn't actually square, though you wouldn't know that from talking to the inhabitants" or some such.

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