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Comment by pdonis | Hacker News Reader

I think the article headline is somewhat misstating the conclusion of the actual paper (linked to by alex_young). The actual paper says the stellar mass density will reach a maximum only 5% higher than its current value. But the stellar mass density is affected by two processes: star formation and star destruction. As the paper notes, the process of star destruction "recycles" some fraction of the mass of the destroyed star, making it available for new star formation. So the stellar mass density reaching a maximum does not mean that all star formation stops, which is what the article headline implies.

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> the stellar mass density is affected by two processes: star formation and star destruction

Hang on, it sounds like you're talking about the total stellar mass, not density. I'm not an astronomer, but assuming they use the normal definition of "density" there are two things that affect it: total stellar mass (which, as you said, can be further broken down into formation and destruction) and the volume it's contained within.

Isn't the universe expanding? (Again, I'm not an astronomer.) If the density is going to remain similar to now then that means that the total stellar mass is going to continue increasing too. That's consistent with what your comment literally says but is quite different from how I think most people would interpret it.

I suppose a better restatement would be:

"The universe has about as many stars as it will ever have."

Still not quite about density but rather count but closer!

Even that isn't necessarily true if big stars are destroyed to make smaller stars.

Agreed, that's what I meant about count vs density. It could have been:

"The universe has about as much star as it will ever have."

That's just confusing, haha.

The top comment already has the term that everyone keeps glossing over: stellar mass density.

The universe has about as much stellar mass density as it will ever have.

This isn't that hard.

That headline is both correct and hard to understand for people who are not into astronomy. I.e. pretty bad for a popular science article.

This is super hard.

On the other hand, this one is incorrect, so it's a bad trade-off no matter how you put it.

Besides, the meaning of "stellar mass density" ought to be obvious to anyone who's gone through high-school level science classes, even if they're not "into" astronomy. Even if that weren't the case, it's pretty easy to look up a simple explanation of the term. I doubt someone who isn't willing to put even that tiny amount of effort into it would even bother reading popular science articles in the first place.

To put it another way: it takes less time and effort to figure it out if you don't know what it means that it takes to even read the article. The overlap between "people reading the article" and "people who don't know what SMD is, can't figure it out from the name, and aren't willing to look it up" is unlikely to be too high.

Optimizing for lazy readers isn't good scientific journalism, it just makes the experience worse for interested readers -- the ones who are willing to do things like pay for a subscription, for example. It's a bad trade-off to make.

Would one expect the average size to change?

I wish there was a way to flag posts as "appropriate for HN but has a wildly misleading headline".

I would imagine some kind of a/b testing algorithms have come up with "wildly misleading headline" => more interest.

If you assume that interestingness of headlines is somewhat randomly distributed, and that for each article there are more misleading headlines than accurate headlines, your relation is bound to be true, even if being misleading by itself doesn't help.

I think the "nautil.us" domain name on the end usually suggests that.

You can email the mods (well, currently just dang) with concerns and/or alternate suggestions (splices from subheads/content are strongly preferred). He's appreciative and responsive. hn <at> ycombinator <dot> com

that's not just somewhat misstating, that's a complete different meaning.

So far our stellar neighborhood is at about 1-2% metal abundance, there's a lot of space for that to go up before stars will stop forming.

Reminded me of this xkcd comic (Cosmologist Genres):

https://xkcd.com/2340/

I think there are two ways to understand that. One is that the total number of stars probably won't ever be much higher (which is iffy, given that I'm not clear if average stellar mass is going to stay the same) and one is that there is very little formation of new stars, so the ones we have right now are all that they're going to be.

I think they were going for the former interpretation and I'm not clear that this interpretation is actually supported by the paper.

Thanks for pointing this out.

> One is that the total number of stars probably won't ever be much higher

I don't see how the article title supports that interpretation. "Has made almost all the stars it will ever make" doesn't seem to me to be consistent with "more stars will continue to be made but the total number of stars won't get any higher".

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