Others, like Pets.com, didn't make it. But 20 years ago this week, in an office at NASA's Goddard Space Flight Center in Greenbelt, Maryland, gamma ray astronomers Robert Nemiroff and Jerry Bonnell created a simple website that still thrives today: the Astronomy Picture of the Day , or APOD.

It's not that easy, right? As someone who was around for the arrival of the World Wide Web, even I have trouble remembering what was around in those early days. Google didn't start until 1997. Angelfire and Craigslist launched in 1996.

Try to name as many websites as you can that are more than 20 years old.

APOD has been around longer than Google or Craigslist APOD serves its titular purpose with minimal flare. Every day — the site updates at 12AM ET — there's one featured image (or video) of our cosmos. That's accompanied by a short description with some links for anyone who wants to dig a little deeper. The site is available in 20 languages, has a Twitter account with a million followers, a Google+ page — don't scoff, the astrophotography community actually thrives there — with over 900,000 fans, and nearly 200,000 likes on Facebook. There's an Instagram account, countless apps, and there's even a dedicated subreddit. All that helps account for more than 1 million visits to the APOD website each day – a far cry from the first day 20 years ago when it barely cracked a dozen. APOD launched on June 16, 1995. In advance of its milestone birthday, I spoke on the phone with the two guys who have run the site by hand for two decades, a seemingly unfathomable task in the age of ephemeral content. How do they do it? A combination of Microsoft Word, a fiery passion for astrophotography, and lots and lots of emails. This interview has been lightly edited for length and clarity.

So where did the idea originally come from? Robert Nemiroff: Jerry Bonnell and I shared an office at NASA Goddard Space Flight Center, and we were both — we’re still — active researchers. But the web was growing up, and so we brainstormed to try to figure out how we could contribute to this web. One idea, we thought, was maybe we can make lots of money, and buy a Hawaiian island or something. But that never worked out. [Laughs.] So we were getting these emails that had these image attachments, sometimes about the Hubble Space Telescope, sometimes from something else, and the people sending these emails had no idea what that was. It would say, "Look at this, it’s colorful and something astronomical. Isn’t that cool?" So we thought maybe something we could do was take these images and explain them one after the next. Jerry Bonnell: When Bob and I started doing APOD we were both gamma ray astronomers. We were working in an energy regime that’s way beyond visual wavelengths [of light]. So we have a very broad concept of what an "image" might be, and I think we’ve translated that to some degree into APOD. I’m still impressed at the imaging we can do beyond the visual spectrum. I’m always on the lookout for a picture that you could never see with your eyes. Under the hood, how does APOD work? Robert Nemiroff: I just open up Microsoft Word on my PC. I bring up the text file from an old APOD post from a couple of days ago. I delete out the old stuff, I put the new stuff in, then I transfer it to [the network at] NASA Goddard and I look it over, and with the VI editor I make changes, because I almost always make some kind of mistake somewhere. And then I look at the result and see if it looks reasonable, and if so then I just leave it alone.

On the left, the first ever APOD post. On the right, a recent one from June of 2015.

The design of the site really hasn't changed much at all. It reminds me of Craigslist; it serves a purpose so well that it doesn't need to look any different. Robert Nemiroff: Maybe a couple times a year we get emails from somebody who says, "I’m a web designer, your page is out of date. Don’t worry, I’ll do it for free!" And so far we’ve declined all those requests, because it’s functional. We’re translated into 20 different languages, and there’s also apps and things like that that read our files. If we were to change our structure it would cause a domino effect down the line. It’s just simple. There’s one image, and that’s the image of the day. It’s pretty much been the same since 1995. You might notice the 1995 ones the picture’s not centered, because there was no center tag. So we did upgrade to the center tag. But we haven’t done much else. "That was a breakthrough for me in HTML coding, when I learned how to center something." Jerry Bonnell: Boy that was a breakthrough for me in HTML coding, when I learned how to center something. The design has evolved very little. I like the idea that it’s very simple, it’s still very bytes-small. What kind of routine do you maintain to update the site daily? Robert Nemiroff: I usually do the beginnings of the weeks and Jerry does the ends of the weeks, and Wednesday can go either way. I will do several in a row. I’ll do most of my week maybe on Thursday or Friday, sometimes on Saturday or Sunday. Sometimes I’ll leave Wednesday to the night before in case there’s some kind of breaking news. Jerry will do the ends of the weeks, he usually waits until the night before, and works on it during the afternoon. Both Jerry and I, we surf the web all the time anyway incessantly, we can’t stop it. If APOD was to die tomorrow we would still be surfing the web and saying, "Oh, that’s a cool astronomy image." So I’ve accumulated some that I’ve seen, many were submitted. People submit a lot of images. Jerry Bonnell: I get ideas at all times, and I try to pay attention to things coming in and what’s going on in astronomy. Ideas tend to present themselves. I would say it’s unusual to have things queued up a week in advance. We usually run only a few days in advance. But that’s one of the things that I’ve enjoyed and still enjoy about APOD over the years. Robert Nemiroff: If, however, there’s a very topical image that comes out, then it’s understood that either of us will stop what we’re doing and work until they’ve created an APOD post based on that image, move it over to NASA Goddard, and then it will be in the queue for the "robot" to update at midnight Eastern time. Do you have a favorite type of image that you look forward to seeing on the site? Robert Nemiroff: I just like the stuff where you look at it and say "Wow, what’s that!" I’m somewhat jaded after 20 years. It has to work for me before I try to make it work for other people. Jerry Bonnell: I seem to be a sucker for the big, beautiful spiral galaxy images. How does the process of searching for the right image compare to 20 years ago? Jerry Bonnell: We used to use the pretty pictures that came from observatories and NASA, stuff like that, for the picture of the day. But now I think it’s much more heavily weighted toward the amateur communities and non-institutional imaging. We get tons of images submitted, so now I have to spend much of my day looking through my email, whereas it didn’t used to be that way. I used to have to be more proactive. I would explore what was online and available in the NASA archives online, and I would also make occasional trips to photo libraries that I could find at Goddard and NASA headquarters and look at the prints.