Vaguely related - this reminded me of a support call I had where similarly the real world apparently merged into the digital world.<p>I was doing IT support for a small Australian company back in '98. A guy called me from a remote office, and after a few pleasantries he explained that the screen saver had fallen off the monitor of his dumb terminal, bounced on one of the keys on his keyboard, and now terminal was locked up. He wanted to know what key to press to unlock the terminal.<p>Eh?<p>I knew the guy, and although he wasn't trained in IT, he knew his way around the basics, he wasn't completely clueless.<p>I asked him to explain the problem again as I wasn't sure I'd understood. He repeated exactly what he'd said the first time.<p>I replied "What do you mean the screen saver fell off the monitor, that's impossible? Besides, it's a dumb terminal, they don't have screen savers."<p>After a little more fumbling around this weird upside-down world he was presenting me with, it suddenly clicked. He was talking about the physical CRT anti-glare screen filter [0] that used to be common around then, that literally hung in front of the screen. This has come unstuck and hit the scroll lock on the terminal. He called this a screen saver.<p>Since then the phrase "Screen saver" seems to have now morphed to mean what I used to call a desktop wallpaper, but that's a separate topic.<p>[0] <a href="https://dylbs6e8mhm2w.cloudfront.net/productimages/500x500/EJ1013042011.JPG" rel="nofollow noreferrer">https://dylbs6e8mhm2w.cloudfront.net/productimages/500x500/E...</a>
I love this kind of stuff. When you're sure the thing that seems to be happening couldn't possibly be happening, and then you find out that literally the speed of light is coming into play.<p>We had a similar problem at one of my first jobs where I was a programmer and backup network support guy. One employee was having a problem with his CRT monitor flickering. It was very subtle, but just enough to drive him nuts.<p>So we replaced the monitor with one that worked fine on another machine. Same problem. We tried replacing cables, power cords, and did a bunch of other troubleshooting things. Problem persisted. Eventually we replaced his entire computer. Same problem.<p>Finally I put his computer and monitor on a cart with an extension cord and wheeled it out into the hallway. The problem went away. It turned out to be bad electrical shielding in his office.
The best part - the consultant who patched the server is on Hacker News! He commented on his part here:<p><a href="https://news.ycombinator.com/item?id=23775404">https://news.ycombinator.com/item?id=23775404</a>
Somewhat related but not really. Back in 2007 when I worked for a large ISP as a second line support technician for various services, ADSL was very much still in vogue. And the technology, over copper wire, had a max distance of where it would be stable. Some clients were on a special plan that tried to up this distance by a bit, maybe 2-3 more km but really it was still quite unreliable but still usable for browsing the internet, generally.<p>But during the summer I received a call from a client that had been unable to use his IPTV service during the day for almost a month without hickups and disturbances and his internet was slow as a glacier from time to time and as I was measuring the equipment, packet loss and all the usual stuff it struck me that he was very far away from his nearest telephone station. After some back and forth with a technician and lots of measuring we came to the conclusion that since it was so hot out during that summer the line just expanded over to a distance that was just far away enough that the line would become unstable during daytime when it became hotter outside.<p>We could not really do anything to help him. I do not miss the copper net.
tangentially related: 15 or maybe 20 years ago i worked at a repair shop and someone brought in a TV that they said switched to spanish every night at 5pm.<p>they were watching over the air channels and there was only a setting in the tv for menu language. sure enough though, at 5pm that night we watched as the tv started speaking in spanish. we tried a few more channels and found that all but one or two were in spanish.<p>as it turns out, some stations broadcast audio in multiple languages and some tvs allow you to change the preference. sadly for this person, the used tv they bought came from a spanish speaking country and didn't have anyway to change that preference.
Ah, the true mother of all leaky abstractions:<p>The actual underlying transmission protocol of the relativistic universe shining through when trying to send an email.
Great story!<p>At lunch today I was just talking about Sendmail, which I can assure you is a rather rare occurrence. I was talking about the first time I set up sendmail, back in '91 or '92. I was using the bat book and nearly tore my hair out over a week getting that first setup working. I eventually came to understand and appreciate the m4 config, but I ended up moving to qmail and postfix in the mid '90s and never looked back.
This sort of kind should be [1997] rather than 2002, but then even Trey can't remember: <a href="https://www.ibiblio.org/harris/500milemail-faq.html" rel="nofollow noreferrer">https://www.ibiblio.org/harris/500milemail-faq.html</a>
Related. Others?<p><i>The case of the 500-mile email (2002)</i> - <a href="https://news.ycombinator.com/item?id=29213064">https://news.ycombinator.com/item?id=29213064</a> - Nov 2021 (93 comments)<p><i>We can't send email more than 500 miles (2002)</i> - <a href="https://news.ycombinator.com/item?id=23775404">https://news.ycombinator.com/item?id=23775404</a> - July 2020 (135 comments)<p><i>500 miles (2002)</i> - <a href="https://news.ycombinator.com/item?id=18675375">https://news.ycombinator.com/item?id=18675375</a> - Dec 2018 (32 comments)<p><i>The case of the 500-mile email (2002)</i> - <a href="https://news.ycombinator.com/item?id=14676835">https://news.ycombinator.com/item?id=14676835</a> - July 2017 (56 comments)<p><i>The 500-mile email (2002)</i> - <a href="https://news.ycombinator.com/item?id=9338708">https://news.ycombinator.com/item?id=9338708</a> - April 2015 (139 comments)<p><i>The case of the 500-mile email</i> - <a href="https://news.ycombinator.com/item?id=2701063">https://news.ycombinator.com/item?id=2701063</a> - June 2011 (18 comments)<p><i>The case of the 500-mile email</i> - <a href="https://news.ycombinator.com/item?id=1293652">https://news.ycombinator.com/item?id=1293652</a> - April 2010 (24 comments)<p><i>The case of the 500-mile email</i> - <a href="https://news.ycombinator.com/item?id=385068">https://news.ycombinator.com/item?id=385068</a> - Dec 2008 (28 comments)<p><i>The case of the 500-mile email</i> - <a href="https://news.ycombinator.com/item?id=123489">https://news.ycombinator.com/item?id=123489</a> - Feb 2008 (7 comments)
I've wondered how feasible it would be to do something like this to have a website that could only be accessed when a client is within a certain physical proximity of the host. Could make for a fun CTF!
i think about this story often and i find that the person who figured out that it was 500 miles actually deserves more credit than they get in the story. have to really think out of the box to figure that one
Every time I read this story the part that always surprises me again is the units command. Converting from 3 millilightseconds to miles is brilliant, and I am delighted every time that the units command can do this.
Also relevant here is the FAQ the author wrote about this story: <a href="https://www.ibiblio.org/harris/500milemail-faq.html" rel="nofollow noreferrer">https://www.ibiblio.org/harris/500milemail-faq.html</a><p>(Tries to answer a lot of the questions folks have in the comments, so definitely a good /F/AQ!)
I did a startup making a mp3 player that was attached to whole house audio distribution systems.
We got an angry email from a customer saying he woke up to ABBA playing full blast at 3:00am. While it was likely an integration/timer issue, he was wondering 'why ABBA? what is the player trying to tell me?"<p>The control system was sending 'play' with nothing else, which was more of an edge case based on our UI, and so it started at the beginning of the list of artists, and ABBA was at the beginning of that list.<p>Other players might have started at the beginning of the list of songs, but for some reason (25 years ago) we chose the beginning of the list of artists.
Later on it was configurable - random, favorite playlist, etc.
There is a blog created to collect similar stories: <a href="https://500mile.email/" rel="nofollow noreferrer">https://500mile.email/</a><p>This blog has also been discussed in a few other threads:<p><a href="https://news.ycombinator.com/item?id=23908171">https://news.ycombinator.com/item?id=23908171</a><p><a href="https://news.ycombinator.com/item?id=29215383">https://news.ycombinator.com/item?id=29215383</a><p><a href="https://news.ycombinator.com/item?id=35708339">https://news.ycombinator.com/item?id=35708339</a>
Does this add up? If the connection timeout is 3ms, then that means there's 3ms for a roundtrip, 1.5ms each way. So the maximum distance would actually be roughly 250 miles. But even then, packets don't actually travel at the speed of light in fiber optic cables. It also assumes that the cables are laid as the crow flies, which they aren't.
My memory is vague. Anyone remember the related one about wife reporting some office app won't print on $day?<p>edit: here it is <a href="https://bugs.launchpad.net/ubuntu/+source/cupsys/+bug/255161/comments/28" rel="nofollow noreferrer">https://bugs.launchpad.net/ubuntu/+source/cupsys/+bug/255161...</a>
Fun read! Along the way I was trying to guess the cause and my best guess was TTL-related. However I don’t quite understand the actual cause! If the connection timeout is 3ms in practice, shouldn’t that be for a packet round-trip? So ~250 miles? And wouldn’t we expect at least a small delay on the remote SMTP server to process the packet?
I love these sort of debugging stories! It sounds like that timeout would be based on the round trip travel time to the remote host rather than the one way distance, wouldn’t that make a 250 mile cutoff?
Does anybody think that limiting email to 500 miles might be a Good Thing?<p>I don’t have a very well-formed use-case in mind, but I strongly suspect there is one: suggestions welcome.
Here is the guy who came up with this: <a href="https://www.linkedin.com/in/treyharris" rel="nofollow noreferrer">https://www.linkedin.com/in/treyharris</a><p>And here is the other webpage that has this article: <a href="https://www.ibiblio.org/harris/500milemail.html" rel="nofollow noreferrer">https://www.ibiblio.org/harris/500milemail.html</a>
I don’t get why this story is so popular here. None of the technical details adds up.<p>Multiple back and forth due to protocol handshakes and router delays would add enough latency to prevent any connection from happening at all if the timeout was set to 0 as stated.<p>I guess people just like the “it was the time light took to travel” vibe.
_The_ classic CS story (I personally think! ;) <3 :')))) ;'D). I think it will be hard to beat this one. :')<p>Ah, the good ol' days....Wait, no, we're still living in 'em now! Just go to the edge of a quiet, non-hypey, but still expanding field.<p>Tons of fun. ;)))) <3 <3 <3 <3 :)
For those on a Mac the millilightseconds unit probably won't work, in which case you can try:<p><pre><code> 586 units, 56 prefixes
You have: 3 lightyear / 365.25 / 24 / 60 / 60 / 1000
You want: miles
* 558.83525
/ 0.0017894361</code></pre>
I have a story from my current workplace which threw me and the other IT staff for a loop.<p>Get a support ticket from one of the staff saying that the screen of their laptop keeps "going black" when they are using the computer. So I set up a time to take a look and ventured away from my desk to see what's going on.<p>It's worth noting that this is a laptop, less notable is that it is a shared device as different people work this shift, regardless, all the staff that share it are adamant it only happens with this one user. So I asked them to demonstrate, they open a browser and start typing, sure enough after a sentence or two the screen goes black and the machine locks / goes to sleep.<p>I ask to take a look at the laptop and log back in, open notepad and start banging away on the keyboard like a cracked out chimpanzee, nothing happens. I hit every key on the keyboard, double checked hotkey / function keys, can't get it to happen. Now I had written a small exe for our staff that locks their workstations when unplugging their security keys and killed it just to make sure that wasn't causing issues, nope that's not it.<p>Then they tell me they even swapped laptops and the problem follows this user... So I blow out the user profile and log them back in and let it sync again, issue still persists. Now I am watching them type like a hawk trying to see if I can spot what key sequence or wizardry is happening to cause this issue.<p>I can't find any reason that makes sense, when I check the event logs it just says "Machine sleep due to lid closure or button press". Happens on 2 different laptops so it's unlikely to be a faulty lid switch or loose / sticky button. I notice a bracelet on this persons wrist and joke about it not being a super magnet or something and she laughed and said no, but it does use a magnet to hold it together.<p>I didn't think much of it at the time and ventured back to my office defeated and confused. I am going over the issues with one of my co-workers and mention the machine sleep due to lid closure or button press, then something clicked. We grabbed a spare nametag with a magnet and started waving it around the same model laptop surfaces and sure as shit the screen goes black and it goes to sleep.<p>The magic spot on this laptop was to the right of the trackpad, the user wore the magnetic jewelry on their right wrist and when they arranged their hands just right it triggered the lid closure sensor which on these models uses a magnet in the lid.<p>In real life this issue persisted for a few weeks before we figured out what was going on, I thought I was going crazy though when it was happening.
<p><pre><code> "You waited a few DAYS?" I interrupted, a tremor tinging my voice. "And
you couldn't send email this whole time?"
"We could send email. Just not more than--"
"--500 miles, yes," I finished for him, "I got that. But why didn't
you call earlier?"
"Well, we hadn't collected enough data to be sure of what was going on
until just now." Right. This is the chairman of *statistics*. "Anyway,
I asked one of the geostatisticians to look into it--"
"Geostatisticians..."
"--yes, and she's produced a map showing the radius within which we can
send email to be slightly more than 500 miles.
</code></pre>
Pure gold. I love that the stats department put in such rigorous testing before submitting the ticket.
This excellent tale has appeared many times on HN; here's dang, in 2021, listing some of the past threads:<p><a href="https://news.ycombinator.com/item?id=29213472">https://news.ycombinator.com/item?id=29213472</a>