5 ms·

I heard a story about an astronomer loosing the chance to be the first to report a commet one cold winter night - just as he wanted to send the email to report

I heard a story about an astronomer loosing the chance to be the first to report a commet one cold winter night - just as he wanted to send the email to report it, the Internet connection was dead! He ran from the observatory to the nearest place with Internet connectivity, but by the time he sent the email from there, there was already a report from another astronomer elsewhere, a few minutes ago. Reason for the mysterious network outage ? Thermal contraction! The observatory was connected to the Internet via an optical link to a highrise building in the city that contracted ever so slightly due to the very low temperature, moving the laser beam of the optical link out of alignment, shutting down the connection.

bgirard 5y ago
When I started dating my wife she lived in a shared student residence. She would tell me that her internet didn't work when her room was cold. She had to wait for her space heater to heat up the the room. I didn't believe her at first but it turned out be true. She lived there for a year so I observed it several times. Never did find out what the problem is. I don't know if thermal contraction could effect solders between ~10C -> 22C.
- Animats 5y ago
  Yes. Not uncommon with bad soldering jobs. Problems like that can be diagnosed with freeze spray if necessary.[1] [1] https://www.techspray.com/using-freeze-spray-to-diagnose-faulty-electronics https://www.techspray.com/using-freeze-spray-to-diagnose-fau...
- ethbr0 5y ago
  We had it on a copper cable line in university. The line was hung overly-tight without slack (old job). When it got just cold enough in the winter: no connection. Warmed up: connection. Finally realized it was the line, got Comcast to redrop from pole, and situation was resolved.
- TheOtherHobbes 5y ago
  Yes, and not at all unusual. The gap between the ideal world of textbook circuits and the messy and random world of real circuits is a source of constant distraction and surprise. Thermal stresses, RF interference, issues caused by lighting, rain, and condensation, bad solder joints, other kinds of temperature sensitivity, designs with marginal component tolerances, component drift over time, vibration sensitivity, strange failure modes in damaged ICs, timing issues, power supply noise, coupling between circuit tracks and/or adjacent wiring, logic errors due to radiation (sometimes from surrounding metal), dust, insects, and animal damage - and on and on.
- stephen_g 5y ago
  Some electronic parts are not rated to work below 0° C - for ‘commercial’ equipment the range is usually 0° to 50°C, and you often have to pay extra to get ‘industrial’ or extended range versions of parts that have ranges like -45° to 85°C (some fairly common parts you can even get to 105°C). It it’s failing at 10°, I’d suspect there is a crack in a PCB somewhere or a badly soldered joint that isn’t actually making proper contact until there’s some thermal expansion. We don’t do anything special with the PCBs or soldering specifically, and all the stuff we make is tested down to -35° and up to 55°C with no issues…
walrus01 5y ago
one of the reasons why free space optics gigabit and 10GbE ethernet laser based links are a tiny niche product in the ISP space, millimeter wave (71-86 GHz) fills the purpose much better. also they don't do as well in rain as something that can adapt modulation.
- m4rtink 5y ago
  Yeah, that is likely why terrestrial FSO seems to be mostly dead these days as far as I can tell. Even back then there used to be a backup RF link in case of fog - why not have a proper RF link instead, especially if its going to be much better due to all the money dumped into RF technology in comparison to free space optics.
treeman79 5y ago
In college we had a transmitter that linked several campuses. If internet went out on any campus we would go and replace the lightbulb left on the transmitter. A couple minutes later all would be good.

bgirard 5y ago

When I started dating my wife she lived in a shared student residence. She would tell me that her internet didn't work when her room was cold. She had to wait for her space heater to heat up the the room. I didn't believe her at first but it turned out be true. She lived there for a year so I observed it several times. Never did find out what the problem is. I don't know if thermal contraction could effect solders between ~10C -> 22C.

Animats 5y ago
Yes. Not uncommon with bad soldering jobs. Problems like that can be diagnosed with freeze spray if necessary.[1] [1] https://www.techspray.com/using-freeze-spray-to-diagnose-faulty-electronics https://www.techspray.com/using-freeze-spray-to-diagnose-fau...
ethbr0 5y ago
We had it on a copper cable line in university. The line was hung overly-tight without slack (old job). When it got just cold enough in the winter: no connection. Warmed up: connection. Finally realized it was the line, got Comcast to redrop from pole, and situation was resolved.
TheOtherHobbes 5y ago
Yes, and not at all unusual. The gap between the ideal world of textbook circuits and the messy and random world of real circuits is a source of constant distraction and surprise. Thermal stresses, RF interference, issues caused by lighting, rain, and condensation, bad solder joints, other kinds of temperature sensitivity, designs with marginal component tolerances, component drift over time, vibration sensitivity, strange failure modes in damaged ICs, timing issues, power supply noise, coupling between circuit tracks and/or adjacent wiring, logic errors due to radiation (sometimes from surrounding metal), dust, insects, and animal damage - and on and on.
stephen_g 5y ago
Some electronic parts are not rated to work below 0° C - for ‘commercial’ equipment the range is usually 0° to 50°C, and you often have to pay extra to get ‘industrial’ or extended range versions of parts that have ranges like -45° to 85°C (some fairly common parts you can even get to 105°C). It it’s failing at 10°, I’d suspect there is a crack in a PCB somewhere or a badly soldered joint that isn’t actually making proper contact until there’s some thermal expansion. We don’t do anything special with the PCBs or soldering specifically, and all the stuff we make is tested down to -35° and up to 55°C with no issues…

walrus01 5y ago

one of the reasons why free space optics gigabit and 10GbE ethernet laser based links are a tiny niche product in the ISP space, millimeter wave (71-86 GHz) fills the purpose much better. also they don't do as well in rain as something that can adapt modulation.

m4rtink 5y ago
Yeah, that is likely why terrestrial FSO seems to be mostly dead these days as far as I can tell. Even back then there used to be a backup RF link in case of fog - why not have a proper RF link instead, especially if its going to be much better due to all the money dumped into RF technology in comparison to free space optics.

treeman79 5y ago

In college we had a transmitter that linked several campuses. If internet went out on any campus we would go and replace the lightbulb left on the transmitter. A couple minutes later all would be good.