7 ms·

As it's not directly explained on the link, I'll ask here... How/Why is it still burning? I have light bulbs in my house that blow after only a few months use,

As it's not directly explained on the link, I'll ask here... How/Why is it still burning? I have light bulbs in my house that blow after only a few months use, and normally only blow when I turn them on, if this bulb was power cycled, would it blow?

dvh 5y ago
Every time you increase temperature by 10 degree, it shorten the lifespan of electric device by 50%. If you run device that was meant to run at 4600°C at 600°C, well you do the math...
arcticbull 5y ago
Modern lightbulbs use thinner filaments that are substantially more efficient than the thick one used in this bulb, but they don't last as long. Further, this particular bulb never gets turn off and back on again which I'm led to believe causes wear. If it were turned off and back on it would likely be fine. Always a fun segue into the Phoebus Cartel [1] which pushed for shorter lifespans for bulbs - including by mandating thinner filaments. They did it to keep people on the treadmill but it was actually a substantial improvement in energy efficiency. [1] https://en.wikipedia.org/wiki/Phoebus_cartel https://en.wikipedia.org/wiki/Phoebus_cartel
- edb_123 5y ago
  I also do think that the filament thickness has a lot to say for longevity. I have a "decor type" large warm glowing light bulb with a quite thick and long filament that's been on for hours daily and turned on and off multiple times daily for 10 years now and counting. And yes, it is a real incandescent bulb, not LED :)
  - CelestialTeapot 5y ago
    The same game is still played today with LED bulbs (whether there's a cartel behind it or not, I do not pretend to know). See: https://www.youtube.com/watch?v=klaJqofCsu4 https://www.youtube.com/watch?v=klaJqofCsu4
kbutler 5y ago
Some factors: - low voltage (below spec) - constant on, instead of cycling - strong element - backup power - generally a protected environment
thescriptkiddie 5y ago
Incandescent light bulbs have a trade-off between brightness and longevity. This bulb specifically appears to be running at a fraction of its original designed brightness. https://www.mercurynews.com/2011/02/03/tests-shine-light-on-the-secret-of-the-livermore-light-bulb/ https://www.mercurynews.com/2011/02/03/tests-shine-light-on-...
biggieshellz 5y ago
The carbon filament has gotten thin enough that it runs at a lower temperature and doesn't draw much current (or produce as many lumens), so it doesn't wear out as quickly.
longwave 5y ago
The bulb was accidentally off for nine hours in May 2013 due to a faulty UPS - originally installed to ensure the bulb would not go out in the case of a power failure - but fortunately it did not blow when power was restored.
giantrobot 5y ago
Besides the other great answers, there's also survivorship bias. This bulb wasn't necessarily designed to last a hundred years. It's just an outlier that has lasted that long. We wouldn't give a shit about it had it burned out fifty years ago. We don't talk about other bulbs (today) that lasted fifty years even though that's an extremely impressive number itself. If the Internet was around fifty years ago we might have half a dozen webcams pointing to the "Half Century Bulbs" and being fascinated with them lasting fifty years and wondering if any will get to a hundred years.
- jbay808 5y ago
  "Survivorship bias" is a favourite go-to for contrarians, but it's not a strong effect and when you see something surprising way out at the tail end of a distribution, attributing it to survivorship bias is a lost opportunity to learn something important. When something survives 2x longer than expected, it might be survivorship bias. When it survives 10x, 100x, or 1000x longer than expected, you should probably look closer and see what material or operational differences might be responsible, because there's going to be something worth learning. Even if what you learn is just that any incandescent lightbulb can have a greatly extended life if you run it at below-spec brightness.
  - giantrobot 5y ago
    When you have an outlier like this bulb you can't make any good statistical judgements about it unless it was part of a controlled experiment. This bulb is a sample size of one. We might roughly know some details about its original construction and early operational life but not enough to really draw conclusions from. The only way to get more details about it will be a postmortem examination of its physical qualities. Due to its age we have little knowledge of its specific construction details. Were the factory specs followed exactly (or even recorded) or was some of the fabrication machinery tuned by the operator? Did this bulb end up with thicker than normal glass or filament? What was the mortality rate of other bulbs in its batch? Does the fire station have better (or worse) than typical wiring? Did it have bad wiring early in the bulb's life to unintentionally under-load it? Sometimes extreme outliers are just extreme outliers. A postmortem examination of the bulb might tell you it had a manufacturing defect giving it thicker than typical filament that combined with babying it for the past 50 years extended its life. Sorry it's not just being contrarian. Outliers are outliers. Just because something is an outlier in a distribution doesn't automatically mean there's some hidden truth of the universe to be revealed.
devindotcom 5y ago
As I understand it the issue with ordinary incandescents is that the alternating heat and cold from being used eventually causes the glue attaching the glass to the metal part to crack, which lets air into the bulb (ordinarily a vacuum/inert gas). The next time you turn it on, the air causes the filament to burn, causing the characteristic flare-up and scorch.
- MisterTea 5y ago
  Er, that glue only holds the glass bulb in the socket. The atmosphere contained within is completely glass sealed. What happens is the filament sputters away (like evaporation) and becomes thinner over time. It eventually becomes so thin it breaks from thermal shock when turned on. The dark spot on dead bulbs in the evaporated tungsten. Fun fact: In theater a blown bulb can ruin a production so some of the more critical lamps are dimmed instead of power cycled to avoid blowing a lamp.
  - devindotcom 5y ago
    Really? I was under the impression that the glass isn't a fully enclosed "bulb" so to speak, but is cut off at one end to accommodate the rest of the necessary hardware, and glue completes the seal. Perhaps you're right. I can't seem to find a diagram or anything that shows this, though.
    - MisterTea 5y ago
      If you examine a clear incandescent bulb, you will see that the support for the filament is hollow and has a tube inside extending down. This little "straw" is the point of connection for evacuation where the air is removed and then back-filled with argon. The argon coaxes the tungsten back onto the filament preventing rapid sputtering which would happen in a pure vacuum. After the argon the little tube is heated until it hits melting point and crimped off for a near perfect hermetic seal. The argon pressure is still well below atmosphere so the bulb is still considered under "vacuum" compared to atmosphere.
    - xenadu02 5y ago
ars 5y ago
The simple reason is that it's not a light bulb, it's a heater. They are running it at much lower than specified voltage, so are generating mostly heat, and almost no light, so the filament is not very hot. It's glowing a dull red, not white. There is a quadratic relationship between temperature; and efficiency plus bulb life. You may have heard of the phoebus cartel - they specified a specific bulb life, which directly translates into a particular energy efficiency. There's nothing about the manufacture of the bulb that they casued to be worse, rather if the bulb lasts too long, you just up the temperature and make a more efficient bulb (uses less electricity). You can buy stage bulbs that last barely 10 hours, and run extremely hot, and also efficient, and for film that is the tradeoff they prefer (I guess they need a lot of light, and they don't really keep bulbs for long).

dvh 5y ago

Every time you increase temperature by 10 degree, it shorten the lifespan of electric device by 50%. If you run device that was meant to run at 4600°C at 600°C, well you do the math...

arcticbull 5y ago

Modern lightbulbs use thinner filaments that are substantially more efficient than the thick one used in this bulb, but they don't last as long. Further, this particular bulb never gets turn off and back on again which I'm led to believe causes wear. If it were turned off and back on it would likely be fine. Always a fun segue into the Phoebus Cartel [1] which pushed for shorter lifespans for bulbs - including by mandating thinner filaments. They did it to keep people on the treadmill but it was actually a substantial improvement in energy efficiency. [1] https://en.wikipedia.org/wiki/Phoebus_cartel https://en.wikipedia.org/wiki/Phoebus_cartel

edb_123 5y ago
I also do think that the filament thickness has a lot to say for longevity. I have a "decor type" large warm glowing light bulb with a quite thick and long filament that's been on for hours daily and turned on and off multiple times daily for 10 years now and counting. And yes, it is a real incandescent bulb, not LED :)
- CelestialTeapot 5y ago
  The same game is still played today with LED bulbs (whether there's a cartel behind it or not, I do not pretend to know). See: https://www.youtube.com/watch?v=klaJqofCsu4 https://www.youtube.com/watch?v=klaJqofCsu4

kbutler 5y ago

Some factors: - low voltage (below spec) - constant on, instead of cycling - strong element - backup power - generally a protected environment

thescriptkiddie 5y ago

Incandescent light bulbs have a trade-off between brightness and longevity. This bulb specifically appears to be running at a fraction of its original designed brightness. https://www.mercurynews.com/2011/02/03/tests-shine-light-on-the-secret-of-the-livermore-light-bulb/ https://www.mercurynews.com/2011/02/03/tests-shine-light-on-...

biggieshellz 5y ago

The carbon filament has gotten thin enough that it runs at a lower temperature and doesn't draw much current (or produce as many lumens), so it doesn't wear out as quickly.

longwave 5y ago

The bulb was accidentally off for nine hours in May 2013 due to a faulty UPS - originally installed to ensure the bulb would not go out in the case of a power failure - but fortunately it did not blow when power was restored.

giantrobot 5y ago

Besides the other great answers, there's also survivorship bias. This bulb wasn't necessarily designed to last a hundred years. It's just an outlier that has lasted that long. We wouldn't give a shit about it had it burned out fifty years ago. We don't talk about other bulbs (today) that lasted fifty years even though that's an extremely impressive number itself. If the Internet was around fifty years ago we might have half a dozen webcams pointing to the "Half Century Bulbs" and being fascinated with them lasting fifty years and wondering if any will get to a hundred years.

jbay808 5y ago
"Survivorship bias" is a favourite go-to for contrarians, but it's not a strong effect and when you see something surprising way out at the tail end of a distribution, attributing it to survivorship bias is a lost opportunity to learn something important. When something survives 2x longer than expected, it might be survivorship bias. When it survives 10x, 100x, or 1000x longer than expected, you should probably look closer and see what material or operational differences might be responsible, because there's going to be something worth learning. Even if what you learn is just that any incandescent lightbulb can have a greatly extended life if you run it at below-spec brightness.
- giantrobot 5y ago
  When you have an outlier like this bulb you can't make any good statistical judgements about it unless it was part of a controlled experiment. This bulb is a sample size of one. We might roughly know some details about its original construction and early operational life but not enough to really draw conclusions from. The only way to get more details about it will be a postmortem examination of its physical qualities. Due to its age we have little knowledge of its specific construction details. Were the factory specs followed exactly (or even recorded) or was some of the fabrication machinery tuned by the operator? Did this bulb end up with thicker than normal glass or filament? What was the mortality rate of other bulbs in its batch? Does the fire station have better (or worse) than typical wiring? Did it have bad wiring early in the bulb's life to unintentionally under-load it? Sometimes extreme outliers are just extreme outliers. A postmortem examination of the bulb might tell you it had a manufacturing defect giving it thicker than typical filament that combined with babying it for the past 50 years extended its life. Sorry it's not just being contrarian. Outliers are outliers. Just because something is an outlier in a distribution doesn't automatically mean there's some hidden truth of the universe to be revealed.

devindotcom 5y ago

As I understand it the issue with ordinary incandescents is that the alternating heat and cold from being used eventually causes the glue attaching the glass to the metal part to crack, which lets air into the bulb (ordinarily a vacuum/inert gas). The next time you turn it on, the air causes the filament to burn, causing the characteristic flare-up and scorch.

MisterTea 5y ago
Er, that glue only holds the glass bulb in the socket. The atmosphere contained within is completely glass sealed. What happens is the filament sputters away (like evaporation) and becomes thinner over time. It eventually becomes so thin it breaks from thermal shock when turned on. The dark spot on dead bulbs in the evaporated tungsten. Fun fact: In theater a blown bulb can ruin a production so some of the more critical lamps are dimmed instead of power cycled to avoid blowing a lamp.
- devindotcom 5y ago
  Really? I was under the impression that the glass isn't a fully enclosed "bulb" so to speak, but is cut off at one end to accommodate the rest of the necessary hardware, and glue completes the seal. Perhaps you're right. I can't seem to find a diagram or anything that shows this, though.
  - MisterTea 5y ago
    If you examine a clear incandescent bulb, you will see that the support for the filament is hollow and has a tube inside extending down. This little "straw" is the point of connection for evacuation where the air is removed and then back-filled with argon. The argon coaxes the tungsten back onto the filament preventing rapid sputtering which would happen in a pure vacuum. After the argon the little tube is heated until it hits melting point and crimped off for a near perfect hermetic seal. The argon pressure is still well below atmosphere so the bulb is still considered under "vacuum" compared to atmosphere.
  - xenadu02 5y ago

ars 5y ago

The simple reason is that it's not a light bulb, it's a heater. They are running it at much lower than specified voltage, so are generating mostly heat, and almost no light, so the filament is not very hot. It's glowing a dull red, not white. There is a quadratic relationship between temperature; and efficiency plus bulb life. You may have heard of the phoebus cartel - they specified a specific bulb life, which directly translates into a particular energy efficiency. There's nothing about the manufacture of the bulb that they casued to be worse, rather if the bulb lasts too long, you just up the temperature and make a more efficient bulb (uses less electricity). You can buy stage bulbs that last barely 10 hours, and run extremely hot, and also efficient, and for film that is the tradeoff they prefer (I guess they need a lot of light, and they don't really keep bulbs for long).