Recent comments in /f/mildlyinteresting

Busy_Bitch5050 t1_iybl08v wrote

Reply to comment by shrimpcest in While replacing a wall in my basement, I found a 100-year-old marriage certificate. by woden_spoon

Thank you! Maybe it will help OP, or maybe they've already forgotten about it. But at some point, someone is bound to look up their genealogy from the Evans family and possibly find this post. I figured it would be cool for them to be able to see their ancestors' marriage certificate was found in their old home and is preserved in the walls lol.

59

crispy1989 t1_iybk11u wrote

Reply to comment by D_daKid in My thermostat uses the expansion/contraction of a drop mercury to conduct electricity and trigger when to turn off and on. by Iain_MS

/u/gilareefer explained how the mechanism works, but to answer your question more generally, this type of switch mechanism is used because it's very resistant to oxidation/corrosion, and because a traditional mechanism used with a bimetallic strip would be prone to arcing.

The temperature-sensitive part is a bimetallic strip shaped in such a way so as to "tilt" one way or the other based on temperature due to the difference in the metals' thermal expansion coefficients. A simple switch mechanism based on this might be to just allow the strip (or a contact attached to the strip) to touch another contact in a certain position; but this type of switch is prone to corrosion over time due to being exposed to the elements. The complicated liquid-metal-drop-inside-sealed-vial mechanism prevents corrosion because there's no oxygen inside the vial.

Additionally, a simple switch contact mechanism used here would likely cause arcing and damage to the contacts since the switch would open and close extremely slowly. Things like normal light switches prevent this by integrating a "snap" mechanism to very quickly open and close the circuit; but a bimetallic strip supplies very little force, not enough to operate such a snap mechanism. The liquid-metal-inside-sealed-vial mechanism solves this problem by a) surface tension keeps the drop of mercury together so once the vial tilts even a little the whole drop will quickly slide over and complete the connection; and b) any damage due to arcing would be minimized in a low-oxygen environment inside the vial.

For both of these reasons, mercury metal is used because it's the only metal that's liquid across the usual range of human environmental temperatures, so is the only metal suitable for use in this type of switch mechanism.

7

8-15ToTheCity t1_iybibq0 wrote

Reply to Makeshift sign over FDR Drive, NYC that reads: Arrest Trump by supercoincidence

I'm not American nor do I really care for Trump or Biden,

But I wonder what there is to arrest him for?, His house was raided by the FBI and they found nothing, He was impeached twice and nothing was found,

Where as look at the likes of Hunter he had clear evidence of breaking the law on a laptop, There's evidence to suggest Nancy's husband Paul has had insider trading information, Why are we not asking for them to be investigated,

Regardless of the colour you vote, We should hold criminals accountable.

−26