Physics

In the summer the warm exhaust from the fridge gets dumped into the kitchen along with heat from cooking. Then the cooling system has to work harder, or if there is no cooling system it just means less comfort and fans running more.

So I have to ask, why don’t refrigerators have a duct so the warm air can be vented outside in the summer?

In the winter I actually adjust the fridge temp to be colder so food lasts longer because the output is beneficial anyway.

cross-posted from: https://lemmy.dbzer0.com/post/9350839

The manual for an ultrasonic cleaner says:

• “Cold, clean tap water is generally best suited as cleaning fluid. The cleaning effect can be enhanced by the addition of approximately 3 drops of washing-up liquid. Do not use caustic cleaners, ammonia, bleach or heavily perfumed detergents.” (emphasis mine)

I know a professional jeweler with decades experience who cleans jewelry (mostly gold) using “Mr. Clean”¹ and ammonia, diluted, in an ultrasonic tub. The cheap ultrasonic I bought for myself is not for pros - but jewelry cleaning is the advertised purpose and it has a stainless steel tub just like the pro models have.

So the question is, what’s the purpose of the ammonia avoidance guidance, and is the pro jeweler I know making a mistake by using ammonia?

UPDATE: I also have to question why the manual of my cheap domestic ultrasonic says to use cold water. Pro ultrasonics have built-in heating elements. The pro jeweler waits until the solution is hot before using it. So why is manual of the cheap ultrasonic saying to add cold water? Since there is no heating element in my cheap one, I’m tempted to start with hot water.

footnote:

① out of curiosity, is there a brand-neutral name for “Mr. Clean” (aka “Mr. Propre” in French regions)?

^ The above was posted in a chemistry forum to ask the question about ammonia, but I thought I’d try physics for the question about cold water. Normally I would want to fill the ultrasonic tub with boiling water for a better cleaning effect. But the manual says to use cold water, and it also says to give the device a cooling off period if it’s been used continuously. Is some ultrasonic hardware actually sensitive to heat?

I saw a build-your-own ultrasonic video where someone glued a ultrasonic generator to a sink to make a big ultrasonic tub. So I wonder if the cheap home device I bought might have used a glue as well, which perhaps would lose adhesion if the tub heats and cools (expansion/contraction).

The BIG news in physics is that a new type of gravitational wave has been detected using pulsar timing arrays. In this video we're chatting about what a pulsar timing array actually is, what's been found, and why the gravitational waves might be from pairs of supermassive black holes orbiting each other, but there's evidence that they could be from new physics processes occurring in the early Universe...

I was inspired by someone's username and found this video. A video much like this one was one of the things that got me into studying physics to begin with over a decade ago.

The characteristic blue glow is caused by Cherenkov radiation, which is analogous to a sonic boom, but instead of a jet breaking the sound barrier, it's charged particles moving faster than the phase velocity of light in a medium (normally water).

Pretty cool, I think.

Not strictly physics related, but who's gunna stop me?

Let me preface this by saying I am not at all well versed in QM, but I've just recently finished a course that took us through most of Griffiths and I have some thoughts.

The thing that blows me away the most about QM isn't necessarily all the standard "weirdness", like tunneling and superposition and whatever, but rather that all of this weirdness can be accurately described by (mostly) pre-existing mathematics. Linear algebra was a growing, but already established field, and the concept of abstract linear vector spaces, and later Hilbert space, came just before and evolved alongside QM.

The fact that we discovered a mathematical language before finding out what that language could describe just blows my mind. I understand this isn't the first time the maths came before the physics, but considering how groundbreaking and unintuitive the theory is I think that fact is quite exceptional. Even more so is that we can use this mathematical formalism to derive physically observable phenomena. I don't know if you get what I mean, but wow. I think that's nuts haha