Physics

• https://piped.video/watch?v=4Stzj2_Rlo4
• https://www.youtube.com/watch?v=4Stzj2_Rlo4

Absolutely everything you think about yourself and the universe could be an illusion. As far as you know, you are real and exist in a universe that was born 14 billion years ago and that gave rise to galaxies, stars, the Earth, and finally you. Except, maybe not.

Other explanations for Boltzmann Brains did not require an 'inside-out black hole', for example https://en.wikipedia.org/wiki/Boltzmann_brain, so this inclusion came as a surprise to me. Not sure if it's necessary.

What baffles me about the theory: If it's true, and reality is (mostly, statistically speaking) imagined ... the physical reality could be anything. It could be very different from the reality we live in. But we created our models of the universe in this one reality we know, and the theory of Boltzmann Brains emerged from that.

So based on these physical models we arrive at the idea of BBs. But if this idea is true, the physical reality could be completely different.

Or what do you think?

Here is a question I encountered sometime ago.

For a current carrying wire of finite length the value of B is less than that of an infinitely long wire (u can look up online for formulae or their derivation) at a same distance from the wire. So consequently the circulation of B on the path shown falls short of the value u times i. The biot savart law suggests the equation written above. The puzzle is to find the mistake.

Professor Philip Moriarty takes issue with a paper by scientists claiming to achieve room temperature superconductivity.

The First Room-Temperature Ambient-Pressure Superconductor: https://arxiv.org/abs/2307.12008

Key critique points:

• Team has little to no background in superconductivity
• Evidence of levitation can be explained without superconductivity
• Graph showing drop in resistance uses a scale which is orders of magnitude off the scale
• Graph showing drop in resistance shows it does not drop (close) to zero

Phil regrets this bad publication which received so much attention could have a negative impact on credibility of science as a whole.

• https://piped.video/watch?v=zl-AgmoZ5mo
• https://www.youtube.com/watch?v=zl-AgmoZ5mo

In this preprint, the authors synthesize LK-99-like samples, and observe half-levitation similar to that seen in other recent videos. However, they perform a careful magnetization measurement and conclude that the sample is ferromagnetic. They also did a resistance measurement on a larger sample and found that the majority of the material is a semiconductor. This points to the half-levitation effect, which is mostly what got people excited, being a consequence of ferromagnetism (+ mechanical effects due to friction and sample shape), rather than the Meissner Effect.

Unless someone can demonstrate full levitation or better resistivity data for LK-99, this appears to be fatal for the claims of room temperature superconductivity.

It's by far the best video to explain special relativity.

This replication by Huazhong University includes PPMS data, showing a strong signal of a diamagnetism transition at around 320K. It does not include a resistance measurement, however.

cross-posted from: https://discuss.tchncs.de/post/1312651

TLDR: To remove by shaking one would need accelerations high as 24g, which can damage the ear. A couple drops of vinegar or alcohol in the ear will lower the surface tension and make the fluid easier to remove

Hopefully not too off-topic.

Graphite is normally very soft and slippery, and is even able to act as a dry lubricant when finely powdered, however many sources claim that graphite powder can be highly abrasive, to the point of potentially destroying milling machines. Does anyone know how such a soft material can abrade metals?