Why It Was Almost Impossible to Make the Blue LED

I was watching a YouTube video from a Scottish YouTuber recently and heard him refer to a light as being a LED bulb. He, however, pronounced LED as if it were the element lead. I, an American, pronounce those bulbs as their three separate letters El Ee Dee, like an acronym. 

Neither, of course, is correct, nor is it at all relevant to this video.

This video, just over half an hour long and produced by Dr Derek of Veritasium, goes through the quantum mechanic explanation of how semiconductors conduct at room temperature which also explains how LEDs produce light and - eventually in the video - how LEDs can be tuned to produce different colors.

This video is also a great exploration of how doped semiconductors conduct electricity. 

I'm really happy that I don't have to teach this concept in my chemistry - or material science - classes because this really pushes my understanding of quantum mechanics and electronics. I didn't thoroughly understand it when I first heard about it back in 1993 or 1994, and I don't entirely understand it now. I do, however, fully accept that there are people who do understand these concepts and that we owe those people a massive debt because the widespread use of LEDs has been a huge revolution in energy savings for our world.

Plus it lets people wrap their cars in Christmas lights.

This Genius Magnet Stops Dangerous Leaks in Seconds!

I found the above video on Reddit (warning: NSFW word in the subreddit title) but with non-English narration. 

I then found the embedded video in likely AI-generated English.

From there I found the Magnaseal website from Neothane which had the following two video embedded.

...and...

Sadly the Neothane website doesn't list any prices just a button to request a quote. 

Other sites selling the MagnaSeal, however, suggest that it's a rather pricey item, so I don't think I'll be picking one up to demonstrate in my classroom.

All the Metals We Mined

 

Source - Visual Capitalist and USGS Mineral Commodity Summaries (2022) before that

I have a simple question about this graphic.

The iron presented is shown in weight of iron ore mined not of actual iron produced, and the rare earths are listed as "rare earth oxides", which I would also interpret as ore.

Some of the other metals seem to be presented in weight of actual metal produced (aluminum, for example, being listed as "smelted/refinery production"). 

Those quantities don't necessarily seem equivalent to me.

This Bridge Should Have Been Closed Years Before It Collapsed

The Fern Hollow Bridge collapsed on January 28, 2022.

Today's video sees Grady looking at the NTSB's report on the collapse of the bridge. 

The main issue can be mostly summarized as inspections that identified critical repair and maintenance on the bridge were ignored instead of being acted upon.

The report doesn't exactly fill me with reassurances that our infrastructure is safe for our daily use.

How to Make a Warning Last 10,000 Years

Alan Wiseman's The World Without Us has a chapter titled "Hot Legacy" that explores our efforts to create warnings that will last at least 10,000 years into the future and will tell future archeologists that the interesting stuff they've found at some of our nuclear waste repositories should not be explored.

Much of the research is being done at the Waste Isolation Pilot Project is New Mexico, USA, and it's that work that SciShow details in today's video.

I remember that the Wiseman chapter also mentioned the placement of various magnets around the site as a warning that something was at least weird in this location. The video doesn't mention that, and I'm surprised because I found that one of the more interesting ideas.

How Japanese Masters Turn Sand Into Swords

This isn't a replacement for the Nova episode "Secrets of the Samurai Sword". 

...but the Nova episode tends to appear and disappear from YouTube and DailyMotion with fair frequency, so you might need another video that goes through the ancient art of creating samurai swords from the initial collecting and smelting of iron-rich sand through to the slicing of tatami mats to demonstrate the sword's quality and the sword wielder's technique.

This video's contents...

• 2:00 - why bronze was used for sword and was eventually replaced
• 3:00 - cyanobacteria creating oxygen that precipitated iron from ancient oceans
• 6:30 - carbon + iron = steel, initial interstitial positions shown...why alloys are harder than pure metals
• 10:30 - slag formation and removal from the 'ancient' forge
• 13:30 - forging the steel by master swordsmiths
• 14:30 - folding the steel - how and why
• 16:15 - how carbon atoms migrate to different positions and form ferrite, cementite, perlite, and martensite
• 18:30 - differential cooling rates via clay thickness creating different steel types and the distinct blade shape

Another great video from Veritasium and one that shows that he's got a team of folks making videos with/for him at this point...and it's short enough at about half an hour - to get through in a single class period, unlike the Nova episode.

Why Are Chip Bags So Hard To Recycle? | World Wide Waste | Business Insider

Multilayer packages - MLP's - that's why.

It's not a tough answer at the most basic of levels. We've taken multiple materials - each of which accomplishes something useful for the overall chip package - and have fused them together in ways that make them nearly impossible to separate again and recycle.

Now, how are we trying to recycle them in spite of all the steps we've taken to make sure the materials couldn't easily separate?

Step one is to find a way to separate the un-separateable through heat, pressure, and high pH.

From there it's mostly down to regular recycling, but that first step is a doozy.