Six Science Posts - #75

Volt at NIST, math to the moon, models and trains and more

Author

Harshal Chhaya
June 01, 2025

Six tweets that celebrate engineering and all things STEM.

I scroll so you don’t have to.

Hello new and known friends! Please share this with your own friends and family and encourage them to sign-up.

(KH has shared a really interesting “non-standard unit of measurement”. Watch for it later in this issue. Thanks, KH!)

#1 🤯 

Some more context: A volt is the measure of electromotive force needed to move one coulomb of electrons through one ohm of resistance. In order to standardize such things, most industrialized nations will have their own standard meter, pound, gram, etc. In this case, it’s the US standard of the volt.

Test equipment is calibrated using calibration equipment. That gear is calibrated with even more expensive equipment. That equipment is calibrated with this.

More details: https://www.nist.gov/programs-projects/quantum-voltage-project

#2 🤯 

🤩 

#3 🤯 

People who know his impact better than I do wonder what he could have done for mathematics and the world had he not been killed so early.

#4 🤯 

#5 🤯 

The reminds me of my favorite Calvin and Hobbes comic strip.

#6 🤯 

5 years ago, the 2nd panel would have looked very different. And it would have made perfect sense too!

About

This newsletter is my way of sharing interesting science-related news with my curious friends. I enjoy finding science and math connections in our world.

Please share this newsletter with others. Let’s encourage curiosity.

- Harshal (@hschhaya on X/Twitter)

KH sent me this note:

An addition to your collection of non-standard units of measure - a "Ferris Wheel-sized" object. He shared this news item: “University of Maryland, College Park, led a study published in November 2021 suggesting that the Ferris wheel-size asteroid may be a massive boulder ejected from the moon by an impact.”

It’s not as if we have a dearth of ways to measure objects. But I guess this is a good way to have readers visualize the size than specific numbers like “120 ft long” or something similar.

Thanks, KH for sharing this.

Do you have a favorite measurement unit that’s not in the textbooks? Let us know!

This is issue #75. Here’s what makes 75 interesting:

  • 75 is a “self” number because there is no integer that added up to its own digits adds up to 75.

    • Example: 21 is not a self number, because it can be written as 15 + 1 + 5 using n = 15. But 20 is. So is 75. These numbers were first described in 1949 by the Indian mathematician D. R. Kaprekar.

  • 75 is a reserved international calling code in Russia

  • 75 is the atomic number of Rhenium - symbol Re.

    • With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust.

    • Rhenium was originally discovered in 1908 by Masataka Ogawa, but he mistakenly assigned it as element 43 (now known as technetium) rather than element 75 and named it nipponium. It was rediscovered in 1925 by Walter Noddack, Ida Tacke and Otto Berg, who gave it its present name. It was named after the river Rhine in Europe, from which the earliest samples had been obtained and worked commercially. Element 113 (nihonium, Nh) was also discovered by a team of Japanese scientists and was named in respectful homage to Ogawa's work.

That’s it for this issue.

Hit ‘reply’ to tell me what you think.

And hit ‘forward’ to share with your friends and family.

Let’s all celebrate science and engineering and curiosity.

Best wishes,

Harshal