Six Science Posts #69

Comparing cars to cheese, why are zebras striped and more

Author

Harshal Chhaya
April 20, 2025

Six STEM Tweets

Six tweets that celebrate engineering and all things STEM.

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In issue #68 of the newsletter, I noted that

As a decimal number, 68 is the last two-digit number to appear for the first time in the digits of pi.

and asked: (Can anyone explain this to me? Thanks!)

I am so glad to have amazing subscribers and friends like MS who wrote:

About 68 and pi. I think it means that you can find any two digit numbers (between 00 and 99) in the digits of pi before you find 68.

If I was not retired, I would write a quick Python program to prove it, using the data below 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128481117450284102701938521105559644622948954930381964428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273724587006606315588174881520920962829254091715364367892590360011330530548820466521384146951941511609433057270365759591953092186117381932611793105118548074462379962749567351885752724891227938183011949129833673362440656643086021394946395224737190702179860943702770539217176293176752384674818467669405132000568127145263560827785771342757789609173637178721468440901224953430146549585371050792279689258923542019956112129021960864034418159813629774771309960518707211349999998372978049951059731732816096318595024459455346908302642522308253344685035261931188171010003137838752886587533208381420617177669147303598253490428755468731159562863882 35378759375195778185778

Thanks, MS! That makes a lot of sense.

Now on to today’s newsletter…

#1 🤯 

This is some really interesting engineering - using gene splicing to make more detectable bateria.

The paper abstract says:

The bacteria were detectable outdoors under ambient light from up to 90 m in a single 4,000-m2 hyperspectral image taken using fixed and unmanned aerial vehicle-mounted cameras. The dose–response functions of the chemical sensors were measured remotely. Hyperspectral reporters (HSRs) enable large-scale studies and applications in ecology, agriculture, environmental monitoring, forensics and defense.

#2 🤯 

The shift from 'V' to 'c' reflected Einstein's realization that light speed was a universal constant (c from Latin 'celeritas').

#3 🤯 

The law of large numbers isn’t a suggestion, it’s the law

#4 🤯 

I love this data visualization - because it doesn’t make any sense but it so interesting.

Didn’t you ever want to know how Feta cheese compares to a Honda Accord on a per-pound basis? 😆 

#5 🤯 

The best way to prove a hypothesis is to do the experiment!

#6 🤯 

A good burn is priceless!

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)

This is issue #69 of the newsletter. Nice.

  • 69 is a semiprime because it is a natural number that is the product of exactly two prime numbers (3 and 23), and it is an interprime between the numbers of 67 and 71

  • In decimal, 69 is the only natural number whose square (4761) and cube (328509) use every digit from 0–9 exactly once

  • It is also the largest number whose factorial is less than a googol (10100 or ten to the power of one hundred).

  • 69 is equal to 105 octal (base 8), while 105 is equal to 69 hexadecimal (base 16)

  • Visually, in Arabic numerals, 69 is a strobogrammatic number because it looks the same when viewed both right-side and upside down.

  • 69 is a pernicious number because there is a prime number of 1s when it is written as a binary number (1000101), and an odious number as it is a positive integer that has an odd number of 1s in its binary expansion.

    (Don’t you just love all the different names the number theory folks give to numbers?)

  • *69 is the “last call return” code in US and Canada (other countries have different numbers for the functionality. Details at https://en.wikipedia.org/wiki/Last-call_return)

  • 69 is the atomic number of Thulium, symbol Tm - the second-least abundant lanthanide in the Earth's crust, after radioactively unstable promethium. It is named after Thule, an Ancient Greek place name associated with Scandinavia or Iceland. Thulium's atomic symbol was initially Tu, but later changed to Tm.

  • There’s no international country dialing code mapped to 69.

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