Six STEM Tweets

Best wishes to all and to all a happy new year!

Harshal Chhaya — Wed, 24 Dec 2025 16:10:04 +0000

Namaste y’all,

I wish you all and all your loved ones a peaceful holiday season. Whatever festival you celebrate, I hope it brings you love and joy and peace. 🎄 🎅

Thank you for another great year of sharing amazing stories from the world of science and technology and math and engineering - in other words, stories from the world around us.

STEM is not just an acronym or a classroom subject.

It is all around us.

But you know this already. Which is why you are a member of the “curious club” - subscribers to this newsletter. 😃

See you in the new year!

Stay curious, friends!

Love,

Harshal

P.S. Please share the newsletter with your friends and family. Nothing makes a holiday dinner more fun and asking “so, have you signed up to any fun newsletters recently?” 😂

P.P.S. There’s a school of thought that I am procrastinating working on issue #100 by sending out special issues (2 in the last week!) and this message. All I can say is “no comment” 😁

P.P.S. If you like fountains (and who doesn’t?), follow “HarshalLovesFountains” on Instagram - https://www.instagram.com/harshallovesfountains/

Six Math posts - special Ramanujan edition

Harshal Chhaya — Mon, 22 Dec 2025 15:20:34 +0000

Hi friend,

Today, Dec 22, is Srinivas Ramanujan’s birthday.

It is celebrated as National Mathematics Day in India.

In his short life, Ramanujan had an outsized impact on mathematics and astounded contemporary and modern mathematicians with his knowledge.

Today’s issue is a special newsletter dedicated to the “man who loved numbers”.

If you haven’t yet seen the movie based in Ramanujan’s life (“The Man Who Knew Infinity”), the upcoming holidays are a great opportunity to catch up. (https://en.wikipedia.org/wiki/The_Man_Who_Knew_Infinity)

His wikipedia page at https://en.wikipedia.org/wiki/Srinivasa_Ramanujan makes for fascinating reading

The next time your store or restaurant receipt comes to 17.29, remember the self-taught savant who loved all numbers.

Love

Harshal

P.S. Stay curious!

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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

Special past issues

Six Science posts - Special Solstice Edition

Harshal Chhaya — Mon, 22 Dec 2025 00:45:59 +0000

Hi friend,

Today, Dec 21st, is the solar solstice - shortest day in the Northern hemisphere, longest in the Southern. First day of winter in the north, first day of summer in the south.

It’s a special occasion that deserves it’s own special issue of the newsletter.

Here’s 6 informative tweets about this day and its significance.

Admittedly, most of these are from the Northern hemisphere POV - hence the focus on the winter solstice.

Love,

Harshal

P.S. The next regular issue is #100. 😃

P.P.S. Share the newsletter with a loved one. ‘Tis the season to be informed. And awed.

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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

Special past issues

Six Science posts #99

Harshal Chhaya — Sun, 14 Dec 2025 23:37:04 +0000

Hi friend,

This holiday season, give your loved ones the gift of knowledge. And curiosity.

Forward this email to them and ask them to sign up at https://sixstemtweets.beehiiv.com/subscribe

They will appreciate your thoughtfulness.

Love

Harshal

P.S. I scroll so you don’t have to.

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This is issue #99. Let’s see what makes 99 an interesting number:

99 is:

a “square prime” of the form 3² * q
a palindrome in base 10
the sum of the cubes of three consecutive integers: 99 = 2³ + 3³ + 4³
often used in prices for psychological reasons
in the name of many movies, TV shows and songs
Atomic number of Einsteinium - a synthetic chemical element; it has symbol Es
- Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952.
- As the effort which had led to the design of the first hydrogen bomb was codenamed Project PANDA, element 99 had been jokingly nicknamed "Pandemonium" but the official names suggested by the Berkeley group derived from two prominent scientists, Einstein and Fermi
- The symbol for einsteinium was first given as "E" and later changed to "Es" by IUPAC
There is no country with 99 as the international country code

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

Special past issues

Six Science posts #98

Harshal Chhaya — Sun, 30 Nov 2025 22:04:05 +0000

Hi friend,

Thank you for all your replies to my “Black Friday sale” email. 😄

I hope you shared the “100% off” offer with a friend.

Thank you for reading, for sharing and for staying curious!

Here’s another issue of the newsletter with six interesting posts.

As always, hit ‘reply’ to let me know what you think. And hit ‘forward’ to share with a friend.

Love,

Harshal

P.S. I recently started sharing my love of fountains on Instagram. Check out “HarshalLovesFountains” if you want to follow along.

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This is issue #98. Let’s see what makes 98 an interesting number:

98 = 1⁴ + 2⁴ + 3⁴
(Harshal’s note: That’s it?!? No other interesting number connections? To be honest, I am a little surprised and feel bad for 98.)
Windows 98 was a very popular operating system for the PC platform
98 is the atomic number of Californium - a synthetic chemical element with symbol Cf. It was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory) by bombarding curium with alpha particles.
- From the Wikipedia article: The discoverers named the new element after the university and the state. This was a break from the convention used for elements 95 to 97, which drew inspiration from how the elements directly above them in the periodic table were named. However, the element directly above element 98 in the periodic table, dysprosium, has a name that means "hard to get at", so the researchers decided to set aside the informal naming convention.They added that "the best we can do is to point out [that] ... searchers a century ago found it difficult to get to California".
The international calling code for Iran
98 Degrees (stylized as 98°) is an American pop and R&B vocal group

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

Special past issues

Six Science Posts - Black Friday edition

Harshal Chhaya — Fri, 28 Nov 2025 20:29:04 +0000

Hi friend,

Since this is Thanksgiving week in the US, I wanted to take this opportunity to say that I am thankful to you for subscribing to this newsletter and sharing my curiosity about the world around us. I appreciate each and every one. And I love it when you reply and share your feedback with me (there’s a really fun one at the end of this)

If you have friends who love a Black Friday deal, please send them to this newsletter. Our Black Friday deal - 100% off! - lasts all year!

But for this week only, any one who signs up gets 200% off! And this is on top of the low, low price of zero.

So, go ahead, make their day! Send this to a friend, a family member, a neighbor, a co-worker - anyone who appreciates a deal. I guarantee you, they will love this!

Stay curious!

Love and with gratitude,

Harshal

P.S. the previous issue of the newsletter - #97 - was published on 11/23 - aka Fibonacci day.

Reader and friend KHH, sent an interesting post by Kit Yates, a math educator from the UK and a brilliant communicator of all things math. He had found an interesting coincidence earlier this year.

https://x.com/Kit_Yates_Maths/status/1916540517203984754?s=20

Prof. Yates followed this up with a very good essay on this observation.

(The essay is a fun read because it includes other fun topics of how continental drift was first discovered)

The intriguing sequence completed by Liverpool’s title win

Why spotting patterns is important for scientific discovery and how coincidences can be misleading.

kityates.substack.com/p/the-intriguing-sequence-completed?triedRedirect=true

Happy reading!

And remember to share this newsletter’s Black Friday deal with people you love.

Six Science posts #97

Harshal Chhaya — Sun, 23 Nov 2025 22:04:06 +0000

Welcome new friends!

If you like this, share it with a friend. Stay curious!

Today - 11/23 (in the mm/dd format) - is Fibonacci Day

The Fibonacci series is a series of numbers where each number is the sum of previous two.

It goes: 1, 1, 2, 3, 5, 8, 13, 21, 34 - notice the 11/23?

It is a very interesting sequence of numbers - occurs in nature in many ways.

We had a special issue on the topic last year. Here’s the link for you to enjoy.

Six STEM Tweets - Special Fibonacci Edition

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ....

sixstemtweets.beehiiv.com/p/six-stem-tweets-special-fibonacci-edition

Remember, next year - you need to read it twice. And then 3 times in 2027. 😃

I scroll so you don’t have to.

Love,

Harshal

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This is issue #97. Let’s see what makes 97 an interesting number:

The largest two-digit prime number in base 10
a Proth prime and a Pierpont prime as it is 3 × 2⁵ + 1.
- a Pierpont prime is a prime number of the form 2^u ⋅ 3^v + 1
- A Proth number is a natural number N of the form N = k × 2ⁿ + 1
  where k and n are positive integers, k is odd and 2ⁿ > k
the highest two-digit number where the sum of its digits is a square.
the number of primes less than 2⁹ .
The numbers 97, 907, 9007, 90007 and 900007 are all primes, and they are all happy primes.
- a happy number is a number which eventually reaches 1 when the number is replaced by the sum of the square of each digit
- 97 is a happy number because:
  - 9² + 7² = 81 + 49 = 130
  - 1² + 3² + 0² = 1 + 9 = 10
  - 1² + 0² = 1
However, 9000007 (read as nine million seven) is composite and has the factorization 277 × 32491.
an emirp with 79 (emirp is prime, backwards)
Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is named after the city of Berkeley, California.
- Just over one gram of berkelium has been produced in the United States since 1967. There is no practical application of berkelium outside scientific research
There’s no country with 97 as their international country code. Instead, here’s all the country codes in the 97x series:
- 970 - Palestine (interchangeably with 972)
- 971 - United Arab Emirates
- 972 - Israel (also Palestine, interchangeably with 970)
- 973 - Bahrain
- 974 - Qatar
- 975 - Bhutan
- 976 - Mongolia
- 977 - Nepal
- 978 - unassigned (formerly assigned to Dubai, now part of 971 United Arab Emirates)
- 979 - Universal International Premium Rate Service (UIPRS); (formerly assigned to Abu Dhabi, now part of 971 United Arab Emirates)

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

Special past issues

Six Science posts #96

Harshal Chhaya — Sun, 16 Nov 2025 22:04:08 +0000

Hi friend,

96 is a semiperfect number (a multiple of 6) but IMO, this issue #96 is perfect!

Agree? Disagree? Either way - let me know!

And share this with someone who might like to stay informed and entertained while learning.

Stay curious!

Love,

Harshal

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This is issue #96. Let’s see what makes 96 an interesting number:

96 is:

rotationaly symmetric (i.e. strobogrammatic) in bases 10 (96₁₀), 11 (88₁₁) and 95 (11₉₅).
palindromic in bases 11 (88₁₁), 15 (66₁₅), 23 (44₂₃), 31 (33₃₁), 47 (22₄₇) and 95 (11₉₅).
divisible by the number of prime numbers (24) below 96.
the smallest natural number that can be expressed as the difference of two nonzero squares in more than three ways:
- 10² − 2²
- 11² − 5²
- 14² − 10²
- 25² − 23²
an untouchable number - a positive integer that cannot be expressed as the sum of all the proper divisors of any positive integer.
- 4 is not untouchable because it is the sum of the factors of 9 (4 = 1+3)
- there is NO number whose factors add up to 96
the atomic number of “Curium” - a synthetic chemical element with symbol Cm
- Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium.
- The element was named after Marie Curie and her husband Pierre Curie, who are known for discovering radium and for their work in radioactivity
Ninety Six is a town in Greenwood County, South Carolina, United States. If you are interested to know more, check out https://en.wikipedia.org/wiki/Ninety_Six,_South_Carolina

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

Special past issues

Six Science posts #95

Harshal Chhaya — Tue, 11 Nov 2025 12:20:06 +0000

Hi friend,

This issue is a bit delayed because I was out of town this weekend.

Was literally touching grass.

Recommended!

Also drove a tractor. Not recommended unless you have a very brave and competent co-pilot. Which I had, thankfully!

Thanks to everyone who hits ‘reply’ and sends a note. Plethora. That means a lot.

Please continue to read and reply. And send this to others who might enjoy it.

I scroll so you don’t have to.

Love,

Harshal

P.S. Thanks to reader and dear friend, VV, who sent me a really cool video for the newsletter about the interesting math behind the A4 paper size. Look for it in a future issue.

Also a thanks to reader and dear friend, KH who has asked for a sequel to the special issue on Venn diagrams (original special issue is below). Soon…

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This is issue #95. Let’s see what makes 95 an interesting number:

the 30th distinct semiprime and the fifth of the form (5.q).
the last member in the third triplet of distinct semiprimes 93, 94, and 95.
the first composite Thabit number or a 321 number that is an integer of the form 3 x 2ⁿ − 1
- 95 = 3 × 2⁵ -1
- (Harshal: I love these kind of named numbers with interesting characteristics)
Martin Luther's 95 Theses
- Wikipedia says: The Ninety-five Theses or Disputation on the Power and Efficacy of Indulgences is a list of propositions for an academic disputation written in 1517 by Martin Luther, then a professor of moral theology at the University of Wittenberg, Germany. The Theses are retrospectively considered to have launched the Protestant Reformation and the birth of Protestantism, despite various quasi- or proto-Protestant groups having existed previously.
In statistics, a 95% confidence interval is considered satisfactory for most purposes.
Followers of the Baháʼí Faith use prayer beads to repeat the prayer Alláh-u-Abhá (God is most glorious) 95 times.
95 — the racing number of Lightning McQueen from Disney Pixar's Cars franchise.
The international calling code for Myanmar
Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x line of operating systems, released in Summer 1995.
95 is the atomic number of Americium - a synthetic chemical element, symbol Am. It is located under the lanthanide element europium and was thus named after the Americas by analogy.
- Most americium is produced by uranium or plutonium being bombarded with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains about 100 grams of americium.
- Americium is used in the most common type of household smoke detector, which uses ²⁴¹ Am in the form of americium dioxide as its source of ionizing radiation.
- The amount of americium in a typical new smoke detector is 1 microcurie (37 kBq) or 0.29 microgram.

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

Special past issues

Six Science posts #94

Harshal Chhaya — Mon, 03 Nov 2025 22:04:10 +0000

Here’s 6 more posts that highlight the beauty and wonder of our world through the math, engineering and science lens.

I scroll so you don’t have to.

Love,

Harshal

P.S. Please forward to others who might enjoy such nuggets of ntersting nformation.

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This is issue #94. Let’s see what makes 94 an interesting number:

94 is:

a semiprime number of the form: 2*q
the second number in the third triplet of three consecutive distinct semiprimes, 93, 94 and 95
Used as a nonsense number by the British satire magazine Private Eye. Most commonly used in spoof articles end halfway through a sentence with "(continued p. 94)". The magazine never extends to 94 pages: this was originally a reference to the enormous size of some Sunday newspapers.
The international calling code for Sri Lanka
a “Smith” number because the sum of its digits is equal to the sum of the digits of its prime factors
- Sum of its digits: 9 + 4 = 13
- Prime factors: 2, 47
  - Sum of digits of prime factors: 2 + 4 + 7 = 13
- According to Wikipedia, Smith numbers were named by Albert Wilansky of Lehigh University, as he noticed the property in the phone number (493-7775) of his brother-in-law Harold Smith:
  4937775 = 3 · 5 · 5 · 65837
  while
  4 + 9 + 3 + 7 + 7 + 7 + 5 = 3 + 5 + 5 + (6 + 5 + 8 + 3 + 7)
  (Harshal’s note: What?!? 🤯 )
the atomic number of Plutonium (symbol: Pu)
- Since uranium had been named after the planet Uranus and neptunium after the planet Neptune, element 94 was named after Pluto, which at the time was also considered a planet.
- Plutonium is the element with the highest atomic number known to occur in nature.
- The heavy isotope plutonium-244 has a half-life long enough that extreme trace quantities should have survived primordially (from the Earth's formation) to the present, but so far experiments have not yet been sensitive enough to detect it.
- Unlike most materials, plutonium increases in density when it melts
- The Fat Man bombs used in the Trinity nuclear test in July 1945, and in the bombing of Nagasaki in August 1945, had plutonium cores.

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

Special past issues

Six Science posts #93

Harshal Chhaya — Tue, 28 Oct 2025 21:51:40 +0000

Hi friend,

This issue is delayed because I was away from my PC, volunteering at a local high school robotics competition, on Sunday.

I enjoy volunteering at these events, at science fairs, debate competitions and other similar K-12 contests because they give me hope. It is very inspiring to see the next generation showcase their talents and learn important life skills like team work, resilience and problem solving.

Most of these volunteer roles do not need any prior technical expertise. If you are interested, let me know and I can share ways that you can get involved.

Now, on to other inspiring info - 6 posts chock full of science and engineering and technology.

Love,

Harshal

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This is issue #93. Let’s see what makes 93 an interesting number:

93 is:

the 9th semiprime the form (3.q) where q is a higher prime.
- the first number in the 3rd triplet of consecutive semiprimes, 93, 94, 95
a repdigit in base 5 (333₅), and 30 (33₃₀).
palindromic in bases 2, 5, and 30.
The atomic number of neptunium - symbol Np
- It’s named after the planet Neptune since it is after Uranium that was named after Uranus
The code for international direct dial phone calls to Afghanistan.
One of two ISBN Group Identifiers for books published in India.
The historical definition of the “astronomical unit” (AU) (a measurement of length) was the average Earth-Sun distance which was about 93 million miles.
- The astronomical unit is used primarily for measuring distances within the Solar System or around other stars
- In 2012, the AU was re-defined to be exactly equal to 149597870700 m (about 92.95 million miles)

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

Special past issues

Six Science posts #92

Harshal Chhaya — Wed, 22 Oct 2025 21:04:12 +0000

Thank you for your patience for this delayed issue.

I was traveling (in planes, trains and automobiles!) and didn’t have access to all the information I needed to publish this issue on the regular schedule.

My family and I recently celebrated the Hindu festival of Diwali recently where we light lamps to banish darkness. The light represents good, knowledge and hope that removes the darkness of despair, evil and ignorance.

May this newsletter serve as a light to spread knowledge and curiousity.

Happy Diwali, y’all!

Love,

Harshal

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This is issue #92. Let’s see what makes 92 an interesting number:

92 is palindromic in other bases, where it is represented as 232₆, 161₇, 44₂₂, and 22₄₅.
There are 92 numbers n such that 2ⁿ does not contain all digits in base ten (the largest such number is 168, where 68 is the smallest number with such a representation containing all digits)
- The full list of these 92 numbers is at https://oeis.org/A130696
92 is the international calling code for Pakistan
Uranium is a chemical element; it has symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. Uranium radioactively decays, usually by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes, making them useful for dating the age of the Earth.
- The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after planet Uranus which had been discovered eight years earlier by William Herschel (my guy!)
- A uranium-based device (codenamed "Little Boy") became the first nuclear weapon used in war when it was detonated over Hiroshima, Japan, on 6 August 1945.

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

Special past issues

Six Science Posts - all past specials

Harshal Chhaya — Wed, 22 Oct 2025 00:16:05 +0000

Hi friend,

Since issue #92 is delayed (I was traveling the past few days), here’s a list of all the special issues of this newsletter to tide you over while I work on issue 92.

If there’s a topic that you would like to see a special issue on, let me know.

Feel free to forward this (and all other) issues of the newsletter to folks you know.

Thanks for all your support.

Stay curious!

And stay tuned for issue #92

Love,

Harshal

P.S. 92 is the international calling code for Pakistan and the atomic number of Uranium. This and other fun facts about 92 in the next issue.

Six Science posts #91

Harshal Chhaya — Sun, 12 Oct 2025 15:10:00 +0000

Hi friend,

The last issue of the newsletter - #90 - included a list of cars with the number 90 in their name.

JC, a very astute reader and self-described “part time car enthusiast” sent me a few more cars that also include 90 in their name.

Volvo XC90 - on the market presently
BMW E90 - internal BMW numbering for 5th generation 3 series
Porsche 90 - an iconic Porsche 1961-63 356B Super Coupe...

I find this rather interesting. Why is 90 so prevalent in the names of these cars?

Any thoughts? Speculations?

Stay curious, friend!

Love,

Harshal

P.S. I am going to be traveling next week so issue #92 will be delayed by a couple of days. You can always get your fix to sate your curiosity in the archives at https://sixstemtweets.beehiiv.com/ - 100+ issues, 600+ fascinating bits of information.

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This is issue #91. Let’s see what makes 91 an interesting number:

Ninety-one is a version of solitaire, played with a deck of cards. The details are at https://en.wikipedia.org/wiki/Ninety-One_(solitaire) IMO - this doesn’t seem like a very interesting game but if you have played it, let me know.
91 is the second semiprime of the form (7.q), where q is a higher prime.
91 is the smallest positive integer expressible as a sum of two cubes in two different ways if negative roots are allowed (alternatively the sum of two cubes and the difference of two cubes):
91 = 6³ + (−5)³ = 4³ + 3³ .
This implies that 91 is the second cabtaxi number.
the smallest positive integer expressible as a sum of six distinct squares:
91 = 1² + 2² + 3² + 4² + 5² + 6² .
The only other ways to write 91 as a sum of distinct squares are:
91 = 1² + 4² + 5² + 7² and
91 = 1² + 3² + 9² .
a repeated digit (aka repdigit) in base 9 (111₉).
palindromic in bases 3 (10101₃), 9 (111₉), and 12 (77₁₂).
91 is the octane rating of “premium gasoline” in many countries
Protactinium is a chemical element; it has symbol Pa and atomic number 91. It is a dense, radioactive, silvery-gray actinide metal which readily reacts with oxygen, water vapor, and inorganic acids.
- Protactinium is one of the rarest and most expensive naturally occurring elements.
- The element was first identified in 1913 and named "brevium" because of the short half-life of the specific isotope studied, ^234m Pa. A more stable isotope of protactinium, ²³¹ Pa, was discovered in 1917/18. In 1949, the IUPAC chose the name "protactinium". The new name meant "(nuclear) precursor of actinium,"suggesting that actinium is a product of radioactive decay of protactinium.
91 is the international country calling code for India

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

Special past issues

Six Science Posts - Enderlin EF5 tornado special issue

Harshal Chhaya — Tue, 07 Oct 2025 23:25:36 +0000

Hi,

Tornadoes are rated on the “enhanced Fujita” (EF) scale - from EF0 to EF5 based on the damage they cause.

The EF Scale was revised from the original Fujita Scale to include the actual damage caused by the tornado. (source: https://www.weather.gov/oun/efscale)

So what? Why have a special issue about this?

For the first time in US weather tracking history, a tornado has been classified as EF5 based on mathematical analysis of the damage it caused - not just the wind speed.

The June 20th tornado in Enderlin, North Dakota is now officially an EF5 tornado.

This breaks a 12 year “drought” in EF5 tornadoes in the US

This is HUGE! (at least in the weather-watcher world)

This is a new approach to classifying tornadoes.

The official NWS report is at https://www.weather.gov/media/fgf/Enderlin.pdf

It has lots of really interesting analysis and pictures.

Below are 6 posts about this and what it means. There’s also some cool math and physics first proposed by a weather-watcher and officially used by the National Weather Service to classify the tornado.

Stay curious, friends!

Harshal

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Here’s the math showing how they estimated the speed of the tornado:

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

Special past issues

Six Science posts #90

Sun, 05 Oct 2025 15:10:00 +0000

Hi friends,

Thanks for your feedback and for sharing this newsletter with your fellow curious humans.

There’s lots of wonder and awe in science, math, engineering - let’s help spread it.

To commemorate this issue #90 of the newsletter, here’s a pro-tip: If you ever get cold and don't have a sweater, stand in a corner for a few minutes; they're usually about 90 degrees. (Of course, this joke only works in places that use F-reedom units)

Here’s one more: 90 degrees is pretty hot for most people. But for mathematicians, it's just right. 😁

Have a great week!

Love,

Harshal

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This is issue #90. Let’s see what makes 90 an interesting number:

90 is a pronic number as it is the product of 9 and 10 - A pronic number is a number that is the product of two consecutive integers that is, a number of the form n ( n + 1 ).
- The study of these numbers dates back to Aristotle. They are also called oblong numbers, heteromecic numbers, or rectangular numbers;
- Along with 12 and 56 one of only a few pronic numbers whose digits in decimal are also successive.
90 is divisible by the sum of its base-ten digits, which makes it the thirty-second Harshad number
- a Harshad number (or Niven number) in a given number base is an integer that is divisible by the sum of its digits when written in that base
- Harshad numbers were defined by D. R. Kaprekar, a mathematician from India. The word "harshad" comes from the Sanskrit harṣa (joy) + da (give), meaning joy-giver. The term "Niven number" arose from a paper delivered by Ivan M. Niven at a conference on number theory in 1977.
An angle measuring 90 degrees is called a right angle. In normal space, the interior angles of a rectangle measure 90 degrees each, while in a right triangle, the angle opposing the hypotenuse measures 90 degrees, with the other two angles adding up to 90 for a total of 180 degrees.
90 can be expressed as the sum of distinct non-zero squares in six ways, more than any smaller number
- ( 9² + 3² ) , ( 8² + 5² + 1² ) , ( 7² + 5² + 4² ) , ( 8² + 4² + 3² + 1² ) , ( 7² + 6² + 2² + 1² ) , ( 6² + 5² + 4² + 3² + 2² )
90 is the atomic number of Thorium - a chemical element with symbol Th. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air. It is named for Thor - the Norse god of thunder
90 is the international calling code for Turkey
Interestingly enough, there are many car models with ‘90’ in the name (all links below are to Wikipedia)
- Audi 90, a compact executive car produced by Audi
- Saab 90, a compact executive car produced by Saab
- Sunbeam-Talbot 90, a compact executive car produced by Sunbeam-Talbot
- Alfa Romeo 90, an executive car produced by Alfa Romeo
- Tatra 90, a prototype mid-size car
- Rover 90, a saloon produced by the Rover Company

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

Special past issues

A follow-up to "Six Science posts #89"

Harshal Chhaya — Thu, 02 Oct 2025 22:02:14 +0000

Hi friend,

I have a follow-up to a couple of things in issue #89 of the newsletter

1.

Post #3 of the newsletter mentioned the Haber process which makes fertilizer production more efficient and has resulted in significant improvement in agriculture yield.

A reader, FF, alerted me to the fact that the process is not all good. There’s some pretty bad side-effects of the process.

Part of the problem is that the conventional Haber-Bosch process is bad for the environment because it's highly energy-intensive, consumes a significant amount of global energy, and is a major source of greenhouse gas emissions, including CO2 and N₂O.

However, there are mitigations.

Also, this experience is similar to a few other scientific discoveries - the initial impact of the solution is lauded as the “best thing ever” but subsequent research shows significant side-effects that were either unknown or ignored during the original research.

A few other examples I can think of are DDT, leaded petrol, asbestos and more.

This is a cautionary tale that any “perfect solution” might have secondary problems that may not be evident initially.

2.

As with previous issues, issue #89 had a pretty fun list of facts about the number 89.

Here’s what it said:

89 is

the atomic number of Actinium, a chemical element, symbol Ac
- The actinide series, a set of 15 elements between actinium and lawrencium in the periodic table, are named for actinium.
- the introduction of the actinides in 1945 was the most significant change to Dmitri Mendeleev's periodic table since the recognition of the lanthanides
- Owing to its strong radioactivity, actinium glows in the dark with a pale blue light, which originates from the surrounding air ionized by the emitted energetic particles
- The name actinium originates from the Ancient Greek aktis, aktinos , meaning beam or ray.
the 24th prime number, following 83 and preceding 97.
a Pythagorean prime - a prime number of the form 4 n + 1
- Pythagorean primes are exactly the odd prime numbers that are the sum of two squares
- In this case: 89 = 5² (25) + 8² (64)
The 11th Fibonacci number and thus a Fibonacci prime as well.
There are exactly 1000 prime numbers between 1 and 89² =7921.
(Harshal: This is such a cool and interesting and kind of pointless fact. I love it! 😀 )
There is no country with 89 as its international calling code

But wait there’s more…

Hellin's law, also called Hellin-Zeleny's law, is an empirical observation in demography (study of human populations) that the approximate rate of multiple births is a power of 89. So, twin births occur about once per 89 singleton births, triplets about once per 89² , quadruplets about once per 89³ , and so on.

And you thought 89 was just another number! 😄

That’s it for this update, folks.

Stay curious! And share this newsletter with friends and family and everyone who would appreciate staying informed and entertained.

Love,

Harshal

Six Science posts #89

Harshal Chhaya — Sun, 28 Sep 2025 16:17:53 +0000

Thanks to everyone who wrote in and agreed that “Back to the Future” is the BEST. MOVIE. EVAR! (this was in reference to last issue’s “fun facts about 88” that referenced 88mph as the magical speed for the DeLorean in that movie)

Y’all are alright! 😄

Those that don’t agree just haven’t seen it with the right friends. Let me know if you want to co-watch the movie so you can come around to seeing the facts.

Stay curious, friend!

Love,

Harshal

P.S. If you enjoy this newsletter, please forward it to a friend, a colleague, anyone who would appreciate being informed. Thanks!

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This is issue #89. Let’s see what makes 89 an interesting number:

89 is:

the atomic number of Actinium, a chemical element, symbol Ac
- The actinide series, a set of 15 elements between actinium and lawrencium in the periodic table, are named for actinium.
- the introduction of the actinides in 1945 was the most significant change to Dmitri Mendeleev's periodic table since the recognition of the lanthanides
- Owing to its strong radioactivity, actinium glows in the dark with a pale blue light, which originates from the surrounding air ionized by the emitted energetic particles
- The name actinium originates from the Ancient Greek aktis, aktinos , meaning beam or ray.
the 24th prime number, following 83 and preceding 97.
a Pythagorean prime - a prime number of the form 4 n + 1
- Pythagorean primes are exactly the odd prime numbers that are the sum of two squares
- In this case: 89 = 5² (25) + 8² (64)
The 11th Fibonacci number and thus a Fibonacci prime as well.
There are exactly 1000 prime numbers between 1 and 89² =7921.
(Harshal: This is such a cool and interesting and kind of pointless fact. I love it! 😀 )
There is no country with 89 as its international calling code

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

Special past issues

Six Science posts #88

Harshal Chhaya — Sun, 21 Sep 2025 15:10:00 +0000

If you appreciate someone’s work or their talents or whatever, let them know. Now!

I had recently started came across a trivia lover who posted a daily question on X and who loved sharing what they loved. I would occasionally reply with an answer, hit ‘like’ and move on. Found out that they passed away a couple of days back - a freak health issue. 😢

On a more mundane note, last week had a special unique date - 9/16/25 (or 16/9/25 - doesn’t really matter, it was that awesome!)

The three parts form a Pythagorean triplet - 3² , 4² and 5² - three sides of a right-angled triangle. 😃

Stay curious (and appreciative), friends!

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This is issue #88 Let’s see what makes 88 an interesting number:

Number 88 symbolizes fortune and good luck in Chinese culture, since the word 8 sounds similar to the word fā (發, which implies 發財, or wealth, in Mandarin or Cantonese).
In addition, 88 is also used to mean "bye bye (拜拜)" in Chinese-language chats, text messages, SMSs and IMs, because its pronunciation in Mandarin is similar to "bye bye".
In amateur radio, 88 is used as shorthand for "love and kisses" when signing a message or ending an exchange. These number codes originate with the 92 Code adopted by Western Union in 1859.
a palindromic number in bases 5 (323₅), 10 (88₁₀), 21 (44₂₁), and 43 (22₄₃).
a strobogrammatic number
A strobogrammatic number is a number whose numeral is rotationally symmetric, so that it appears the same when rotated 180 degrees. In other words, the numeral looks the same right-side up and upside down (e.g., 69, 96, 1001).
the largest number in English not containing the letter 'n' in its name, when using the system of numbers where 10⁹ is a billion
Atomic number of Radium - symbol Ra, a volatile, lustrous and radioactive silvery-white metal
- All isotopes of radium have half-lives much shorter than the age of the Earth, so that any primordial radium would have decayed long ago.
In the Back to the Future films, 88 miles per hour is the speed that Doctor Emmett Brown's Delorean car had to reach in order to attain time travel. (aside, the best movie EVAR!!)
In music, '88s' is slang for a piano, as a standard keyboard has 88 keys.
In astronomy, the International Astronomical Union lists 88 named constellations
There’s no country with 88 as the international calling code

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

Special past issues

Six Science posts #87

Harshal Chhaya — Sun, 14 Sep 2025 14:05:51 +0000

Last week, Google joined my efforts to foster curiosity by having two really fun Google Doodles

One on quadratic equations (click the link to learn more)

and the other on DNA (click the link to learn more)

I love it when organizations with large reach use their platforms to talk about math and science topics. 🤩

Stay curious, friend!

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This is issue #87. Let’s see what makes 87 an interesting number:

87 is:

the sum of the squares of the first four primes (87 = 2² + 3² + 5² + 7² ).
together with 85 and 86, forms the last semiprime (an integer multiple of a prime number) in the 2nd cluster of three consecutive semiprimes; the first comprising 33, 34, 35.
5! - 4! - 3! - 2! - 1! = 87
the last two decimal digits of Graham's number (click here to learn about Graham’s number - a mind-bogglingly large number. Truly 😮 🤯 )
- Though too large to ever be computed in full, the sequence of digits of Graham's number can be computed explicitly via simple algorithms; the last 10 digits of Graham's number are ...2464195387.
- Harshal’s note: This is so interesting to me. The number itself is too large to compute but we know the last few digits! Wh..aa..t!
Francium is a chemical element; it has symbol Fr and atomic number 87. It is extremely radioactive; its most stable isotope, francium-223 has a half-life of only 22 minutes. It is the second-most electropositive element, behind only caesium, and is the second rarest naturally occurring element (after astatine).
As a consequence of its extreme instability, bulk francium has never been seen.
- It was the last element first discovered in nature, rather than by synthesis.
Cricket in Australia holds 87 as a superstitiously unlucky score and is referred to as "the devil's number". This originates from the fact that 87 is 13 runs short of a century. 187, 287, and so on are also considered unlucky but are not as common as 87 on its own.
87 is by far the most commonly used octane rating of gasoline in the United States, Canada, Australia, and New Zealand.
There’s no country with 87 as it’s international calling code. 870 was assigned to the – Global Mobile Satellite System (Inmarsat)

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.

Love,

Harshal