On 29 October 1675, Gottfried Wilhelm Leibniz wrote a single elongated letter S in his notebook, creating the integral sign that would become the mathematical foundation of modern science. This episode explores how a simple symbol quietly rewired humanity’s understanding of the universe, then moves through three other significant moments from this date: John Glenn’s return to space at seventy-seven in 1998, the Lion Air Flight 610 tragedy in the Java Sea in 2018 that exposed fatal flaws in the Boeing 737 MAX, and China’s announcement ending its controversial one-child policy in 2015 after thirty-five years. From calculus notation that still powers every satellite launch to demographic experiments that reshaped a nation, these stories reveal how human ambition, tragedy, and policy decisions echo across centuries.

• Intro A German mathematician in Paris writes a single symbol that will quietly rewire human understanding of the universe.
• Leibniz and the Long S: The Symbol That Built the Modern World On 29 October 1675, Leibniz creates the integral sign, a stretched S for summa that becomes the visual grammar of calculus. His notation proves superior to Newton’s, spreading through European mathematics and becoming the foundation for classical mechanics, electromagnetism, quantum mechanics, and every engineering calculation since.
• John Glenn Goes Back to Space at Seventy-Seven In 1998, the first American to orbit Earth returns to space aboard Discovery at age seventy-seven. Glenn serves as a research subject studying how spaceflight affects older bodies, contributing to ageing science whilst proving extraordinary lives need not end at retirement.
• Lion Air Flight 610: The Java Sea Tragedy In 2018, Lion Air Flight 610 crashes into the Java Sea twelve minutes after takeoff, killing all 189 people aboard. A faulty automated system on the Boeing 737 MAX repeatedly pushes the nose down despite pilot efforts. A second MAX crash five months later leads to a worldwide grounding lasting nearly two years.
• China Ends the One-Child Policy In 2015, China announces the end of its thirty-five-year one-child policy, introduced in 1980 to address overpopulation. The policy slowed population growth but involved coercion, created gender imbalances, and reshaped family structures. Its end addresses an ageing population and shrinking workforce, though birth rates remain lower than officials anticipated.
• Outro Four moments from 29 October: a symbol, an astronaut, a tragedy, and a policy. History rarely arrives tidy.

• https://www.britannica.com/biography/Gottfried-Wilhelm-Leibniz
• https://mathshistory.st-andrews.ac.uk/Biographies/Leibniz/
• https://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-95.html
• https://www.nasa.gov/feature/john-glenn-s-return-to-space
• https://reports.aviation-safety.net/2018/20181029-0_B38M_PK-LQP.pdf
• https://www.bbc.co.uk/news/world-asia-46014463
• https://www.theguardian.com/world/2019/mar/10/ethiopia-airlines-crash-boeing-737-max-8-latest-news
• https://www.bbc.co.uk/news/world-asia-34665539
• https://www.theguardian.com/world/2015/oct/29/china-abandons-one-child-policy