Shoulders of Giants

Carl Sagan was the greatest science communicator who ever lived. An astronomer, cosmologist, and author, he co-developed the Pioneer plaque and Voyager Golden Record — humanity's greetings to the cosmos. His 1980 TV series "Cosmos: A Personal Voyage" was the most widely watched PBS series in history. He coined the phrase "billions and billions" and gave us the humbling "Pale Blue Dot" perspective. Sagan believed deeply in the power of science to illuminate human existence and the importance of skeptical thinking.

“The cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself.”

• ✦Cosmos: A Personal Voyage (1980)
• ✦Pale Blue Dot (1994)
• ✦Contact (1985)
• ✦The Demon-Haunted World (1995)

Katherine Johnson was a mathematical genius whose orbital calculations made human spaceflight possible. She computed the trajectory for Alan Shepard's first American spaceflight (1961) and the Apollo 11 Moon landing (1969). John Glenn famously refused to fly the Friendship 7 mission unless Johnson personally verified the computer's numbers. Her work was classified and unpublished for decades until the book and film "Hidden Figures" (2016) brought her story to the world. NASA named a building after her in 2016. President Obama awarded her the Presidential Medal of Freedom.

“I counted everything. I counted the steps to the road, the steps up to church. Anything that could be counted, I did.”

• ✦28 research reports at NASA
• ✦Featured in "Hidden Figures" (2016)
• ✦Presidential Medal of Freedom (2015)
• ✦Congressional Gold Medal (2019)

Neil deGrasse Tyson is the most recognisable astrophysicist alive. Director of the Hayden Planetarium in New York City, he made the audacious — and controversial — decision to demote Pluto to dwarf planet status. He hosted "Cosmos: A Spacetime Odyssey" (2014), the update to Carl Sagan's iconic series, reaching 135 million viewers in 181 countries. His podcast "StarTalk" has 40 million+ listeners. He writes, speaks, and advocates with infectious enthusiasm for making astrophysics accessible to everyone.

“We are part of this universe; we are in this universe, but perhaps more important than both of those facts, is that the universe is in us.”

• ✦Cosmos: A Spacetime Odyssey (2014)
• ✦Astrophysics for People in a Hurry (2017)
• ✦StarTalk Podcast (40M+ listeners)
• ✦Death by Black Hole (2007)

Vera Rubin gave us our first solid observational evidence for dark matter. By studying how stars orbit at the edges of galaxies — which should slow down like the outer planets of our solar system but don't — she concluded that invisible mass, now called dark matter, must permeate galaxies and hold them together. This discovery revolutionised cosmology. Dark matter now accounts for 27% of the universe's energy content. The Vera C. Rubin Observatory in Chile, opening in the 2020s, is named in her honor.

“Fame is fleeting. My numbers mean more to me than my name. If astronomers are still using my data years from now, that's my greatest compliment.”

• ✦Dark matter galaxy rotation curves (1970s)
• ✦Vera C. Rubin Observatory (her legacy)
• ✦National Medal of Science (1993)
• ✦Gold Medal of the Royal Astronomical Society (1996)

Stephen Hawking was perhaps the most famous physicist since Einstein. Diagnosed with ALS at 21 and given two years to live, he went on to revolutionise our understanding of black holes and the Big Bang over a 55-year career. His greatest discovery — "Hawking radiation" — showed that black holes aren't truly black: they slowly emit thermal radiation and eventually evaporate, connecting quantum mechanics with general relativity for the first time. His popular science book "A Brief History of Time" sold 25 million copies and stayed on the Sunday Times bestseller list for 237 weeks.

“Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist.”

• ✦A Brief History of Time (1988 — 25M copies sold)
• ✦Hawking Radiation theory (1974)
• ✦The Universe in a Nutshell (2001)
• ✦Director of Research, Cambridge (DAMTP)

Mae Jemison shattered barriers as the first African American woman to travel in space. A physician, engineer, and polyglot (she speaks four languages), she flew on Space Shuttle Endeavour in September 1992, conducting bone cell and materials processing experiments. Jemison left NASA in 1993 to found the Jemison Group and lead the 100 Year Starship project — a DARPA-funded initiative to develop the science needed for interstellar travel within the next century.

“Never be limited by other people's limited imaginations. If you adopt their attitudes, then the possibility won't exist because you'll have already shut it out.”

• ✦STS-47 mission, Space Shuttle Endeavour (1992)
• ✦100 Year Starship Project (DARPA)
• ✦Founded the Jemison Group
• ✦National Women's Hall of Fame inductee

Kip Thorne won the 2017 Nobel Prize in Physics for his role in detecting gravitational waves with LIGO — confirming Albert Einstein's 1916 prediction after 100 years. He co-founded LIGO (Laser Interferometer Gravitational-Wave Observatory) which detected the collision of two black holes 1.3 billion light-years away in 2015 — the first gravitational wave ever observed. Thorne also served as the scientific advisor for Christopher Nolan's "Interstellar" (2014), and the visualisation of the black hole Gargantua was directly based on his equations.

“The warped side of the universe — objects and phenomena that are made from warped spacetime — is a place of amazing richness and diversity.”

• ✦Nobel Prize in Physics (2017)
• ✦LIGO Co-Founder
• ✦Black Holes and Time Warps (1994)
• ✦Scientific Advisor, Interstellar (2014)

Chris Hadfield brought daily life on the International Space Station to millions of people through social media, YouTube, and a David Bowie cover that became one of the most famous videos in space history. As ISS commander from December 2012 to May 2013, he posted stunning photographs of Earth from orbit and demystified life in microgravity. He was the first Canadian to walk in space (2001, STS-100). His approach — making space feel personal, immediate, and human — inspired a generation to look up.

“Decide in your heart of hearts what really excites and challenges you, and start moving your life in that direction. Every week, do something that your future self will thank you for.”

• ✦ISS Commander, Expedition 35 (2013)
• ✦First Canadian spacewalk (2001)
• ✦"Space Oddity" in orbit — YouTube phenomenon
• ✦"An Astronaut's Guide to Life on Earth" (2013)

Valentina Tereshkova became the first woman to fly in space on 16 June 1963 aboard Vostok 6, spending 3 days in orbit and completing 48 orbits of Earth. At the time, she had accumulated more time in space than all American astronauts combined. A textile factory worker and amateur parachutist before her selection, she was chosen from 400 applicants and needed just 18 months of training. Her call sign was "Seagull." She remains the only woman to have flown solo in space.

“If a woman can be a railroad engineer, why not a pilot? And if a pilot, why not an astronaut?”

• ✦Vostok 6 mission (June 1963)
• ✦Hero of the Soviet Union
• ✦Order of Lenin
• ✦UN Special Ambassador for Women

On 12 April 1961, Yuri Gagarin became the first human being to travel to space, orbiting Earth once aboard Vostok 1 in 108 minutes. A 27-year-old Soviet Air Force pilot from a small village, his famous words on launch were "Let's go!" ("Poyekhali!"). His mission proved that humans could survive in space. He became a global hero, toured the world as a symbol of Soviet achievement, and inspired generations. April 12 is now celebrated as "Yuri's Night" — the world space party.

“The Earth is blue. How wonderful. It is amazing.”

• ✦Vostok 1 mission (April 12, 1961)
• ✦Hero of the Soviet Union
• ✦UN Space Medal
• ✦April 12 = Yuri's Night (celebrated worldwide)

Annie Jump Cannon created the Harvard Classification Scheme for stellar spectral types — the O, B, A, F, G, K, M system still used by every astronomer in the world today. Working as one of the "Harvard Computers" (women hired by Edward Pickering), she classified over 350,000 stars by hand, examining glass photographic plates. She could classify 300 stars per hour. Her work was the foundation on which all modern stellar astrophysics is built. Our Sun is a G-type star — a category she defined.

“In these days of great trouble and unrest, it is good to have something outside our own world, to study... the stars are absolutely democratic.”

• ✦Harvard Classification Scheme (OBAFGKM)
• ✦Henry Draper Catalogue (350,000 stars)
• ✦Henry Draper Medal (1931)
• ✦Honorary doctorate from Oxford (1925 — first woman)

Elon Musk founded SpaceX in 2002 with the explicit mission of making humanity multiplanetary — specifically, to establish a self-sustaining city on Mars. What followed was the most ambitious private space program in history. SpaceX became the first private company to dock with the ISS (2012), developed the first reusable orbital rocket booster (Falcon 9, 2015), flew NASA astronauts to the ISS aboard Crew Dragon (2020), and is building Starship — the most powerful rocket ever constructed. The plan: 1 million people on Mars by 2050.

“I think it's very important that we make life multiplanetary. It's going to be really quite dangerous and quite difficult and it'll be exciting.”

• ✦SpaceX Falcon 9 reusable booster (2015)
• ✦Crew Dragon crewed ISS mission (2020)
• ✦Starship first successful flight (2023)
• ✦10,000+ Starlink satellites deployed

In 499 CE — when he was just 23 years old — Aryabhata wrote the Aryabhatiya, a 118-verse mathematical and astronomical treatise over a millennium ahead of its time. He calculated π as 3.1416 (within 0.01% of the modern value), computed the length of Earth's sidereal day as 23 hours, 56 minutes, 4.1 seconds — within 0.01 seconds of the modern value — and measured Earth's circumference to within 0.2% accuracy. He correctly explained that solar and lunar eclipses are caused by shadows, not by a mythical demon swallowing the Sun. He stated that the Moon and planets shine by reflected sunlight — a fact Europe would not accept for another thousand years. His work was adopted by Islamic astronomers in Baghdad and transmitted to Renaissance Europe, forming part of the intellectual bedrock of modern astronomy.

“Just as a person in a moving boat sees stationary objects moving in the opposite direction, so the stars appear to move westward for a person on Earth — it is the Earth that rotates.”

• ✦Aryabhatiya (499 CE) — written at age 23
• ✦π = 3.1416 — within 0.01% of modern value
• ✦Sidereal day: 23h 56m 4.1s — within 0.01s of modern value
• ✦India's first satellite (1975) named "Aryabhata"

Brahmagupta's Brahmasphutasiddhanta (628 CE) — written at age 30 — changed mathematics forever. He was the first scholar in history to formally define arithmetic rules for zero as a number. He established rules for negative numbers and described gravity using the Sanskrit term gurutvākarṣaṇam — "gravitational attraction" — writing: "it is the nature of the earth to attract and to keep things," roughly 1,000 years before Newton. His treatise was translated into Arabic at the court of Caliph al-Mansur in Baghdad, directly transmitting zero and the rules of arithmetic to the Islamic world — and through them, to Renaissance Europe. Every calculation ever performed with zero traces back to this man from Bhinmal, Rajasthan.

“The sum of zero and a positive number is positive. Zero subtracted from zero is zero. A number multiplied by zero is zero.”

• ✦Brahmasphutasiddhanta (628 CE) — 1,008 verses
• ✦First complete rules for arithmetic with zero
• ✦gurutvākarṣaṇam — gravity as attractive force
• ✦Translated into Arabic — shaped global mathematics

Vikram Sarabhai founded ISRO (Indian Space Research Organisation) in 1969 and built India's space programme from scratch. A physicist trained at Cambridge, he convinced the Indian government that space technology was not a luxury but a necessity for national development. In 1963 he established the Thumba Equatorial Rocket Launching Station in Kerala — on the magnetic equator — and launched India's first rocket. He proposed using space and satellite technology to solve India's most pressing challenges: education, agriculture, meteorology, and communications for remote communities. He died in 1971 before seeing his dream realised — but every Indian satellite, every PSLV launch, every Chandrayaan and Mangalyaan mission stands on the foundation he built.

“There are some who question the relevance of space activities in a developing nation. To us, there is no ambiguity of purpose. We do not have the fantasy of competing with economically advanced nations in exploring the Moon or the planets or manned spaceflight.”

• ✦Founded ISRO (1969)
• ✦Established Thumba Equatorial Rocket Launching Station (1963)
• ✦Padma Bhushan (1966)
• ✦Bharat Ratna (posthumous, 1966)

APJ Abdul Kalam — the "Missile Man of India" — led the development of India's first indigenous satellite launch vehicle, SLV-3, which successfully placed the Rohini satellite in orbit in 1980. He then directed India's Integrated Guided Missile Development Programme (IGMDP), developing the Agni and Prithvi missiles. He served as Principal Scientific Adviser to the Government of India before being elected the nation's 11th President (2002–2007). Kalam inspired hundreds of millions with his humble origins — born to a poor family in Rameswaram, Tamil Nadu — and his extraordinary rise through science. He was mid-lecture to a classroom of students when he passed away at 83. He is remembered as much for the dreams he ignited as for the rockets he built.

“You have to dream before your dreams can come true.”

• ✦SLV-3 — India's first satellite launch vehicle (1980)
• ✦Integrated Guided Missile Development Programme (IGMDP)
• ✦11th President of India (2002–2007)
• ✦Wings of Fire — autobiography (1999)

Kalpana Chawla became the first Indian woman — and the second Indian — to reach space aboard Space Shuttle Columbia in November 1997 (STS-87), logging 376 hours in orbit. A mechanical and aerospace engineer with a PhD from the University of Colorado, she was selected by NASA in 1994. She returned for a second mission on STS-107 in January 2003. On 1 February 2003, Columbia disintegrated during re-entry over Texas, claiming Kalpana and all six crewmates 16 minutes before landing. She is remembered not as a victim but as a pioneer who burned bright — her story transformed STEM aspirations for an entire generation of Indian girls. NASA's asteroid 51826, a Mars orbital station, and India's first operational meteorological satellite series are all named in her honour.

“When you look at the stars and the galaxy, you feel that you are not just from any particular piece of land, but from the solar system.”

• ✦STS-87 mission, Space Shuttle Columbia (1997)
• ✦STS-107 mission (January 2003)
• ✦Congressional Space Medal of Honor (posthumous)
• ✦Asteroid 51826 Kalpanachawla — named in her honor