In 1859, Charles Darwin shook the world with 'On the Origin of Species'. He proposed natural selection: species change over time, and traits that improve survival are passed on to offspring.
It was revolutionary but not fully proven in his time. 🧵1/6
Darwin did not know about genetics. He observed patterns, fossils, and species variation but could not explain how traits were inherited. This gap led some to doubt evolution despite strong observational evidence. 🧵2/6
Gregor Mendel’s work on pea plants, rediscovered in 1900, explained inheritance. Traits are passed through discrete units called genes. This connected Darwin’s ideas to a mechanism and launched modern evolutionary biology. 🧵3/6
Through the 20th century, evidence grew from fossils, embryology, comparative anatomy, and later DNA sequencing. Life clearly changes over time, and evolution occurs through natural selection, mutation, genetic drift, and gene flow. 🧵4/6
Today evolution is observable. Bacteria develop antibiotic resistance. Viruses like influenza and COVID-19 evolve constantly. Experiments show changes in real time. Evolution is a fact supported by overwhelming evidence. 🧵5/6
Science defines theory as a framework explaining facts. Evolution is both a fact because species change over time and a theory because natural selection explains how.
From Darwin to modern genetics, evolution is undeniably real. 🧵6/6
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Carl Sagan wrote about the cosmos, but he was always writing about us.
If you want to feel wonder, sharpen your reason, stay humble, and experience that rare sense of cosmic awe, these books are where you should start. 🧵1/12
Sagan’s most famous book and still one of the best introductions to our place in the universe. He takes you from the birth of stars to the birth of human curiosity and shows how every scientific discovery is a story of relentless courage, doubt and imagination.
Why you should read it: It teaches the joy of understanding the world and it renews your sense of awe. 🧵2/12
Inspired by the Voyager image of Earth from the edge of the Solar System. This is Sagan at his most reflective and humane. He writes about responsibility, stewardship and the fragile beauty of our only home.
Why you should read it: It puts every fear, ego, war and conflict into perspective. 🧵3/12
I am all for miracles because the universe we live in is far richer than we can imagine. The alchemy of stars, hydrogen atoms seemingly awakening to explore themselves, the scale and depth of everything around us... nothing we know is short of a miracle. 🧵1/8
And yet, most of the universe remains beyond our understanding. Approximately 95% of it lies hidden and dark, composed of dark matter and dark energy. Even in the small fraction we do know, we barely scratch the surface. That is too little to claim certainty about anything. 🧵2/8
From the little we do know, we see our place in the galaxy. We revolve around a supermassive black hole. Our sun is one among 100 to 400 billion stars in our galaxy, which itself is one among 200 billion to 2 trillion galaxies across the universe. 🧵3/8