What scientific discovery changed the world the most?

 Pinpointing the single most world-changing scientific discovery is a complex question. Different discoveries have had profound impacts on various aspects of human life, making a clear-cut choice difficult. Here are some contenders for the title, each with strong arguments:

• Electricity: Understanding and harnessing electricity revolutionized nearly every facet of society. It powers our homes, industries, communication systems, and countless technologies we rely on daily.

• Germ Theory of Disease: The discovery that microorganisms cause diseases led to advancements in hygiene, sanitation, and medical treatments. This dramatically improved public health and life expectancy.

• Penicillin and Antibiotics: The development of antibiotics revolutionized medicine by effectively combating bacterial infections. This saved countless lives and improved overall health outcomes.

• Theory of Evolution by Natural Selection: Charles Darwin's theory fundamentally changed our understanding of life on Earth. It explains the diversity of species and has had a profound impact on biology, medicine, and even philosophy.

• The Internet: The invention of the internet has dramatically transformed communication, information access, and global connectivity. It has revolutionized how we work, learn, and interact with the world.

Ultimately, the "most important" discovery depends on what aspect of the world you value most. Each of these discoveries has had a lasting impact on humanity's trajectory.