The Course Of Human History Was Forever Altered By These 30 Key Moments

He noticed a mold killed bacteria in a petri dish, leading to the development of antibiotics, which revolutionized medicine and saved countless lives.

Stanislav Petrov was the Soviet duty officer in charge of an early-warning system on September 26, 1983. The system detected a missile launch from the United States. Then another... and another (up to 6 total). He decided that the reports were false alarms (spoiler... they were), and probably saved humanity from a nuclear holocaust. In an investigation later conducted by the Soviet military it was discovered that the sun's reflection was creating false positives on the warning system.

The invention of vaccines revolutionized public health by preventing the spread of deadly diseases, saving millions of lives worldwide. It drastically reduced the impact of pandemics, leading to longer life expectancies and enhanced global health security.

During the 19th century, Russia occupied Poland and enforced limits on education demaning schools will trach nothing past what is required to be a peasant. The polish people began underground universities. One of the many graduates of these universities was Maria Curie.

It allowed the proliferation and spread of ideas at an exponentially higher rate and it allowed books to become something the masses could afford. The Enlightenment and by extension the modern world never could have happened without it. It represented as big of an information revolution as the Internet does today.

Vasily Aleksandrovich Arkhipov was a high-ranking officer in the Soviet Navy who played a pivotal role in averting the launch of a nuclear torpedo from a Soviet submarine targeting U.S. Navy ships during the Cuban Missile Crisis in October 1962. While the potential consequences of such an action remain uncertain, some have speculated that it could have led to a full-scale nuclear conflict.

It ended centuries of religious infighting in Europe and first introduced (or at least popularized) the idea of a sovereign, bordered nation state as opposed to quasi-tribal ideological/feudal principalities.

We'd still be using letters for communication, contruction tools wouldn't allow us to build any structure more than 10 or so stories, spark is a key part of an internal combustion engine- so no cars unless you had a steam engine

Take any major changes between modern geopolitics and that of 50 years ago. The net is a big part of the underlying causes.

Cyrus the Great's decision to let the Jews return to Judea, and to build the second temple for them.
Without this, Judaism likely dies off as a major world religion. Without Judaism, no Christianity, and no Islam.
There would surely be other religions appear to take their place, and other religious conflicts throughout the millenia. But when Christianity and Islam in their many forms account for over 4.3 billion followers worldwide, it's hard to overstate how important that decision was in shaping the world forever after.

The volcanic winter of 536 was the most intense climatic cooling event in the Northern Hemisphere in 2,000 years, caused by at least three volcanic eruptions. These eruptions released sulfate aerosols, blocking sunlight and cooling the atmosphere for years. In March 536, Constantinople saw darkened skies and a drop in temperatures.

Daniel Yergin's The Prize is the best book on it. It not only explains every direct conflict in the Middle East but even indirect issues such as the beginnings of the Cold War, US LatAm policy, Israel and many others. It's like almost everything is one or two degrees of separation away from the Middle East.

It wasn't tiny or overlooked but the ripple effect from that decision has been an order of magnitude greater than I think anyone would have expected

In exchange for Chinese cooperation, the US managed to isolate the Soviet's even further. In hindsight, we could argue if the trade-off was worth it as China is now the enemy.

If Charles Martel lost, Christendom would have been destroyed by the Umayyad Caliphate. There would be no Papal States, no Charlemagne, no Holy Roman Empire, No Germany, no third reich. Quite frankly history as we know it would turn out quite different.

Charlotte was the daughter of George IV and was the last hope for the Hanoverian line and was very popular. After she died in childbirth in 1818, she and her stillborn son were greatly mourned. Her death made George IV’s brothers dump their mistresses and many illegitimate children and marry princesses and father legitimate children, this lead to a baby being born who would become Queen Victoria, also known as the Grandmother of Europe.

It was the first practical use for the newly developed File Transfer Protocol and predecessor of things that now are known colloquially as the "Internet"

Bankrupting Scotland was a direct precursor to the act of Union. Without this, Scottish and British history would be very different. 

Seems insignificant but it revolutionized how we organized documents in offices worldwide. Before that, people would literally punch holes in papers and tie them together with string. My grandma worked as a secretary in the 50s and told me how it completely changed their workflow

It was a forged document discovered by the midici that gave early Catholics land and power , no one really knows who wrote it , but because of it the Catholics got as powerful as they did.