I have assembled a list of the most controversial Wikipedia articles from the data on this page: https://en.wikipedia.org/wiki/Wikipedia:Database_reports/Talk_pages_by_size
There are 66 pages from the main article namespace listed there, and they are, in order of total size of all talk page archives, as follows:
- Donald Trump
- Intelligent design
- Climate change
- Barack Obama
- Race and intelligence
- Jesus
- United States
- Catholic Church
- Homeopathy
- Circumcision
- Chiropractic
- Monty Hall problem
- Muhammad
- Gaza War (2008-2009)
- Evolution
- Gamergate controversy
- Abortion
- Sarah Palin
- Prem Rawat
- Christ myth theory
- World War II
- India
- Jehovah's Witnesses
- Cold fusion
- Climatic Research Unit email controversy
- September 11 attacks
- Atheism
- Anarchism
- George W. Bush
- Falun Gong
- Armenian Genocide
- Neuro-linguistic programming
- Israel
- Cities and towns during the Syrian civil war
- Jerusalem
- Mass killings under communist regimes
- Transcendental Meditation
- British Isles
- Libertarianism
- Kosovo
- Christianity
- Thomas Jefferson
- International recognition of Kosovo
- United States and state terrorism
- United Kingdom
- Acupuncture
- Israel and the apartheid analogy
- Syrian civil war
- Adolf Hitler
- COVID-19 pandemic
- Russo-Georgian War
- Second Amendment to the United States Constitution
- Tea Party movement
- Murder of Meredith Kercher
- Genesis creation narrative
- Historicity of Jesus
- Electronic cigarette
- List of best-selling music artists
- Shakespeare authorship question
- List of sovereign states
- Taiwan
- Michael Jackson
- 0.999...
- European Union
- Chronic fatigue syndrome
- Russian interference in the 2016 United States elections
0.999... tripped me out so hard when I first learned about it. I'm not surprised it's controversial because it's pretty weird if you've never thought about it before. My favorite proof is the one where you multiply 3 by 1/3 or 0.333.... It equals 1, and therefore so does 0.999...
Similarly amazing was learning about the Euler identity: e^(πi) = -1
Taking one transcendental number to the power of another transcendental number times the square root of -1 somehow equals -1. Took me a long while to understand that one!
It is weird because it is not taught properly in schools, and people aren't made to understand that the decimal representation is just a representation, it's not the number itself, and one number can have many different ones.