1.11 The Great DebateApril 14, 2023

What are the biggest scientific controversies in

science today? What about physics? What about

astronomy?

Idiotic controversies

• Homeopathy, astrology, bracelet with holograms, charcoal with meals, nutritional semen, detox, ghosts, mind-reading, tarot cards, tea leaves,

Real controversies in science

• Dark matter, dark energy, string theory, M theory, abiogenesis, extra-terrestrial abiogenesis, earth-like exoplanets, anthropic global warming, anthropic principle

Aims

• Describe the Great Debate• Explain how the debate was decided

1920’s

• The great debate was between Harlow Shapely and Heber Curtis

• Amongst many things the debate centred on whether nebulae were within the Milky way galaxy or were separate galaxies themselves

Faint fuzzies

• These nebula were either island universes themselves like our own Milky Way but incredibly far away OR

• They were nearby clouds of gas.• Shapely won the debate initially but Curtis was

ultimately right about the huge distances involved.

• The Universe quickly became a whole lot bigger!

Questions

• What was Shapleys new observation about the nebula?

• Read about the great debate of 1920 in your textbook. Copy the table below and write the main ideas of the two astronomers in two columns. Who seemed to have stronger evidence. Who was later proved correct.

• What new observations showed that there were objects outside the Milky Way?

Homework

• Read ‘How did the Universe begin’ for next lesson.