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Flashcards in Historical milestones in Astronomy Deck (24):

Why did the earth-centred solar-system/universe model fall out of favour?

Retrograde orbits could not be accurately explained.


When was the size of the Earth first accurately estimated?

By Eratosthenes in 240BC


How was Einstein's theory of relativity proven correct?

Through the testing of the curvature of space-time.


Who devised the first heliocentric (sun centric) model of the solar system?



What is the geocentric model?

Geocentric means earth centric.


Who was Aristarchus?

He devised the first heliocentric model of the solar system.

He also devised a way of measuring the size of the moon relative to size of earth (but this was wrong as he didn't understand how shadows work).


How did the Babylonians contribute to Astronomy?

They devised the model of measuring a circle i.e. 360 degrees (based on their view of a year being 360 days).


Who was Copernicus?

He perfected heliocentric model 1,750 years later (after Aristarchus) - but only planets up to Saturn were known - he took orbits to be circular (rather than elliptical).


Who was Eratosthenes?

He measured circumference of earth (accurately!) using Pythagoras's Theorem.


Who was Hipparchus?

He invented star catalogues.


Who was Ptolemy?

He "perfected" geocentric model.


Who was Tycho Brache?

Data collector (with silver nose!) but his student Johannes Kepler created the models including heliocentric ellipses and precursor to Newton's law of gravity.


Who was Galileo?

Inventor of modern scientific method - he did the experiments, recorded results and publicised them in Italian to make them accessible to the general population.

Improved (but not invented) the telescope.

Discovered the first 4 of Jupiter's moons, sunspots and the rings of Saturn!

Proving Copernicus's heliocentric model got him under house arrest for the last 9 years of his life.


What are Retrograde Orbits?

These occur due to the amount of time the planets take to orbit the sun and the difference between the planets (e.g. Earth:Mars 1yr:c2yrs). So when Earth passes inside Mars it looks at though Mars has travelled back on itself.


Who was Newton?

Provided theory of gravity.

Explained Kepler's laws.

Co-inventor of calculus.


Who was Herschel?

Discovered Uranus.


Who was Le Verrier?

Discovered Neptune (by mathematical prediction).


Who was Einstein?

Provided general theory of relatively (GR) which unifies space and time into space-time.

Proved Newton's theory of gravity = curvature of space-time.

Determined that nothing is straight - "matter tells space how to behave, space tells matter how to move".


Who was Hubble?

Provided Hubble's Law and "Hubble expansion" i.e. the universe is expanding and that galaxies are rapidly moving away from each other.

Don't know why universe expansion is accelerating but refer to this as "dark energy".


Who was Zwicky?

Discovered "dark matter".

But we have no idea what it is but believe it is what holds galaxies together.


Who are Penzias & Wilson?

Discoverers of the Cosmic Microwave Background (CMB) i.e. a hot relic of the Big Bang.

Accidentally discovered by Penzias & Wilson due to "hiss" heard and nothing to do with pigeons!


Where does the word 'planet' come from?

Planet = comes from Greek word 'to wander'.


What makes a shadow?

Umbra (narrowing shadow directly behind an object) and penumbra (expanding shadow directly behind an object).


When was the first exoplanet discovered?

1995 --> first planet outside of our solar system discovered "exoplanet"