Kepler’s contributions to astronomy?
What makes Kepler’s universe different from Ptolemy’s?
Who did Kepler work for to test his ideas?
Why did Kepler’s ideas describe observations better than Copernicus?
- Understood the motions of the planets (see Kepler’s 3 Laws)
- No perfect circles but elipses
- Kepler worked for Tycho, used his observation data, especially of Mars, that helped him deduce his 3 Laws of Planetary Motion
- He replaced Copernicus’ circular orbits but with ellipses and they matched up perfectly
Newton’s contributions to astronomy?
What were his discoveries and what are their significances?
How did those discoveries affect others?
- Kepler’s laws described elliptical orbit but not why, Newton set the standard for scientific theory and natural law.
- Newton’s Laws of Motion, described everyday concepts such as concepts such as force, velocity, acceleration, and mass.
- Newton’s laws of motion are essential to our understanding of
the motions of the planets and all other celestial bodies.
Contributions of Galileo to astronomy?
Discoveries and signficance?
How did discoveries affect others?
- Galileo used the telescope for the first time to study the heavens
- Moon not smooth but cratered (planets not perfect like the Greeks thought); Jupiter had its own 4 moons (another centre of motion in universe); Venus had phases like the moon (geocentrism impossible)
- Sun at centre allowed Newton to formulate his Law of Gravity
3 Important Pillars of the Scientific Approach:
Why are there no 100% facts in science?
- 3 Fundamental Steps:
- The process of observation in nature
- Construction of a model, or some other explanation (hypothesis or theory)
- Testing B against A, and revising B to better predict A
- If your hypothesis/model cannot be tested against nature, it is not valid science, but a philosophy!
Summarize the recent observation by the ALMA array in Chile of the proto-planetary disk surrounding HL Tau:
What does it confirm about the Solar Nebula Theory, what is surprising about it?
Why is this observation important?
- ALMA with new configurations, pointed antennas at HL Tauri, found fine detail in the disk of leftover bits from the star’s birth. Showed rings separated by gaps
- Confirms that young planet-like bodies form in the star’s birth.
- Young stars like HL Tauri are born in clouds of gas and dust, collapsed under the effects of gravitation, forming dense hot cores and ignites making stars
- These young stars are initially cocooned in the remaining gas and dust, which eventually settles into a protoplanetary disk
- Suprising because HL Tauri is very young, only 1 mil and already forming planets!
- Helps us understand how our Solar System formed. May show us how our solar system looked like 4 billion years ago.
History and significance of Neptune’s discovery?
Relevant names involved?
Why was the discovery significant to physics?
- Galileo actually discovered Neptune 233 years before its discovery in 1846. Astronomers noted irregularities in Uranus’ orbit that couldn’t be explained without another orbital influence nearby, it was Neptune tugging at Uranus.
- 2 astronomers: John Couch Adams and Urbain Le Verrier made mathematical calculations on a hypothetical 8th planet
- Adams and Le Verrier used mathematics to predict that the gravity from another planet beyond Uranus was affecting the orbit of Uranus. They figured out not only where the planet was, but also how much mass it had. Using those calculations they found the planet in a Berlin Observatory as Galle found out in 1846
Describe the role of the greenhouse effect on the climate of Venus
How does this effect work?
Why does the greenhouse effect not cause the planet Mars to become hot?
- Scientists think that Venus used to be more similar to Earth, with lower temperatures and even liquid water on the surface of the planet.
- At some point, billions of years ago, the planet started to heat up.
- all the water on the surface evaporated into the atmosphere.
- Water vapor is an even more powerful greenhouse gas than carbon dioxide and this caused temperatures to rise even more.
- Then the surface of Venus got so hot the carbon trapped in rocks sublimated into the atmosphere and mixed with oxygen to form even more carbon dioxide.
- Light from the Sun strikes the ground of Venus, and warms it up.
- The ground tries to radiate heat back into space;
- but the carbon dioxide traps much of it around the planet keeping it so warm.
- Mars is smaller and colder than Venus, receives less solar energy, has a thinner atmosphere of CO2 so it does not absorb as much
Why does an initially spherical spinning cloud flatten into a disk as it collapses?
What regularities in our solar system does this flattened spinning disk explain?
Which planets or planets in our solar system show strange behaviours?
- First giant cloud of gast and dust, cold, various elements from previous dead stars
- the cloud collapses under its own self-gravity
- once collapse starts then gravity takes over
- the gravitational energy of infalling particles into thermal energy heating the disk
- The Sun rotates in the same direction as the planets revolve; and the planets rotate in the same direction as they revolve; all planets have the same spin rotation as the Sun
- Retrograde orbits like the ones found in Venus, Uranus and Pluto all contradict the nebula hypothesis
