Test 1 Short Answers Flashcards
Which Wavelengths can we see?
400nm - 700nm.
How is Light Made?
Movement of electrons - photons with more energy emitted.
What Colour are the Hottest Things?
Blue.
Why does Colour Change with Temperature?
Hotter an object is, the more luminous it is - L = AoT^4.
How are Planets Formed?
Disc of crumbling star material gradually forms planets.
What is Inwards of the Snow Line?
Refractory material.
How do we Study the Earth’s Interior?
Seismic waves bouncing off transitions between different materials, densities and temperatures.
What is the Structure of Earth’s Core?
Inner core (solid), outer core (liquid), stiff mantle.
Why is the Earth’s Core Solid?
Increased pressure = higher melting points.
What is the Purpose of the Magnetic Field?
Protects against solar wind.
Which 2 Factors Changed our Atmosphere?
Outgassing and bombardment of meteorites/comets.
How does the Greenhouse Effect Occur?
Sun’s radiation heats the surface, gases in atmosphere absorb infrared light (heat energy re-radiated as infrared radiation).
What are the Human Effects on the Atmosphere?
Greenhouse effect, destruction of the ozone layer (absorbs UV).
How does the Moon Rotate?
Rotates on its axis at the same rate as it orbits the Earth.
Why does Mercury have a 3:2 Resonance?
Differential gravity field creates asymmetry and extra mass in one direction (higher force due to gravity will act on this bulge).
How do we know about the Solar System’s Formation?
We have a record of impacts (craters).
What are the 3 Main Properties of Mercury?
It is the densest, oldest and most massive of the inner planets.
Why is Venus Inhospitable?
It has too much greenhouse effect.
What happened to the Water on Venus?
It evaporated due to runaway greenhouse effect.
What are the 4 Pieces of Evidence for Water on Mars?
Outflow channels from floods, splash craters, gullies from debris flow, central channel in valley suggests long-term flowing water.
What is the Structure of Jupiter?
Core, metallic hydrogen, molecular hydrogen.
What are the 4 Galilean Moons?
Io, Europa, Ganymede, Callisto.
Why are there Gaps in Saturn’s Rings?
Orbital resonances with Saturn’s moons - gravity of moons impact orbits of ring systems.
Why is there a Euche Gap?
Pan collects material from Saturn’s rings.
Why does Uranus have such an Extreme Tilt?
Something really big hit it.
Why is there a Limit to the Closeness of Inner Moons around Planets?
The Roche limit.
What are the 4 Requirements for a Dwarf Planet?
Orbits the Sun, sufficient mass for round shape, not cleared neighbourhood around its orbit, not a satellite of another planet.
What are the 5 Main Dwarf Planets?
Ceres, Pluto, Haumea, Makemake, Eris.
What is Differentiation in Asteroids, Comets and Meteors?
Dense material sinks, light material floats.
What are the 4 Techniques for Detecting Extra Solar Planets?
Transits, radial velocity, micro-lensing, direct lensing.
How do we Use Transit to Detect Extra Solar Planets?
Plot brightness vs time, every so often the star becomes dimmer as a planet passes in front of it.
How do we Use Radial Velocity to Detect Extra Solar Planets?
Planet orbiting star shifts it ever so slightly backwards and forwards leading to absorption lines.
How do we Use Micro-Lensing to Detect Extra Solar Planets?
Two stars line up exactly and the star in the foreground appears brighter (there is a bump in the data if a planet is involved).
Which Star is the Planet Orbiting in Micro-Lensing?
Planets are orbiting around foreground star.
How do we Use Direct Imaging to Detect Extra Solar Planets?
Block out light of the star, allowing us to photograph the planet itself.
What Range does a Planet’s Radius have to be for it to be Habitable?
0.8 - 2.5K.
Why can’t a Planet’s Radius be too Small?
Too small for an atmosphere.
Why can’t a Planet’s Radius be too Large?
It will become a gas giant.
Which Model did Eudoxus Propose?
27 spheres.
Which Model did Aristotle Propose?
55 spheres in the heavens, imperfect earth at the centre.
Which Model did Aristarcus Propose?
Ordered the planets, said stars were suns (ideas rejected).
Why did the Greeks think Earth was Stationary?
Not part of the ‘Heavens’, little change in Heavens but much change on Earth, our senses.
What did Galileo Achieve?
Changed ‘faith-based’ science to ‘observation-based’ science, found evidence for Copernicus’ model of the Universe.
What were Galileo’s 5 Major Discoveries?
Galilean moons of Jupiter, rings of saturn, craters of the moon, sun spots, phases of Venus.
What were Tycho-Brahe’s Achievements?
Measured planets, said sun going around Earth, but all other planets going around Sun.
What is Important to Remember about Circular Motion?
It needs a force.
How are Tides Formed?
Moon pulls on liquids to give high tides when moon is close. Combined with Sun gives even higher tides.
What does Special Relativity say about the Speed of Light?
It is the same for all observers no matter how they’re moving.
Why can’t we Travel Faster than the Speed of Light?
We get too heavy - E = mc^2.
Why does Light Bend?
Light travels along the curved space taking the shortest path between 2 points - stronger gravity = greater bend in the light path.
How do we Measure Distance to the Sun?
Transit of Venus.
How do we Measure Size of the Sun?
Angular size and distance.
How do we Measure Mass of the Sun?
Kepler’s Law and Newton.
How do we Measure Density of the Sun?
Mass/volume.
How do we Measure Surface Temperature of the Sun?
Measure energy arriving at Earth and use Boltzmann’s Law.
How are Sunspots Formed?
Convections are suppressed.
How are Prominences Formed?
Trapped gas in magnetic field lines.
How are Flares Formed?
Twisted magnetic field lines snap.
How Long is a Sunspot Cycle?
11 years.
What is Important to Remember about the Sun’s Core?
It rotates 4x faster than the surface.
How is Nuclear Fusion the Energy Source of the Sun?
Nuclei able to get close enough for strong nuclear forces to act - nuclei fuse and energy released.
