Space physics

• What is at the center of our solar system?

  The Sun
• What does it mean that the solar system is heliocentric?

  It means the Sun is at the center of the solar system.
• Name two dwarf planets that orbit the Sun.

  Pluto and Ceres
• What other celestial bodies are found in our solar system besides planets and dwarf planets?

  Asteroids and comets
• How is our solar system positioned within the Milky Way galaxy?

  It is a small part of the Milky Way galaxy.
• What is the mnemonic to remember the order of the planets in our solar system?

  • My Very Early Morning Jam Sandwich Usually Nauseates (people)
• What are the primary compositions of smaller and larger planets?

  Smaller planets are primarily made of rock, while larger planets are primarily made of gas.
• Do all planets orbit the Sun on the same plane?

  Yes, all planets orbit the Sun on the same plane.
• Do all planets rotate at the same speed?

  No, planets rotate at different speeds.
• What can cause a planet to rotate in the opposite direction or on a skewed axis?

  Past collisions can throw a planet's axis off balance.
• Why do larger planets have rings?

  Because their strong gravitational field attracts debris.
• What was the initial model of the solar system?

  • Geocentric model
  • Earth at the center
  • Planets, moon, and sun orbited Earth
  • Everything orbited in perfect circles
  • Fixed background of stars
• What model replaced the geocentric model and what was its main evidence?

  The heliocentric model replaced it, with Mars' retrograde motion as evidence.
• What is retrograde motion?

  It is when a planet appears to reverse its direction in the sky due to the relative motion of Earth.
• Who observed moons orbiting Jupiter, providing evidence against the geocentric model?

  Galileo
• What did Kepler discover about planetary orbits?

  He showed that planets orbit in ellipses, not circles.
• What causes a planet to change direction as it orbits the Sun?

  The gravitational force from the Sun causes the planet to change direction constantly.
• How does the velocity of a planet change as it orbits the Sun?

  The velocity is always changing due to the gravitational force acting on it.
• What happens to a planet's speed as it moves closer to the Sun?

  The orbital speed of the planet increases as it moves closer to the Sun.
• What is the first step in the life cycle of a star?

  A dust and gas cloud is present in a galaxy.

  
• What causes the dust and gas cloud to become more concentrated?

  The gravitational attraction between the gas and dust particles draws them together.
• What happens to the temperature and pressure of the cloud as particles get closer together?

  The temperature and pressure of the cloud increase.
• What occurs when the pressure in the cloud becomes great enough?

  Gas and dust particles are able to fuse together.
• What is produced when hydrogen nuclei fuse together?

  Helium nuclei are formed, releasing a large amount of energy.
• What does the energy released from fusion do in the context of star formation?

  It opposes the gravitational collapse of the cloud.
• What happens when a star runs out of gas to fuse?

  The star collapses as it is no longer in equilibrium.
• What happens to a massive star after it collapses?

  It produces a supernova and may leave behind a neutron star or black hole.
• What occurs to a normal-sized star after it collapses?

  It produces a planetary nebula and leaves behind a white dwarf.
• What is red shift in relation to galaxies?

  Light appears red shifted from galaxies that are moving away from Earth.
• What does the change in distance of each galaxy's speed indicate?

  It is evidence of an expanding universe.
• How can the expansion of the universe be visualized?

  • Imagine the start of the big bang as an un-stretched balloon.
  • Galaxies are on the surface of the balloon.
  • As the universe expands, the balloon expands, increasing the distance between galaxies.
• What happens to the wavelength of light from a galaxy as it moves away from us?

  The wavelength appears to get larger, becoming red-shifted.
• How does the frequency of light change as a galaxy moves away?

  The frequency appears to decrease as the source moves further away.
• What does red shift evidence suggest about the universe's origin?

  It suggests that the universe is expanding and must have formed from a single point.
• What is Cosmic Microwave Background radiation (CMB)?

  It is radiation present everywhere in the sky, emitted when the universe was very young.
• What happens to the short-wavelength radiation emitted by the early universe as it expands?

  It gets stretched to become microwaves.
• What does the presence of CMB indicate about the universe's history?

  It proves that the hot young universe has cooled and expanded since.
• Why is the Big Bang model widely accepted?

  Because it accounts for all the experimental evidence observed.
• What are two major unknowns in our understanding of the universe?

  Dark mass and dark energy.