Physics - Topic 7 - Astronomy

• What is the formula for weight in physics?

  W = mg
• What does weight (W) represent in the formula W = mg?

  Weight in Newtons (N) is the product of mass in kilograms (kg) and acceleration due to gravity in m/s²
• How does the value of g affect the weight of an object?

  A greater value of g results in a greater weight of the object
• What is the relationship between the mass of a planet and the value of g?

  A greater mass of the planet results in a greater value of g on that planet
• Why does more mass lead to a stronger gravitational pull?

  More mass results in a stronger gravitational pull, leading to a higher value of gravitational acceleration
• What are the main components of our Solar System?

  • The Sun at the center
  • Eight planets orbiting the Sun
  • Natural satellites orbiting the planets
  • Dwarf planets orbiting the Sun
  • Asteroids and comets
• List the eight planets in our Solar System.

  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• What mnemonic can help remember the order of the planets?

  My Very Early Morning Jam Sandwich Usually Nauseates
• How do the compositions of smaller and larger planets differ?

  Smaller planets are primarily made of rock, while larger planets are primarily made of gas
• What is the orbital plane of the planets in our Solar System?

  All planets orbit the Sun on the same plane
• Do all planets rotate at the same speed?

  No, all planets rotate at different speeds
• What can cause a planet to rotate in the opposite direction?

  Past collisions can throw a planet's axis off balance, causing it to rotate in the opposite direction
• Why do larger planets have rings?

  Larger planets have strong gravitational fields that attract debris, forming rings
• What were the key features of the geocentric model of the universe?

  • Earth was at the center
  • Planets, the Moon, and the Sun orbited Earth
  • Everything orbited in perfect circles
  • Fixed background of stars
• What evidence led to the development of the heliocentric model?

  • Mars' retrograde motion
  • Galileo's observations of moons orbiting Jupiter
  • Kepler's discovery of elliptical orbits
• What causes a planet to change direction while orbiting the Sun?

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

  The speed of the planet remains constant while its velocity changes
• What happens to a planet's velocity as it orbits the Sun?

  The velocity is always changing due to the constant change in direction
• What is required for a stable orbit?

  • The planet must move closer to the Sun (decreasing orbital radius)
  • Gravitational attraction to the Sun increases
  • Force and acceleration increase, causing an increase in velocity
• What does red shift indicate about galaxies?

  Red shift indicates that galaxies are moving away from Earth
• What does the emission spectrum show from distant galaxies?

  The emission spectrum shows black absorption lines shifted towards the red end, indicating red shift
• How does red shift provide evidence for an expanding universe?

  The red shift increases with distance from Earth, indicating that the universe is expanding
• How can the expansion of the universe be visualized using a balloon analogy?

  • Imagine the universe as an un-stretched balloon
  • Galaxies are on the surface of the balloon
  • As the balloon expands, the distance between galaxies also expands
  • Light from galaxies appears red-shifted as they move away
• What happens to the wavelength and frequency of light from a galaxy as it moves away?

  The wavelength appears larger (red-shifted) and frequency decreases as the galaxy moves away
• What evidence supports the Big Bang theory?

  • Red shift indicates the universe is expanding
  • Cosmic Microwave Background (CMB) radiation shows the universe has cooled and expanded
  • The Big Bang model accounts for all experimental evidence
• What is Cosmic Microwave Background (CMB) radiation?

  CMB is radiation that was emitted when the universe was very young and has since cooled and expanded
• How does the CMB provide evidence for the Big Bang?

  CMB radiation is present everywhere in the sky, indicating the universe has cooled and expanded since its hot, young state
• What is the Steady State Theory of the universe?

  • As the universe expands, matter is constantly created
  • There is a constant density of matter in the universe
  • Suggests the observable universe is the same at any time and place
• What evidence contradicts the Steady State Theory?

  Different stars present at different eras of the universe show that the universe has evolved
• Why does the Steady State Theory not account for CMB?

  The theory does not explain the presence of Cosmic Microwave Background radiation
• What is the life cycle of a star?

  1. Dust and gas cloud forms in a galaxy
  2. Interstellar matter clumps to form nebulae
  3. Gravitational attraction draws particles together
  4. Temperature and pressure increase
  5. Fusion occurs, forming a star
  6. Star runs out of gas and collapses
  7. Depending on size, it may become a neutron star, black hole, or white dwarf
• What initiates the fusion process in a star?

  Fusion occurs when the pressure becomes great enough for gas/dust particles to fuse together
• What happens to a massive star after it runs out of gas to fuse?

  A massive star collapses, leading to a supernova, and may leave behind a neutron star or black hole
• What happens to a normal-sized star after it runs out of gas to fuse?

  A normal-sized star swells into a red giant and eventually contracts into a white dwarf
• How have telescopes evolved for observing the universe?

  • Early refracting telescopes evolved into reflecting telescopes
  • Reflecting telescopes can be larger and cheaper
  • Technological advances allow measurement of other parts of the EM spectrum
• Why do some telescopes need to be outside the atmosphere?

  Telescopes measuring X-rays, Gamma, and UV need to be outside the atmosphere as it blocks these wavelengths
• What wavelengths can be measured to observe the universe?

  Any wavelength in the electromagnetic spectrum can be used for observations