Year 9 Science: Astronomy Notes

Learning Intentions

  • Understand the timeline of key events of the Big Bang Theory.

  • Explain how evidence has led to the development of the Big Bang Theory.

  • Understand the changing nature of scientific theories.

The Big Bang Theory

  • Universe formed about 13.7 billion years ago from a singularity (a point of infinite density).

  • Rapid expansion began, continuing today.

Key Timeline Events

  • 13.7 billion years ago: Universe was in a singularity, extremely hot and dense.

  • Fraction of a second post-Big Bang: Universe expanded beyond atomic size; protons and neutrons formed.

  • 380,000 years later: Universe cooled to 3000 Kelvin; atoms formed, allowing light to travel freely.

  • 100 million years post-Big Bang: First stars and galaxies began to form.

  • 9 billion years later: Formation of our Solar System.

Concept of Gravity

  • Gravity acts as an attractive force between masses, enabling star formation from gathered matter.

  • Proposed by Sir Isaac Newton in 1687.

Observable Universe

  • Movement of galaxies observable through light emissions, with the universe expanding over time.

  • The night sky is constantly changing due to this expansion.

The Doppler Effect

  • Relates to the movement of stars towards or away from Earth, affecting the pitch of sound and light frequency.

  • Light waves shift towards red (moving away) or blue (moving closer).

Spectroscopy

  • Method to analyze light from celestial objects to determine their composition.

  • Black lines in spectrum represent elements that absorb specific wavelengths of light.

Evidence for Expanding Universe

  • Redshift indicates galaxies moving away, confirming expansion.

  • Hubble’s Law relates the speed of galaxies to their distance from Earth, establishing the universe is expanding.

Hubble’s Law relates the speed of galaxies to their distance from Earth, establishing that the universe is expanding. Galaxies further away from Earth are moving away at a faster rate than those closer to Earth.

The Doppler Effect relates to the movement of stars towards or away from Earth, affecting the pitch of sound and light frequency. Light waves shift towards red (moving away) or blue (moving closer).