The universe and the Big Bang Theory

More than thousand years ago the Earth was believed to be at the centre of the universe as shown in Figure 13. The planets, the Moon and the Sun were believed to be in orbit around the Earth. In 1543 Nicolaus Copernicus proposed that the Earth was a planet, and that the Earth and the other planets orbit around the Sun. This model is shown in Figure 14.Discuss how evidence has changed our views of the universe.

in 1543, Nicolaus Copernicus suggested a different model — the heliocentric model, in which the Sun is at the centre and the planets, including Earth, orbit around it.In the early 1600s, Galileo Galileidiscovered moons orbiting Jupiter, proving that not everything revolves around the Earth.In the 20th century, Edwin Hubble discovered that distant galaxies are moving away from us, showing that the universe is expanding. This led to the Big Bang theory, which suggests the universe began around 13.8 billion years ago and has been expanding ever since.

The Big Bang theory is one theory for the origin of the Universe. The Big Bang theory suggests: • the Universe had a beginning • the Universe is still expanding. The Steady State theory is also a theory about the origin of the Universe. Give one similarity and one difference when comparing the Big Bang theory with the Steady State theory.

Similarity : both have expanding universe.

Difference : Steady State, universe has no beginning.

The Big Bang theory gives an explanation for the origin of the Universe. Explain how evidence supports the ideas that • the Universe is expanding • the Universe began at a single point.

Light from distant galaxies is red-shifted, showing they are moving away from us and that the Universe is expanding. The further away a galaxy is, the greater its red-shift, meaning the Universe is expanding in all directions.

If it’s expanding now, it must have once been smaller and denser, suggesting it began at a single point — the Big Bang.

Evidence for this also comes from the cosmic microwave background radiation, which is the remnant heat from the Big Bang, filling the Universe and showing it began as a hot, dense state that has cooled as it expanded.

A long time ago, scientists believed that the Earth was at the centre of the Solar System. Evidence has since proved that the Sun is at the centre of the Solar System. State one other idea about the Solar System that has changed over time

Scientists used to believe that the planets moved in circular orbits, but we now know that planets move in elliptical orbits around the Sun.

Satellites are used to gather data about the origin of the Universe. The Big Bang theory is a theory about the origin of the Universe. Evidence for the Big Bang theory is provided by red-shift and CMB radiation. (i) Describe what is meant by red-shift.

Wavelenght of EM radiation increases as the star moves away from us.

Explain how red-shift provides evidence for the Big Bang theory

The universe is expanding, the galaxies are moving away from each other.

The Cosmic Background Explorer (COBE) satellite observed CMB radiation from 1989 to 1993. State what the 'M' in CMB radiation stands for.

microwave

State what is meant by 'cosmic background radiation'.

Radiation that comes from the universe.

Explain how the presence of CMB radiation provides evidence for the Big Bang theory.