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Student Learning Goals:
Student Learning Goals:
To appreciate how scientific thinking is refined over time
To recall how the universe began
To describe the evidence to support the Big Bang theory
To explain how this evidence supports the Big Bang theory
The beginnings of a theory
Albert Einstein, a theoretical physicist, developed the theory of General Relativity between 1907 and 1915. He proposed the existence of a ‘cosmological constant’, a term that he pioneered in 1917. The implication of it was that the universe was static or non-evolving.
In 1927, Georges Lemaître, a Catholic priest, astronomer, mathematician and cosmologist, published a solution to the equations of General Relativity that built the case for an expanding universe. This was radically different to what the scientific community believed at that time.
In 1929, Edwin Hubble and his team published a paper demonstrating that other visible galaxies seemed to be speeding away. This supported Lemaître’s views. At this point, Einstein revised his equations, dropping the cosmological constant and accepted the expanding universe.
Lemaître explored the consequences of the expanding universe even further. He reasoned that since the universe was expanding, then at some point in the past, it must have originated from an initial point. He proposed that the beginning of the universe came from a single point he called the ‘Primeval Atom’. It was a bold proposal, and the scientific community met it with scepticism. Yet this idea was the start of what we are now familiar with: the Big Bang theory.
The term ‘big bang’ was first used by steady state astronomer Fred Hoyle while he was on a radio talk show for the BBC in 1949. The term stuck. However, it took another thirty years for the expanding universe to be generally accepted.
Cosmic Microwave Background Radiation
Cosmic Microwave Background Radiation
It was the discovery of cosmic microwave background radiation in 1964, by Arno Penzias and Robert Wilson, both radio astronomers, that proved conclusive.
Evidence for the Big Bang
The Big Bang theory suggests that the universe was created 13.7 billion years ago from a very small, yet very dense singularity. Three main pieces of evidence support the Big Bang theory:
Almost all galaxies are red shifted, which means that almost all galaxies are travelling away from each other. This suggests that the universe is expanding.
The abundance of smaller elements in the universe is consistent with them being created in a Big Bang and not inside stars through nuclear fusion.
Radiation left over from the Big Bang, called cosmic microwave background radiation, is consistent with the rate of cooling calculated from such an explosion.
Cosmic microwave background
Radiation is the name that we give to all frequencies of the electromagnetic spectrum. Radiation was emitted from the Big Bang, and we can still observe that radiation today. It exists in the form of very low-frequency waves, even lower frequency than radio waves, and was discovered in the 1960s, almost by accident.
Two radio astronomers noticed a subtle continuous buzzing that came from the skies and initially thought that it was some type of interference coming from their antenna. They soon realised they were detecting the cosmic microwave background.
Dark energy
We know that the universe is expanding because of the fact that light from other galaxies is red shifted. What is really interesting is that galaxies are not just moving away from all other galaxies, but they are doing so at an accelerating rate. It seems that there is some sort of unobservable pressure that is making the universe expansion rate accelerate. This unknown pressure has been termed dark energy.
Figure 6.24 The history of the universe
Age of the universe
Edwin Hubble made his observations about galaxies in the 1920s, and observed that many ‘clouds’ of dust and gas were actually distant galaxies. He noticed that these distant galaxies were different sizes and concluded that the smaller ones must be further away.
Hubble calculated the recessional velocity of the galaxies (that is, the speed that they are travelling away from us) by recording the red shift of their spectra. The further the spectral lines are shifted towards red, the faster the galaxy is moving. Hubble found that the further a galaxy is from us, the faster it is travelling away from us, so he proposed a relationship between distance and recessional velocity. This relationship is called Hubble’s law.
Hubble’s law demonstrates that the universe is not just expanding outwards from Earth, but rather it is expanding from everywhere.
Edwin Hubble, one of the most important astronomers of all time
Research and feasibility
1 Using the information in Table 6.2 on the following page, research how you could create a formula to assist you to convert all values from millions of kilometres to more manageable units (metres or centimetres).
Lesson Title: The Big Bang Theory: Understanding the Origin of the Universe
Duration: 60 minutes
Grade Level: High School
Materials:
Images of the universe and the Big Bang theory
Whiteboard or blackboard and markers
Laptops or tablets for students
Handouts or worksheets for students
Introduction (10 minutes):
Start with a hook by asking students if they have ever heard of the Big Bang theory and what they know about it.
Write down students' responses on the board.
Explain that the Big Bang theory is a scientific explanation for the origin and evolution of the universe.
Direct Instruction (25 minutes):
Show images of the universe and the Big Bang theory on a projector or whiteboard.
Use the handouts or worksheets to guide students in understanding the key components of the Big Bang theory, such as the expanding universe, cosmic microwave background radiation, and the abundance of light elements.
Discuss the evidence that supports the Big Bang theory, such as the cosmic microwave background radiation, the redshift of light from distant galaxies, and the abundance of light elements in the universe.
Use the whiteboard to draw diagrams or graphs to help explain difficult concepts.
Guided Practice (15 minutes):
Have students work in pairs or small groups to research and present information about a specific aspect of the Big Bang theory and the evidence that supports it.
Encourage students to use scientific evidence to support their ideas.
Provide students with laptops or tablets to access online resources, such as scientific journals or educational videos.
Independent Practice (10 minutes):
Assign a homework task where students write a short essay on the age of the universe and how the Big Bang theory is used to explain it.
Encourage students to use scientific evidence to support their ideas.
Conclusion (10 minutes):
Recap the key learning points of the lesson.
Highlight the importance of scientific evidence in understanding the origin and evolution of the universe.
Ask students to share their favorite thing they learned about the Big Bang theory.
Preview the next lesson and what students can expect to learn.
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