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(6) Other evidence for the 'Big Bang Theory' of the universe

• As well as the 'red-shift' evidence, there is other evidence for the Big Bang theory of the origin of the universe, and not the steady state theory.

• Cosmic microwave background radiation

  • (CMBR or CMB radiation)

  • Apparently both the Steady State model and Big Bang model both explain the observed red-shifts and expansion of a universe from our observations that objects like galaxies are moving away from us in all directions, BUT, the Steady State model cannot explain CMBR.

  • Radio-astronomers have detected low frequency microwave radiation coming from all directions from all parts of our universe - known as cosmic background microwave radiation (CMBR).

    • Microwave radiation is part of the electromagnetic spectrum, but the CMBR is of lower frequency than in your microwave cooker!

    • This microwave radiation was accidentally discovered, and still studied, using a radio telescope.

  • It is believed that this radiation comes from radiation that was present shortly after the beginning of the universe, i.e. soon after the 'Big Bang' started.

  • CMBR is associated with low temperatures as the young universe was cooling down and the background radiation reduces in frequency.

• The ‘Big Bang’ theory is currently the only theory that can explain the existence of CMBR.

• If other evidence comes to light, the theory may have to be modified - 'watch this space'!

• INDEX for physics notes on COSMOLOGY

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Key points for Physics - cosmic background radiation and other evidence

Information sources for Doc Brown's key points: IGCSE-GCSE physics are based on textbooks & syllabus-specifications for students taking the UK AQA, Edexcel, OCR 21st Century Science, OCR Gateway science suite, WJEC, CCEA and CIE GCSE physics 9-1 level science examinations.

A set of summary revision notes on evidence for the Big Bang Theory beyond red-shift, tailored for WJEC, CCEA, CIE, AQA, Edexcel, and OCR GCSE/IGCSE Physics students:

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Evidence for the Big Bang (Beyond Red-Shift)

1. Cosmic Microwave Background Radiation (CMBR)

• What is it? Faint microwave radiation detected from all directions in space.
• Origin: Leftover heat from the early Universe, now cooled to about -270°C.
• Why it matters: Predicted by the Big Bang Theory; cannot be explained by the Steady State model.
• Supports: The idea that the Universe began hot and dense, then expanded and cooled.

2. Relative Abundance of Elements

• The Big Bang model predicts specific ratios of hydrogen, helium, and lithium.
• Observations match these predictions across the Universe.
• Suggests a common origin for all matter.

3. Structure of the Universe

• The distribution of galaxies and cosmic structures aligns with simulations based on the Big Bang.
• Galactic clustering and voids support an expanding Universe that began from a single point.

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Student Tips

• Learn the full name: Cosmic Microwave Background Radiation (CMBR).
• Use diagrams to show how CMBR fills the Universe.
• Practice explaining why CMBR supports the Big Bang but not the Steady State theory.
• Remember: CMBR = leftover heat, element ratios = early Universe chemistry.
• Use past paper questions to get used to phrasing like “describe evidence for the Big Bang other than red-shift.”

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Keywords, phrases and learning objectives for the CMBR evidence of the big bang theory of the universe

Know there is the cosmic microwave background radiation (CMBR, CMB) from all directions in our universe.

Know that cosmic microwave background radiation (CMBR) is a form of electromagnetic radiation filling the universe.

Know that cosmic microwave background radiation provides  other evidence for the 'Big Bang Theory' of the universe (the other is the red shift in spectral lines from distant objects in the Universe).

Know that cosmic microwave background radiation does not fit in with the steady state model of universe.

Appreciate that the ‘Big Bang’ theory is currently the only theory that can explain the existence of CMBR.

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