Evidence for the Big Bang Theory PPT - International A-Level Physics Edexcel

EVIDENCE FOR THE BIG BANG THEORY
Lesson Objective: Starter:
To explain the evidence for the ‘Big Write down what do yo
Bang’ Theory and apply red-shift remember about the ‘Bi
equations. Bang’ Theory from GCS


Lesson Outcomes:
Describe the evidence for the Big
Bang Theory. Keywords:
Explain how red-shift provides Big Bang Theory, Dopp
evidence for the Big Bang Theory Effect, Red-shift,
Apply red-shift equations to solving Atomic Line Spectra,
problems in various contexts speed of recession

,Evidence for the ‘Big Bang’ Theory



• Galaxies receding
• Chemical composition of early galaxies
(mostly hydrogen with ~25% helium and
traces of lithium and beryllium)
• Cosmic microwave background
radiation, which corresponds to a
temperature of the universe of about 2.7K

,How do we know galaxies are receeding?



▶What is the Doppler Effect (you studied this last year) – Write an
explanation.




▶What is an absorption spectrum (you studied this last year) –
Write an explanation

, The Doppler Effect
As the ambulance travels
forwards:
The sound wave in front is
compressed
- decreasing its wavelength
- increasing its frequency

A B C D The sound wave behind is
A B C D E stretched out:
- increasing its wavelength
- decreasing its frequency



ambulance
sound demo