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Hubble's law and the Big Bang theory — FAQ
Frequently asked questions for 9702 Hubble's law and the Big Bang theory. Direct answers first, then deeper explanation — then practise with marking.
What is the primary evidence supporting the Big Bang Theory?
The primary evidence supporting the Big Bang Theory includes the observed galactic redshift (indicating universal expansion), the cosmic microwave background radiation (a remnant heat from the early universe), and the observed abundance of light elements like hydrogen and helium in the universe.
Why is Hubble's constant not truly 'constant'?
While called 'Hubble's constant,' its value has been refined over time as measurement techniques improve. More significantly, it represents the expansion rate at our current moment in cosmic time. Evidence suggests the expansion rate has changed over the universe's history. However, for A-Level Physics calculations, it's treated as a fixed constant.
How do astronomers know the original wavelength of light from distant galaxies to measure redshift?
Astronomers identify specific absorption or emission lines in galactic spectra that correspond to known elements (e.g., hydrogen, helium). They can measure the exact wavelengths of these lines in laboratories on Earth (the 'original' or 'rest' wavelength) and then compare them to the shifted wavelengths observed from distant galaxies to determine the redshift.