This definitions covers Key Terms within Red Shift & Big Bang for GCSE Physics. Revise Red Shift & Big Bang in Space Physics for GCSE Physics with 13 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 7 of 14 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 7 of 14
Practice
13 questions
Recall
12 flashcards
📖 Key Terms
- Red shift
- The increase in wavelength (shift towards the red end of the spectrum) of light from a source moving away from the observer. Caused by the Doppler effect for light.
- Doppler effect
- The change in observed frequency/wavelength of a wave when the source and observer are moving relative to each other. Light from a receding source is red-shifted; from an approaching source it is blue-shifted.
- Expanding universe
- The observation that the universe is getting larger over time — space itself is stretching, carrying galaxies apart from each other.
- Big Bang
- The prevailing cosmological model for the origin of the universe, describing it as beginning from an extremely hot, dense state about 13.8 billion years ago, followed by rapid expansion.
- Cosmic Microwave Background Radiation (CMBR)
- Faint microwave radiation detected from all directions in space, at a temperature of about 2.7 K. The cooled-down afterglow of the early hot universe; strong evidence for the Big Bang.
- Hubble's Law
- The observation that the recession velocity of a galaxy is proportional to its distance from us. The constant of proportionality is the Hubble constant.
- Absorption spectrum
- Dark lines in the spectrum of a star or galaxy, caused by specific elements absorbing specific wavelengths. The positions of these lines shift with red shift, allowing recession velocity to be measured.