Cosmic Microwave Background Radiation
Physics: Cambridge International GCSE Supplement, topic 6.2.8
Cosmic Microwave Background Radiation
CMBR
- Scientists detect microwave radiation coming from all directions in space.
- This is called cosmic microwave background radiation (CMBR).
Origin
- CMBR was produced shortly after the Big Bang, when the Universe was very hot.
- At that time, the radiation was in the visible and infrared regions of the spectrum.
Universe expansion
- As the Universe expanded, the radiation’s wavelength was stretched.
- This stretching moved it into the microwave region of the electromagnetic spectrum.
Big Bang
- The discovery of CMBR is strong evidence for the Big Bang theory.
- It shows that the Universe once began in a hot, dense state and has been expanding ever since.
Speed of a Galaxy
Redshift
- When we look at light from distant galaxies, we often see a redshift.
- Redshift means the wavelength of the starlight is stretched.
- This happens because the galaxy is moving away from Earth.
- The faster the galaxy moves away, the greater the redshift we observe.
Hubble's Law
- The speed of the galaxy can be calculated from the change in wavelength of its starlight.
- Astronomers can also estimate the distance of far galaxies.
- Distance can be found using the relationship between redshift and the expansion of the Universe (Hubble’s law).
- Together, speed and distance measurements give evidence that the Universe is expanding.
Test yourself on Cosmic Microwave Background Radiation
What is cosmic microwave background radiation (CMBR)?
When was CMBR produced?
Why is background radiation now observed in the microwave region?
What does the presence of CMBR support?
Which statement about CMBR is true?