The Cosmic Microwave Background
- The discovery of the CMB (Cosmic Microwave Background) led to the Big Bang theory becoming the currently accepted model since it is not supported by the Steady State theory
- The CMB is a type of electromagnetic radiation which is a remnant from the early stages of the Universe
- It has a wavelength of around 1 mm making it a microwave, hence the name Cosmic Microwave Background
- In 1964, Astronomers discovered radiation in the microwave region of the electromagnetic spectrum coming from all directions and at a generally uniform temperature of 2.73 K
- They were unable to do this any earlier since microwaves are absorbed by the atmosphere
- Around this time, space flight was developed which enabled astronomers to send telescopes into orbit above the atmosphere
- According to the Big Bang theory, the early Universe was an extremely hot and dense environment
- As a result of this, it must have emitted thermal radiation
- The radiation is in the microwave region
- This is because over the past 14 billion years or so, the radiation initially from the Big Bang has become redshifted as the Universe has expanded
- Initially, this would have been high energy radiation, towards the gamma end of the spectrum
- As the Universe expanded, the wavelength of the radiation increased
- Over time, it has increased so much that it is now in the microwave region of the spectrum
The CMB is a result of high energy radiation being redshifted over billions of years
- The CMB radiation is very uniform and has the exact profile expected to be emitted from a hot body that has cooled down over a very long time
- This phenomenon is something that other theories (such as the Steady State Theory) cannot explain
- The CMB is represented by the following map:
The CMB map with areas of higher and lower temperature. Places with higher temperature have a higher concentration of galaxies, Suns and planets
- This is the closest image to a map of the Universe
- The different colours represent different temperatures
- The red / orange / brown regions represent warmer temperature indicating a higher density of galaxies
- The blue / green regions represents cooler temperature indicating a lower density of galaxies
- The temperature of the CMB is mostly uniform, however, there are minuscule temperature fluctuations (on the order of 0.00001 K)
- This implies that all objects in the Universe are more or less uniformly spread out