The cosmic microwave background is one of the greatest pieces of evidence for the big bang, but what is it?

source

We can see extremely cool radio waves in all directions

The cosmic microwave background (CMB) is approximately 2.725 degrees kelvin. Zero degrees kelvin is absolute zero, the lowest possible temperature. Absolute zero is equal to about -273.15 degrees celsius or -459.67 degrees fahrenheit. The CMB is like this because it has been getting cooler for almost the entire age of the universe.

The CMB Was Emitted 14.7 Billion Years Ago

This was about 380,000 years after the big bang. Before the CMB was created there was a cloud of disconnected protons and electrons with too much energy to stay together and form atoms. Suddenly at one point that all changed, the cloud disappeared and the photons trapped by them were able to fly away. This happened when the universe as a whole fell below 3000 degrees Kelvin (2700 celsius). In a universe with no center, that meant until they hit something they will never stop. If that something is one of our instruments, we can measure them. We found extremely small differences in temperature. These differences show the start of galaxies and other objects in the universe. Where it is slightly hotter the matter is denser, which will naturally attract more matter to form every major structure we see today.

These photons from the early big bang fill the entire universe today. There are about four hundred photons per cubic centimeter.

(source)

We require highly tuned and accurate instruments to measure this change. The change is within about 0.0002 degrees kelvin, from the hottest (red) to the coolest (blue). The large red area in the middle is interference from our home galaxy, the Milky Way. The picture above is the most accurate picture we have taken of the CMB, taken by the Planck satellite.

citation1
citation2
citation3

The CMB Was Predicted Before It Was Found

The Big Bang theory was first proposed in 1927, while the CMB was discovered in 1965. That’s a whole 38 years apart! Although, the specifics were far from ironed out and they did not expect a CMB until much later. The CMB was predicted by the Big Bang theory, in 1948, which gives support to the Big Bang theory.

The CMB was originally found by accident by two astronomers named Arno Penzias and Robert Wilson. They found access radio noise with a receiver they were building. They did not realise what they had found. Researchers at the nearby Princeton University, led by Robert Dicke and including Dave Wilkinson of the WMAP science team, realised that Arno and Robert had found the CMB. They later won a Nobel Prize for the discovery.

citation

The Study of the CMB

NASA has played a major role in the study of the CMB, being the leader in many projects. The first mission was in 1989, called COBE (Cosmic Background Explorer). This found that it was the same average temperature in every direction, attaining an average of 2.73 Kelvin John Mather and George Smoot were awarded the Nobel Prize of Physics in 2006 for this discovery. Later NASA did another mission, to capture it in greater detail. This mission, called Wilkinson Microwave Anisotropy Probe (WMAP), helped establish the standard model of cosmology. Finally the ESA (European space agency) was launched the Planck satellite in 2009. This was to give an even higher level of detail on the CMB.

citation

source

Measuring Radio Waves

We have three main parts, a dish antenna and analyzer. The dish collects radio waves and focuses them onto the antenna. The antenna turns them into electrical signals which are given to the analyzer. The analyzer (which is usually a computer) takes the charges and measures them. To be able to measure radio waves this cool the entire system must be extremely precise.

citation

Measuring the CMB can give us insights to how our universe formed and evolved. The history of our universe helps us see the future.

---

Want to learn more science? Subscribe and upvote!