How do we know how old the universe is?

  • Thread starter Anonymous_1
  • Start date
  • Tags
    Universe
In summary: ThanksGoogle "surface of last scattering"In summary, the cosmic background radiation comes from all directions and is a record of the universe's surface at a certain point in time, which is when the plasma became transparent.
  • #1
Anonymous_1
5
0
As the title says, my question is how do we know how old the universe is? Thanks
 
Space news on Phys.org
  • #3
So measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang,[2] and measurements of the expansion rate of the universe can be used to calculate it's approximate age by extrapolating backwards in time gives us the estimate of thirteen billion years as the age of the universe. Where does the cosmic background radiation come from? Thanks
 
  • #4
Anonymous_1 said:
Where does the cosmic background radiation come from? Thanks

Google "surface of last scattering"
 
  • #5
Anonymous_1 said:
Where does the cosmic background radiation come from? Thanks
As you extrapolate the expansion backwards, at some point the matter in the universe becomes so hot and dense that it turns into plasma(i.e., the electrons get stripped off atoms). Plasma is not transparent to light. Which means that before that point in time, light couldn't travel freely through the universe, bouncing off the free nuclei instead. This constant bouncing meant that all the matter was roughly at the same temperature, as the radiation would quickly transfer heat from the hotter parts to the colder. This in turn meant that the light looked as if it was emitted by a body of a certain temperature(look up blackbody radiation). That is, it had a certain range of well defined spectra.
So as the expansion passed that moment, i.e., the universe cooled enough for the nuclei to combine with electrons to form atoms, all the light that could not travel freely earlier could now escape. CMBR is that light. It's spectrum looks like that of a body at a temperature of some 3000 kelvin(which is when the plasma became transparent), stretched 1090 times. Hence you can hear of CMBR as being at 2.7 kelvin.
Since every bit of the universe was filled with plasma back then, and the expansion made all the plasma transparent at roughly the same moment, the radiation comes from all directions.
That transition from opaqueness to transparency occurred some 380 thousand years after the expansion started, and the "boundary" that CMBR creates in the sky is called "the surface of last scattering".
 

1. How do scientists determine the age of the universe?

The age of the universe is determined through a combination of observations, measurements, and scientific theories. Scientists use data from the cosmic microwave background, the expansion rate of the universe, and the composition of the universe to estimate its age.

2. What is the current estimated age of the universe?

The most recent estimate of the age of the universe is around 13.8 billion years old. This is based on data from the Planck satellite and other astronomical observations.

3. How accurate is our current understanding of the age of the universe?

Our current understanding of the age of the universe is constantly evolving as new data and theories emerge. However, the current estimate of 13.8 billion years is believed to be accurate within a few hundred million years.

4. How does the age of the universe relate to the Big Bang theory?

The age of the universe is closely tied to the Big Bang theory, which is the prevailing scientific explanation for the origin of the universe. The estimated age of the universe aligns with the timeline of events proposed by the Big Bang theory.

5. Could the age of the universe change in the future?

It is possible that our understanding of the age of the universe may change in the future as new data and theories emerge. However, the current estimate of 13.8 billion years is widely accepted by the scientific community and is not expected to change significantly.

Similar threads

  • Cosmology
Replies
11
Views
1K
Replies
38
Views
682
Replies
54
Views
3K
  • Cosmology
2
Replies
57
Views
3K
Replies
5
Views
1K
Replies
13
Views
425
Replies
3
Views
242
  • Cosmology
Replies
5
Views
1K
Replies
3
Views
1K
Back
Top