If one has accurate measurements of these parameters, then the age of the universe can be determined by using the Friedmann equation.This equation relates the rate of change in the scale factor a(t) to the matter content of the universe.In contrast, theories of the origin of the primordial state remain very speculative.
billion years, slightly higher but within the uncertainties of the earlier number derived from the WMAP data.
By combining the Planck data with external data, the best combined estimate of the age of the universe is Calculating the age of the universe is accurate only if the assumptions built into the models being used to estimate it are also accurate.
The uncertainty has been narrowed down to 21 million years, based on a number of projects that all give extremely close figures for the age.
These include studies of the microwave background radiation, and measurements by the Planck satellite, the Wilkinson Microwave Anisotropy Probe and other probes.
Though the universe might in theory have a longer history, the International Astronomical Union presently use "age of the universe" to mean the duration of the Lambda-CDM expansion, or equivalently the elapsed time since the Big Bang in the current observable universe.
Since the universe must be at least as old as the oldest thing in it, there are a number of observations which put a lower limit on the age of the universe; these include the temperature of the coolest white dwarfs, which gradually cool as they age, and the dimmest turnoff point of main sequence stars in clusters (lower-mass stars spend a greater amount of time on the main sequence, so the lowest-mass stars that have evolved off of the main sequence set a minimum age).
The age of the universe based on the best fit to Planck 2015 data alone is billion years uses Gaussian priors based on earlier estimates from other studies to determine the combined uncertainty).
This number represents an accurate "direct" measurement of the age of the universe (other methods typically involve Hubble's law and the age of the oldest stars in globular clusters, etc.).
This is referred to as strong priors and essentially involves stripping the potential errors in other parts of the model to render the accuracy of actual observational data directly into the concluded result.
Although this is not a valid procedure in all contexts (as noted in the accompanying caveat: "based on the fact we have assumed the underlying model we used is correct"), the age given is thus accurate to the specified error (since this error represents the error in the instrument used to gather the raw data input into the model).
Apart from the Planck satellite, the Wilkinson Microwave Anisotropy Probe (WMAP) was instrumental in establishing an accurate age of the universe, though other measurements must be folded in to gain an accurate number.