If one extrapolates the Lambda-CDM model backward from the earliest well-understood state, it quickly (within a small fraction of a second) reaches a singularity called the "Big Bang singularity".
This singularity is not understood as having a physical significance in the usual sense, but it is convenient to quote times measured "since the Big Bang" even though they do not correspond to a physically measurable time.
The uncertainty has been narrowed down to 21 million years by the agreement of a number of scientific research projects, such as microwave background radiation measurements by the Planck satellite, the Wilkinson Microwave Anisotropy Probe and other probes.
Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang, of cosmological time.
Most of these marine fossils do not form in the far depths of the sea known as the Abyssal Zone because the sediment at the bottom of the Abyssal zone is generally dragged into the mantle of the Earth, as opposed to rising to the land.
As said above, fossils usually form in water because sedimentation occurs.
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 can be determined by measuring the Hubble constant today and extrapolating back in time with the observed value of density parameters (Ω).It is also used in radiocarbon dating to calibrate radiocarbon ages.New growth in trees occurs in a layer of cells near the bark.The amount of Argon sublimation that occurs is a function of the purity of the sample, the composition of the mother material, and a number of other factors.These factors introduce error limits on the upper and lower bounds of dating, so that final determination of age is reliant on the environmental factors during formation, melting, and exposure to decreased pressure and/or open-air.Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in order to analyze atmospheric conditions during different periods in history.