Age of the universe

<p>In <a href="/facts/Physical_cosmology/ww4ChbEq">physical cosmology</a>, the age of the universe is the <a href="/facts/Cosmological_time/yl6n1wqe">time</a> elapsed since the <a href="/facts/Big_Bang/I5T1vTnv">Big Bang</a>: 13.79 billion years. Astronomers have two different approaches to determine the age of the <a href="/facts/Universe/lfoqc5m6">universe</a>. One is based on a particle physics model of the early universe called <a href="/facts/Lambda-CDM_model/DmlhJHQU">Lambda-CDM</a>, matched to measurements of the distant, and thus old features, like the <a href="/facts/Cosmic_microwave_background/ThB2HkLS">cosmic microwave background</a>. The other is based on the distance and relative velocity of a series or "ladder" of different kinds of stars, making it depend on local measurements late in the history of the universe. 
These two methods give slightly different values for the <a href="/facts/Hubble_constant/FJYfELCP">Hubble constant</a>, which is then used in a formula to calculate the age. The range of the estimate is also within the range of the estimate for the <a href="/facts/List_of_oldest_stars/8lh1MQjd">oldest observed star</a> in the universe.
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Age of the universe open-in-new

Age of the universe