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The timeline of the universe begins with the Big Bang, 13.799 ± 0.021 billion years ago, [1] and follows the formation and subsequent evolution of the Universe up to the present day. Each era or age of the universe begins with an " epoch ", a time of significant change.
Several unanswered questions ... (after 1.8 billion years ... covers the period from 712 to 545 million years ago—a time span containing the Sturtian and ...
For example, 201.4 ± 0.2 Ma, the lower boundary of the Jurassic Period, is defined as 201,400,000 years old with an uncertainty of 200,000 years. Other SI prefix units commonly used by geologists are Ga (gigaannum, billion years), and ka (kiloannum, thousand years), with the latter often represented in calibrated units (before present).
According to evidence from radiometric dating and other sources, Earth formed about 4.54 billion years ago. [7] [8] [9] The current dominant theory of planet formation suggests that planets such as Earth form in about 50 to 100 million years but more recently proposed alternative processes and timescales have stimulated ongoing debate in the planetary science community. [10]
This is an accepted version of this page This is the latest accepted revision, reviewed on 23 January 2025. Scientific projections regarding the far future Several terms redirect here. For other uses, see List of numbers and List of years. Artist's concept of the Earth 5–7.5 billion years from now, when the Sun has become a red giant While the future cannot be predicted with certainty ...
A new study says complex life began 1.5 billion years ... Most scientists agree that complex life likely formed during the Ediacaran Period some 600 million years ago—right on the cusp of the ...
The rotational period of the Earth was only about six hours shortly after its formation 4.5 Ga but increased to 21 hours by 2.4 Ga in the Paleoproterozoic. The rotational period increased again, starting 700 million years ago, to its present value of 24 hours.
Until roughly 2.3 billion years ago, oxygen was probably only 1% to 2% of its current level. [9]: 323 The banded iron formations, which provide most of the world's iron ore, are one mark of that mineral sink process. Their accumulation ceased after 1.9 billion years ago, after the iron in the oceans had all been oxidized. [9]: 324