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Welcome to our Physics lesson on What is the Age of the Universe?, this is the sixth lesson of our suite of physics lessons covering the topic of Expansion of the Universe, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
If the expansion process of the Universe has occurred at a constant rate (speed), it is easy to calculate its actual age t0. Thus, if a certain galaxy has a distance r from us and is receding at the speed v, the time taken to reach this distance since the beginning of Universe where all galaxies were at a single point, is
Substituting the formula of Hubble's Law in the above equation, we obtain
Substituting the value in seconds found for Hubble Constant in the example solved earlier, we obtain
Let's express this value in years. We know from previous exercises that 1 y = 3.1557 × 107 s. hence, we have for the age of the Universe in yeras:
Giving that the Hubble's constant contains its margins of error by 2.4/73.8 of the exact value, scientists believe that Universe is actually about 13.7 billion years old. Hence, the value found in the example is within the margin of error allowed. Moreover, we are not sure whether the Universe has always been expanding at a constant rate. Last, the age of Universe depends on which model of expansion we are considering. Thus, if the universe is assumed as stable, its age is calculated by the formula
However, the first formula is taken as a reference when calculating the age of Universe as the idea of an expanding universe nowadays is widely accepted.
You have reached the end of Physics lesson 22.9.6 What is the Age of the Universe?. There are 6 lessons in this physics tutorial covering Expansion of the Universe, you can access all the lessons from this tutorial below.
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