The present age of the universe is said to be between 10 and 20 billion years old.

The age of the universe is based on the combined estimates of the ages of radioactive elements, the age of our galaxy, the age of the oldest stars, and the amount of time it takes light from the optical limit of the universe to reach the Earth.

The age of the universe is measured in various ways, and different methods give different results.

For example, if it takes light 15 billion years to reach the Earth from the optical limit, then it can be said that the age of the universe is at least 15 billion years old. However, the amount of time it takes for light to reach the Earth from a distant galaxy depends on an exact measure of the distance, and different astronomers use different methods to calculate the distances of stars and galaxies.

In general, there is no agreement as to which methods of determining the age of the universe are the most accurate.

Until astronomers find better ways of predicting time and distance on a large scale, the exact age of the universe will remain uncertain.