Question

How do scientists measure the size of the universe?

Answer 1

The size of the universe is its age times the speed of light

Explanation:

The age of the universe is computed using Friedman's equation, which basically says how fast the universe expands given the density of matter present. This age is 14.4 billion years. The size of the universe is then `4.4 10^26` meters.

To compute all this a model is used, called the `lambda`CDM model, where $lambda# is the cosmological constant for dark energy and for cold dark matter (CDM).