Earth is tiny beside the observable universe
Earth is about 12,700 kilometers across. The observable universe—the region whose light has had time to reach us—is roughly 93 billion light-years across. A light-year is the distance light travels in one year, so even the observable universe’s diameter is about 70 quintillion times Earth’s.
That comparison is possible because astronomers can estimate both sizes. Earth’s diameter can be measured directly; the observable universe’s size is inferred from the age and expansion of the universe and from observations of distant light.
“Observable” does not mean “all that exists”
The universe has been expanding while its light travels toward us. As a result, matter that emitted light billions of years ago is now much farther away than the distance that light has covered. That is why the observable universe’s estimated diameter is far greater than 13.8 billion light-years, the approximate age of the universe expressed as a distance light could travel.
Beyond the observable region, the universe may continue. We cannot see what lies there because its light has not reached Earth, so science cannot give a confirmed size for the entire cosmos. The firm comparison is therefore with the observable universe—not necessarily with everything that exists.
