How wide is the universe?
Astronomers estimate the size of the universe to be 93 billion light-years, but estimate the margin of error to be about 10%. Then 84-102 billion light years should be a pretty safe answer.
Scientists have managed to detect this limit despite the fact that the age of the universe is about 13.8 billion years and despite the fact that the speed of light is the fastest possible speed.
The explanation is that the universe is constantly expanding.
Consider a nebula cluster 87 million light-years away from Earth. The light starts its journey from there and towards the earth, but as the universe expands, the path gets longer and the light has to travel a longer way in the end than the distance it was at the beginning.
With that, the light has to go further than 87 million light years.
In fact, the distance is 173 million light years when the light finally reaches us.
And how far has the light traveled? The answer is: Somewhere between 87-173 light years.
We need to apply the same thinking to the rest of the universe as the light emitted by the very first nebulae.
The expansion of the universe and thus the extension of distance is determined by the distribution of matter and energy.
Red light shows the dimension of the universe
The size of the universe is measured by the so-called redshift, which is caused by the expansion of the universe.
If all the energy in the universe were in the form of radiation, then the light that now reaches Earth after a journey of 13.8 billion light years, would come from celestial bodies now 27.6 billion light years away.
If there were only matter in the universe, light that reaches Earth after a journey of 13.8 billion light years would come from planets that are now 41.4 light years away.
Radiation and matter combined with so-called dark energy gives the real result – a distance of 46.5 billion light years to the farthest visible places in the universe. And it is at the same time the distance of the Earth from the outer limits of the visible universe.
The total dimension of the universe is obtained by multiplying that number by two, say 93 billion light years.
