How big is the universe?

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The stars, galaxies, and planets we talk about are so far away. The starts that seem the close can take tens of thousands of years to reach from the Earth.

The universe is huge. But just how big is it?

This could be something that we can never know. Sarah Gallagher told Live Science that the size of the universe is one of the common questions of astrophysics. It might be not possible to get the right answer but that doesn’t stop scientists from their research and try.

The closer an object is in the universe, the easier its distance is to measure, Gallagher said. The sun? Piece of cake. The moon? Even easier. All scientists have to do is shine a beam of light upward and measure the amount of time it takes for that beam to bounce off the moon’s surface and back down to Earth.

Most distant objects in our galaxy are more complex, Gallagher said. After all, reaching them will take a strong beam of light. And even if we had the technological abilities to reflect light that far, who has thousands of years to wait around for the beam to bounce off the universe’s distant exoplanets and return to us? 

Scientists have a few methods for dealing with the most faraway objects in the universe. As stars grow, they change color, based on that color, scientists can estimate how much light, and energy, those stars give off. For instance, two stars with the same energy and brightness will not appear the same from Earth if one of them is much greatly far away. The farther one will naturally seem dimmer. The scientist can compare the star’s actual brightness with what we see from the Earth and use that difference to calculate the actual distance of the star from the earth.

To know about the absolute edge of the universe? How do scientists calculate the distances to objects that far away? And here things can get complicated.

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But by calculating the size of that little bubble, scientists can estimate what’s outside of it.

The universe is 13.8 billion years old. This means the object whose light has taken 13.8 billion years to reach Earth must be the very farthest object that we can see. You might think that gives us a clear answer for the size of the universe: 13.8 billion light-years. But also keep in mind that the universe is continuously expanding at an accelerating rate.