The scale of space does not fit into the head. He's great. Very large. What is there - just incredibly huge! Back in the early twentieth century, scientists believed that the Milky Way is 300,000 light years across, and this is just one of many, many galaxies.
More accurate calculations showed a smaller number: the size of the Milky Way is "only" 150,000 light-years across. How big is the universe we observe? Oh, its diameter is some 93 billion light years.
Scientists have recently discovered a way to measure interstellar distances. They use radio waves and measure the time it takes them to travel from Earth to Mars, for example. Knowing one variable in the equation, you can find all the other data.
In the middle of the last century, astronomers learned that the universe is constantly expanding. The faster galaxies move away from us, the more red light in the spectrum we receive. The strongest red radiation so far has come from galaxies that are 13.8 billion years old. This is the age of the Universe, which at the moment of formation immediately began to expand very quickly. Thus, it turns out that the most distant galaxies in the visible part of the Universe are 46.5 billion light years from Earth.
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Astronomers at Oxford University have concluded that the entire universe is about 250 times larger than what we can observe. Most likely, neither we, nor even our descendants will be able to even see what lies so far away.
