How can the universe be larger than 90 billion light-years, if the universe is only 13.7 billion years old?

It is not possible to travel faster than the speed of light. The Big Bang happened 13.7 billion years ago. Why is the diameter of the universe more than 90 billion light-years and not 27.4 billion light-years?

A hundred years ago, astronomers believed that the universe was infinitely old. This changed in the 1920s when scientist Edwin Hubble calculated distances to the Andromeda Galaxy and dozens of other spiral galaxies. Hubble estimated the age of the universe at two billion years. The farthest spiral galaxies he saw were 140 million light-years away, giving astronomers a diameter of 280 million light-years.

We now know that the universe is much larger. The farthest objects are 47 billion light-years from Earth, making the universe about 94 billion light-years in diameter. Examples of distant objects include the star Earendal (28 billion light-years), the HD1 galaxy and the UNCOVER Z-13 galaxy (33 billion light-years). Amazing distances.

Why are these things so far away from us?
This is due to the expansion of the universe. When we look at the UNCOVER Z-13 galaxy with a telescope, we see light from the galaxy that took 13.4 billion years to reach Earth. However, the universe was much smaller 300 million years after the Big Bang than it is today. So the light came from a much closer distance to the Earth (which did not yet exist at that time).

Just imagine…you are standing on the road. There is one person a meter in front of you, another person a meter away, and this goes on indefinitely. Now imagine that the road is growing every minute. After one minute, the person in front of you is two meters away, the person next is four meters away, the person next is six meters away, and so on. After two minutes the distance between them became three metres, after a minute four metres, and very gradually, it was no longer possible to reach the farthest people. You can compare the universe to this growing road. Mutual distances increase, while the objects themselves do not (or barely) move.

What if we left Earth now with a spacecraft traveling at the speed of light: could we reach a distant galaxy like UNCOVER Z-13 or HD1? no not like that. As the universe expands, distances continue to increase, and distant galaxies – even if we travel at the speed of light – are inaccessible.

Space photo of the week
This week’s satellite image is the image above from HD1. Light was emitted from this galaxy 13.5 billion years ago, but the distance between it today would be 33.4 billion light-years. Astronomers discovered this distant celestial body after spending more than 1,200 hours staring at the night sky using various telescopes. HD1 is extremely bright in ultraviolet light, which may be because the galaxy is home to a supermassive black hole with the mass of a hundred million suns. We may learn more about HD1 thanks to the James Webb Telescope.