We have a lot to learn about the younger days of the universe

There are many astronomers who are a little weird but Edwin Hubble was unique.

Although born in Missouri, in the U.S., Hubble affected a stilted English upper-class accent and was a master of self-promotion. In his pictures, he is always decked out in suit and tie and striking an epic pose, usually with a pipe firmly between his teeth.

However, he was also a meticulous and determined scientist who helped change our view of the universe.

In the early years of the 20 century, Vesto Slipher, an American astronomer, discovered distant galaxies were receding from us and the universe was expanding.

Hubble was determined to extend his work. Using the 100-inch telescope at Mount Wilson, he took detailed images of distant galaxies. Those images were recorded on glass plates and required exposures of many hours. It involved staying up night after night making sure the telescope remained pointed accurately at the target galaxy, because a moment's inattention could have destroyed many nights' work.

Modern imagers are far more sensitive and today we can record a huge number of short exposures, throw away the bad ones and combine all the others to obtain high-quality, sensitive images.

Along with making his images, he recorded the spectra of the light from the galaxy being observed. From that, he could determine how fast that galaxy was moving away from us. Then, he looked at the myriad of star images on the plate to find any cepheid variable stars in that galaxy. They cycle in brightness over a time related to how much light the star is radiating. Then, by measuring how bright the star looks to us, we can calculate how far away that star, and the galaxy it lives in, happens to be.

Hubble did that for a good number of galaxies and when he plotted a graph with the speed of recession plotted against distance, he found one was proportional to the other.

If you find a galaxy with double the recession speed compared with another galaxy, then it lies at twice the distance. That suggests the universe is expanding by some percentage every billion years. The relationship between distance and recession velocity became known as Hubble's Constant. It meant that if we measure the recession velocity of a galaxy, which is relatively easy to do, we can estimate the distance.

Another implication is the expanding universe has a beginning, when it started out much smaller than it is now, around 14 billion years ago.

Since Hubble's time, telescopes and other astronomical instruments have improved hugely, enabling us to see further out, and because the light from distant objects takes a long time to get to us, further back in time.

We were surprised to see that long ago the universe was expanding slower than it is now, suggesting the expansion is speeding up. This was not what we might have expected. If you throw a stone in the air it ascends slower and slower, then accelerates back downwards. It does not go up faster and faster unless something is pushing. We call this mysterious force accelerating the universe's expansion "dark energy". However, giving it a name does not mean we know what it is.

Now things are becoming more complicated. In the youth of the universe the relationship between recession velocity and distance seems to be different. Moreover, new methods to determine this relationship are giving answers that don't agree with one another. That means we have a lot to learn about the younger days of the universe. Fortunately, we have instruments such as the James Web Space Telescope to help us.

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• Venus is very low and hard to see in the sunset glow.

• Around mid-evening, Saturn lies low in the south-west.

• Brilliant Jupiter is high in the south-east. If you have a telescope or binoculars, have a look at it.

• Mars can be found low in the north-east.

• The Moon will reach first quarter on Nov. 8.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.