Understanding the Universe: what we know and what we’ve yet to discover

Patrick Moore contemplates how far we’ve come in our understanding of the Universe, and how far we’ve yet to go.

By Patrick Moore

Published: Monday, 06 March 2023 at 12:00 am

Cast your mind back to 1962. We thought we knew a great deal about the structure and origin of the Universe.

Well, we certainly knew something, but many of the ideas that were current at that time have since been cast aside.

First, consider the age of the Universe. It was known that the Universe was very old, but estimates ranged from below 10 billion years to over 20 billion years.

Secondly, how did it begin – and how will it end?

Here, we were on slightly firmer ground. At least we were sure that the stars and galaxies formed by condensation from a vast cloud of tenuous material.

Thirdly, how did stars generate their energy? Einstein’s theory of relativity had become generally accepted by 1962, though there were some astronomers who doubted it – and there still are. 

At least we know now that the age of the Universe is 13.8 billion years and we are confident that this time we are not far wrong.

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Globular cluster Messier 79, as seen by the Hubble Space Telescope. Credit: NASA and ESA. Acknowledgement: S. Djorgovski (Caltech) and F. Ferraro (University of Bologna)

But how will the Universe end? Here we have not made a great deal of progress and it is by no means certain that there will be an end at all.

The expansion of the Universe was accepted by most astronomers in 1962 but there were still some doubters. Certainly the idea of a static Universe had been generally discarded. 

When we come to the source of stellar energy, there have certainly been major changes in our outlook.

All kinds of theories had been put forward, such as the collision of atoms with each other to heat the material, but of course we now know that this is completely wrong.

The stars generate their energy by nuclear reactions. Hydrogen is the essential key, and is also the most plentiful substance in the entire Universe.

Four atoms of hydrogen can combine to make one atom of helium, admittedly by a rather roundabout route. 

Every time one helium atom is formed, a little mass is lost and a little energy is released.

It is this energy that makes the stars shine; the loss of mass amounts to a staggering four million tonnes per second.

Luckily for us, there is as yet no prospect of all the available hydrogen being used up.

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Illustration showing the expansion of the Universe from the Big Bang to the present day.
Credit: Andreus / iStock / Getty Images Plus

With regard to the expansion of the Universe, this was generally accepted 50 years ago. It now seems that in its outer regions the rate of expansion is actually increasing, and this leads us on to the mysteries of dark matter and dark energy.

Here we have to admit we are still very much in the dark. 

I think most people accept the idea of dark matter, which we cannot see but which betrays its presence by its gravitational effect on the objects we can see.

We have no idea what dark matter is but the evidence in favour of its existence is very strong.

Dark energy is a different proposition altogether – it is assumed to be responsible for the acceleration of expansion of remote parts of the Universe, but what it actually is remains a total mystery.