The Expansion of the Universe, Dark Energy, and God

The structure of the universe, with billions of galaxies, has been figured out only in the last 100 years. In the US, Edwin Hubble in 1929 (the same name as in the Hubble Telescope) measured the speed of galaxies and found that all the galaxies were moving apart from each other — the universe was expanding.

Expansion of the Universe
Georges Lemaitre, a Belgian priest in the Catholic church, in 1927 had proposed the expansion of the universe started from a primeval super-atom. This became known as the Big-Bang theory. And measurements of stars and galaxies gave its origin as almost 14 billion years ago. The Big-Bang is kind of like one of those Chinese fireworks that explodes up in the air, and causes a shower of lights that bursts outwards in all directions, before they start drifting downwards.

For decades it was believed that gravity, a small force pulling any two galaxies together, would slow down the expansion of all the galaxies. But in 1998, Australian and US scientists, in two separate teams discovered that galaxies were moving apart, not at a steady rate, but they were accelerating apart. This was shocking, because it would require a force that would overcome gravity and push two galaxies away from each other. The nature of such a force was and still is unknown to physics, but came to be called dark energy. It occupies 70% of the universe.

DESI
Now comes the Dark Energy Spectrosopic Instrument, DESI, at the Kitt Peak Observatory near Tucson, Arizona. Aside: In 1981, I heard a lecture by an astronomer who worked there, talking about the intense energy coming from certain objects in the sky. The energy was too great to be explained by normal stars or galaxies. Now in 2025 we know these objects were black holes.

DESI consists of 5,000 optical fibers, each acting like a miniature telescope, and controlled by a robot that allows it to scan a galaxy at high speed. The DESI collaboration involves more than 900 researchers from more than 70 institutions around the world.

DESI can measure distance between galaxies that have the same redshift (i.e. these existed at the same cosmic time say 2 billion years ago), and average these. Then it looks at galaxies with a different redshift, i.e. existing at a different cosmic time (say 1 billion years ago), and measures the average distance between these galaxies. If the numbers agree with a consistent acceleration of outwards expansion, this is one thing.

But if not, this would be unexpected, and may tell us something about dark energy. The scientists have said there are hints that the force exerted by dark energy has changed over time. But be careful, they say, it could be just a “blip” in the data, which might go away after more measurements.

Over the next two years, DESI will take measurements from 50 million more galaxies (wow!), to see if dark energy has indeed changed over time.

The Euclid Mission
More details on the nature of Dark Energy will be obtained by the Euclid mission of ESA, the European Space Agency. Euclid, launched in 2003, is a space telescope that will look further out in the universe than DESI can, and obtain greater detail.

Euclid is the most powerful telescope ever created. In just one day, images obtained by Euclid are equivalent to the same amount of data that the Hubble Telescope will collect in its entire lifetime (wow!).

The hope with Euclid is that it will provide the extra detail scientists need to solve the dark energy problem. There exist lots of theories about dark energy and hundreds of models that need to be screened in or out by the new data. As one scientist said, the advanced data from Euclid may take a special person to interpret it and explain dark energy, and that person may be a new Albert Einstein.

Euclid will observe billions of galaxies out to a distance of 10 billion light years (i.e. the outermost of these will be 10 billion years old). Euclid will create a great map of a third of the sky to explore how the universe has expanded and how structure like galaxies and black holes formed over time. This should reveal more about dark energy, its nature, and its role in making the expansion of the universe faster.

We should be proud of what the astrophysicists have discovered, but humbled by what they do not yet know. And grateful that God has given each of us brains and heart and desire to understand the glory of his creation.
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The heavens are telling of the glory of God;
And the expanse [of heaven] is declaring the work of His hands.

Day after day pours forth speech,
And night after night reveals knowledge.
There is no speech, nor are there [spoken] words [from the stars];
Their voice is not heard.

Yet their voice [in quiet evidence] has gone out through all the earth,
Their words to the end of the world.

[Psalm 19]