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It has been demonstrated since 1929 that the Universe is expanding, that is, the distance between any two given gravitational unbound parts of the observable Universe is increasing with time.[1] It is an intrinsic expansion in which the scale of space changes. The Universe does not expand "into" anything, nor does it necessitate the existence of space "outside" it. This expansion does not involve space or objects in space "moving" in the traditional sense, but rather the metric that governs the size and geometry of space-time evolving in scale.

As the spatial part of the Universe's space-time metric increases in scale, objects become more distant from one another at ever-increasing speeds. To any observer in the Universe, it appears that all of space is expanding, and that all but the nearest galaxies (which are bound by gravity) recede at speeds that are proportional to their distance from the observer.

Scientists once predicted that the Universe would continue to expand against its own gravity, creating a spontaneous backward gravitational force that would gradually force the expansion to stop when it reached a certain limit and then draw the compartments of the Universe (stars, moons, planets) back on themselves, similar to how when we throw a football up, it first speeds up, then gradually slows down until it stops, then begins falling backwards again.

In fact, the celestial bodies are constantly accelerating farther from each other. This acceleration increases proportionally with their distance increase from the centre of the Universe, which is supposed to be the centre of the cosmic gravity – the farthest of these bodies at the edge of the visible Universe (i.e., about 13.8 billion light years away) are flying away at an extraordinary speed almost as fast as the speed of light. What drives these galaxies away with such an enormous speed? Twenty-first century scientists have found themselves after all the tremendous development in scientific and technological possibilities at the puzzle.

There must be a cosmic force superior to the force of gravity that can push galaxies with such superpowers. Scientists have called this force Dark Energy because it is a force that could not be seen but only realized through its impact on celestial bodies. Even more strange is that this energy forms most of the Universe we know.

Much amazing is the fact that we see through our observatories and astronomical binoculars, which rely on the greatest technology known in history, not more than 4% of the Universe, of which 0.4% are star matter and 3.6% cosmic dust distributed in the sky between stars and galaxies, while dark energy, is believed to constitute about 73% of the known Universe.

Dark matter was known a few years before dark energy, which is a material that does not interact with light to become visible and accounts for about 23% of the remaining physical Universe, as shown in the following figure

Scientists believe that dark energy is one of the characteristics of cosmic space; it cannot be reduced or faded as the Universe expands; rather, the larger the Universe, the greater its dark energy. This result may be difficult to grasp: the first principle of thermodynamics states that energy must be preserved, which means that the energy of any isolated system must remain constant and cannot arise from nowhere. However, evidence of increased acceleration of celestial bodies as they diverge shows that dark energy is constantly increasing.

In the annals of scientific discovery, the year 1916 stands as a pivotal moment—a juncture where the fabric of our understanding of the cosmos began to stretch and expand. At the heart of this revelation was none other than the brilliant physicist Albert Einstein, whose groundbreaking work in general relativity had already transformed our perception of space, time, and gravity.

Einstein's field equations, elegant mathematical expressions that encapsulated the curvature of spacetime in response to mass and energy, yielded an unexpected consequence: an expanding Universe. Yet, Einstein, ever the skeptic, hesitated to embrace this emergent Universe. His intuition recoiled at the notion of a creation event—an origin point for all that exists.

In a daring move, Einstein introduced the cosmological constant—a term within his equations—to counteract this cosmic expansion. This constant acted as a cosmic brake, attempting to maintain a static Universe, akin to a celestial equilibrium. However, observations by astronomers, notably Edwin Hubble, revealed that galaxies were hurtling away from one another, like cosmic seeds scattered by an unseen hand. The Universe was not static; it was dynamic, evolving, and inexorably expanding.

Einstein, humbled by the evidence, famously referred to the cosmological constant as his "biggest blunder." He abandoned it, acknowledging that the Universe, as far as it is continuously expanding, demanded a beginning—an epoch when time itself ignited. In this surrender, he glimpsed the presence of a superior intellectual power—an architect of cosmic extents.

Thus, the expanding Universe became a cornerstone of modern cosmology—a testament to both scientific curiosity and the delicate dance between reason and wonder. Einstein's journey from reluctance to acceptance echoes through the ages, reminding us that even the greatest minds can stumble upon profound truths."

Recently, scientists have resurrected Einstein's cosmological constant (denoted by the Greek capital letter lambda) to explain dark energy, a mysterious force that appears to be counteracting gravity and causing the Universe to expand at an accelerating rate.[2]. According to the researchers, a new study confirms that the cosmological constant is the best fit for dark energy and provides the most precise and accurate estimate of its value yet[3]. The discovery stems from a measurement of the Universe's geometry, which indicates that our Universe is flat rather than spherical or curved. Christian Marinoni and Adeline Buzzi of France's Université de Provence discovered a new way to test the dark energy model that is completely independent of previous research. To measure the curvature of space, they use distant observations of pairs of galaxies.

"The most exciting aspect of the work is that there is no external data that we plug in," Marinoni told SPACE.com, meaning that their findings aren't dependent on other calculations that could be flawed.

The researchers probed dark energy by studying the geometry of the Universe. The shape of space depends on what's in it? That was one of the revelations of Einstein's general relativity, which showed that mass and energy (two sides of the same coin) bend space-time with their gravitational force.

Marinoni and Buzzi set out to calculate the contents of the Universe -- i.e., how much mass and energy, including dark energy, it holds -- by measuring its shape.

There were three main options for the outcome:

The Universe can either be flat like a plane, spherical like a globe, or hyperbolically curved like a saddle. Previous studies have favored the flat Universe model, and this new calculation agreed.

By providing more evidence that the Universe is flat, the findings bolster the cosmological constant model for dark energy over competing theories such as the idea that the general relativity equations for gravity are flawed.

"We have at this moment the most precise measurement of soft lambda that a single technique can give," Marinoni said. "Our data points towards a cosmological constant because the value of the lambda we measure is close to minus one, which is the value predicted if dark energy is the cosmological constant."

Unfortunately, knowing that the cosmological constant is the best mathematical explanation for how dark energy is stretching out our Universe doesn't help much in understanding why it exists at all.

"Many cosmologists regard determining the nature of dark energy and dark matter as the most important scientific question of the decade," wrote Alan Heavens of Scotland's University of Edinburgh in an accompanying essay in Nature. "Our picture of the Universe involves putting together a number of pieces of evidence, so it is appealing to hear of Marinoni and Buzzi's novel technique for testing the cosmological model, not least because it provides a very direct and simple measurement of the geometry of the Universe."

So, given this new discovery, what is the Universe's future? The second principle of thermodynamics explains how events in the world change using a concept known as "entropy," an expression indicating that events always change in one direction towards the future, as indicated by an arrow pointing to the future on the axis of time; we call such a change irreversible (i.e., events cannot take place in the direction of the past).

In other words, if we leave nature to its own devices, it tends to be random and chaotic. For example, if an earthquake occurs and the letters from a printing press are scattered on the ground, these letters will almost certainly not form Shakespeare's poetry. The randomness of events is related to the number of free choices available, or Freedom Degree; for example, the number of random numbers produced by throwing two dice is much lower than that produced by throwing five pieces.

The change in events from lower entropy to higher entropy is a state of degeneration and decline in creation perfection; a fresh egg is in a lower entropy state or ordered state and a cracked or scrambled egg is in a higher entropy state or disordered state. This process is irreversible, which means we can't restore the cracked egg into its original form again. A raw egg exemplifies the asymmetry of time; which means, time flows in one direction forward, we could also say: the broken egg has a higher entropy.

Scientists believe dark energy is responsible for changing the world in a single irreversible direction.[4] Dark energy causes chaos and randomness, leading to the end of the Universe.

Dark energy is pushing the Universe outwards, consistent with its expansion continuing forever, leading to The Heat Death or Big Freeze, which is an end to astrophysical activity marked by increasing isolation, inexorable decay, and an eons-long fade into darkness.

Dark energy accelerated expansion could also lead to the Big Rip, where stars, planets, and atoms will be ripped apart.

Not to worry, though, whatever it looks like, the end probably won’t be nigh for at least 200 billion years[5].

In the sacred text of the Quran, a profound reference is made to the vastness of the cosmos in Surah Al-Dhariyat, Verse 47 (51-47). It eloquently states,

"With formidable might, we have built the heavens, and indeed, we are the ones who continue to unfold its vastness."

Meanwhile, the Quran also contemplates the potential end of the universe in Surah Al-Infitar, verses 1 and 2 (82:1,2). It paints a vivid picture of a cataclysmic event, possibly akin to what modern science refers to as the 'Big Rip'. This event could cause the very fabric of the cosmos to rupture, leading to the scattering of celestial bodies. The verses read,

"When the heavens are rent asunder, and when the stars disperse in all directions."


These verses not only reflect the grandeur of the universe but also its transient nature, reminding us of the delicate balance that holds everything together. They beautifully encapsulate the infinite expansiveness of the cosmos and its potential dissolution, resonating with some of the most profound theories of contemporary astrophysics.

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[1] . Overby, Dennis (20 February 2017). "Cosmos Controversy: The Universe Is Expanding, but How Fast?". The New York Times. Retrieved 21 February 2017.

[2] . Clara Moskowitz, Einstein's 'Biggest Blunder' Turns Out to Be Right, SPACE.com, published November 24, 2010.

[3] . Cosmology: geometry of the universe.

Heavens A, Nature. 2010 Nov 25;468(7323):511-2. doi: 10.1038/468511a.

[4] . Time arrow is influenced by dark energy, A. E. Allahverdyan and V. G. Gurzadyan, Phys. Rev. E 93, 052125 – Published 13 May 2016

[5] . Nature 584, 187 (2020).