The 'Theory of Everything': Dark Energy and an Ever-changing Universe

When leaves flutter in a passing wind, when sunlight turns the sky a stunning blue, when the mornings add a fresh hue to the mundane, we begin to ask the same question again to ourselves: What does it mean? Our existence, written in an indelible ink of curiosity.

The very act of seeking answers provides meaning even as the ultimate answer remains elusive. Yet, science keeps reading and translating for humanity the vast volume of the universe, one page at a time.

The quest continues, and here are a few explanations science has provided so far.

Current human understanding about the brass tacks of the universe revolves around the concepts of dark energy, black holes, and an expanding (will it shrink later?) universe. The pursuit for a 'theory of everything' is ongoing.

The History of the 'Theory of Everything' in a Nutshell

In 1916, Austrian physicist, Ludwig Flamm, was the first one to predict the possibility of the existence of a cosmic phenomenon that he called a ‘white hole’. Einstein’s theory of general relativity was the basis of this prediction. The theory, published in 1915, is about the impact of gravity on space and time. In very simple terms, the theory can be explained like this- the gravity of mammoth objects can bend or rather, warp space and time. The theory predicted that light bends around massive objects like the sun because of gravity.

The example of a trampoline is often cited to explain this phenomenon. On a trampoline, if a massive ball is placed at the centre, there will be a depression, a dent, where the ball sits. Now, if we try to roll a much smaller ball around the big one, the small one will be circling towards the bigger ball. This is the nature of the pull of gravity in space and time, and this is the nature of the fabric of space, according to the general theory of relativity.

However, in our universe, for this gravitational pull to become felt, the body that causes it has to be supermassive. Later on, scientists proved that when light travels near the sun, the gravity of the sun causes it to bend. This is why a quasar (a cosmic body) named, Einstein's cross, which is behind the sun when viewed from earth, appears as four images of itself instead of one. The light from it bends at all the four sides of the sun, thus creating an illusion of a combination of four images.

For bodies with lesser mass, the gravity bending that they cause on light is negligible. Now, think about this- we see space only because there is the light that shows it to us. When light bends, for all purposes of physics, it is space that bends. When light from an object reaches us bending in many ways, and thus through many paths, we might be seeing the object at many different points in time. So, we can conclude that gravity bends space and time.

Gravity and its impact on light change the calculations of Newtonian classical physics. But it changes the equations of the properties of light only by a few microscopic degrees. Still, the future possibilities of knowledge and technology that this small difference open up for humanity could be life-changing; even the possibility of time travel and finding new universes.

Evolution of the science of Gravity and Blackholes

We all know that all objects have gravity. Earth is seen from space because light has a velocity that transcends earth's gravitational pull. For any object, there is an escape velocity, which is the speed at which an object has to travel to escape from another object's surface by overcoming its gravitational pull. Imagine a cosmic body that has a gravity that exceeds the escape velocity of the light particle? What if light cannot escape from it owing to the huge gravitational pull? The cosmic body then will be invisible. Reverend John Michell in 1784 and Pierre Simon Laplace in 1796 postulated independently that this could be possible. Laplace called such light-trapping and invisible massive cosmic entities, the ‘non-luminous bodies’.

In 1916, Karl Schwarzschild proved this postulate. He found that for any mass of matter, there is a given radius and density that provides it with an optimal gravity and makes it impossible for light to escape its surface. For any object with a certain mass, the pull of gravity attains a certain level at a given radius and then it becomes strong enough to keep light from escaping. This is because the escape velocity becomes equal to the speed of light. This is also the point when that mass becomes a black hole by collapsing on itself due to the immense gravitational pull. This is what scientists call, a black hole. For the earth to become a black hole in this manner, it will have to shrink to a radius of 1 centimetre, while retaining its present mass.

Blackholes to Wormholes

On the one side, black holes came into the scientific discourse; on the other, Einstein predicted the bending of space-time owing to gravity. In 1935, Albert Einstein and Nathan Rosen explored the idea of gravity further and observed that there could be ‘bridges’ in existence between space and time. Suppose a star shrinks to the black hole radius. Then occurs an event horizon surrounding it, a space that pulls everything in, once entered. However, the entire mass of that star would be concentrated at an exceptionally tiny point at the centre of this event horizon, a place where there is infinite gravity. This imaginary point is named a singularity by the scientists.

More about it, later. Now, back to black holes and gravity pull. Suppose many cosmic bodies have become black holes. What if the ensuing bending and curving of spaces cause two different and far away points in space and time, to meet? Then won’t that practically function as a shortcut in space and time? A wormhole, in theory, is not only capable of connecting time and space, but also different universes. This is why wormholes became the all-time favourite of science fiction writers and moviemakers. Again, theoretically, they could facilitate time travel. In 2020, Roger Penrose, Reinhard Genzel, and Andrea Ghez won the Nobel prize in Physics for their research on black holes. They together confirmed the existence of a supermassive black hole in our galaxy, the Milky Way. This black hole is now named, Sagittarius A*.

Wormholes can be looked at as speculative cosmic phenomena that could allow the transmission of signals or matter between two separate spaces and time, and even let these two far-apart space-time entities be in thermal contact with each other. In other words, wormholes allow the matter or information to travel from one point in space to another far off point, in no time; and theoretically, from one point in time to another. They are shortcuts in space and time.

As shown in the movie, 'Gravity', a wormhole, if it exists, allows you to touch someone who is millions of light-years away. So far wormholes have been created only at a microscopic scale in laboratories. Ever since the dream has been to create a macro level wormhole that allows human passage.

So far what we have discussed refers to the macro universe and cosmic bodies. What about the behaviour of matter at microscopic or even super-microscopic levels? Paralell to theories of universe, quantum theory evolved trying to answer the above question.

Quantum Entanglement

Quantum entanglement is a subatomic phenomenon where subatomic particles such as pairs of photons and electrons show common behaviour even when they are separated in space by miles or even, in theory, many light-years. They remain connected somehow across vast distances. Albert Einstein called this a “spooky” connection but he thought there could be a hidden variable involved.

In 2017, a new theory suggested that wormholes are two black holes 'entangled' together. This was an attempt to unite the two most significant theories of physics, namely, the cosmic scale theory of gravity and the subatomic theory of quantum physics. The new theory suggests that when a black hole is born, its pair is also simultaneously generated. At the subatomic level, this theory also postulates that the entanglement of subatomic particles is nothing but wormholes.

The Notion of Singularity

As discussed before, it is theoretically derived that there is a singularity at the centre of a black hole. This is a central point where the density is infinite because gravity has compressed all matter to no volume at all. This phenomenon arises only in mathematical calculations as a result of taking the idea of gravity to its logical extreme.

A singularity is also a point where the rules of physics and mathematics no more apply, that is, they break down. It is postulated that when an object has more than six times the mass of the sun, its gravity will be so strong that it will collapse into an infinitely small point, a pure singularity.

We can understand a black hole as a singularity surrounded by an event horizon, unseen by the outside world. We will be able to understand singularity (or what is inside a black hole) completely only when we can develop a quantum theory of gravity, a theory that explains how gravity works at quantum level.

Quantum level wormholes are a reality now- only if we agree that quantum entanglement is equivalent to a real wormhole created. Are they the same? What is inside a black hole? How do you imagine, visualise, or describe a singularity? The Big Bang theory about the origin of the universe necessitates us to think that the bang happened from a singularity, an infinitesimally tiny point, which is equal to nothing. Was it a singularity that exploded and expanded to become this universe? Are there other universes? Can black holes lead us to wormholes and to new universes? Questions abound. Science is at work to find the answers.

Amidst investigations about gravity and quantum behaviour, which are the two major frontiers of modern physics, a third and equally significant horizon of understanding was opened up: the dark energy that constitutes 68% of our universe. (Another 27% is dark matter which is not visible because it absorbs light but its presence materialises as gravity. Only the remaining 5% is ordinary matter- the planets, stars, and we, the living and non-living things on earth.)

The Dark Energy

The dark energy is supposed to be the driving force behind the (foreever) ongoing expansion of the universe. In his field equations of general relativity, Einstein hypothesised the existence of a cosmological constant (denoted as Λ). He speculated that this cosmological constant could be the force that counteracts gravity and thus allows the universe to remain stable despite all cosmoc bodies being pulled from all sides by the gravitational forces. When he presented this hypothesis, the world of science had not yet discovered that the universe was ever-expanding.

Though Einstein did not take into account the expansion of the universe when he formulated Λ, the cosmological constant, the concept held the ground in an entirely different context. The mathematical calculation was robust and later on scientists discovered that it represents the 'dark energy' that drives the expansion of the universe. Dark energy is understood as an intrinsic property of space time and unlike other energy forms that we are familiar with, it is not an energy emitted by some matter.

The expansion of the universe was proven when Einstein was alive and he thought that this discovery contradicted his idea of a cosmological constant. He even declared his notion of a cosmological constant as his "biggest blunder". After Einstein's death, during the late 20th century, scientists discovered that the expansion of the universe was accelerating as time passes. This discovery made them revisit Einstein's mathematical calculation involving the cosmological constant, Λ, and surprisingly, they found out that the equation of  Λ that Einstein derived is the simplest mathematical description of dark energy that drives the expansion. What Einstein thought was the constant force that holds the universe stable is actually the force that delivers the expansion of the universe.

How do we tie together gravity, quantum mechanics, and dark energy into a single 'theory of everything'? The current understanding might lead to the idea that gravity and dark energy are not fundamental forces but could be the results of quantum processes. Any further conclusion could be derived only from what discoveries science makes next. The 'theory of everything' has yet universal miles to go before it can sleep.

References

The Shadow of the Black Hole, John W. Moffat, 2020.

Black Holes, Cosmology and Extra Dimensions, Kirill A. Bronnikov and Sergey G. Rubin, 2022.

Wormhole Tunnels in Spacetime May be Possible, New Research Suggests, Brendan Z. Foster, 2021, Scientific American.

Black Hole Scientists Win Nobel Prize in Physics, Lee Billings, Scientific American, 2020.

Einstein’s Theory of General Relativity, Nola Taylor Tillman, Meghan Bartels, and Scott Dutfield, space.com

What is Entanglement and Why Is It Important? Caltech.edu

New Theory Suggests Quantum Enlargement and Wormholes are Linked Together, Tibi Puiu.

Magnetic Wormhole Created in Lab, Tia Ghose, Scientific American.

What is a Singularity? Paul Sutter, LiveScience.

https://www.desi.lbl.gov/

Survey of 41 million galaxies confirms current best model of the universe, ucl.ac.uk

Exploring a Unified Theory of Everything: Combining Gravitation, Quantum Mechanics, Dark Energy, and Extra Dimensions, Rahim Shoara, Shiraz University, February 26, 2025.

New theory suggests gravity is not a fundamental force, Andrey Feldman, Advanced Science News, April 21, 2025.