When we think of the word "dark energy," most of us probably think of Voldemort, Darth Vader, or the image of the unpleasant man in the office—not many think of the stars and the universe.
Humans have been studying stars since ancient times. We use the night sky to guide us, explain inexplicable things, and seek insight into human conditions and experiences. These vexing questions may once have been answered only by faith or religious doctrine, although it is safe to assume that at least some people are curious about the nature of space, stars, and galaxies.
As the famous nursery rhyme says: "Twinkle, twinkle, little star." How I want to know what kind of person you are. ”
Today, science is answering questions about stars and the universe. Scientists have discovered that dark energy is a repulsive force that causes the universe to expand at an ever-increasing rate.
This essence has long plagued astronomers and cosmologists, denying the natural pull of gravity and the expected eventual deceleration. We still don't know anything about dark energy, but here's a brief guide to what we've known so far.
What is Dark Energy?
When the cosmic explosion existed, as assumed to occur during the Big Bang, the initial velocity should be a fixed velocity of motion.
Newton's second law states that the acceleration of an object is equal to the force acting on it divided by its mass. Thus, over time, the once-early universe will become more massive. Theoretically, this would lead to a sustained deceleration as the mass grew more widely, but the initial force remained the same.
Instead, we see acceleration and expansion in the measurements of the universe.
The existing unambiguous observations measure the distances between space objects through acoustic oscillations, so that amplified quantum fluctuations can be observed when measuring the recombination of galaxy clusters.
Tracking these clusters would allow scientists to map the expansion of the universe's history, a technique similar to using a Type Ia supernova explosion, an explosion that occurred a few light-years away, as a beacon to measure distant distances in space.
The rate at which the universe is pushed outward seems to be increasing. As a result, the scientists saw coverage of longer distances in less time.
So what is the unknown source of this accelerated expansion of the universe? A mysterious force is seen as dark energy.
This concept is hard to imagine, especially since dark energy is not dark— it is invisible.
Think about jumping over a rock on the water. When the stone jumps, it will move away from you, eventually slowing down and falling into the water.
The universe is performing some kind of similar action, albeit to a much more complex degree.
Let the stone represent matter. As matter moves farther and farther, its speed is expected to decrease.
But matter continues to spread outwards and never falls into space that already exists or collapses into itself.
So, in this case, stone is matter, water is space, and the self-perpetuating force behind the constant jump is dark energy.
Explanations for the accelerated expansion of the universe driven by dark energy can also be broken down into simple concepts like baked goods.
Imagine the blueberry muffin batter in the oven. Blueberries are substances and batters are spaces.
The batter thickens, rises and expands as heated, pushing the blueberries farther away.
The same thing is happening in our universe. As our universe expands, matter (planets, moons, galaxies, and stars) gets farther and farther apart.
Dark Energy: The biggest mystery in our expanding universe
Why is dark energy important?
There are many kinds of energy – mechanical, nuclear, and potential energy, to name a few. While we know a lot about these types of energies, we still know very little about dark energies. We must understand dark energy and how it works, because for the most part, it is an integral part of our universe and determines its fate.
It is estimated that dark energy accounts for about 68% of the universe.
Dark matter accounts for the other 27 percent, and visible matter accounts for less than 5 percent of the universe.
This common visible substance is called baryonic matter and consists of protons, neutrons, and electrons.
What is dark matter and how does it differ from dark energy?
Essentially, dark energy accelerates the expansion of the universe, while dark matter slows it down.
Unlike ordinary matter, dark matter is a particle that is not easily baryons, and radiation will detect baryons or ordinary matter.
And it's not antimatter either. Antiparticles, in contrast to baryonic particles, do not see the gamma rays produced by the annihilation of antimatter when we try to probe the properties of dark matter.
The main current theoretical estimates of dark matter are most likely unknown or hypothetical particles, such as axions. Therefore, these are the most likely candidates for dark matter.
Axions are hypothetical dark matter particles that contain weak particles and low masses. These are also known as weakly interacting mass particles (WIMPS).
In fact, it's not clear what dark matter is made of, but we do know it exists because of its ability to alter the current gravitational state of galaxies.
Not only do galaxies move away from where they were first observed, but space objects such as stars and planets that are furthest from the center of the galaxy move at the same speed as near the center of the galaxy.
This means that unknown matter is acting on baryonic matter from outside the Milky Way rather than from the core of the most concentrated matter.
We have reason to believe that the repulsive forces of dark matter and energy are driving the expansion of the universe and increasing as they accelerate.
Still, dark matter and dark energy are still not widely understood, giving way to one of the most important scientific mysteries in the universe.
Who discovered dark energy?
Like many scientific theories and discoveries, dark energy is discovery that different scientists have made collaboratively over time.
The discovery of dark energy dates back to the 1920s.
American astronomer Edwin Hubble — after whom the Hubble Space Telescope is named — speculates that galaxies are moving away from our parent galaxy (the Milky Way). In addition, he assumed that their speed of movement was proportional to the distance they traveled. His conjecture is due to an evaluation of Newton's second law, in which the acceleration of the universe depends on the primordial explosive force divided by its mass.
These distant observations were made while studying supernovae, which create the forces of black holes when they collapse.
This argument holds that our universe is no longer the stable entity it is supposed to be, but an unstable, moving entity.
The theory that the instability of the Milky Way caused space to move appeared at about the same time, that is, the history of the universe and the existence of dark matter itself can be traced back to a single specific event, the Big Bang.
The Big Bang showed that the origin of the universe was separated by a single primordial atom and caused a catastrophic explosion. The explosion emitted all the material we see today, with a total mass estimated at 3 times 10 to the power of 55.
This theory was proposed by the Belgian priest and cosmologist George Lemaëtre. He was later credited with the discovery and is credited with being the founder of the Big Bang theory.
But the name of the modern theory that will change the path of cosmologists in the coming decades is not in Lemaëte's hands.
Rather, it was the result of an English cosmologist named Fred Hoyle who strongly opposed the theory and labeled it as such to condemn its validity, but the name remains.
Einstein's cosmological constant
When Einstein proposed his theory of relativity, several equations were derived in which the explanations and theories were consistent in the process of representing variables and settings. However, when Einstein's equations do not accurately describe reality, an observable problem arises.
Albert Einstein's cosmological constant was a temporary solution to the larger picture.
In Einstein's day, the theory was that the universe was stationary rather than accelerating.
This theory leads to the lack of equilibrium solutions to equations of Einstein's theory of general relativity(which explains the influence of gravity on the structure of space-time).
To compensate, he casually inserted a value that was roughly negative to balance it. But, of course, since the known universe would expand, this value can be inserted and treated as a variable, representing the gravitational repulsion of dark matter.
When solving for this variable, it holds almost the same value as Einstein predicted the static universe.
What was once considered Einstein's biggest mistake is now the leading mathematical induction of dark energy forces, something he didn't know.
Has dark energy been proven?
Evidence behind pervasive expansion
Some scientific findings support dark energy and the expansion of the universe.
In the late 1990s, two astronomy teams were studying a known white dwarf (a shrunken star state that occurred before supernova formation) that exploded long ago, leading to the supernova we've only recently seen.
In conducting the study, they hope to determine how fast the cosmic speed is falling.
To reinforce their claims, they used the redshift phenomenon.
Redshifting is the use of wavelengths to determine distance changes over a specific time interval.
Large space bodies have the ability to emit and absorb light.
Using redshift techniques, as the space body gets closer to the observer point, the red color becomes brighter as the wavelength decreases.
As it gets farther and farther away, it gets darker and darker as the wavelength increases dramatically.
The astronomers are using the supernova's redshift to determine how close it is approaching Earth, which would predict a decline in the cosmic speed.
They expected bright redshifts, but what they found was an extremely faint color.
The remarkable color change indicates that the distance has increased over time since the last observation, which means that the universe is expanding and accelerating.
Gravitational lensing provides another piece of evidence.
Gravitational lensing is the bending of visible light through cosmic giants, such as galaxies.
Galaxies have a huge gravitational pull. In exceptional cases, it can act as a rough lens, distorting the body image behind it or making it look more important than it actually is.
Astronomers use gravitational lensing to observe the space objects behind them to prove the existence of dark energy.
They found that these images, which should be kept near constants, were much smaller, meaning that some unknown force caused them to accelerate faster than expected, which further provided evidence of dark energy.
In the 1960s, astrophysicist Arnold Penzias and astronomer Robert Wilson observed unique radio signals and microwave amplification at the Homedale Satellite Mast in New Jersey.
While trying to build a radio telescope, they encountered unexpected interference—a static buzz.
After considering what the noise might be, the two concluded that the noise might be the remnants of a Big Bang explosion.
Today, what was once just a nasty interference is now called cosmic microwave background or cosmic background radiation, which may be the remnants of an explosion when the Big Bang created the universe.
Think again about the jumps of the stone as it moves over the water; the ripple effect caused by the stone continues to seep outward.
This residual wave movement is similar to the microwave radiation or echo effect of the Big Bang that Penzias and Wilson stumbled upon.
The future of dark energy
Particle astrophysics is at the forefront of research in astronomy and high-energy particle physics.
There are two important observatories for astrophysicists to study dark matter and dark energy and its effects on the universe: The Ice Cube Neutrino Observatory has the most powerful neutrino detector on Earth. In addition, the VERITAS Gamma-ray Observatory is home to VERITAS and complements NASA's Fermi mission.
It seems that the more we discover this mysterious power, the more questions we have.
Will the universe expand forever? What happens as it continues to accelerate?
As the universe continues to evolve and the distances between our current galaxies grow farther and farther apart, future humans on Earth may not be aware of the existence of many stars and planets because they will become too far away to see.
Scientists once thought that gravity would slow down and could one day reverse the expansion of the universe. If the universe contains enough matter, the idea that gravity might replace inflation and cause the universe to collapse into itself is a hypothetical phenomenon known as the Great Compaction.
Dark energy remains a mystery
We know very little about the nature of cosmic acceleration and dark energy. To be sure, the expansion of the universe is not slowed down by gravity as many people think, but rather accelerated.
While we are convinced of the existence of dark energy, we know very little about it. For example, scientists can only speculate about what dark energy is made of. Still, people in the fields of astronomy, cosmology, and astrophysics are working hard every day to learn more about the nature and existence of dark energy.