It all started with a Big Bang, and now, we are here. The ever-mysterious and mesmerising universe never stopped amazing astronomers or us. We may run out of paper but the list of its strangeness will go on.
Here are some of the most fascinating facts about the Universe:
Age may just be a number but when it comes to the Universe, it is quite a significant one. From ancient times, scientists have been curious about its age and tried to figure it out. Most recent research suggests it is approximately 13.8 billion years old. It can be 170 million years more or less. Finding this number was not a piece of birthday cake though!
First of all, astronomers studied the oldest stars and globular clusters in the interior of the Universe and then calculated the expanding rate before they could get to its age. Indeed, the oldest object of the Universe cannot be older than itself. Alternatively, scientists worked backwards to calculate the age using the expansion rate. Astronomers have followed these two methods to solve the mystery.
During the 1920s, cosmologist Edwin Hubble made a groundbreaking discovery. He discovered that the Universe is not static; in fact, it is still expanding. Although, for a long time, it was believed that the gravity of matter would slow this process or even cause it to contract.
A few years later, in 1998, the Hubble Space Telescope examined extremely distant supernovas and found that, ages ago, the Universe was not expanding as fast as it is today. This perplexing revelation suggested that a mystifying power, called dark energy, is kindling the extension. Dark energy is perhaps the greatest puzzle in science since its discovery remains elusive to scientists.
The growth spurt is accelerating
In 2011, Adam Riess, Brian Schmidt, and Saul Perlmutter won the Nobel Prize in physics for their 1998 discovery, where they stated that the Universe is not only expanding; it is accelerating as well. According to their research, the farther a galaxy is from Earth, the faster it is moving away.
This acceleration also affirms Einstein's theory of general relativity. Scientists are seeking help from Einstein's cosmological constant to explain the ever-mysterious dark energy that seems to be counteracting gravity and making the Universe expand at an accelerating pace.
Could be flat
"Flat Earth" might sound ridiculous, but "flat universe" is quite a possibility! The Universe is "closed" if its density exceeds a specific critical value, just like the surface of a sphere. This means that the cosmos is not infinite, but there is no end.
In this case, if a "great crisis" occurs, the Universe will eventually stop expanding and begin to collapse on its own. Scientists have named it - "Big Crunch". If the cosmos' density is less than the critical density value then its shape is "open". In this case, it is endless and will continue to expand forever.
However, if the density is equal to the critical density, the Universe's shape will be "flat" like a piece of paper. Here, it has no boundaries and will expand forever, but the expansion speed will gradually approach zero after an infinite time. Recent measurements indicate that the cosmos is flat with an error margin of about two percent.
Full of invisible objects
The vast majority of the Universe is made up of invisible things. According to astronomers, detectable stars, planets, and galaxies account for only four percent of them. The remaining 96 percent consists of invisible substances or substances that are not easily understood.
These elusive substances, called dark energy and dark matter, have not yet been discovered. Still, astronomers base their existence on the gravitational influence that also applies to normal matter, the visible part of the Universe.
Echoes of its birth
The cosmic microwave background is composed of light waves left over from the Big Bang that created the Universe 13.7 billion years ago. This relic of the Big Bang blast stays near the Universe as a veil of radiation.
The European Space Agency's Planck mission illuminated the entire sky with microwaves to reveal new clues about the origin of the Universe. Planck's observation is the most accurate view of the cosmic microwave background obtained so far.
Scientists hope to use the data collected from this mission to solve some of the most controversial issues in cosmology such as - what happened immediately after the formation of the Universe?
Possibility of more universes
We live in a multiverse and our universe is one of them. This idea comes from a theory called "eternal inflation", which states that shortly after the Big Bang, time and space expanded at different speeds in different places. According to this theory, the Big Bang created a bubble universe which could function according to their independent laws of physics. This concept has always been controversial and it is only a pure hypothesis.
It was not until recent research that the cosmic microwave background was used to search for physical markers of the theory of the multiverse. Researchers searched for the best available observations of the cosmic microwave background for signs of bubble universe collisions but found no conclusions.
Researchers say that if two universes had collided, it would have left a circular pattern in the cosmic microwave background.
When physicists started cracking the nuclear code in the 1940s, they did not know that their machinations would unravel one of the most puzzling mysteries in astronomy: how stars work. They found that nuclear fusion of hydrogen is how stars have powered themselves for billions of years. They also found that the preconditions of nuclear fusion are not always human-made, they can be found in nature: in the core of the stars.
The equations that physicists use to understand the process are exactly what they use to convert nuclear reactions into usable energy. From the tiniest atom to the biggest star, nuclear physics is a relatively new term in the physics world, yet tying the Universe together in surprising ways.
Law of motion
With a simple example, we can understand the law of motion. Think that two cars collide. According to the law of conservation of energy and momentum, the total energy and momentum before the collision must be equal to the total energy and momentum after the crash. Using these simple statements, we can reconstruct the scene of the accident to determine which driver was at fault and caused the collision.
Scientists use these principles to understand almost everything in the Universe; colliding stars, merging galaxies, mixed gas clouds, etc. Why does a gas cloud emit energy? Why does a neutron star change its rotation speed? What happens when these galaxies collide? The answer is "conservation of energy and momentum."
Einstein's general theory of relativity is the modern theory of gravity, telling us how gravity works: matter and energy bend time and space. And this curvature of time and space shows how matter moves.
The math is a bit complicated: it requires a set of 10 interrelated equations to describe all these bending, warping, and movement. But these equations contain tremendous power. For instance, in the limit of weak gravity, Einstein's equation reduces the more familiar Newtonian gravity expression, explaining the trajectory from throwing a baseball to a hydroelectric dam.
Einstein went beyond the surface of the earth and performed more control. Here, relativity equations provide accurate positioning of the GPS and accurately predict the orbits of all planets.
These identical equations, without any modification, have achieved greater success, revealing the existence of black holes and their operations, the growth of the largest structure in the Universe, the presence of dark matter inside galaxies, and the Big Bang itself.
All of this comes from a set of 10 equations covering cosmic space and cosmic time-in fact; this shows the Universe has a finite age in the first place.