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Before we start discussing about Light Years lets’ learn about our cosmos. Everything in the cosmos is. It encompasses all of the stuff and energy that exists in space. It encompasses everything, including time itself and you, of course.
The other planets and their numerous moons, as well as Earth and the Moon, are all a part of the cosmos. The planets revolve around the Sun, as do comets and asteroids. The Milky Way galaxy has hundreds of billions of stars, the majority of which have exoplanets, or stars with their own planets. The Sun is one of these stars
In the observable universe, there are billions of galaxies, including our own Milky Way, all of which are believed to contain supermassive black holes as their centres. The cosmos contains all the stars in all the galaxies as well as everything else that astronomers are unable to see. Simply said, it is everything.
Even though it might appear like a bizarre place, the universe is not far away. Outer space is only 62 miles (100 kilometres) away from where you are right now. The distance to outer space is only a few dozen miles above you, regardless of the time of day or night, where you are—indoors or out, napping, eating lunch, or nodding off in class. It is also beneath you.
On the other side of the planet, 8,000 miles (12,800 kilometres) below your feet, is the merciless vacuum and radiation of space.
Our planet, Earth, is a haven in both time and space. Although it may seem unchanging, the entire world is a transient object in the scheme of the cosmos. Earth was not even a part of the cosmos for approximately two-thirds of its history. Likewise, it won’t remain this way forever. In a few billion years, the Sun will enlarge and cover Earth’s sky while consuming Mercury and Venus.
It might possibly enlarge to the point that Earth would be swallowed. It’s challenging to know for sure. After all, we humans are only now starting to understand the universe.
The distant past is slightly easier to anticipate with any degree of accuracy than the distant future. It has been discovered by scientists investigating the radioactive decay of isotopes on Earth and in asteroids that the solar system and our planet were formed about 4.6 billion years ago.
On the other hand, it appears that the universe is only 13.8 billion years old. By calculating the ages of the earliest stars and the speed at which the universe is expanding, scientists were able to determine that figure. By detecting the Doppler shift in the light from galaxies, almost all of which are moving away from us and from one another, they were also able to measure the expansion. T
he distance between galaxies increases with their rate of distance travel. Galaxies should move apart from one another more slowly because to gravity, but this is not what is happening; scientists are unsure of the cause. The galaxies will be so far away in the future that Earth won’t be able to see their light.
In other words, last Sunday, the universe’s matter, energy, and everything else was more compact than it is right now.
The Big Bang theory provides the greatest explanation for the origin of the universe. Galaxies are moving away from one another on average, according to observations of far-off galaxies. According to astronomers, this motion indicates that the universe is expanding because, on the greatest scales, the distances between galaxies increase over time. This implies that the cosmos was earlier than it is now, and it was also hotter and denser.
Astronomers can determine the age of the universe by connecting its contents to the history of its expansion thanks to Einstein’s general relativity theory. The universe is currently thought to be 13.787 billion years old, based on a wide range of data, including far-off supernovas(opens in new tab), the cosmic microwave background(opens in new tab), and the abundance of light elements.
The singularity is a place where the cosmos was initially compressed into an infinitely small volume. NASA claims that after the singularity, space expanded, creating the universe we know today (opens in new tab).
Scientists are unsure of what existed prior to the Big Bang. They are aware, however, that the singularity is an artefact of general relativity, which happens when the equations fail to adequately capture a physical condition. A theory of quantum gravity, which is a physical theory of strong gravity at incredibly minute scales, must be the source of a genuine explanation for the singularity.
While there is no such theory as of yet, there are a number of contenders, including loop quantum gravity and string theory.
All the energy and matter in the universe are present. As the simplest atomic element with simply a proton and an electron, hydrogen makes up a large portion of the universe’s observable matter (if the atom also contains a neutron, it is instead called deuterium).
A molecule is made up of two or more atoms sharing electrons. An aggregate of several trillions of atoms is a dust particle. An asteroid is created by mixing a few tonnes of carbon, silica, oxygen, ice, and a few metals. Or create a Sun-like star by combining 333,000 Earth masses of hydrogen and helium.
The majority of the universe’s materials are in a form that is now unknowable to modern physics. Dark energy, a hypothesised type of energy that seems to live in the vacuum of space-time itself, makes up about 68% of the universe’s total energy. However, the Universe Forum at Harvard University claims that physicists are unable to explain why this energy is so powerful or where it comes from (opens in new tab).
Dark matter, which is thought to be an invisible kind of stuff that does not interact with light, is thought to make up around 27% of the matter and energy in the universe. While most physicists believe that dark matter is a new type of fundamental particle (or particles), this has not yet been proven.
Stars, planets, and enormous gas clouds make up the remaining 5% of the cosmos, which is made up of common, everyday matter.
We must correctly estimate the contents of the universe before we can comprehend how the universe will end. Dark energy, which makes up the majority of the cosmos, will determine how it evolves in the future. The expansion of the cosmos is speeding as a result of dark energy, which is its primary effect.
Therefore, the universe is not only expanding daily but also expanding at an increasing rate. Astrophysicist Kevin Pimbblet stated in The Conversation that if dark energy does not change (which is a large assumption given that we do not yet understand the nature of dark energy), then this accelerated expansion would eventually push nearly every galaxy beyond of our observable sphere
In a few hundred billion years, practically every galaxy will vanish from our view. The Milky Way will eventually run out of new gas needed to produce stars. The final stars will burn out billions of years from now, leaving behind a thin soup of fundamental particles that will gradually cool to absolute zero.
Melodysheep explains it beautifully through this youtube video.
A light-year measures distance rather than time (as the name might imply). A light-year is the distance a light beam travels in one year on Earth, which is roughly 6 trillion miles (9.7 trillion kilometers).
Given the extremely enormous numbers being discussed, it is difficult to measure lengths in miles or kilometres on the scale of the universe. Astronomers can measure the distances of stars from Earth in a lot less time than it takes for light to cross that vast distance. For instance, Proxima Centauri, the star closest to our sun, is 4.2 light-years away from us, which means it takes just over four years for the star’s light to reach us.
It is highly precise knowledge that the speed of light is constant throughout the cosmos. Light moves at a speed of 670,616,629 mph (1,079,252,849 km/h) in a vacuum. You multiply this speed by the number of hours in a year to calculate the distance of a light-year (8,766).
The answer is that 5,878,625,370,000 miles make up one light-year (9.5 trillion km). This can appear to be a very far distance at first, but the vastness of the universe dwarfs it. According to one calculation, the known universe has a diameter of 28 billion light-years.
Given the magnitude of the figures being utilised, measuring in miles or kilometres at an astronomical scale is not practicable. Starting in our immediate cosmological vicinity, the Orion Nebula, which is the nearest star-forming region to us, is only 1,300 light-years distant, or 7,861,000,000,000,000 miles, away.
Our galaxy’s centre is roughly 27,000 light-years away. The Andromeda galaxy, which is 2.5 million light-years from our galaxy, is the closest spiral galaxy to it. We can observe galaxies that are billions of light-years away from us. With a distance of 13.4 billion light-years from Earth, the galaxy GN-z11 is regarded to be the most distant observable galaxy.
Astronomers can establish how far back in time they are looking by measuring in light-years. Everything we see in the night sky has already happened since it takes light time to reach our eyes. In other words, if you see something from a distance of 1 light-year away, you see it precisely as it was a year ago.
The Andromeda galaxy is visible to us as it was 2.5 million years ago. The cosmic microwave background, which is the farthest object we can observe, is also our oldest perspective of the universe, having been created just 13.8 billion years after the Big Bang.
Along with the light-year, astronomers also use parsecs. A parsec, short for parallax-second, is derived from the use of triangulation to estimate the separation between stars. It is, to be more precise, the distance to a star whose apparent position changes by 1 arcsecond (1/3,600 of a degree) in the sky following Earth’s half-circle around the sun. The distance of 3.26 light-years is one arcsecond.
Astronomers will continue to measure distances in our vast and majestic cosmos in either light-years or parsecs.
The age of the universe is close to 14 billion years; the age of our solar system is 4.6 billion years; the age of life on Earth is perhaps 3.8 billion years; and the age of humanity is only a few thousand years. In other words, compared to the age of our species, the cosmos is around 56,000 times older.
By that standard, practically everything that has ever occurred occurred before humans. Given that we have only recently arrived in the cosmos, we naturally have many questions. Our research into our own solar system has just just begun in the past few decades. In just one human lifetime from now, our knowledge of the universe and our place in it will have surely advanced beyond anything we can currently comprehend.
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