Everything in the cosmos is. It encompasses all 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 centers. 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 km) 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 km) below your feet, is the merciless vacuum and radiation of space.
In actuality, you are currently in space. People use the phrase "out in space" as if it were there, and they were there, as if Earth were a different entity from the rest of the cosmos. But much like the other planets, Earth is a planet that exists in space and is a part of the cosmos. It so happens that life exists here and that the conditions close to this planet's surface are favorable for life as we know it. The tiny, delicate planet Earth stands out in the universe. Practically the entire galaxy is a hostile and cruel place for humans and other creatures that live on our planet.
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. The distance between galaxies increases with their rate of distance travel. Galaxies should move apart from one another more slowly because of 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.
All the energy and matter in the universe are present. Individual hydrogen atoms, the simplest atomic element with simply a proton and an electron (if the atom additionally has a neutron, it is referred to as deuterium), make up a large portion of the observable matter in the universe. 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.
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