Theory Earth In the Universe. Where Are We?

Earth (7,830 miles in diameter) is part of the solar system. The solar system is the ensemble of planets orbiting the Sun. Earth is the third planet from Sun after Mercury and Venus. Beyond Earth are still found Mars, the gas giants -Jupiter, Saturn, Uranus, Neptune- and Pluto. Between Mars and Jupiter's orbits is found the asteroid belt. Asteroids are boulders or small planetoids. Beyond Neptune, between 2.8 billion and 28.6 billion miles (4.5 billion and 46 billion kilometers) -300 Astronomical Units (AU) -300 times the distance Sun-Earth-, lies the Kuiper Belt, a disk-shaped reservoir of comets and diverse leftovers of solar system's formation; further beyond, at the solar system boundaries another comets' reservoir exists, the Oort Cloud. This cloud begins where Kuiper Belt ends. Solar system is protected by heliosphere. This Sun's magnetic field is separating solar system from interstellar medium

click to a illustration to where are we?

Earth is 93 million miles (150 million kilometers) away from Sun. Pluton, farthest planet, is 3.7 billion (6 billion kilometers) miles away. Oort Cloud stretches to nearly 1 or maybe 2 light-years (1 light-year is 5,880 billion miles). Beyond solar system boundaries interstellar medium is beginning. Distances become so important that usual terrestrial measure units are not used anymore, but specific units instead. Light-year is distance which light travels in one year at speed of 300,000 km per second (671 million miles per hour), i.e. 5,880 billion miles (9,000 billion kilometers). Beginning at faraway limits of solar system, Astronomical Unit (AU) is used. It is Sun-Earth distance -93 million miles (150,000,000 km). Light-year is at the same time location of an objet in space, and in time: a star located at 500 light-years is at 500 times 5,880 billion miles as its light took 500 years to reach us. This star is seen as it was 500 years ago, about 1500 AD

a galaxy seen edge-on is well showing why we can see our own Milky Way Galaxy like the Milky Way only! picture site 'Amateur Astronomy'

Our Sun is a star. A star is a celestial body which is emitting energy -which the star yields through the nuclear fusion process- under the form of light and varied radiations. Stars have been born from the gravitational collapse of interstellar clouds made of gas and dust. Like billion of other stars the Sun belongs to the Milky Way Galaxy. The Milky Way Galaxy is a galaxy. A galaxy is an ensemble of hundreds of billion stars. Our Milky Way Galaxy, might we seen it from the outside, would look like those spiral galaxies popularized by terrestrial and space observatories: a central bulge with spiraling arms. Our Galaxy is 100,000 light-years wide. Would the Sun be the size of the dot of an 'i' on this page, the Milky Way would stretch from Los Angeles to New-York. Sun is located 28,000 light-years away from center and it is orbiting the Galaxy in 250 million years (143 miles per second; 230 km/s), as it's about 20 light-years above the center of the plane of the disk. Locally, Sun is situated in a zone of thin density (0.3 particles per cm³). In this zone, the mean distance between stars is about 5 to 6 light-years. A black hole is found in Milky Way center as in other galaxies. A black hole is a place of huge gravity swallowing matter and from which even light cannot come out. Milky Way is containing 400 billion stars. Our Galaxy outer reaches are marked by a globular clusters halo

Milky Way in turn is part of a group of galaxies wich is called the Local Group. The Local Group is 10 million light-year-wide. It contains 3 large galaxies (of them the famous Andromeda Galaxy, M31) and more than 30 smaller ones. In the Local Group, Milky Way is second in size after M31 as the Triangulum Galaxy is the third. Closer to our Milky Way, in a 1 million light-years wide inner circle, satellites or companions galaxies are found, like the Large and Small Magellanic Clouds (irregular dwarf galaxies, 179,000 and 210,000 light-years distant respectively, as both Magellanic clouds are interacting which fuels star formation)

The Local Group itself, through successive memberships, is taking place in other groups. The Norma Cluster (Abell 3627) is the closest massive galaxy cluster to the Milky Way as itlies about 220 million light-years away. Due to the enormous mass concentrated here, and the consequent gravitational attraction, that region of space is known to astronomers as the Great Attractor, and it dominates our region of the Universe. Such clusters of galaxies eventually line up into a filamentary web which the Universe was recently discovered to look like. Originating at Universe very beginnings, this network of vast filaments is shaping the Universe. Galaxies are found at its nodes, at a total number of 125 billions. The Universe is 28 billion light-year-wide. It is flat, that is that two parallel lines never meet, and that it's expanding. It has no other boundaries than the ones its draws as it's unfolding. A recent estimate shows that there are about 70 thousand billion of billion stars in Universe (7 sextillion or 7 and 22 zeros), as much as grain sands found on all Earth's beaches. Recentest advanced theories state that this Universe itself would be only a minute part of a more giant cosmos still. Our Universe would be a kind of bubble of trillions light-year-wide. And this bubble would be only one out of many

Another way to figure out the vastness of the Universe is to consider what the duration of some journeys would be, aboard a spacecraft sporting the current, beginning of the 21st century technology. The immense distances then become obvious as we would need about 6 months to reach Mars and about 10 years to reach Pluton (using a gravity-assisted flyby). We would then need a journey lasting 18,000 years to reach a star close to our Sun (they are at an average of 5 light-years from us)! And 357 million years would be required to cross the entire width of the Milky Way Galaxy. Crossing the entire length of the Local Group, our own galaxy cluster would, eventually, need about 32 billion years...

-> A Memento to Where our Earth is Lying Into!
From our Earth to the Universe at large, we can have a description of how the Universe's structures are unfolding. As the Earth is located into the solar system, the solar system itself is into the Local Interstellar Cloud, which in turn lies into the Local Bubble. Then comes the Gould Belt, a hypothetical arm of the Galaxy. It is located into the Orion-Cygnus Arm of our Milky Way Galaxy. The Milky Way, like a galaxy, is part of varied set of galaxies: the Milky Way subgroup, then the Local Group, the Virgo Supercluster and the Pisces-Cetus Supercluster Complex (by contrast to galaxy clusters which are bound together by gravity, most superclusters are not and the component clusters are generally shifting away from each other due to the expansion of the Universe. Superclusters, which typically contain dozens of galaxy clusters and groups and span hundreds of millions of light-years were discovered in the 1980's). From there we are reaching to the observable Universe, that familiar view of the net of hydrogen and galaxy clusters filaments! Than can be summarized like:
Earth -> Solar System -> Local Interstellar Cloud -> Local Bubble -> Gould Belt -> Orion–Cygnus Arm -> Milky Way -> Milky Way subgroup -> Local Group -> Virgo Supercluster -> Pisces-Cetus Supercluster Complex -> Observable universe