Space…the place beyond our own world. It is a vast and seemingly endless expanse, and we’ve just barely scratched the surface of what is out there. Astronomers, who study the stars, have been watching the skies with great interest for centuries. But it’s only within the last 75 years or so that we have begun to physically explore what lies beyond the Earth.
For many years, it was believed that the Earth was the center of the universe. However, through the work of scientists like Copernicus, Galileo, Kepler and Isaac Newton, it was shown that the Earth revolves around the sun, as do the rest of the planets in our “solar system”. A solar system is a group of planets that revolve around a star, or sun. In our case, it’s kind of like our space “backyard”.
There are currently eight recognized planets in our own solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A ninth, Pluto, was until recently considered the smallest and furthest planet in the solar system. However, in 2006 the term “planet” was officially defined by the International Astronomical Union (IAU) in such a way that Pluto did not make the cut, and it was reclassified as a “dwarf planet”.
To qualify as a planet under the IAU’s definition, a celestial structure must be mostly round in shape, orbit around the sun, and have “cleared the neighborhood” around its orbit. The last point is the key that keeps Pluto out. Clearing its neighborhood means that over time, as a planetary object orbits around the Sun, it will disperse most other large objects in the path of its orbit and become the “dominant” object. Pluto shares its orbit with many other large objects within its orbital range, and thus was kicked out of the planet club.
Planets vary wildly in size, from tiny Mercury at just over 3,000 miles in diameter, to Jupiter at 86,881 miles in diameter. They are also made up of different materials. Jupiter, Saturn, Neptune and Uranus are “gas giants”, which means they are not solid. Jupiter, for example, is mostly made of hydrogen and helium, meaning you can’t actually stand on the planet’s surface. The smaller planets closer to the sun (Mercury, Venus, Earth and Mars) are made of rock.
How do we know so much about other planets? After all, it’s not as if any humans have ever visited these other worlds in person. Space is a vacuum – no matter exists in outer space, and humans certainly can’t breathe in it, which makes traveling through it difficult. It hasn’t stopped humans from visiting the moon, however, in 1969. But distance is another factor to consider – many of these planets are very far away, and could take many years to reach. Sending humans to visit them in a vessel that can keep them alive and healthy for the long journey is a serious undertaking.
In the meantime, we send machines! In 1970, the Venera 7 probe reached Venus, and became the first space probe to land on a planet and send information from that planet back to Earth. Since then, humans have been using powerful rockets to send unmanned crafts to other planets to collect and transmit their data, so that we can learn more about the other worlds in our solar system. Sometimes these crafts simply perform “fly-bys” where they take photographs of the planet from space. Other times, they enter the planet’s atmosphere and even land on its surface, gathering data and transmitting the information back to Earth.
For now, this is as far as we have gotten in terms of reaching other planets. However, many people now believe it is time to start working on sending humans to other planets. The most likely candidate is Mars, as it’s one of the closest planets to Earth and likely the easiest for humans to survive on. Some scientists have even proposed the idea of colonizing Mars to have permanent settlements of humans there! In the meantime, we’ll have to be content with what unmanned machines can tell us about the far reaches of space.
That isn’t to say that we can’t learn much from them – they tell us quite a bit! The Hubble Space Telescope, a large and extremely powerful telescope that was launched into low orbit around earth in 1990, can view areas that are several billion light years away. This amazing device takes stunning photographs of galaxies, nebulas and other incredible phenomena that teach us much about the ways of the universe. It’s not the same as being there, but for now it’s the closest we can get.
Check Out All of Our Space Themed Products: