Space Exploration
History
For millenia, people looked at the night sky and saw the stars fixed to the heavens and 7 planets. But these planets were a little different than what you know of. Sure, there were Mercury, Venus, Mars, Jupiter, and Saturn. But, there was also the Sun and Moon. Since they moved in the sky, they fell under the word, "planet," which means "wanderer." Ptolemy attempted to bring order to the universe by devising a model that was used for more than 1,000 years. Of course the Earth is at the center, the Moon goes around the Earth, and the Sun goes around the Earth beyond the Moon. Where everything fell into place was Ptolemy's genius. He placed each object in a crystal sphere (crystal because we can see through it and sphere because that was the perfect shape) where nothing could move between them. Earth -> Moon -> Mercury -> Venus -> Sun -> Mars -> Jupiter -> Saturn -> the fixed Stars. This was the order of the spheres. As far as anybody was concerned, it made sense and was rarely questioned until the 1500s. I'm sure people questioned the information because the math required to maintain the crystal sphere model in light of observations became more and more abstract. Points were invented outside of the Earth in order to explain observed motions of the planets.
Things changed in the 1540s. Nicholaus Copernicus was a math genius who was a trained cleric (worked for the Catholic Church) living in Poland. In Poland, Copernicus observed the motions of the planets and tried to use math reconcile what he was seeing. The only thing that worked was putting the Sun at the center instead of the Earth. His book provided mathematical models for heliocentrism, whereas geocentrism relied on personal stories. Other great observers made contributions to our understanding of the universe, even if they didn't necessarily believe in heliocentrism. Johannes Kepler gave us his laws of planetary motions (orbits are not circles but ellipses). Tycho Brahe gave us the observations Kepler used for his laws. Then, there was Galileo. He did a very novel thing: he pointed the newly invented telescope at the sky. He saw sunspots (whether he saw them first is still up for debate), he saw craters on the Moon, he saw that Venus has phases like the Moon, and he saw things orbiting Jupiter. He figured that if objects orbited Jupiter and not solely the Earth, then the Earth could not be at the center of the universe.
We've already seen that other planets were discovered later, so I won't repeat those things here. Let's move on to telescopes.
For millenia, people looked at the night sky and saw the stars fixed to the heavens and 7 planets. But these planets were a little different than what you know of. Sure, there were Mercury, Venus, Mars, Jupiter, and Saturn. But, there was also the Sun and Moon. Since they moved in the sky, they fell under the word, "planet," which means "wanderer." Ptolemy attempted to bring order to the universe by devising a model that was used for more than 1,000 years. Of course the Earth is at the center, the Moon goes around the Earth, and the Sun goes around the Earth beyond the Moon. Where everything fell into place was Ptolemy's genius. He placed each object in a crystal sphere (crystal because we can see through it and sphere because that was the perfect shape) where nothing could move between them. Earth -> Moon -> Mercury -> Venus -> Sun -> Mars -> Jupiter -> Saturn -> the fixed Stars. This was the order of the spheres. As far as anybody was concerned, it made sense and was rarely questioned until the 1500s. I'm sure people questioned the information because the math required to maintain the crystal sphere model in light of observations became more and more abstract. Points were invented outside of the Earth in order to explain observed motions of the planets.
Things changed in the 1540s. Nicholaus Copernicus was a math genius who was a trained cleric (worked for the Catholic Church) living in Poland. In Poland, Copernicus observed the motions of the planets and tried to use math reconcile what he was seeing. The only thing that worked was putting the Sun at the center instead of the Earth. His book provided mathematical models for heliocentrism, whereas geocentrism relied on personal stories. Other great observers made contributions to our understanding of the universe, even if they didn't necessarily believe in heliocentrism. Johannes Kepler gave us his laws of planetary motions (orbits are not circles but ellipses). Tycho Brahe gave us the observations Kepler used for his laws. Then, there was Galileo. He did a very novel thing: he pointed the newly invented telescope at the sky. He saw sunspots (whether he saw them first is still up for debate), he saw craters on the Moon, he saw that Venus has phases like the Moon, and he saw things orbiting Jupiter. He figured that if objects orbited Jupiter and not solely the Earth, then the Earth could not be at the center of the universe.
We've already seen that other planets were discovered later, so I won't repeat those things here. Let's move on to telescopes.
Telescopes
There are two main types of telescopes: refractor and reflector. Reflector telescopes rely on mirrors to focus light from the heavens to your eye. Refractor telescopes bend light through convex and concave lenses to focus the light. Reflector telescopes tend to be smaller than refractors. In a refractor, if you increase the lens, you not only have to increase the width of the tube, but also the length. So once a certain size is reached, the refractor telescope becomes too long and heavy to manage effectively.
There are two main types of telescopes: refractor and reflector. Reflector telescopes rely on mirrors to focus light from the heavens to your eye. Refractor telescopes bend light through convex and concave lenses to focus the light. Reflector telescopes tend to be smaller than refractors. In a refractor, if you increase the lens, you not only have to increase the width of the tube, but also the length. So once a certain size is reached, the refractor telescope becomes too long and heavy to manage effectively.
Into Space
In 1957, something humans made left Earth for the first time. Sputnik 1 looked like a silver beach ball with 4 antennae sticking off of it, but it made history as being the first artificial satellite to orbit the Earth (the Moon is considered a natural satellite)...and it was made by the Russians. That really scared America. We sent up our first satellite a year later. From there it was a race to be first between Russia and USA. They put the first satellite, the first living things (two dogs), and the first human in space (Yuri Gagarin). We put humans on the Moon. We've since dominated the exploration of space by sending probes, landers, rovers, and satellites to the Sun (Helios); Mercury (Messenger, Mariner); Venus (Magellan, the Russians sent the Venera probes); Moon (Apollo); Mars (Viking, Curiosity, Spirit, Opportunity); Asteroid Belt (Dawn); Jupiter (Galileo); Saturn (Cassini); Pluto (New Horizons); and space in general (Voyager I and II - both have left the Solar System). The Hubble Space Telescope has been taking breathtaking images of the universe since 1990. We'll soon replace it with the James Webb Space Telescope. We are still probing the reaches of the Solar System and the universe. More discoveries are definitely waiting to be made.
In 1957, something humans made left Earth for the first time. Sputnik 1 looked like a silver beach ball with 4 antennae sticking off of it, but it made history as being the first artificial satellite to orbit the Earth (the Moon is considered a natural satellite)...and it was made by the Russians. That really scared America. We sent up our first satellite a year later. From there it was a race to be first between Russia and USA. They put the first satellite, the first living things (two dogs), and the first human in space (Yuri Gagarin). We put humans on the Moon. We've since dominated the exploration of space by sending probes, landers, rovers, and satellites to the Sun (Helios); Mercury (Messenger, Mariner); Venus (Magellan, the Russians sent the Venera probes); Moon (Apollo); Mars (Viking, Curiosity, Spirit, Opportunity); Asteroid Belt (Dawn); Jupiter (Galileo); Saturn (Cassini); Pluto (New Horizons); and space in general (Voyager I and II - both have left the Solar System). The Hubble Space Telescope has been taking breathtaking images of the universe since 1990. We'll soon replace it with the James Webb Space Telescope. We are still probing the reaches of the Solar System and the universe. More discoveries are definitely waiting to be made.