1. 1. 4000 BC to the 1500's — Geocentric Era
  2. 2. 1500's to current — Heliocentric Era
  3. 3. Most Notable Space Missions
  4. 4. Video Gallery

Since the dawn of man, the universe has been a mysterious wonder that has captivated and influenced the evolution of the human race. Every culture around the world is filled with stories and religious beliefs that involve the stars, moons, planets, and even the sun. This fascination as time moved on became a catalysis for the creation of the astronomer as ancient "scientist" began to ponder, what is out there? Today, we have a greater understanding of the universe and a basic knowledge through current technologies of what is beyond our own planet. However, as much as we know, there is so much more that we still have yet to learn.

In the distant past, there have been many correlations between religious ceremonies and beliefs that were centered around the planets of our solar system. Ancient peoples such as the Mayans, Incas, Egyptians studied the celestial bodies that surrounded our planet and used this information to mark certain events such as when to prepare soil for planting and when to begin harvesting. They were also used in the determination of when religious rites were performed. Whatever the reasons for man to look towards the heavens, this was the beginning of the study of the universe and its planetary systems.

4000 BC to the 1500's - Geocentric Era

Constellation of Orion on an ivory tabletConstellation of Orion on an ivory tablet /

Although there was found an image of the constellation of Orion on an ivory tablet dating as old as 32 thousand years, the first actual recordings showing astronomy activity began about 4 thousand BC. Images from around the world depicted the world as being flat and the sun as a God moving across the heavens to underneath the world and to return the next morning. Night scenes were filled with billions of stars filling the sky with the moon (usually depicting a Goddess) hovering in the sky watching over the world until the sun could reappear. This was a common image of the sun and moon found in many engravings and religious temples from this time period. Although the God and Goddess (Sun and Moon) had different names, the concept of them was the same.

It was also about this time that shamans, medicine men, and tribal leaders began studying closer into what happened within the heavens to aid them in making decisions and predictions. By keeping track of celestial bodies such as the sun and moon, it gave them an idea of when to plant and harvest crops. It was also a means to track when religious ceremonies were to be performed to appease their Gods to ensure prosperity. Ancient Mesopotamian tablets show Priest standing atop pyramid like towers (called Ziggurats) watching the skies and keeping track of the celestial bodies they are able to see with the naked eye.

Ancient Mayan CalendarAncient Mayan Calendar /

During this time period a form of calendar came about as well. Each culture used a different means of tracking days and seasons based on these calendars. Some calendars were based on solar and some were based on lunar positions. The calendars we use today were based off these earlier designs but primarily follow the solar calendar more so than the lunar calendar though the lunar calendar is still used in some regions of the world.

As time progressed, constellations are beginning to be recorded and used as a means of determining location for travelers. These constellations are still used in Astronomy to this day as a means of mapping most especially when mapping celestial bodies and their location. This is also when a geocentric concept was developed as ancient "astronomers" came to the idea that the sun and other celestial objects revolved in a perfect circle around the Earth rather then the other way around.

Anaximander's universeAnaximander's universe /

Around 600 BC, Greek astronomer Anaximander suggested that the Earth is not flat but instead rounded based on tales from sailors who stated that a different set of constellations were seen as they traveled further North or South when sailing. It would be several hundred years before the idea that the world is round and not flat would be accepted but this is the first concept of it. It was about this time that the idea that the Earth also rotated on an axis first appeared as well. This concept was discovered by Heracleides. He believed that the movement of the sun, moon, and stars in the sky could only be best explained if this idea was true.

It was in 250 BC the first measurements of the size of the Earth was determined by Eratosthenes using geometry. The basic concept was that when in Syene during the summer solstice, he noticed the sun was directly over head. However, when he was in Alexandra on the same day which was further North, the sun was at an angle rather then over head at the same moment. He determined this angle to be 7.2 degrees which is 1/50th of a 360 degree circle. He also surmised that the angle of the shadows cast from the sun between Alexandra and Syene would be about the same as it would be from the center of Earth. Using these three points of reference and the distance between Alexandra and Syene he was able to calculate the size of the Earth within 1% to 16% accuracy.

An illustration of the Ptolemaic geocentric system by Bartolomeu Velho, 1568An illustration of the Ptolemaic geocentric system by Bartolomeu Velho, 1568 /

Around the same time Aristarchus determined the distance between the Earth and Moon using trigonometry by measuring the length of a lunar eclipse and comparing it to the length of the month. He then takes this information and begins to determine the distance between the Earth and the Sun. During his calculations he came to realize that it was not the Sun that circled the Earth but the Earth that circled the Sun. However, this idea did not take root because there was no evidence to support his theory at the time.

Although the concept of a heliocentric universe was suggested during the latter part of this time frame, it was not until in the 1500's that the idea took root. Many astronomers who came to the belief in the heliocentric idea, risked their lives and social standing to deliver this concept. This is also when an interest in astronomy and the worlds beyond our own began to flourish much more so then before. Technology also began to push forward as better methods for "seeing" the universe came about.

1500's to current - Heliocentric Era

Scenography of the Copernican world systemScenography of the Copernican world system /

During this time, astronomers were still viewing the universe through the naked eye. A larger portion of the planets we know today have yet to be discovered and much of what was known is based on theories determined by mathematical calculations made by mathematicians and astronomers. The frustration of being unable to prove many of these theories prompted the advancements of telescopes for viewing what they were calculating. This would come about sometime during the 1600's when the first actual telescopes were created.

The invention of the telescope by Hans Lippershey gave astronomers the medium they so sought for to prove their theories. The ability to be capable of seeing the universe beyond our world opened a whole new understanding of what was out there. The heliocentric idea was brought to light, proven, and now has taken root in society. With this came more questions that needed to be answered. How big was our Universe, What else is out there, Who else is out there... along with thousands of other questions that we have yet to answer. With each passing era the telescopes became more and more powerful allowing both professional and amateur astronomers to view further into our solar system. Discoveries of planets not known before were found along with other celestial bodies.

Apollo 11 launchApollo 11 launch /

It would not be until the 1900's when the universe was brought more into focus. During the 1960's the cold war between the United States and Russian spurred on what was called the Space Race. Each country was determined to be the first to have a successful mission into space. This is about when NASA (Nation Aeronautics Space Administration) began to gain notoriety. On April 12, 1961 Yuri Gagarin was the first human in space. On July 20, 1969 Neil Armstrong was the first human to set foot on a foreign land, our moon. These accomplishments opened the window for the world of astronomers.

Technological advancements took leaps and bounds as a result of this time period. Between 1966 and 1972 four Satellites, Orbiting Astronomical Observatories (OAO), were launched. Two of these satellites were such a success that it instigated the creation of the Hubble Space Telescope in 1990. Hubble is a long range telescope that stays within low Earth Orbit (below an altitude of 2,000 km or 1,243 miles). With the use of Hubble we have come to a greater understanding of our own solar system never before achieved. Size, composition, and behavior of various known planets and newly discovered planets and objects within our solar system were explored through the use of the Hubble Space Telescope.

Hubble Space TelescopeHubble Space Telescope /

With this came even more of a desire to explore our universe. Probes such as Voyager I and II, Deep Impact, and Rosetta were sent into space each carrying a single directive, explore and send back information. Images and spectrographs of various celestial objects even from the far reaches of our solar system were sent back to Earth giving us a clear view, solving many of the mysteries that man has pondered since the first person looked up towards the heavens.

International Space StationInternational Space Station /

In 1998, the first joint effort space station ISS (International Space Station) was created between various countries in exploration of the solar system along with biology, human biology, physics, meterology, and various other fields. This station has held a crew continuously for the past 15 years with a 6 month rotation for the crew members. There were 4 other space stations before ISS, three of which were conducted by Russian (Salyut, Almaz, and Mir) and Skylab by the US, but these stations were primarily for military use and not so much for science.

Today, many achievements have been made in the world of Astronomy. Much of what was unknown is known but there is still so much more to learn. Our ability to reach beyond our planet to explore other worlds is quickly coming giving us a better view of our celestial neighbors. Projects such as the Mars Rovers, launched starting in 1971, was a major mile stone for astronomers as they were able to explore another world other then our own moon. Future projects for settlement of planets such as Mars have already begun which gets closer to being about the explore further into our solar system. It also gives a closer look at our closest solar system neighbors in our quest for better understanding of how the universe was created and where it is going.

Most Notable Space Missions

Although there were many accomplishments in the world of astronomical sciences over the centuries, the most notable have occurred most recently starting from the 1970's to date. These events offered mankind an amazing view of our solar system and provided new discoveries never before conceived. Many of the probes that were sent over the years are still out there recording data, though some are no longer sending information back at this time, scientist anticipate their return so that the data can be collected.

Buzz Aldrin is photographed by Neil Armstrong on the MoonBuzz Aldrin is photographed by Neil Armstrong on the Moon /

Apollo — this was one of the most notable missions in the history of man. The Apollo, launched in 1969, was the first manned space craft to land on a foreign object, our moon. Carrying a three man crew Neil Armstrong, Buzz Aldrin, and Michael Collins were the first men to reach the moon and return to Earth. On July 20, 1969, Neil Armstrong emerged from the Apollo space craft and the famous line "One small step for man, one giant leap for mankind" was spoken as he placed the first human foot print on the surface of the moon.

Artist's impression of KeplerArtist's impression of Kepler /

Kepler — launched in 2009, is a large telescope that trails behind the Earth as it makes its rotation about the sun. This telescope examines the brightening and dimming of the stars in other systems giving us information on what other planets are out there. So far, as of this year, the Kepler telescope has discovered 4,302 objects in other systems called exoplanets (planets in other solar systems). These discoveries can help scientist to discover the possibility of Earth type planets in our neighbor systems for future exploration and settlement or even the discovery of intelligent life abroad.

Artist's impression of Pioneer 10Artist's impression of Pioneer 10 /

Pioneer 10 and 11 — at this current time, these two probes are no longer sending back information however, they are still active and have moved into the outer area of our solar system. During their initial launches in 1972 and 1973, they sent back the most amazing images of Jupiter, Saturn, Neptune, the asteroid belt, and much more. For the first time astronomers were able to get a full view of gas giants Jupiter and Saturn's rings as well as Jupiter's red eye. Pioneer 10 also traveled to the asteroid belt located between Mars and Jupiter a year and a half after it was first sent into space. Pioneer 11, during its flyby of Saturn sent back images of previously unknown moons and a new ring around the same time.

Artist's conception of rover on MarsArtist's conception of rover on Mars /

Spirit and Opportunity — rovers launched in 2004 were on a mission to explore the red planet, Mars. Intended to last only 90 days, these two rovers have shocked and amazed the world by remaining active and vigilant in their missions to this day. These two rovers, although not the first ones sent to Mars, have sent back incredible information and the discovery that Mars has liquid water was discovered during their exploration.

Artist's Concept of VoyagerArtist's Concept of Voyager /

Voyager 1 and 2 — everyone has at one time or another heard of the Voyager probes. The Voyager probes were sent on a mission to explore various planets and moons in our system including the Moons of Jupiter, the planets Saturn, Neptune, and Uranus, and are now located near the edge of our solar system. These two probes were designed with enough power within their systems to remain active and sending back data all the way up until 2025.