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32,500 BCE
Upper paleolythic
During this era people used to keep track of the moon's phases by engraving lines into animal bones -
4900 BCE
Gosseck circle in Germany
is believed to be the world’s earliest Sun observatory enabling ancient people to accurately measure its path during the course of a solar year -
2137 BCE
first recorded solar eclipse
The first known eclipse was recorded in china -
800 BCE
Heliocentric concept
Indian astronomer Yajnavalkya proposes a heliocentric concept of the universe in which the Earth is spherical and the Sun is at “the center of the spheres.” -
596 BCE
Invention of astronomy
Greeks first to develop astronomy from being an observational science related to religion into a theoretical science about the structure of the universe. Pioneers during this period include Pythagoras, Thales, Plato and Aristotle who proposed a geocentric model of the Universe with the Sun circling the Earth -
450 BCE
Stars are actually suns
Greek philosopher Anaxagoras suggest that the stars are actually suns, similar to our own, but located at such vast distances that we are unable to feel their heat back on Earth. His theory attracted disapproval from religious groups, though, and he was exiled from Athens -
150 BCE
The Antikythera mechanism
Ancient astronomical computer, the Antikythera mechanism constructed in ancient Greece capable of predicting star and planet positions, as well as lunar and solar eclipses (reproduced opposite) -
Johannes Kepler
Johannes Kepler discovered that the planets orbit about the Sun in an elliptical and not circular motion, and so proposed his three laws of planetary motion. -
Galileo
Galileo used the newly invented telescope to make some incredible astronomical observations, including viewing the planet Jupiter’s rotating moon system, and noting there were obviously objects in the heavens which didn’t revolve around the Earth. Galileo’s attempts to defend the heliocentric model of the universe landed him in direct conflict with the powerful church. In 1632 he was tried for heresy, forced to recant and condemned to spend the rest of his life under house arrest -
Isaac Newton
Sir Isaac Newton invented the first reflecting telescope which used a curved mirror instead of a lens to look further into space. Newton later publishes his hugely influential book called ‘Philosophiae Naturalis Principia Mathematica’ in which he agrees that the Earth rotates around the Sun and explains the reasons behind Kepler’s three laws. He also establishes the law of universal gravitation, which ushered in a new Age of physics and Enlightenment -
1725
Astronomer James Bradley began to notice that light aberration, which caused objects in space to be displaced slightly from their true position, and nutation of earth’s axis, which are small, periodic changes of the path earth’s axis would take, prohibited the accuracy of astronomy -
William Herschel
William Herschel would discover the soon to be named planet Uranus. He also hypothesized that changes in positions of stars also meant that the solar system itself was also moving through space and that the solar system was within a larger system which we now know as the Milky Way galaxy. -
The Doppler effect
The Doppler effect, a phenomenon that frequency of sound shifts as the source or observer moves farther or closer, was proven to be true for light when Hermann Karl Vogel noticed redshifts from opposing sides of the rotating sun (where the opposing sides were not the axes of rotation); the inverse was also true. This would be important for future astronomical cataloging -
E = mc2
In the early 20th century, physicists were starting to have conflicts with contradictions between Newtonian physics and electromagnetic theory. Albert Einstein created a hypothetical scenario in which all reference frames were capable of physics and that, as mentioned before, the speed of light was constant regardless of the reference frame. We now know these revelations as the special theory of relativity which is also where the famous equation E = mc2 was derived from. -
the universe originated from a single atom
A priest named Georges Lemaitre thought that the universe originated from a single atom. Edwin Hubble’s discovery of an expanding universe gave this theory some headway. Robert Wilson and Arno Penzias would later discover cosmic microwave background radiation in 1965. These ideas would soon be known as the big bang theory which would revolutionize cosmology -
Sputnik 1
The first man-made satellite Sputnik 1 was sent to space from the Soviet Union in order to make observations without interference with Earth’s atmosphere. The very next year in 1958, the U.S. sent Explorer 1 which had radiation detectors installed. This allowed for the satellite to discover the Van Allen Belt, or zones in which charged particles mostly from solar winds are trapped by the Earth’s magnetic field -
Pioneer 10
The Pioneer 10 would be the first satellite to make it through the Asteroid belt and observe the planet of Jupiter, also sending back pictures of the planet -
Pioneer 11
The Pioneer 11 would take pictures of Saturn along with the noticeable ring that surrounded it. All of the observations that these satellites made would go on to intrigue many about the strange planets around us and our understanding of them. -
current day
We are still trying to discover all that we can about the fundamental nature of this universe with astronomy. One of the beauties of the subject is that there will most probably always be an aspect of reality that we will strive to understand and that astronomy and physics can be a guide to doing so. It allows for the human to be a part of something that is both literally and metaphorically so much bigger than themselves