Major Events in Astronomy


Ancient Egyptians - Olmecs

Approx. 4000 BCE

Many Egyptian buildings were built with an astronomical orientation. The temples and pyramids were constructed in relation to the stars, zodiac, and constellations. In different cities, the buildings had different orientations based on the specific religion of that area. For instance, some temples were constructed to align with a star that either rose or set at harvest. Others were oriented toward the solstices or equinoxes. As early as 4000 B.C.E., temples were built so that sunlight entered a room at only one precise time of the year.

England / Europe- Celts

2000 BCE

At this time, there was the first astronomical observatory/calendar- the Stonehenge. The Stonehenge is located north of Salisbury, Wiltshire, England. The Revd. Edward Duke was the first person to associate astronomy with Stonehenge, describing it as a planetarium full of significant astronomical alignments - although he named none. Sir Norman Lockyer then identified the reason for the orientation of the Stonehenge. He realised that on the summer solstice the sun rose at the end of the main axis- as it would have done in the second and third millenniums BC. In 1906, he then published his findings in a book. It's clear the stones placement was planned. This could've been Stone Age brilliance or it could've just been any observer's knowledge of the sky. There are no found records from its makers, so we just don't know.

Nicolaus Copernicus


In 1543, Nicolaus Copernicus found the first geometric proof of the heliocentric theory. However, due to fears that the publication of his theories would lead to persecution by the church (as well as, perhaps, worries that his theory presented some scientific flaws), he withheld his research until a year before he died. When published, the church did not agree and banned ownership of the proof.

Galileo Galilei Uses Telescope


When Galileo heard about the Dutch invention of the telescope he built one for himself. Even though his telescope wasn't very powerful compared to the equipment available today, he was able to make a number of stunning discoveries which changed the face of astronomy. He saw the craters, mountains, and valleys of the Moon, noticed the huge number of stars making up the Milky Way, kept precise records of sunspot activity and the phases of Venus, and discovered four moons orbiting Jupiter. These moons are still called the Galilean Moons today, in honor of the earth-shattering scientific effects of the discovery. During a time when the Earth was still considered to be at the center of the universe, he publicized the fact that other astronomical bodies were clearly revolving around something other than the Earth. Galileo's support of the Copernican model frightened the Church, which put Galileo on trial. He was forced to renounce his Copernican views and was held under house arrest.

Kepler Publishes The Laws of Planetary Motion


When Kepler got a hold of Tycho's observations, he tried to puzzle them out. In 1609, he published his first two laws:
1) Planets move in ellipses, with the Sun at one focus.
2) The line from the Sun to the planet covers equal areas in equal times.
Then in 1619 Kepler published his third law:
3) The square of the orbital periods is proportional to cubes of the ratio of the average orbital distance for only two objects orbiting the same body.
This is Kepler:

Albert Einstein


At this time, Einstein publishes the theory of general relativity. In it, he determined that massive objects cause a distortion in space-time, which is felt as gravity.

Edwin Hubble- An American Astronomer


Hubble began to work at the Mount Wilson Observatory just as the new 2.56-meter Hooker Telescope, the most powerful on Earth, was completed. With it, he was able to peer into the sky with greater detail than anyone could previously. After years of observation, Hubble made an extraordinary discovery in 1923. He spotted a Cepheid variable star in what was known as the Andromeda Nebula. Using Henrietta Leavitt’s techniques, he was able to show that Andromeda was nearly 1 million light years away and clearly a galaxy- not a gas cloud. By 1929 Hubble and his assistant had formulated what became known as Hubble’s Law, which basically states that the greater the distance of a galaxy from ours, the faster it recedes. It was proof that the Universe is expanding.

Brian Shmidt, Saul Perlmutter, and Adam Reiss


In 1998, two teams of astronomers —one led by the Australian National University’s Brian Schmidt— reached the same conclusion: the expansion of the Universe is not slowing down, as most people had assumed, it is accelerating. The discovery triggered a flurry of activity to understand more about dark energy, the hypothetical driving force pushing the Universe apart and counteracting gravity. It has also brought the Nobel Prize in Physics to Schmidt, Adam Riess, and Saul Perlmutter.
To calculate the Universe’s rate of expansion, both teams were studying Type Ia supernovae as a means of measuring distances across the cosmos. The further away the star, the fainter the stellar explosion appears. By combining those distances with the supernovae’s redshifts, where light from receding stars is shifted towards the red end of the spectrum, the astronomers could gauge how fast the Universe was expanding at different stages of its life.