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Four amazing astronomical discoveries from ancient Greece
The first astronomical calculator
The Antikythera Mechanism is the word's oldest surviving mechanical calculator. The device was discovered in an ancient shipwreck in 1900 and dates between the 3rd and 1st centuries BC.
When manually rotated by a handle, the gears span dials on the exterior showing the Moon's phases, the timing of lunar eclipses, and the positions of the five planets then known (Mercury, Venus, Mars, Jupiter, and Saturn) at different times of the year.
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Strange discovery from early history
In the Histories by Herodotus (484BC to 425BC), Herodotus recounts the story of Phoenician sailors who were dispatched by King Neco II ofEgypt (about 600BC), to sail clockwise around continental Africa, starting in the Red Sea.
The voyage took years. As they rounded the southern tip of Africa, and following a westerly course, the sailors observed the Sun as being on their right-hand side, above the northern horizon. Because they still thought the Earth was flat, the observation did not make sense at the time.
The planets orbit the Sun
The earliest known heliocentric theory of the solar system came from Aristarchus of Samos (310BC to 230BC). He argued that the Sun was central. He also placed all the then known planets is their correct order of distance around the Sun. His original text was unfortunately lost to history.
Nicolaus Copernicus rediscovered the theory in the 16th century. He acknowledged Aristarchus during the development of his own work.
The size of the Moon
In one of Aristarchus' books that did survive, he laid out the earliest known attempted calculations of the sizes and distances to the Sun and Moon.
From solar eclipses, where the Moon passes in front of the Sun, they realised that the Sun was further away. Aristarchus estimated that the size of the Moon was approximately one-third that of the Earth, based on the careful timing of lunar eclipses. He was surprisingly accurate in determining the ratio of the size of the Earth to the Moon. (the Moon has a diameter 0.27 times that of Earth).
The Earth’s circumference
- Eratosthenes (276BC to 195BC) relied on measuring the different lengths of shadows cast by poles stuck vertically into the ground, at midday on the summer solstice, at different latitudes. The difference in the shadows demonstrated how much the Earth's surface curved. Eratosthenes estimated the Earth's circumference as approximately 40,000km.
- Another scientist called Posidonius (135BC to 51BC) who lived on the island of Rhodes, arrived at almost exactly the same answer. He observed the bright star Canopus would lie very close to the horizon, but when in Alexandria, in Egypt, Canopus would ascend to some 7.5 degrees above the horizon. 7.5 degrees is 1/48th of a circle, and multiplying the distance from Rhodes to Alexandria by 48, arrived at approximately 40,000km.
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The scientific revolution
Human history is often framed as a series of episodes, representing sudden bursts of knowledge. The Agricultural Revolution, the Renaissance, and the Industrial Revolution are a few examples where ...
Pseudo-Science
Much of the knowledge about the natural world during the middle ages dates back to the teachings of the Greeks and Romans. Many did not question these ideas, despite the many flaws.
- Aristotle taught everything beneath the moon was comprised of four elements: earth, air, water, and fire.
- Greek astronomer Claudius Ptolemy thought that heavenly bodies such as the sun, moon, planets and various stars all revolved around the earth in perfect circles.
- The ancient Greeks and Romans held to the idea that illnesses were the result of an imbalance of four basic substances and was related to the theory of the four elements.
Rebirth and Reformation
- During the Renaissance, there was a renewed interest in the arts and literature. It led to a shift toward more independent thinking.
- In 1517, Martin Luther nailed his 95 theses to the door of the Roman Catholic Church. Luther promoted his thoughts by printing and distributing them, encouraging churchgoers to read the Bible for themselves. This led to the Protestant Reformation.
- In the process, the criticism and reform led to placing the burden of proof ahead in understanding the natural world, paving the way for the scientific revolution.
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The Science Of Rocket Science
Newton’s Third Law Of Motion, which states that every action has an equal and opposite reaction is the heart of rocket science.
The basics of rocket science are not that complicate...
Rockets: Escape Velocity
The thrust required for an object to overcome Earth’s gravity and atmospheric resistance and move towards space is called escape velocity. Besides Earth, the gravitational forces that can affect the object are those coming from the sun, moon and even other planets.
Apart from space vehicles and the military, rockets are used in life-saving rescue flares and fireworks, and even the ejector seats in military planes.
History Of Rockets
- One of the earliest devices that used rocket propulsion was called the aeolipile, designed in the 1st century AD by Heron of Alexandria, and used steam to spin a metal ball.
- Early prototypes of rockets were produced for firework displays in China in the 13th century, with the real, metal versions coming in the 19th century, used in Navy ships as an upgraded version of cannon.
- Early rockets use flammable substances like gunpowder that propel it using the thrust of exhaust gases.
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Pioneer
Pioneer 10 and Pioneer 11 were launched in 1972 and 1973. They were the first spacecraft to visit Jupiter and Saturn in a one-way voyage.
- Pioneer 10 traveled through...
Voyager
Voyager 1 and Voyager 2 probes followed after the Pioneers.
- They made many important discoveries about Jupiter and Saturn.
- Discoveries include rings around Jupiter and volcanism on Jupiter's moon.
- Voyager made the first flybys of Uranus, where it discovered ten new moons.
- It found that Neptune weighs less than first thought.
- Both Voyager crafts can continue to transmit radio signals until at least 2025.
- It is now exploring the edge of the solar system.
WMAP
The Wilkinson Microwave Anisotropy Probe (WMAP) was launched in 2001 and measured the temperature of the radiation left over from the Big Bang.
- The craft can map out the fluctuations in the presumed cosmic microwave background radiation.
- The data from WMAP revealed a better estimate for the age of the universe.
- It confirmed that about 95 percent of the universe is composed of dark matter and dark energy.
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