Aristarchus – Biography and Facts

Aristarchus of Samos was a Greek astronomer who believed that the Earth rotated on its axis and revolved around the Sun. He was born around 310 BCE and died around 230 BCE. On this basis, Cleanthes the Stoic declared in his Against Aristarchus that Aristarchus should be charged with impiety “for setting the hearth of the universe in motion.”

Although Aristarchus’ work on the motion of the Earth has perished, his ideas have been preserved because of allusions by Greek mathematician Archimedes, Greek writer Plutarch, and Greek philosopher Sextus Empiricus. Archimedes said in his Sand-Reckoner that Aristarchus had proposed a new theory that, if true, would expand the universe far beyond what had hitherto been considered. (Unless the stars are far away, a moving Earth should cause a parallax, or annual change, in the fixed stars’ apparent positions.)

Aristarchus Meaning 

The brightest formation on the moon is a crater in the NE quadrant of the moon with a diameter of around 37 kilometres.

Aristarchus Discovery

Aristarchus’ extant work, On the Sizes and Distances of the Sun and Moon, preserves the geocentric view, most likely because he had not yet conceived of the heliocentric model, as scholar Thomas Heath suggests. Aristarchus recognised that the Moon does not cast light but rather reflects it, and argued that by measuring the angle between the Sun and the Moon when the Moon is half-illuminated (an angle suggested by the illumination itself), one might determine their distances.

He calculated the angle to be 87 degrees, which is amazingly close to the real angle of 89 degrees today and based on his calculations, the Sun was 20 times farther away from the Earth than the Moon (it is actually 400 times further away). It’s unclear how this work informed his (alleged) subsequent heliocentric universe model, but it’s probable that his research into the distances of the Sun and Moon from the Earth convinced him that the Sun should be at the centre of all the other planets.

Aristarchus’ model only survived in a line from Archimedes’ The Sand Reckoner, as previously mentioned. Archimedes wanted to know how many grains of sand would fill the universe and needed to know the size of the universe in order to calculate this. In recounting his computations, he references Aristarchus, who thought the universe was far greater than Archimedes’ contemporaries thought:

You, King Gelon, are aware that most astronomers refer to the sphere whose centre is the Earth’s centre and whose radius is equal to the straight line between the Sun’s centre and the Earth’s centre as the “universe.” As you may have heard from astronomers, this is the most prevalent account. However, Aristarchus has published a book containing certain theories, in which it appears that the universe is many times larger than the ‘universe’ just indicated, as a result of the assumptions made. His theories are that the fixed stars and the Sun remain motionless, that the Earth revolves around the Sun on the circumference of a circle, with the Sun in the centre of the orbit, and that the sphere of fixed stars, centred on the same centre as the Sun, is so large that the circle in which the Earth revolves bears the same proportion to the distance of the fixed stars as the centre of the sphere bears to its surface.

Aristarchus’ theory that the Moon’s and Sun’s diameters should be proportional to their distance from the Earth is equally rational, but it yielded incorrect results. Scientists have named a crater on the Moon after Aristarchus because of his brilliance and commitment to science.

Facts

Many philosophers of his day and those who came after him were influenced by Aristarchus, including:

• Aristarchus believed the Greek sphere of the world to be several times larger than what was usually thought at the time, according to Archimedes. Aristarchus, in reality, felt that the sphere was enormously greater than the sphere that the Earth occupied
• Ptolemy, the author of Almagest, shared Aristotle’s idea of the stars and planets as affixed to crystalline spheres that circled the Earth. Ptolemy, on the other hand, came up with the idea of smaller spheres called epicycles working within bigger spheres. However, epicycles were unable to explain some of the odd movements of planets such as Mars, although Aristarchus’ heliocentric theories could
• Nicolaus Copernicus is credited with proposing the first heliocentric hypothesis of the universe. Many ancient allusions to Aristarchus, on the other hand, reveal that 1700 years before Copernicus, he had already conceived a Sun-centred system. Despite the fact that Copernicus credited Aristarchus as his inspiration, both thinkers were unique in their knowledge of a moving Earth, which was counterintuitive to observation and hence impossible to convey to a scientific society

Conclusion 

Aristarchus was one of the first astronomers to compute the Sun’s, Moon’s, and Earth’s relative sizes. He accomplished it by watching the Moon during a lunar eclipse and calculating the Earth’s tilt and size. During the final and first quarters of the Moon, the Sun, the Moon, and the Earth make a nearly perfect angle.

He calculated that the Sun was nineteen times farther away from Earth than the Moon based on this. However, he made a calculating error: he calculated the angle as 87 degrees when the exact angle is 89° 50′. As a result, rather than the nineteen times proposed by Aristarchus, the real distance is 390 times. Despite the fact that the geometric theory is up to date, the calculations were incorrect due to a lack of exact tools rather than a lack of logic.