It is not possible to set a specific date, but it is possible to state that, at least 5 thousand years ago, human beings began to look up in order to connect the luminous points of the sky, creating the first constellations. As these figures were repeated every night, in subtly different positions, it was possible to use them as a reference to move around, plant, build and even mark epochs and seasons, defining a calendar. Since then, people such as the Chinese, Babylonians, Mayans, Greeks, Arabs and many others have studied the sky, observing the Moon, stars and other luminous objects, in an attempt to understand the functioning of the world in which they lived. From there, knowledge about the sky accumulated until they discovered a way to see beyond what the eye can see…
Written in the stars
It is possible to identify several stars by observing the sky with the naked eye, as the ancients did*
PLANETS
Seen from Earth, they shine like stars, but their path in the sky is different. Day after day, it seems that the stars «move» in a block – in fact, it is the Earth that rotates in the opposite direction to them. As the planets are much closer to here, it is possible to observe the individual trajectory of each one.
CONSTELLATIONS
Humanity associated figures with sets of luminous points in the sky long before discovering what stars were. This made it easy to mark dates and seasons and also served as a geographic reference. In the southern hemisphere, for example, the Cruzeiro is a reference to identify the South Pole
GALAXIES
In the 16th century, the Portuguese Fernão de Magalhães navigated guided by blots in the sky – the Magellanic clouds – which, until the 1920s, were cataloged as nebulae. That’s when it was discovered that these fuzzy objects were galaxies, with billions of stars revolving around a common center.
SATELLITES
In addition to the Moon, which revolves around the Earth, man can only observe natural satellites with the help of optical instruments. In 1610, Galileo Galilei used a telescope and saw four bright spots revolving around Jupiter: the satellites Io, Europa, Ganymede and Callisto.
METEORS
As with comets, the ancients considered the light trails that crossed the sky to be mere atmospheric phenomena. Until, in the 18th century, the German physicist Enst Chladni examined a metallic meteorite weighing 700 kg and attested that it was an extraterrestrial object, that is, coming from outside the Earth.
STARS
On a cloudless night, from a location with low lighting, it is possible to observe up to 8,500 stars, shining at various levels of intensity. Among these distant cousins of the Sun, the third brightest in the sky of the southern hemisphere is Alpha Centauri – whose light takes almost five years to reach Earth
COMETS
Although they move at more than 1 million km/h, it is not possible to differentiate a comet from a star with the naked eye. They pass very far from Earth and, to mark changes in position and identify an orbit, only observing them daily. If it passes close to the Sun, it may show a tail formed by gases and dust.
count up
Travel from ancient times to the future of human space adventure
3000 to 500 BC
Ancient people noticed that some «stars» move outside the pattern of the majority and discovered the planets Mercury, Venus, Mars, Jupiter and Saturn
2nd century
Ptolemy systematizes the geocentric cosmological model, with the Moon, planets, Sun and stars revolving around the Earth. It also catalogs 48 of the 88 current constellations.
1543
Nicolaus Copernicus recovers the idea of Aristarchus and systematizes the heliocentric cosmological model, with the planets revolving around the Sun
1609
Based on studies by Tycho Brahe, Johannes Kepler demonstrates that planetary orbits are elliptical rather than circular
1612
Galileo hears about the spyglass, builds one and uses it to observe the sky
1705 to 1758
Edmund Halley discovers that comets also revolve around the Sun and predicts a period of 76 years for the complete orbit of one of them, named Halley’s Comet
1780 to 1834
William Herschel offers a model for the Milky Way with the solar system far from its center, but revolving around it, like the other stars.
1920
Edwin Hubble – after whom the space telescope is named – discovers that galaxies farther from ours are receding faster and proposes that the Universe is expanding