All this is happening above our heads
Telescopes
Eye glued to the end of the telescope.
By Michel Gravereau
Since the beginning of my publications, I've been talking to you about telescopes, those instruments capable of admiring the sky up close, where we find the Moon, the planets, the stars, the nebulae, the galaxies, and more.
But what are these instruments, and who invented the principle?
Before 1671, there was the astronomical telescope, which allowed for the magnification of distant objects. It consisted of a tube with a glass lens at the entrance (where the light enters) and another at the exit (where the observer looks).
In 1608, the Dutch optician Hans Lippershey developed a spyglass, which made it possible to see distant objects more clearly. The problem was that the magnification achieved significantly distorted the objects. The following year, Galileo learned of this invention and undertook to improve it in order to point it towards the stars. Galileo's telescopes were not all of high quality; the image was still quite distorted. However, these telescopes were the most powerful of their time, magnifying celestial objects up to 30 times.
In 1671, the great English scientist Isaac Newton, whom some scientists consider one of the greatest geniuses of all time, presented a completely new observational instrument. This instrument used mirrors instead of glass lenses, like the telescope Galileo had used in 1609: the telescope was born.
Since the beginning of my publications, I've been talking to you about telescopes, those instruments capable of admiring the sky up close, where we find the Moon, the planets, the stars, the nebulae, the galaxies, and more.
But what are these instruments, and who invented the principle?
Before 1671, there was the astronomical telescope, which allowed for the magnification of distant objects. It consisted of a tube with a glass lens at the entrance (where the light enters) and another at the exit (where the observer looks).
In 1608, the Dutch optician Hans Lippershey developed a spyglass, which made it possible to see distant objects more clearly. The problem was that the magnification achieved significantly distorted the objects. The following year, Galileo learned of this invention and undertook to improve it in order to point it towards the stars. Galileo's telescopes were not all of high quality; the image was still quite distorted. However, these telescopes were the most powerful of their time, magnifying celestial objects up to 30 times.
In 1671, the great English scientist Isaac Newton, whom some scientists consider one of the greatest geniuses of all time, presented a completely new observational instrument. This instrument used mirrors instead of glass lenses, like the telescope Galileo had used in 1609: the telescope was born.
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It was only 2.5 cm in diameter.
Later, telescopes improved, but all retained the principle invented by the English scientist. Isaac Newton had studied the behavior of light rays and developed new laws on the propagation of light. He understood that white light from the Sun was composed of the superposition of rays of all the colors of the rainbow. He also noticed that when this light passed through a glass lens, the different colors "separated," as if through a prism.
And this was precisely the problem with the telescope: it was this separation of colors as soon as the light passed through the main lens that blurred the images at the exit.
Applying his theoretical knowledge directly, Newton decided to replace the main lens with a mirror. Indeed, since a mirror reflects light instead of letting it pass through, it does not separate the colors.
But for the mirror to have the same magnifying effect as a lens, it had to be concave, that is, concave, like a spoon. This solution eliminated imperfections and thus avoided making the instrument's body excessively long.
The first telescope built by Isaac Newton was barely 15 cm long but magnified 40 times, something that could only have been achieved with a telescope over 1.5 m long! A brief historical reminder: In addition to his advances in the dispersion of light colors and the invention of the telescope, Newton is credited with the discovery of gravitation in 1687. Thanks to this force that causes masses to attract each other in the universe, he was able to explain the movement of the planets around the Sun, the Moon around the Earth, and the movement of any object falling to the ground.
Legend has it that his inspiration came to him one day in an orchard when he saw an apple fall from a tree.
Other great scientists would go on to improve telescopes over time, leading to those of our time: the Englishman William Herschel, in 1789, built the one that would hold the record for over 50 years: 1.22 m in diameter. With this instrument, he discovered the planet Uranus in 1781.
Much later, in 1949, the record was held by Mount Palomar in California, at an altitude of 1,709 meters, with a diameter of 5.09 meters. With it, quasars and galaxies were discovered.
Even later, in the Atacama Desert in Chile, where it never rains, the ESO built the VLT (Very Large Telescope), consisting of four 10-meter telescopes. In the early 1990s, the project took shape. It seemed the pinnacle had been reached.
But then came the era of space telescopes in 1990 with the Hubble Space Telescope, which orbits 585 kilometers above our heads. With a 2.40-meter diameter mirror and never a cloud in its path, it simply revolutionized astronomy.
Later, telescopes improved, but all retained the principle invented by the English scientist. Isaac Newton had studied the behavior of light rays and developed new laws on the propagation of light. He understood that white light from the Sun was composed of the superposition of rays of all the colors of the rainbow. He also noticed that when this light passed through a glass lens, the different colors "separated," as if through a prism.
And this was precisely the problem with the telescope: it was this separation of colors as soon as the light passed through the main lens that blurred the images at the exit.
Applying his theoretical knowledge directly, Newton decided to replace the main lens with a mirror. Indeed, since a mirror reflects light instead of letting it pass through, it does not separate the colors.
But for the mirror to have the same magnifying effect as a lens, it had to be concave, that is, concave, like a spoon. This solution eliminated imperfections and thus avoided making the instrument's body excessively long.
The first telescope built by Isaac Newton was barely 15 cm long but magnified 40 times, something that could only have been achieved with a telescope over 1.5 m long! A brief historical reminder: In addition to his advances in the dispersion of light colors and the invention of the telescope, Newton is credited with the discovery of gravitation in 1687. Thanks to this force that causes masses to attract each other in the universe, he was able to explain the movement of the planets around the Sun, the Moon around the Earth, and the movement of any object falling to the ground.
Legend has it that his inspiration came to him one day in an orchard when he saw an apple fall from a tree.
Other great scientists would go on to improve telescopes over time, leading to those of our time: the Englishman William Herschel, in 1789, built the one that would hold the record for over 50 years: 1.22 m in diameter. With this instrument, he discovered the planet Uranus in 1781.
Much later, in 1949, the record was held by Mount Palomar in California, at an altitude of 1,709 meters, with a diameter of 5.09 meters. With it, quasars and galaxies were discovered.
Even later, in the Atacama Desert in Chile, where it never rains, the ESO built the VLT (Very Large Telescope), consisting of four 10-meter telescopes. In the early 1990s, the project took shape. It seemed the pinnacle had been reached.
But then came the era of space telescopes in 1990 with the Hubble Space Telescope, which orbits 585 kilometers above our heads. With a 2.40-meter diameter mirror and never a cloud in its path, it simply revolutionized astronomy.
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From Kourou, in December 2021, the James Webb telescope will be positioned at a Lagrange point 1.5 million km from Earth and will deliver a wealth of magnificent infrared images of the universe.
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For over four centuries, human ingenuity has contributed to providing humankind with tools to improve our poor eyesight and thus bring us closer to the canopy of our bed: the sky.
Next step, no doubt: An observatory on the Moon.
Next step, no doubt: An observatory on the Moon.