Over time, it was discovered that the light emitted from the stars is nothing but a small part of the "message": in fact, it is only a minuscule fraction of the electromagnetic spectrum, i.e. the radiation emitted, and this fraction is similar to a window of just a few centimeters in a wall that is several kilometers long. This is how astronomers understood that very different "eyes" were needed to scan the sky and to understand its most profound secrets. Gradually, increasingly sophisticated instruments were developed to open other "windows" in the wall of the electromagnetic spectrum, corresponding to other regions that for us are completely invisible: x-rays, ultraviolet rays, infrared rays and radio waves. The conquests made possible by these modern technologies have one of the most fascinating histories ever told and they all began with the discovery of something that provided evidence for the Big Bang theory, i.e. the huge initial explosion. This dates back to the observations by a professor of mathematics who lived in the first half of the Nineteenth century, Christian Johann Doppler, who had noted that when a sound or luminous source moves away, the wave lengths become longer: in fact, as the source moves away from us, each crest has a longer distance to cover than the one that precedes it. On the contrary, if a source gets closer, the crests seem to be "pushed" against each other and the wave length becomes shorter. This phenomenon, called the Doppler effect, can be verified in our own lives, for example when we are traveling in a car: the sound emitted by an ambulance that approaches at high speed in the opposite lane or in our own becomes more and more acute until the siren has reached our position (the waves which are "compressed") and then fade away just as quickly in lower tones as soon as they pass by (the waves which "expand"). Based on this premise, Edwin Hubble, an American astronomer with great intuition, stated that, since all the spectrums of the galaxies tend to shift towards red (i.e. to have longer waves), they cannot be "stationary" in space, but must be moving away from us. And not only this: after making the necessary calculations, Hubble also discovered that the farther away the galaxy was the faster it was moving away from us and thus he concluded that the universe is expanding like a balloon filled with air. It was 1929: only six years after Hubble had demonstrated that the luminous points we see in the sky are not only stars or clouds of gas, but other galaxies at enormous distances from our own (introducing the famous classification system, which is still used today, of spiral, elliptical, bar and irregular galaxies, depending on their shape). But, even more surprising, only two years had passed from when the Belgian cosmologist Georges Lemaltre had advanced the theory of the Big Bang. The following year, 1930, led to even greater discoveries that were never imagined by the world of astronomy: Bell Telephone Laboratories, the American company on the forefront in the field of communications, had requested a young physicist, Karl Jansky, to study the causes of radio disturbances which interfered with telecommunications. Jansky discovered that a large part of the disturbances were caused by atmospheric perturbations, but that a small part had a completely different origin: initially convinced that they were caused by other Earth transmissions, he soon discovered that they came from another part of the sky and shifted to follow the Earth's rotation. Two years later, in 1933, listening at the 15-meter wavelength, Jansky was able to identify the origin of the disturbances: the Sagittarius constellation, near the center of the Galaxy. It was the proof that signals other than those transmitted by light come from the universe, proof that marked the beginning of radio-astronomy and paved the way to all the "alternative" forms of astronomy, from x-rays to ultraviolet, to infrared.
Over time, it was discovered that the light emitted from the stars is nothing but a small part of the "message": in fact, it is only a minuscule fraction of the electromagnetic spectrum, i.e. the radiation emitted, and this fraction is similar to a window of just a few centimeters in a wall that is several kilometers long. This is how astronomers understood that very different "eyes" were needed to scan the sky and to understand its most profound secrets. Gradually, increasingly sophisticated instruments were developed to open other "windows" in the wall of the electromagnetic spectrum, corresponding to other regions that for us are completely invisible: x-rays, ultraviolet rays, infrared rays and radio waves. The conquests made possible by these modern technologies have one of the most fascinating histories ever told and they all began with the discovery of something that provided evidence for the Big Bang theory, i.e. the huge initial explosion. This dates back to the observations by a professor of mathematics who lived in the first half of the Nineteenth century, Christian Johann Doppler, who had noted that when a sound or luminous source moves away, the wave lengths become longer: in fact, as the source moves away from us, each crest has a longer distance to cover than the one that precedes it. On the contrary, if a source gets closer, the crests seem to be "pushed" against each other and the wave length becomes shorter. This phenomenon, called the Doppler effect, can be verified in our own lives, for example when we are traveling in a car: the sound emitted by an ambulance that approaches at high speed in the opposite lane or in our own becomes more and more acute until the siren has reached our position (the waves which are "compressed") and then fade away just as quickly in lower tones as soon as they pass by (the waves which "expand"). Based on this premise, Edwin Hubble, an American astronomer with great intuition, stated that, since all the spectrums of the galaxies tend to shift towards red (i.e. to have longer waves), they cannot be "stationary" in space, but must be moving away from us. And not only this: after making the necessary calculations, Hubble also discovered that the farther away the galaxy was the faster it was moving away from us and thus he concluded that the universe is expanding like a balloon filled with air. It was 1929: only six years after Hubble had demonstrated that the luminous points we see in the sky are not only stars or clouds of gas, but other galaxies at enormous distances from our own (introducing the famous classification system, which is still used today, of spiral, elliptical, bar and irregular galaxies, depending on their shape). But, even more surprising, only two years had passed from when the Belgian cosmologist Georges Lemaltre had advanced the theory of the Big Bang. The following year, 1930, led to even greater discoveries that were never imagined by the world of astronomy: Bell Telephone Laboratories, the American company on the forefront in the field of communications, had requested a young physicist, Karl Jansky, to study the causes of radio disturbances which interfered with telecommunications. Jansky discovered that a large part of the disturbances were caused by atmospheric perturbations, but that a small part had a completely different origin: initially convinced that they were caused by other Earth transmissions, he soon discovered that they came from another part of the sky and shifted to follow the Earth's rotation. Two years later, in 1933, listening at the 15-meter wavelength, Jansky was able to identify the origin of the disturbances: the Sagittarius constellation, near the center of the Galaxy. It was the proof that signals other than those transmitted by light come from the universe, proof that marked the beginning of radio-astronomy and paved the way to all the "alternative" forms of astronomy, from x-rays to ultraviolet, to infrared.
