Heptaplus , by the Italian philosopher Pico Della Mirandola, is a scholarly exercise in seven volumes, each of seven chapters, which attempts to synthesise the various traditions deriving from the Creation myth: that of the Platonists and the Peripatetic School, that of the Evangelists, Church Fathers and Cabbalists, and that of the Islamic philosophers such as Avicenna Ibn Sina and Averroes Ibn Rushd. This primordial world was form without form, A confused heap, a shapeless melange, A void of voids, an uncontrolled mass, A Chaos of Chaos, a random mound Where all the elements were heaped together, Where liquid quarrelled with solid, Blunt with sharp, cold with hot, Hard with soft, low with high, Bitter with sweet: in short a war In which the earth was one with the sky.
The regularity of so much celestial activity has led many cultures to base their models of the universe on concepts of order and harmony. Around the Mediterranean it was the Pythagoreans who first expressed the idea that the universe is characterised by proportion, rhythm and numerical patterns. They provide only abstract images, which do not allow us to visualise the structure of atoms or the dynamics of space-time or the topology of the universe in any direct sense. It is this fundamental belief in celestial harmony — for which successive generations have found various elaborate expressions: just proportion, equation of the part and the whole, symmetry, constancy, resonance, group theory, strings -that has underlain the development of physics for the past 2, years.
For Kepler, as for the natural philosophers of ancient Greece, the cosmos was an organised system comprising the earth and the visible stars. His avowed intention was to investigate the reasons for the number and sizes of the planets and why they moved as they did. He believed that those reasons, and consequently the secret of universal order, could be found in geometry. Kepler wanted to do more than create a simple model or describe the results of his experiments and observations; he wanted to explain the causes of what he saw. This makes him one of the greatest innovators in the history of science and it led him in particular to formulate laws of planetary motion which are still valid today.
Despite his innovative methods, Kepler wrote two studies of the cosmos in the style of the ancient Greeks: Mysterium Cosmographicum The Secret of the Cosmos in and Harmonices Mundi The Harmony of the World in At this turning point between ancient and modern thinking Kepler was steeped in a tradition which connected cosmology explicitly with the notion of divine harmony. His profound desire to devise a rational explanation for the cosmos led him to establish procedures which resembled those of modern science.
The spawning galaxy in flight is a rainbow trout which goes back against the flow of time towards the lowest waters, towards the dark retreats of duration. Charles Dobzynski Since the time of Newton, we have known that white light, passing through a prism, is decomposed into a spectrum of all colors.
Violet and blue correspond to the shortest wavelengths or, equivalently, to the largest frequencies; red corresponds to the largest wavelengths and to low frequencies. In , the German optician Joseph von Fraunhofer discovered that the light spectrum from stars is streaked with thin dark lines, while that from candlelight has bright stripes. These phenomena remained puzzling until It was then that the chemist Robert Bunsen and the physicist Gustav Kirchhoff analyzed the light created from the combustion of different chemical compounds burned with the now-famous Bunsen burner and saw that each of them emitted light with its own characteristic spectrum.
At nearly the same time, Christian Doppler discovered in that moving the source of a sound produced shifts in the frequency of sound waves, a phenomenon experienced by anyone listening to the siren of an ambulance passing by. The French physicist Armand Fizeau noticed the same phenomenon with light waves: depending on whether a source of light was moving closer or farther away, the received frequencies are either raised or lowered with respect to the emitted frequencies.
The shift becomes larger as the speed of displacement is increased. Since this shift affects the whole spectrum by the same amount, it is easily quantified by looking at the dark or bright stripes, which are shifted together, either towards the blue or towards the red, and it furnishes an incomparable means of measuring the speed of approach or retreat for light sources. Shortly after this discovery, astronomers began an ambitious program of spectroscopy, with the aim of measuring the speed of the planets and stars by using their spectral shifts. The Universe is expanding. What does this really mean?
Some speakers even have the tendency to mime a gesture of expansion with their hands, as if they were holding a piece of space or an immaterial balloon in the process of inflating. The public imagines some matter ejected at prodigious speeds from some center, and tell themselves that it would be better not to be there at the moment of explosion, so as not to be riddled through with particles. None of all this is accurate. At the big bang, no point in the Universe participated in any explosion.
Put simply, if one considers any point whatsoever, we notice that neighboring points are moving away from it. Is this to say that these points are animated by movement, given a speed? No, they are absolutely fixed, and nevertheless they grow apart. To unravel this paradox, it is necessary to make more precise what one exactly means when speaking of a fixed point. The position of a point is fixed by coordinates: one number for a line the miles along a highway , two numbers for a surface latitude and longitude , and three for space in general length, width, and height.
A point is said to be fixed if its coordinates do not change over the course of time. In an arbitrary space, curved or not, the distance between two points is given by the so-called metric formula, which depends on the coordinates and generalizes the Pythagorean theorem. In principle, therefore, the distance between two points does not vary. In an expanding space, on the other hand, this distance grows, while the points do not move, even by a millimeter, meaning that they strictly conserve the same coordinates.
In relativistic cosmology, galaxies remain fixed at comoving positions in space.
They may dance slight arabesques around these positions, under the influence of local gravitational fields, but the motion which moves them apart from each other resides in the literal expansion of the space which separates them. Thus we may perhaps, one day, create new Figures that will allow us to put our trust in the Word, in order to traverse curved Space, non-Euclidean Space. Francis Ponge .
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These postulates would become the keystone for all of geometry, a system of absolute truths whose validity seemed irrefutable. One of the reasons for this faith is that these postulates seem obvious: the first of them stipulates that a straight line passes between two points, the second that any line segment can be indefinitely prolonged in both directions, the third that, given a point and an interval, it is always possible to trace out a circle having the point for its center and the interval as its radius, the fourth that all right angles are equal to each other.
The fifth postulate is however less obvious:. In the nineteenth century, there occurred one of the great sudden revolutions in the history of mathematics and also in human thought, as will be seen by what follows : two new geometries which do not satisfy the fifth postulate, but which are perfectly coherent, were discovered. In one of these geometries, called spherical geometry, no parallel line satisfying the conditions can be traced. In view of the total solar eclipse of Aug 21 through the United States, this is a reminder of the role of solar eclipses in the developments of astronomy and astrophysics.
It is taken from a chapter of my book Glorious Eclipses, presented elsewhere in this blog. Eclipses of the Sun and Moon have never ceased to provide us with a host of lessons about the nature of the universe around us.
The first of these lessons concerned the celestial bodies directly involved in eclipses: namely the Earth, Moon, and Sun. Indeed, back in antiquity, the proof that the Earth was round, and the first measurements of the respective sizes and distances of the Moon and Sun were deduced from the observation of eclipses.
In the 19th century, it was the normally invisible atmosphere of the Sun that was revealed thanks to eclipses. Far from being the perfectly round, and sharply defined ball of hot gas that it appears to the eye — appropriately protected by suitable filters, of course — the Sun is found to be a sprawling giant, overflowing with energy, plasma, and particles, that extends its influence throughout the whole Solar System.
Eclipses also provoked the discovery of helium, the second most abundant element in the Sun, and in the universe as a whole. The first demonstration of an astrophysical nature resulting from eclipses is the one given by Aristotle concerning the fact that the Earth is round. The astronomical views of this Greek philosopher are well-known to us, thanks to his two works, known to us as Meteorology and On the Heavens, dating from the 4th century BC.
Like other thinkers of his day, Aristotle believed that all heavenly bodies were spherical, because to him heavenly bodies were a reflection of divine perfection, and the sphere is the most outstandingly perfect geometrical figure. But this argument was not a physical demonstration, because, naturally, Aristotle did not have any experimental means of confirming the spherical nature of the planets and stars. As far as the Moon was concerned, the philosopher adopted an explanation attributed to the Pythagoreans, namely that the observed appearance of the Moon throughout its various phases corresponded to a spherical body, half of which is illuminated by the Sun.
The golden age of Greek astronomy flourished at Alexandria. Since its foundation under the reign of Ptolemy Soter 3rd century BC , the Alexandrian school brought together brilliant mathematicians and geometers, such as Euclid, Archimedes, and Apollonius. Similarly, the greatest ancient astronomers Aristachus of Samos, Eratosthenes, and Hipparchus, as well as Ptolemy 2nd century BC , all worked there. Aristarchus BC is nowadays known for having been the first to voice the heliocentric theory, i. His statement does not appear in any known work, but it was reported by Archimedes and by Plutarch.
The only work of Aristarchus that has come down to us relates to the sizes and distances of the Sun and the Moon. The Alexandrian astronomer completely reopened this question, which had been discussed since the 4th century BC.
The Pythagoreans had positioned the heights of the celestial bodies according to musical intervals. Eudoxus, the brilliant disciple of Plato, had estimated the diameter of the Sun as nine times that of the Moon. As for Aristarchus, he devised an ingenious geometrical method of calculating the distance ratios of the Sun and Moon. Aristarchus of Samos tried to calculate the relative diameter of the moon and sun, as deduced from the line subtending the arc that divides the light and dark portions of the moon during an eclipse.
He found that the Sun lay at a distance between 18 and 20 times that of the Moon. In fact, it is times as far. By an argument based on the observation of eclipses, he determined the diameter of the Moon as one third of that of the Earth, which is very close to the actual value. He also announced that the diameter of the Sun is seven times that of the Earth.
Even though Aristarchus considerably underestimated the size of the Sun, because it is actually times as large as the Earth, he had grasped the essential fact that the daytime star was much larger than the Earth. It was precisely this result that led him to the heliocentric hypothesis. He did, in fact, argue that under these circumstances, it was logical to believe that the Earth and the other celestial bodies revolved around the Sun, rather than the reverse. Aristachus was before his time. The world had to wait until and the work by Copernicus, before the heliocentric theory was again put forward, this time with success.
A century after Aristachus, and again at Alexandria, Hipparchus developed a complete theory of the Moon. Whence the average of The total solar eclipse mentioned is that of 20 November BC. The actual value of the Earth-Moon distance is 60,4 terrestrial radii. If the Universe is finite, it seems necessary for it to have a center and a frontier. The center poses hardly any conceptual difficulty: it suffices to place the Earth there, like the geocentric systems of Antiquity appearances lead one in this direction , or the Sun, as Copernicus did in his heliocentric system.
In the fifth century BCE, the Pythagorean Archytas of Tarentum described a paradox that aimed to demonstrate the absurdity of having a material edge to the Universe.
His argument would have a considerable career in all future debates on space: if I were at the extremity of the sky, could I extend my hand or stick out a staff? It is absurd to think that I could not; and if I could, that which is found beyond is either a material body, or space.
I could therefore move beyond this once again, and so on. If there is always a new space towards which I can extend my hand, this clearly implies an expanse without limits. There is therefore a paradox: if the Universe is finite, it has an edge, but this edge can be passed through indefinitely. This line of reasoning was taken up by the atomists, such as Lucretius, who gave the image of a spear thrown to the edge of the Universe, and afterwards by all the partisans of an infinite Universe, such as Nicholas of Cusa and Giordano Bruno. Mostly renowned as a cartographer, he also made terrestrial and celestial globes, various instruments such as quadrants, a planetarium and a tellurium.
He invented mechanical devices for improving the technics of printing. As an astronomer, a former student of Tycho Brahe, Willem Blaeu made careful observations of a moon eclipse, he discovered a variable star now known as P Cygni, and carried out a measurement of a degree on the surface of the earth as his countryman Snell did in The Blaeu family has its origin in the island of Wieringen, where about , Willem Jacobszoon Blauwe — the grandfather of Willem — was born.
From his marriage with Anna Jansdochter sprang six children. The second son, Jan Willemsz. From his second marriage with Stijntge, Willem Jansz. Blaeu was born at Alkmaar or Uitgeest. At an early age, Willem Blaeu went to Amsterdam in order to learn the herring trade, in which he was destined to succeed his father. But Willem did not like this work very much, being more inclined to Mathematics and Astronomy.
He did not attend a university and worked first as a carpenter and a clerk in the Amsterdam mercantile office of his cousin Hooft. However, in he became a student of Tycho Brahe The celebrated Danish astronomer demanded a high standard of his pupils. Some were invited by him, others were undoubtedly taken on special recommendation. We may therefore presume that young Blaeu had reached a good standard of education and technical skill, since he was considered worthy to become a student of the great astronomer. As it is well-known, Tycho Brahe had his own cosmic system, a sort of compromise between the Ptolemaic and Copernican.
Willem Blaeu, although a supporter of the Copernican system, remained cautious during the rest of his career. In his books he mentioned the Copernican model as one of the existing theories, besides the Ptolemaic and Tychonic. It will not only save him for confrontations with religious people, but this attitude was also beneficial for his sales.
After his return from Hven in , Blaeu settled in Alkmaar. Very little is known of his stay here. He married, probably in , Marretie or Maertgen, daughter of Cornelis from Uitgeest. Here too, his eldest son Joan was born. Cosmology developed rapidly after the completion of general relativity by Albert Einstein, in In this theory, the Universe does not reduce to a space and a time which are absolute and separate; it is made up of the union of space and time into a four dimensional geometry, which is curved by the presence of matter.
It is in fact the curvature of space-time as a whole which allows one to correctly model gravity, and not only the curvature of space, such as Clifford had hoped. The non-Euclidean character of the Universe appeared from then on not as a strangeness, but on the contrary as a physical necessity for taking account of gravitational effects. The curvature is connected to the density of matter. In , Einstein presented the first relativistic model for the universe.
Like Riemann, he wanted a closed universe one whose volume and circumference were perfectly finite and measurable without a boundary; he also chose the hypersphere to model the spatial part of the Universe. In truth, the cosmological solutions of relativity allow complete freedom for one to imagine a space which expands or contracts over the course of time: this was demonstrated by the Russian theorist Alexander Friedmann, between and At the same time, the installment of the large telescope at Mount Wilson, in the United States, allowed for a radical change in the cosmic landscape.
In , the observations of Edwin Hubble proved that the nebula NGC was situated far beyond our galaxy. Very rapidly, Hubble and his collaborators showed that this was the case for all of the spiral nebulae, including our famous neighbor, the Andromeda nebula: these are galaxies in their own right, and the Universe is made up of the ensemble of these galaxies. Related Stories. Israel's first lunar mission to launch this week Feb 18, Jan 31, Dec 17, Israeli spacecraft gets special passenger before moon journey Dec 17, Feb 15, Oct 10, Recommended for you.
Space weather causes years of radiation damage to satellites using electric propulsion 4 hours ago. Jun 29, Guardians of Apollo: the curators preserving the Moon mission's legacy Jun 29, Jun 28, Jun 27, User comments. Feb 21, But why the Israeli flag? With India's plan to also go to the Moon, are all 4 nations thinking of dividing the Moon into 4 quadrants of lunar real estate? Report Block. I like the idea of telling the universe about the Holocaust.
It was a big deal and cannot be forgotten. Other countries should also do similar things to remember genocides of their people. Need to tell generations that wrong was wrong, is wrong, and will be wrong. The genocide was carried out during and after World War I and implemented in two phases—the wholesale killing of the able-bodied male population through massacre and subjection of army conscripts to forced labour, followed by the deportation of women, children, the elderly, and the infirm on death marches leading to the Syrian Desert.
Driven forward by military Feb 28, This first book, called "Genesis" in English, is called "Bereesheet" in Hebrew. What good is howling about the Holocaust, not just at the moon, but also the Universe, when atrocities continue to this day, with some of the worst being perpetrated by none other than the Israelis? I'll bet they try to claim the land.
Sign in. Forgot Password Registration. What do you think about this particular story? Your message to the editors. Your email only if you want to be contacted back. Why it matters: A new photo, taken by the Event Horizon Telescope, represents humanity's first real look at a black hole, and it could fundamentally alter how we understand these objects and test even the most basic laws of physics. The EHT observations are also helping scientists figure out how black holes generate huge jets of radiation that structure the galaxies around them, something they've only been able to simulate on supercomputers.
How they did it: All of the radio telescopes working with the EHT used atomic clocks to sync up observations of the black hole. But there was too much data to send over the internet. Instead, the team had to ship the data by mail to one facility where it could be processed by a supercomputer. What's next? Eventually, the EHT collaboration hopes that they'll be able to launch a radio telescope to space, allowing them to get an even clearer picture of a black hole. The researchers are also working on taking a clear photo of the black hole in the center of the Milky Way.
What they're saying: "It did bring tears to my eyes.