UNIVERSE
Everything that exists, especially all physical matter, including all the stars, planets, galaxies, etc. in space: everything that exists, especially all physical matter, including all the stars, planets, galaxies, etc. in space:
Five of the most exciting telescope pictures of the universe
Jupiter's North Pole
The first image I’ve chosen was produced by Nasa’s Juno mission, which is currently orbiting Jupiter. The image was taken in October 2017 when the spacecraft was 18,906 kilometres away from the tops of Jupiter’s clouds. It captures a cloud system in the planet’s northern hemisphere, and represents our first view of Jupiter’s poles (the north pole).
The images this picture is based on reveal complex flow patterns, akin to cyclones in Earth’s atmosphere, and striking effects caused by the variety of clouds at different altitudes, sometimes casting shadows on layers of clouds below.
I chose this image for its beauty as well as the surprise it produced: the parts of the planet near its north pole look very different to the parts we had previously seen closer to the equator. By looking down on the poles of Jupiter, Juno showed us a different view of a familiar planet.
The Eagle Nebula
Astronomers can obtain unique information by building telescopes which are sensitive to light of “colours” beyond those our eyes can see. The familiar rainbow of colours is only a tiny fraction of what physicists call the electromagnetic spectrum.
Beyond red is the infrared, which carries less energy than optical light. An infrared camera can see objects too cool to be detectable by the human eye. In space, it can also see through dust, which otherwise completely obscures our view.
The James Webb Space Telescope will be the largest infrared observatory ever launched. Until now, the European Space Agency’s Herschel Space Observatory has been the largest. The next image I’ve chosen is Herschel view of star formation in the Eagle Nebula, also known as M16.
A nebula is a cloud of gas in space. The Eagle Nebula is 6,500 light years away from Earth, which is quite close by astronomical standards. This nebula is a site of vigorous star formation.
A close-up view of a feature near the centre of this image has been called the “Pillars of Creation”. Appearing a bit like a thumb and forefinger pointing upwards and slightly to the left, these pillars protrude into a cavity in a giant cloud of molecular gas and dust. The cavity is being swept out by winds emanating from energetic new stars which have recently formed deeper within the cloud.
The Galactic Centre
This image looks deeper into space to the centre of our Milky Way Galaxy. It also uses infrared light, this time combining data from two Nasa telescopes, Hubble and Spitzer.
The bright white region in the lower right of the image is the very centre of our Galaxy. It contains a massive black hole called Sagittarius A*, a cluster of stars and the remains of a massive star which exploded as a supernova about 10,000 years ago.
Other star clusters are visible too. There’s the Quintuplet cluster in the lower left of the image within a bubble where the stars’ winds have cleared the local gas and dust. In the upper left there’s a cluster called the Arches, which was named for the illuminated arcs of gas which extend above it and out of the image. These two clusters include some of the most massive stars known.
Abell 370
On much larger scales than individual galaxies, the universe is structured as a web of filaments (long connected strands) of dark matter. Some of the most dramatic visible objects are clusters of galaxies which form at the intersection of filaments.
If we look at galaxy clusters nearby (relatively speaking, of course), we can see dramatic proof that Einstein was right when he asserted that mass curves space. One of the prettiest examples which reveals this warping of space can be seen in Hubble’s image of Abell 370, released in 2017.
Abell 370 is a cluster of hundreds of galaxies about five billion light years away from us. In the picture you can see elongated arcs of light. These are the magnified and distorted images of far more distant galaxies. The mass of the cluster distorts spacetime and bends the light from the more distant objects, magnifying them and in some cases creating multiple images of the same distant galaxy. This phenomenon is called gravitational lensing, because the warped spacetime acts like an optical lens.
The most prominent of these magnified images is the thickest bright arc above and to the left of the centre of the picture. Called “the Dragon”, this arc consists of two images of the same distant galaxy at its head and tail. Overlapping images of several other distant galaxies comprise the arc of the dragon’s body.
These gravitationally magnified images are useful to astronomers, because the magnification reveals more detail of the distant lensed object than would otherwise be seen. In this case the lensed galaxy’s population of stars can be examined in detail.
The Hubble Ultra Deep Field
In an inspired idea, astronomers decided to point Hubble at a blank patch of sky for several days to discover what extremely distant objects might be seen at the edge of the observable universe.
The Hubble Ultra Deep Field contains nearly 10,000 objects, almost all of which are very distant galaxies. The light from some of these galaxies has been travelling for over 13 billion years, since the universe was only about half a billion years old.
Some of these objects are among the oldest and most distant known. Here we’re seeing light from ancient stars whose local contemporaries have long since been extinguished.
The oldest galaxies formed during the epoch of reionisation, when the tenuous gas in the universe first became bathed in starlight which was capable of separating electrons from hydrogen. This was the last major change in properties of the universe as a whole.
Universe, the whole cosmic system of matter and energy of which Earth, and therefore the human race, is a part. Humanity has traveled a long road since societies imagined Earth, the Sun, and the Moon as the main objects of creation, with the rest of the universe being formed almost as an afterthought. Today it is known that Earth is only a small ball of rock in a space of unimaginable vastness and that the birth of the solar system was probably only one event among many that occurred against the backdrop of an already mature universe. This humbling lesson has unveiled a remarkable fact, one that endows the minutest particle in the universe with a rich and noble heritage: events that occurred in the first few minutes of the creation of the universe 13.7 billion years ago turn out to have had a profound influence on the birth, life, and death of galaxies, stars, and planets. Indeed, a line can be drawn from the forging of the matter of the universe in a primal “big bang” to the gathering on Earth of atoms versatile enough to serve as the basis of life. The intrinsic harmony of such a worldview has great philosophical and aesthetic appeal, and it may explain why public interest in the universe has always endured.
Earliest conceptions of the universe
All scientific thinking on the nature of the universe can be traced to the distinctive geometric patterns formed by the stars in the night sky. Even prehistoric people must have noticed that, apart from a daily rotation (which is now understood to arise from the spin of Earth), the stars did not seem to move with respect to one another: the stars appear “fixed.” Early nomads found that knowledge of the constellations could guide their travels, and they developed stories to help them remember the relative positions of the stars in the night sky. These stories became the mythical tales that are part of most cultures.
When nomads turned to farming, an intimate knowledge of the constellations served a new function—an aid in timekeeping, in particular for keeping track of the seasons. People had noticed very early that certain celestial objects did not remain stationary relative to the “fixed” stars; instead, during the course of a year, they moved forward and backward in a narrow strip of the sky that contained 12 constellations constituting the signs of the zodiac. Seven such wanderers were known to the ancients: the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. Foremost among the wanderers was the Sun: day and night came with its rising and setting, and its motion through the zodiac signaled the season to plant and the season to reap. Next in importance was the Moon: its position correlated with the tides, and its shape changed intriguingly over the course of a month. The Sun and Moon had the power of gods; why not then the other wanderers? Thus probably arose the astrological belief that the positions of the planets (from the Greek word planetes, “wanderers”) in the zodiac could influence worldly events and even cause the rise and fall of kings. In homage to this belief, Babylonian priests devised the week of seven days, whose names even in various modern languages (for example, English, French, or Norwegian) can still easily be traced to their origins in the seven planet-gods.
The apex in the description of planetary motions during classical antiquity was reached with the Greeks, who were of course superb geometers. Like their predecessors, Greek astronomers adopted the natural picture, from the point of view of an observer on Earth, that Earth lay motionless at the centre of a rigidly rotating celestial sphere (to which the stars were “fixed”), and that the complex to-and-fro wanderings of the planets in the zodiac were to be described against this unchanging backdrop. They developed an epicyclic model that would reproduce the observed planetary motions with quite astonishing accuracy. The model invoked small circles on top of large circles, all rotating at individual uniform speeds, and it culminated about 140 ce with the work of Ptolemy, who introduced the ingenious artifact of displaced centres for the circles to improve the empirical fit. Although the model was purely kinematic and did not attempt to address the dynamical reasons for why the motions were as they were, it laid the groundwork for the paradigm that nature is not capricious but possesses a regularity and precision that can be discovered from experience and used to predict future events.
The application of the methods of Euclidean geometry to planetary astronomy by the Greeks led to other schools of thought as well. Pythagoras (c. 570–c. 490 bce), for example, argued that the world could be understood on rational principles (“all things are numbers”); that it was made of four elements—earth, water, air, and fire; that Earth was a sphere; and that the Moon shone by reflected light. In the 4th century bce Heracleides Ponticus, a follower of Pythagoras, taught that the spherical Earth rotated freely in space and that Mercury and Venus revolved about the Sun. From the different lengths of shadows cast in Syene and Alexandria at noon on the first day of summer, Eratosthenes (c. 276–194 bce) computed the radius of Earth to an accuracy within 20 percent of the modern value. Starting with the size of Earth’s shadow cast on the Moon during a lunar eclipse, Aristarchus of Samos (c. 310–230 bce) calculated the linear size of the Moon relative to Earth. From its measured angular size, he then obtained the distance to the Moon. He also proposed a clever scheme to measure the size and distance of the Sun. Although flawed, the method did enable him to deduce that the Sun is much larger than Earth. This deduction led Aristarchus to speculate that Earth revolves about the Sun rather than the other way around.
Unfortunately, except for the conception that Earth is a sphere (inferred from Earth’s shadow on the Moon always being circular during a lunar eclipse), these ideas failed to gain general acceptance. The precise reasons remain unclear, but the growing separation between the empirical and aesthetic branches of learning must have played a major role. The unparalleled numerical accuracy achieved by the theory of epicyclic motions for planetary motions lent great empirical validity to the Ptolemaic system. Henceforth, such computational matters could be left to practical astronomers without the necessity of having to ascertain the physical reality of the model. Instead, absolute truth was to be sought through the Platonic ideal of pure thought. Even the Pythagoreans fell into this trap; the depths to which they eventually sank may be judged from the story that they discovered and then tried to conceal the fact that the square root of 2 is an irrational number (i.e., cannot be expressed as a ratio of two integers).
SOURCE: The conversation
SOURCE: Britannica
SOURCE: Cambridge dictionary