The invisible universe dark matter and dark energy pdf
The Invisible Universe: Dark Matter and Dark Energy | SpringerLinkThis means that the explosions were farther from us than theory predicted; while theory already took into account our knowledge that the universe is expanding, this discovery indicated it is expanding at an increasing rate. But the matter we knew about in the universe — galaxies of stars and gas, called normal matter, plus invisible dark matter — works by pulling, and therefore something had to be pushing everything apart. That something, which astronomers now call dark energy, is a repulsive force, and it also happens to make up more of the universe than normal and dark matter combined. Discovering dark energy To reveal this mysterious energy, scientists studied type Ia supernovae, all of which have light-intensity curves with very similar shapes. Astronomers can therefore compare and standardize these curves, providing a tool to study the distant cosmos. The curves have the same shape because they start with the same type of source: a densely packed star remnant made of carbon and oxygen. That remnant — a white dwarf — lives in a binary system with a companion star.
What is Dark Matter and Dark Energy?
In the s, a Swiss astronomer named Fritz Zwicky came to a startling conclusion: the galaxies zooming around each other in clusters should not hold together at those incredible speeds. Astronomers Vera Rubin and Ken Ford used a sophisticated spectrometer to clock the subtle shifts in spectra of stars in spiral galaxies near and far. They measured stars outward from the cores of these galaxies, to get an idea of how fast galaxies like our Milky Way must spin and how that spin decreases the farther from the core they clocked. Using the foot radio telescope in Green Bank, Mort Roberts found huge halos of invisible hydrogen gas extending well beyond the visible disks of these galaxies. By clocking that gas, he and others extended the flat rotation curve several times the diameter of the visible galaxy. Clearly, he proved, galaxies are made of much more matter than can be detected by even the largest radio telescopes.
If dark matter acts like cosmic glue, astronomers must be able to explain its existence in terms of the prevailing theory of universe formation. The big bang theory states that the early universe underwent an enormous expansion and is still expanding today. For gravity to clump galaxies together into walls or filaments, there must be large amounts of mass left over from the big bang, particularly unseen mass in the form of dark matter. In fact, supercomputer simulations of the formation of the universe show that galaxies, galactic clusters and larger structures can eventually form from aggregations of dark matter in the early universe. Besides giving the universe structure, dark matter may play a role in its fate. The universe is expanding, but will it expand forever? Measurements of mass density must include both light and dark matter.
The nature and essence of Dark Matter and Dark Energy have become the central as they make up most of the matter and energy content of the known universe. DRM-free; Included format: PDF; ebooks can be used on all reading devices.
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Foundations Built for a General Theory of Neural Networks
Even that 5 percent is increasingly slipping out of sight, as stars and gas tumble into gargantuan black holes at the centers of galaxies. Natarajan, a theoretical astrophysicist and professor at Yale University, creates maps of where dark matter is clumped and how dark energy stretches space. She also models the growth of those supermassive black holes and helped develop the leading theory of their formation in the early universe — a theory that will be tested by telescope observations in the near future. After playing a pioneering role in those pursuits, she landed a professorship at Yale in her late 20s and has been based there ever since. She is also a professor at the University of Copenhagen and an honorary one at the University of Delhi.