The universe is 15 billion years old. 15 billion years ago, all the stuff in the universe was concentrated in a singularity, a mathematical concept, a speck of infinite density. It exploded. This is what astronomers call the Big Bang, the point at which time began. George Gamow coined the term. Primordial energy and matter flew in all directions. It cooled. Gas clouds condensed into galaxies. Galaxies are aggregates of stars, the building blocks of the universe. There are 100 billion galaxies. They are distinctive. The Whirlpool and Sombrero look like works of art. Galaxies are categorized according to their structures. The Milky Way is a spiral. M87 is elliptical. The Magellanic Clouds of the Southern Hemisphere are irregular. They are satellites of the Milky Way. The Milky Way belongs to a Local Group of 31 galaxies. The Andromeda Galaxy M31 is part of the Local Group. M31 is a spiral similar to the Milky Way but larger. It is 2.3 million light-years from us and the fartherest visible object. It is faint. Numbers were assigned to fuzzy patches in the sky by Charles Messier, an 18th century comet hunter. He cataloged 103 objects so as not to mistake them for comets. Nebulas and galaxies were lumped together. The more thorough New General Catalog (NGC) dates from the 19th century. Galaxies are found in clusters, and these in turn comprise superclusters. The Virgo and Coma Berenices superclusters are enormous. Our Local Group is part of the Virgo supercluster. In spite of this, the universe is mostly empty. Proof of the Big Bang came from the work of Edwin Powell Hubble. By applying the Doppler Effect to light, Hubble found that light from galaxies shows a redshift. This suggests that galaxies are receding, travelling away from each other. This is what we mean by the Expanding Universe. If you run it backwards, there is a point at which all galaxies converge. The primeval atom! Furthermore, the farther apart galaxies get, the faster they travel. This is as Hubble's Law. The question becomes whether expansion will continue forever or whether there is enough gravity in the universe to pull it back together. This would be the Big Crunch and suggests an oscillating universe, one which alternately expands and collapses. Black holes may provide the gravity for a Big Crunch. The universe is not expanding in space. Space is being created as the universe expands. The balloon analogy is used, blowing up a balloon with dots on it to represent galaxies. We ask what there was before the Big Bang. The answer is nothing. There was no space, no time and no events. It was the beginning in the true sense. Penzias and Wilson provided more proof of the Big Bang when they detected its background radiation. E.P. Hubble was the greatest astronomy of the 20th century. Shapley was great but believed external galaxies were inside our own. Cosmology was a step I was trying to take since I was a teenager. Carl Sagan's Cosmos series was a breakthrough. To paraphrase Sagan, "The Cosmos is everything that has been, everything that is and everything that will be." Sagan saw man as poised on the shore of the cosmic ocean, intelligent life as a means for the cosmos to know itself. The terms "cosmos" and "universe" are interchangible.
So where does light come from? It seems that it can come from just about anywhere. Does it have weight? How is it related to matter? I was thinking the other day about what would happen if you had a very bright luminous object; lets say a star, and you put it in an enclosed space where no light can escape. What would happen to the accumulated light inside the space? And how does a star continue to burn if fire needs oxygen to burn? I guess it burns helium and hydrogen.
Most of the visible light in the universe comes form stars, there are a couple of very specific other examples, accretion discs (glowing matter around black holes and neturon stars) springs to mind. Light has no rest mass which is how we know it must always travel at the speed of light. Light is made of photons, photons are mediator particles for the electromagnetic interaction, that means that when two charged particles interact they 'communicate' by transferring photons between each other. However they dont always go from particle to particle they can also be released as free particles which we know of as EM radiation. Of course this can still be thought of as communication between a distant star and your eye. If you put a star in a box it would just get very very bright in the box assuming the walls of the box were reflective, which is what i assume you meant. Stars 'burn' by combining 2 hydrogen atoms to make helium. Then when they run low on hydrogen the burn helium to make a variety of light elements such as carbon, nitrogen and oxygen. After this the star is really scraping the barrel but there is another process called the CNO cycle that involves the burning of carbon, nitrogen and oxygen. Eventually there is no fuseable material left and one way or another the star dies.
there is a diffuse glow over much of the sky from the everpresent tenious plasma that pervades this neck of the galaxy, however viewing it requires very long exposure times wide field telescopes.
The Milky Way is our own galaxy, and we are inside it. This is not apparent right away as we look at the glimmering arch in the night sky. The Greeks saw spilt milk. But the Milky Way consists of 400 billion suns 100,000 light years across and 2,000 light-years thick. If we could stand outside the Milky Way, we would see a disk with a bulge in its middle. It is shaped like a flying saucer. Our solar system revolves two-thirds of the way from the center toward the rim. It takes 200 million years for our solar system to revolve around our galaxy. This is a cosmic year. The last time the sun and planets were in this same position, dinosaurs roamed the earth. In the desert in 1979, there was an instant when I felt us revolving around the galactic center. Since we are inside the galaxy, trying to divine its shape is like someone inside a house trying to determine the shape of the house. The structure of the Milky Way and our sun's position in it was ascertained by Harlow Shapley in 1917. We grasp it when we know what we are looking at. The Milky Way circles the sky. Its bulging center lies in the direction of Sagittarius where star clouds are thick. The thin part of the circle, visible in winter, is in the direction of the outer rim. When we look at right angles to the Milky Way, we are looking out the top or bottom of the disk where stars are sparse. As we might expect, more galaxies can be seen out the top or bottom. Dust patches like the Coalsack and Cygnus Rift obscure parts of the Milky Way. People once thought they were holes. Because of dust, radio telescopes are used to study the center of the galaxy. The Milky Way is 10 billion years old.
All the matter that came out of the singularity was finite right? So that means the singularity must of had a limit to it's mass. That means things very very distand would not be effected by this singularity. So is it possible that other then parallel universes (or multiverse) that their our other universes existing which have no bearing on our universe or ours on theirs? Does the term multiverse cover the fact that other universe could exist without being dependant on ours, our are 'parallel' universe the most common explanations in cosmology?
no one actually knows what light is rather like electrons we create models to predict their path and position and reactions but exactly what they are made from eludes us
The term "Have you seen the light?", can indicate that you know what light is. When you see something, you create it. If you see light you create it, therefore we are like God in that way. We create light every time we open our eyes.
Well light is photons, which is the particle emitted by all charged particles. Mathematically these are well understood either classically by Maxwell or more recently quantum mechanically. This is where explaning what something is becomes quite philosophical, to someone good at maths I can explain in quite a lot of detail what one is although explaining is words is significantly harder because of the limitations of vocabulary. If you explain a concept to someone chances are you will try to use an analogy or a metaphor for something common in everyday life. This way they can build a picture up in their mind. This breaks down when what your trying to describe has no real life analog, of course the elementary particles bare no resemblance to anything in everyday life. In certain situations they behave a bit like particles in other situations they behave a bit like waves. So asking to describe these things in terms of appearance or as an analog is a bit like asking what sound red (thats probably the name of a band but u get my point) makes, or some other meaningless question.
you are sitting at the computer right?? where is your house? where is your town? where is your city? where is your country on earth? where is earth? where is the solar system? where is the milky way? where is the universe? our construct of reality is limited by our data - need more data. we have a road map of our place in the universe in the same way that an ant lays down its chemical trail to find position and thus context. we don't actually know if there was a big bang, this is conjecture. its our current theory, then soon enough someones going to come along and throw all this out the window.
