Big Bang Theory - Studying The Universe, Measurement Techniques, Historical Background, The Spiral Nebulae, Implications Of Hubble's Law
atoms including matter finite
The big bang theory is the conceptual and mathematical model that scientists use to describe the origin of the Universe. It states that the Universe began as a tiny, violent explosion about 15 billion years ago. That event produced all of the matter and energy in the universe, including its hydrogen and helium. Some of these light atoms were forged in the cores of stars, over billions of years, into atoms of the heavier elements that exist today, including the atoms of which we ourselves are made. One consequence of the big bang is that today the Universe, which is of finite size and contains a finite amount of matter, is expanding; in fact, the occurrence of the big bang was originally deduced from the fact of the Universe's expansion. In recent years astronomers have made many observations that verify predictions of the big bang theory.
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Since ancient times, people have wondered about the origin of the Universe. Questions about how and when Earth and the heavens formed have been pondered by philosophers, theologians, and scientists. The modern, scientific study of the origin and structure of the Universe is known as the science of cosmology. For many centuries cosmological thought was limited mostly to speculation. For example, it…
All measurements of the stars must necessarily be made from the neighborhood of the Earth, since the distances involved are enormous. The nearest star other than the Sun is more than four light-years away, and most objects seen from earth, even with the naked eye, are much farther off. (A light-year is the distance that light travels in one year: 5.88 trillion miles [9.46 trillion kilometers], or …
In 1905, Danish astronomer Ejnar Hertzsprung (1873–1967) compared the width of various stars' absorption lines to the absolute luminosity, or brightness of the stars as determined from proper motion measurements. Hertzsprung found that that wider lines correspond to larger and brighter stars. This provided a way to determine the absolute brightness of a star from its spectrum. Knowin…
In the early twentieth century, there was a debate among astronomers over the nature of the spiral nebulae, the diffuse spiral-shaped structures visible (through telescopes) in most parts of the sky. Some believed these were nearby objects that were part of our Milky Way Galaxy, while others thought that they were much further away, and in fact were "island universes," or separate ga…
Galaxies are moving away from the Earth in all directions because all galaxies are receding from each other, that is, every galaxy is getting further away from every other galaxy. There is a simple way to visualize this effect. Imagine a partially blown up balloon, on the surface of which a number of spots (representing galaxies) are drawn. As the balloon inflates, each spot gets farther away from…
When Einstein developed his general theory of relativity he added a term, the cosmological constant, to his equations in order to permit a static universe which was neither expanding nor contracting. (He later came to regret this, calling it one of the worst mistakes he ever made; however, the recent discovery that the expansion of the Universe is actually accelerating has brought Einstein'…
The current picture of the big bang can be described briefly as follows. Because current formulations of the laws of physics break down very close to the big bang itself, the account will start one second after the event occurs. At this time, the temperature was 10,000,000, 000K. This was too hot for atoms to exist, so their elementary particle constituents (electrons, protons, and neutrons) exist…
Although the big bang model has done a good job of explaining what is seen in the Universe, there are still many unanswered questions. There is still disagreement about the exact value of the Hubble constant by approximately a factor of two. The Hubble Space Telescope is making observations similar to those made by Edwin Hubble in order to try to measure this quantity more accurately. Preliminary …
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