PHY122 Vocab Part 2

PHY122 Vocab Part 2 - Chapter 15 Cosmology: the study of...

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Chapter 15 Cosmology: the study of the nature, origin, and evolution of the universe. Static: unchanging, not evolving; for example, a static universe, which would have the same overall properties as a function of time, and not be expanding or contracting. Olber’s paradox: the conflict between observation and theory about why the night sky should or should not be dark. Observable universe: the part of the universe that you can see from your location in space and in time. Expanding universe: the observed property of the universe that the average distance between galaxies in increasing with time. Big bang: the high-density, high-temperature state from which the expanding universe of galaxies began. Hubble time: one divided by the Hubble constant. The Hubble time is the age of the universe if it has expanded since the big bang at a constant rate. Cosmic microwave background: radiation from the hot clouds of the big bang explosion. The large red shift makes it appear to come from a body whose temperature is only 2.7K. Recombination: the stage in the early history of the universe within 300,000 years of the big bang when the gas became transparent to radiation. Antimatter: matter composed of antiparticles, which upon colliding with a matching particle of normal matter annihilate and convert the mass of both particles into energy. The antiproton is the antiparticle of the proton, and the position is the antiparticle of the electron. Dark age: the period of time after the glow of the big bang faded into the infrared and before the birth of the first stars, during which the universe expanded in darkness. Reionization: the stage in the early history of the universe when ultraviolet photons from the first stars ionized the gas filling space. Isotropy: the assumption that, in its general properties, the universe looks the same in every direction. Homogeneity: the assumption that, on the large scale, matter is uniformly spread through the universe. Cosmological principle: the assumption that any observer in any galaxy sees the same general features of the universe Closed universe: a model universe in which the average density is great enough to stop the expansion and make the universe contract. Open universe: a model of the universe in which the average density is less than he critical density needed to halt the expansion. Flat universe: a model of the universe in which space-time is not curved. Critical density:
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This note was uploaded on 12/11/2011 for the course PHY 121 taught by Professor Weinstein during the Fall '08 term at SUNY Buffalo.

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PHY122 Vocab Part 2 - Chapter 15 Cosmology: the study of...

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