Catalog Search Results
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
This lecture starts the study of the Universe as a whole-or cosmology. A key finding made by Edwin Hubble in 1929 was that the spectra of distant galaxies are redshifted more than those of nearby galaxies, suggesting that the Universe is expanding.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
Astronomers now have strong evidence that quasars and other active galactic nuclei are powered by supermassive black holes, voraciously swallowing surrounding material. Less active galaxies also appear to harbor these monsters.
83) Understanding the Universe: An Introduction to Astronomy, 2nd Edition: Episode 78Feeding the Monster
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
This lecture explores the disks of gas around supermassive black holes. Material escaping from the vicinity of these objects often follows a highly focused jet along the rotation axis of the disk, sometimes approaching or even appearing to surpass the speed of light.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
The central regions of many galaxies go through an active, very luminous phase early in their development. The most powerful of these active galaxies, called quasars, shine like beacons across billions of light years of space.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
The finite speed of light allows observers to look back in time and see the unfolding history of the Universe. This lecture shows how astronomers search for distant galaxies to compare with better understood, nearby galaxies.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
How do galaxies form and evolve over time? Is it possible to determine what nearby galaxies, or even the Milky Way, once looked like? The answers can be found by examining distant galaxies that formed when the Universe was young.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
The Universe can be thought of as expanding into a mathematical dimension to which we have no physical access. Even an infinite Universe can expand, becoming less dense. The expansion suggests that there was a hot, dense beginning long ago-a Big Bang.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
A few stars end their lives with cataclysmic explosions, expelling gas at huge speeds. At its peak, such a supernova can rival the brightness of an entire galaxy, and its remnants can be seen for centuries. The Crab Nebula is one such remnant.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
The discovery of other galaxies beyond the Milky Way was one of the great scientific detective stories of the early 20th century. Astronomers now know that there are hundreds of billions of galaxies, spanning billions of light years of space.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
If a neutron star exceeds two to three solar masses, it becomes unstable and collapses. The resulting object is called a black hole-a region of such extreme space-time curvature that nothing, not even light, can escape.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
Roughly once per day, somewhere in the sky, there is a short, intense burst of gamma rays. Most of these events originate in very distant galaxies, making them among the most powerful explosions in the Universe-but they are not evaporating black holes.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
This lecture explores observational tests of general relativity. Astronomers exploit its effects by searching for distant objects that are gravitationally lensed, which occurs when an object's light is bent and focused by foreground masses such as galaxy clusters.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
Until a few decades ago, astronomers thought that galaxies were composed primarily of stars. There is now strong evidence that most of the mass of galaxies may be invisible dark matter. Clusters of galaxies are also dominated by dark matter.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
Why is the sky dark at night? In an infinitely old and large Universe the sky should be ablaze with light at all times. There are several possible answers to this paradox, each of which has profound cosmological implications. The relative youth of the Universe is now known to be the main explanation.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
The high luminosity of quasars puzzled astronomers in the 1960s. How could these peculiar, star-like objects be so bright and yet so far away? Only a few light years across, they are in fact even more powerful than entire galaxies.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
How old is the Universe? The Hubble Space Telescope was designed, in part, to answer this question. You follow the chain of reasoning that has led astronomers to conclude that the Universe began 13.7 billion years ago.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
The dark energy that is causing the expansion of the Universe to accelerate makes up about 75 percent of the cosmos. Visible matter accounts for less than 1 percent. The bulk of the remainder is dark matter, most of which may consist of exotic subatomic particles.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
According to one idea, repulsive dark energy having a negative pressure might be the result of a non-perfect cancellation of quantum fluctuations in space-virtual particles created literally out of nothing, as predicted by quantum physics.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (31 minutes): digital, .flv file, sound
Language
English
Description
According to general relativity, the fate of the Universe is tied to its global geometry. If the Universe has positive curvature, like a sphere, it must eventually collapse in a "Big Crunch." If it is flat or has negative curvature, however, it will expand forever.
Publisher
The Great Courses
Pub. Date
2024.
Physical Desc
1 online resource (streaming video file) (32 minutes): digital, .flv file, sound
Language
English
Description
This lecture explores methods used by astronomers to determine the mass density and expansion history of the Universe. To make this measurement, a race developed between two teams of astronomers searching for Type Ia supernovae in distant galaxies.
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