Catalog Search Results
Publisher
The Great Courses
Pub. Date
2024.
Language
English
Description
The unexpected finding that the Universe is expanding at an ever-faster rate lends support for the existence of a non-zero cosmological constant, a formerly discredited idea of Einstein's, which he once called his "biggest blunder."
23) Understanding the Universe: An Introduction to Astronomy, 2nd Edition: Episode 78Feeding the Monster
Publisher
The Great Courses
Pub. Date
2024.
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.
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.
27) Understanding the Universe: An Introduction to Astronomy, 2nd Edition: Episode 7The Celestial Sphere
Publisher
The Great Courses
Pub. Date
2024.
Language
English
Description
As Earth rotates on its axis and orbits the Sun, the night sky changes over a 24-hour period, as well as throughout the year. This lecture explains how to locate celestial bodies and why the sky appears different from place to place.
Publisher
The Great Courses
Pub. Date
2024.
Language
English
Description
What's a black hole really like? Without taking the fatal journey into one, astronomers can calculate the bizarre experiences that would ensue, including dramatic distortions in visual phenomena as a traveler approached the event horizon.
Publisher
The Great Courses
Pub. Date
2024.
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.
Language
English
Description
The leading contenders for a theory of everything are string theories, which postulate that fundamental particles act like tiny, vibrating strings of energy. This approach requires at least 10 dimensions, most of which are curled up on minuscule size scales.
Publisher
The Great Courses
Pub. Date
2024.
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.
Language
English
Description
This lecture looks at problems with the quantum fluctuations explanation for dark energy. One alternative is called quintessence—a class of models that postulate repulsive energy that may be associated with unified forces or fields.
Publisher
The Great Courses
Pub. Date
2024.
Language
English
Description
Though less massive than Jupiter and Saturn, Uranus and Neptune are similar in that they consist mostly of hydrogen and helium. Both have bizarre magnetic fields that are highly tilted relative to the planet's rotation axis and offset from the planet's center.
Publisher
The Great Courses
Pub. Date
2024.
Language
English
Description
Star clusters are gravitationally bound groups of stars that are all about the same age and the same distance from Earth. Astronomers can determine the approximate ages of clusters. This lecture also explains how the distance of extremely remote stars is found.
Publisher
The Great Courses
Pub. Date
2024.
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.
Language
English
Description
Are interstellar voyages possible within a single human lifetime? According to Einstein's special theory of relativity, the answer is "yes" in principle but "no" in practice, given current technology. You explore the reasons for both answers.
Publisher
The Great Courses
Pub. Date
2024.
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.
Language
English
Description
The burned out Sun will eventually contract into a white dwarf. This is the fate of all stars between roughly 0.08 and 8 solar masses. A white dwarf in a binary system may steal matter from its companion star and flare up in an eruption called a nova.
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