Freedman, Wendy L. Observatories of the Carnegie Institution for Science, Pasadena, California.
- Distances to galaxies and measurement
- Microwave anisotropy measurements
- Age of the universe
- Links to Primary Literature
- Additional Readings
A number that characterizes the expansion rate of the universe and is required to determine its age and its observable size. In the standard big bang model, the local universe expands uniformly according to the Hubble law, v = H0, where v is the velocity of a galaxy at a distance d, and H0 is the Hubble constant. The wavelength of radiation is stretched due to the expansion of space so that the spectra of objects become progressively redder at greater distances. (For nearby objects, where the expansion velocities are small, the observed redshift can be described as a Doppler effect.) The constant is named after the American astronomer, Edwin P. Hubble, who discovered that the velocity of recession of a galaxy is proportional to its distance. A reliable and accurate measurement of the Hubble constant, an independent estimate of the ages of the oldest objects in the universe, and an independent measurement of the average mass-energy density in the universe are all separately required in order to test and ultimately provide strong constraints on cosmological models. Measuring an accurate value of H0 was one of the motivating reasons for building the Hubble Space Telescope. See also: Doppler effect; Hubble Space Telescope; Redshift
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information