key term - Edwin Hubble

Definition

Edwin Hubble was an American astronomer who made groundbreaking contributions to our understanding of the universe. He is best known for his observations and discoveries that led to the realization that the universe is expanding, and that galaxies beyond our own Milky Way exist.

5 Must Know Facts For Your Next Test

1. Hubble's observations of the redshift of light from distant galaxies provided evidence that the universe is expanding, a key component of the Big Bang theory.
2. Hubble used Cepheid variable stars to measure the distances to nearby galaxies, demonstrating that they were separate from the Milky Way and much farther away.
3. Hubble's discovery of the relationship between a galaxy's redshift and its distance, known as Hubble's law, allowed for the determination of the expansion rate of the universe.
4. Hubble's work on the classification of galaxies into different types, such as elliptical, spiral, and irregular, laid the foundation for our understanding of galaxy morphology.
5. Hubble's contributions were instrumental in the shift from a static, unchanging universe to the dynamic, expanding universe described by the Big Bang theory.

Review Questions

• Explain how Edwin Hubble's observations of redshift in distant galaxies provided evidence for the expanding universe.
  • Edwin Hubble's observations of the redshift of light from distant galaxies were a crucial piece of evidence supporting the idea of an expanding universe. Hubble found that the farther a galaxy was from the Milky Way, the greater its redshift, indicating that it was moving away from us. This observation, known as Hubble's law, suggested that the entire universe was expanding, a key prediction of the Big Bang theory. Hubble's groundbreaking work on the relationship between a galaxy's redshift and its distance laid the foundation for our modern understanding of the dynamic, evolving nature of the universe.
• Describe how Hubble's use of Cepheid variable stars to measure distances to nearby galaxies led to the discovery of extragalactic nebulae.
  • Hubble's use of Cepheid variable stars, which have a well-established relationship between their luminosity and pulsation period, allowed him to accurately measure the distances to nearby galaxies. This revealed that these 'nebulae' were in fact separate galaxies outside the Milky Way, known as extragalactic nebulae. Hubble's pioneering work in using Cepheid variables to determine the true nature and scale of the universe was a major breakthrough, shifting our understanding from a static, Milky Way-centric universe to a dynamic, expanding cosmos containing countless distant galaxies.
• Analyze how Hubble's contributions to the classification of galaxies and the determination of the expansion rate of the universe were instrumental in the development of the Big Bang theory.
  • Edwin Hubble's groundbreaking work was pivotal in the transition from a static, unchanging universe to the dynamic, expanding universe described by the Big Bang theory. Hubble's observations of the redshift of distant galaxies and the relationship between redshift and distance, known as Hubble's law, provided strong evidence that the universe was expanding. Additionally, Hubble's classification of galaxies into different morphological types, such as elliptical, spiral, and irregular, laid the foundation for our understanding of galaxy evolution. These key discoveries, along with Hubble's use of Cepheid variable stars to measure extragalactic distances, were essential in the development of the Big Bang theory, which explains the universe's origin and evolution. Hubble's contributions were transformative, shifting our cosmic perspective and paving the way for our modern understanding of the dynamic, ever-changing universe.

Related terms

Redshift:

The shift of the spectrum of light emitted by a celestial object toward longer, redder wavelengths, caused by the Doppler effect resulting from the object's motion away from the observer.

Cepheid Variable:

A type of variable star whose luminosity varies periodically, allowing astronomers to measure their distance from Earth.

Extragalactic Nebulae: Distant clouds of gas and dust that were later identified as separate galaxies outside the Milky Way.