key term - Hubble's Discovery of Galactic Recession

Definition

Hubble's discovery of galactic recession refers to the observation made by astronomer Edwin Hubble in the early 20th century that galaxies are moving away from Earth, with their speeds proportional to their distances. This pivotal finding led to the formulation of Hubble's Law, which established a direct relationship between the distance of a galaxy and its velocity, thereby supporting the notion that the universe is expanding. Hubble's work fundamentally transformed our understanding of the cosmos and provided key evidence for the Big Bang theory.

5 Must Know Facts For Your Next Test

1. Hubble first published his findings on galactic recession in 1929, using observations made with the Hooker Telescope at Mount Wilson Observatory.
2. His discovery revealed that the farther away a galaxy is, the faster it appears to be receding from us, which was counterintuitive to previous beliefs about a static universe.
3. The constant of proportionality in Hubble's Law is known as the Hubble constant, which helps estimate the rate of expansion of the universe.
4. Hubble's observations were crucial in shifting scientific consensus from a static model of the universe to one that acknowledges its dynamic nature and ongoing expansion.
5. The discovery paved the way for future research into cosmic background radiation and other aspects of cosmology, further confirming theories about the universe's origins.

Review Questions

• How did Hubble's discovery change our understanding of the structure and dynamics of the universe?
  • Hubble's discovery revealed that galaxies are not stationary but are instead moving away from each other, which suggested that the universe is expanding. This challenged earlier models that viewed the universe as static and unchanging. His findings laid the groundwork for modern cosmology and fundamentally shifted scientific perspectives on how we understand cosmic structures and their evolution over time.
• Discuss how Hubble's Law relates to redshift and what implications this has for measuring distances in space.
  • Hubble's Law states that galaxies recede from us at speeds proportional to their distance, which is evidenced by redshift—the stretching of light waves due to this recession. When astronomers observe redshift in distant galaxies, they can calculate how fast these galaxies are moving away and consequently infer their distances. This relationship is crucial for mapping the scale of the universe and understanding its expansion over time.
• Evaluate the significance of Hubble's discovery in relation to the Big Bang theory and subsequent advancements in cosmology.
  • Hubble's discovery provided compelling evidence for the Big Bang theory by demonstrating that the universe is expanding, suggesting it must have originated from a singularity. This breakthrough shifted scientific inquiry towards exploring cosmic evolution, leading to further discoveries such as cosmic microwave background radiation. The recognition of an expanding universe opened new avenues in cosmology, influencing theories about dark energy, cosmic inflation, and ultimately shaping our current understanding of how galaxies and cosmic structures form and evolve over billions of years.

Related terms

Hubble's Law:

The empirical relationship stating that the recessional velocity of a galaxy is directly proportional to its distance from Earth, typically expressed as v = H₀d.

Redshift: A phenomenon where light from an object moving away from an observer shifts toward the red end of the spectrum, indicating that the object is receding.

Big Bang Theory: The leading explanation for the origin of the universe, proposing that it began as a singularity approximately 13.8 billion years ago and has been expanding ever since.