Hubble's Law and the Expanding Universe
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Questions and Answers

What can be inferred about the motion of galaxies from the observation of redshift?

  • Galaxies are moving away from us (correct)
  • Galaxies are moving towards us
  • Galaxies are stationary with respect to us
  • Galaxies are moving in a circular motion around us
  • What is the physical significance of the slope of the Hubble Law Graph?

  • It represents the density of the universe
  • It represents the age of the universe
  • It represents the velocity per unit distance (correct)
  • It represents the velocity of light
  • What is the unit of the Hubble Constant?

  • m/s/Mpc (correct)
  • 1/s
  • km/s
  • m/s
  • What is the estimated age of the universe based on the Hubble Constant?

    <p>8 to 15 billion years</p> Signup and view all the answers

    What is the range of the Hubble Constant in km/s per megaparsec?

    <p>50 to 100 km/s/Mpc</p> Signup and view all the answers

    What is the relationship between a galaxy's distance from us and its velocity through space?

    <p>Velocity increases as distance increases</p> Signup and view all the answers

    Why are distances to galaxies typically measured using Cepheid variable stars or supernovae?

    <p>Because they have a known brightness</p> Signup and view all the answers

    What is the significance of the Big Bang Theory?

    <p>It explains the origin of the universe</p> Signup and view all the answers

    What can be inferred about the universe from the observation of galaxy recession?

    <p>Galaxies were once much closer together</p> Signup and view all the answers

    What is the term used to describe the distance between galaxies and their recession velocity?

    <p>The Hubble Constant</p> Signup and view all the answers

    What can be inferred about the universe's age from the expansion process?

    <p>The universe is approximately 15 billion years old</p> Signup and view all the answers

    What is the primary difference between the expansion of the raisin bread model and the expansion of the actual universe?

    <p>The raisin bread expands into a pre-existing space, while the universe expands into itself.</p> Signup and view all the answers

    What is the key insight that can be gained from the observation of the raisins in the expanding loaf of bread?

    <p>The space between objects in the universe is expanding, but the objects themselves are not.</p> Signup and view all the answers

    What is the relationship between the distance and velocity of objects in the uniformly expanding loaf of bread?

    <p>The velocity of objects is directly proportional to their distance from the observer.</p> Signup and view all the answers

    What is the significance of the initial singularity in the raisin bread model?

    <p>It represents the point at which space and matter were indistinguishable.</p> Signup and view all the answers

    What is the role of the yeast in the raisin bread model?

    <p>It is merely a mechanism to illustrate the expansion of the bread, and has no cosmological significance.</p> Signup and view all the answers

    What is the implication of the expanding loaf of bread on our understanding of the universe's size?

    <p>The universe is expanding, and its total size is increasing.</p> Signup and view all the answers

    Study Notes

    Hubble's Law

    • Almost all galaxies are redshifted, indicating they are moving away from the Milky Way.
    • The most distant galaxies exhibit the greatest redshift, meaning they are moving away from us the fastest.

    Hubble Constant

    • The slope of the Hubble Law graph represents the Hubble Constant, expressed as velocity/distance (km/s/Mpc).
    • The Hubble Constant has dimensions of 1/s, so the reciprocal of the Hubble Constant (1/H) has dimensions of time, measured in seconds.
    • The Hubble Constant is estimated to be between 50 and 100 km/s per megaparsec.

    Implications of Hubble's Law

    • The universe has been expanding for 8 to 15 billion years, as inferred from the Hubble Constant.

    The Expanding Universe Cosmology

    • The search for origins is a fundamental aspect of human curiosity, and the Big Bang Theory is a result of several important observations.

    The Big Bang Theory

    • In 1927, Edwin Hubble observed that galaxies are redshifted, indicating they are moving away from us.
    • The farther away a galaxy is from Earth, the faster it is receding.
    • This observation suggests that the universe is expanding, and galaxies were once closer together.

    The Hubble Constant

    • The Hubble Constant is the rate at which galaxies are moving away from us, estimated to be between 50 to 100 km/s per kiloparsec.
    • Measuring the recessional velocity of galaxies is easy, but determining their current positions is challenging.
    • Distances to galaxies are typically measured using Cepheid variable stars or supernovae with known brightness.

    The Origin of the Universe

    • Running the expansion process backward suggests that the universe took approximately 15 billion years to reach its present size.
    • The expansion process implies that some event, known as the Big Bang, caused the galaxies to move away from each other.

    Hubble's Law

    • The graph shows a direct relationship between a galaxy's distance from us and its velocity through space.
    • The farther away a galaxy is from us, the faster it is receding from us.

    The Raisin Bread Model

    • The raisin bread model represents the expansion of the universe, where the dough (space) expands, and the raisins (matter) move away from each other.
    • The expansion of the dough does not affect the size of the raisins, illustrating that the matter in the universe is not expanding.
    • The space around the matter is expanding, consistent with the principle of conservation of mass.
    • The velocity of distant objects is directly proportional to their distance away from us, as observed by Hubble.

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    Description

    Understand the implications of Hubble's Law, including galaxy redshift, velocity, and distance. Learn about the Hubble Constant and its significance in astronomy.

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