The Expanding Universe
Knowledge you need to have:
Knowledge that the Doppler effect causes shifts in wavelengths of sound and light.
Knowledge that the light from objects moving away from us is shifted to longer wavelengths (redshift).
Knowledge that the redshift of a galaxy is the change in wavelength divided by the emitted wavelength. For slowly moving galaxies, redshift is the ratio of the recessional velocity of the galaxy to the velocity of light.
Knowledge that the Hubble-Lemaître Law allows us to estimate the age of the Universe.
Knowledge that measurements of the velocities of galaxies and their distance from us lead to the theory of the expanding Universe.
Knowledge that the mass of a galaxy can be estimated by the orbital speed of stars within it.
Knowledge that evidence supporting the existence of dark matter comes from estimations of the mass of galaxies.
Knowledge that evidence supporting the existence of dark energy comes from the accelerating rate of expansion of the Universe.
Knowledge that the temperature of stellar objects is related to the distribution of emitted radiation over a wide range of wavelengths.
Knowledge that the peak wavelength of this distribution is shorter for hotter objects than for cooler objects.
Knowledge that hotter objects emit more radiation per unit surface area per unit time than cooler objects.
Knowledge of evidence supporting the Big Bang theory and subsequent expansion of the Universe: cosmic microwave background radiation, the abundance of the elements hydrogen and helium, the darkness of the sky (Olbers’ paradox) and the large number of galaxies showing redshift rather than blueshift.
Skills you need to develop:
Use of an appropriate relationship to solve problems involving the observed frequency, source frequency, source speed and wave speed.
Use of appropriate relationships to solve problems involving redshift, observed wavelength, emitted wavelength, and recessional velocity.
Use of an appropriate relationship to solve problems involving the Hubble constant, the recessional velocity of a galaxy and its distance from us.
