Stars And The Universe (continued 2)
Visão Geral
Our Sun is one star among hundreds of billions in the Milky Way, which is itself one galaxy among billions in the Universe. The light from those distant galaxies carries a startling message: stretched towards the red, it tells us the whole Universe is expanding.
In this lesson you will learn the scale of the Milky Way and the Universe, what redshift is and why it is evidence for an expanding Universe and the Big Bang, and how cosmic microwave background radiation supports the same theory. You will use the Hubble constant to estimate the age of the Universe.
Objetivos
- Know that the Milky Way is one of many billions of galaxies making up the Universe and that the diameter of the Milky Way is approximately 100 000 light-years
- Describe redshift as an increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies
- Know that the light emitted from distant galaxies appears redshifted in comparison with light emitted on the Earth
- Know that redshift in the light from distant galaxies is evidence that the Universe is expanding and supports the Big Bang Theory
- [Supplement] Know that microwave radiation of a specific frequency is observed at all points in space around us and is known as cosmic microwave background radiation (CMBR)
- [Supplement] Explain that the CMBR was produced shortly after the Universe was formed and that this radiation has been expanded into the microwave region of the electromagnetic spectrum as the Universe expanded
- [Supplement] Know that the speed v at which a galaxy is moving away from the Earth can be found from the change in wavelength of the galaxy’s starlight due to redshift
- [Supplement] Know that the distance d of a far galaxy can be determined using the brightness of a supernova in that galaxy
- [Supplement] Define the Hubble constant H₀ as the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth; recall and use the equation H₀ = v / d
- [Supplement] Know that the current estimate for H is 2.2 × 10-18 per second
- [Supplement] Know that the equation d / v = 1 / H₀ represents an estimate for the age of the Universe and that this is evidence for the idea that all the matter in the Universe was present at a single point
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Avaliação da Lição
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- The diameter of the Milky Way is approximately: A. 100 light-years B. 100 000 light-years C. 1 light-year D. 100 million km Answer: B
- Redshift in the light from a distant galaxy means its observed wavelength is: A. shorter B. longer C. unchanged D. zero Answer: B
- Redshift of distant galaxies is evidence that the Universe is: A. contracting B. expanding C. static D. rotating Answer: B
- Cosmic microwave background radiation is observed: A. only from one direction B. from all directions in space C. only from the Sun D. only from the Milky Way Answer: B
- The Hubble constant H0 is defined as: A. v x d B. v / d C. d / v D. d x t Answer: B
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Secção do manual
Cosmology and Particle Physics
Look at the sky on some clear night when you are away from city lights. There you will see thousands of individual stars and a faint glowing background of millions more. The Milky Way, as it has been called since ancient times, is an arm of our galaxy of stars—the word galaxy coming from the Greek w
"College Physics: Cosmology and Particle Physics" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/34-1-cosmology-and-particle-physics. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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