Red shift | Astrophysics | Physics | FuseSchool

Summary

This video explains how Edwin Hubble used the Doppler effect and redshift to provide evidence that the universe is expanding. It covers the concept of absorption spectra, the Doppler effect with sound and light, and how redshift in distant galaxies indicates they are moving away from us, with further galaxies moving faster. The video also briefly mentions redshift as evidence for the Big Bang theory.

Highlights

Introduction to Redshift and Edwin Hubble00:00:07

The universe is expanding, and we know this due to evidence from redshift. This video will explore Edwin Hubble's use of the Doppler effect to support the expanding universe theory.

Understanding Light Absorption and Fraunhofer Lines00:00:31

Before Edwin Hubble, the universe was thought to be static. Hubble studied light from galaxies, noting that elements in a star's atmosphere absorb specific wavelengths of light. These absorptions create Fraunhofer lines in a star's light spectrum, revealing its chemical makeup and distance.

The Doppler Effect Explained00:01:17

The Doppler effect is a change in wavelength and pitch for sound, or wavelength and color for light, when the source is moving relative to an observer. An example is the changing sound of a police siren as it passes. The same principle applies to light from distant stars.

Redshift and Expanding Universe00:01:44

When a star moves away, its light shifts to a lower frequency, moving towards the red end of the spectrum, known as redshift. Hubble observed that most galaxy light was redshifted, and the further away a galaxy was, the more pronounced its redshift. This led to his conclusion that galaxies are moving away from us, and the universe is expanding.

Analyzing Stellar Spectra and Conclusion00:02:11

Comparing the sun's spectrum to a distant star's shows a shift of the absorption lines towards the red end for the distant star. This confirms their movement away from us. Redshift also supports the Big Bang theory.