Hubble's law and the Big Bang theory

Need to know

What you need to know

• Astronomers investigate objects in space by looking at their emission and absorption spectra.
• Elements in a star's atmosphere absorb specific wavelengths, creating dark lines in its spectrum.
• When comparing the spectra of distant galaxies to those of nearby stars (like our Sun), these spectral lines are found to be shifted.
• For almost all distant galaxies, the lines show an increase in wavelength, a shift towards red.

Explanation

Hubble's law and the Big Bang theory

1. Astronomers investigate objects in space by looking at their emission and absorption spectra.
2. Elements in a star's atmosphere absorb specific wavelengths, creating dark lines in its spectrum.
3. When comparing the spectra of distant galaxies to those of nearby stars (like our Sun), these spectral lines are found to be shifted.
4. For almost all distant galaxies, the lines show an increase in wavelength, a shift towards red.