Question

In the 1920s, astronomer Edwin Hubble determined that the universe was expanding, leading to the Big Bang theory. What wave property did Hubble use to determine galaxies were moving away?

A) Amplitude
B) Wavelength
C) Frequency
D) Speed

Answer 1

Astronomer Edwin Hubble used the change in wavelength, observed as a red shift in the hydrogen spectra of distant galaxies, to determine that the universe is expanding (B).

Step-by-step explanation:

In the 1920s, astronomer Edwin Hubble used the wavelength property of light from galaxies to determine that the universe was expanding. This discovery was evidenced by observing a red shift in the hydrogen spectra of galaxies, which indicated that their wavelengths were being stretched as they moved away from us.

This phenomenon, often referred to as the cosmological red shift, is not exactly akin to the Doppler shift—because it is not the galaxies moving through space, but the space itself expanding, causing the red shift of the light from distant galaxies.