Question

in the early 1900s, scientists discovered that certain properties of light were changed depending on the distance between earth and the object being observed. in 1929, edwin hubble compared this phenomenon to the relative distances between a certain set of stars. hubble found that when the two sets of data were graphed against one another, each star appeared to be farther from one another than what the relative distance indicated. with this information, hubble concluded the universe is expanding.
what phenomenon was discovered by early astronomers and used by hubble to confirm that the universe is expanding?
○ the light emitted by the galaxies becomes brighter as they move away from one another.
○ the light emitted by the galaxies becomes whiter as they move away from one another.
○ the wavelength of the light emitted by the galaxies shifts to the blue region of the spectrum as the galaxies move away from one another.
○ the wavelength of the light emitted by the galaxies shifts to the red region of the spectrum as the galaxies move away from one another.

Explanation:

The phenomenon used to confirm the universe's expansion is redshift. When galaxies move away, the light's wavelength shifts to the red region (longer wavelengths). The first option is incorrect (light doesn't get brighter with distance), the second is incorrect (whiter isn't related), the third is incorrect (blue shift is for approaching objects). The fourth option correctly describes redshift.

Answer:

The wavelength of the light emitted by the galaxies shifts to the red region of the spectrum as the galaxies move away from one another.