What does the observation of red-shift suggest about the movement of galaxies?

The observation of red-shift in the light from galaxies provides strong evidence that galaxies are moving away from each other. This phenomenon occurs due to the Doppler effect, where light from an object moving away from the observer is stretched, resulting in an increase in wavelength and a shift toward the red end of the spectrum.

This red-shift is a key element in the understanding of the expanding universe. Observations show that more distant galaxies exhibit greater red-shifts, implying that the farther a galaxy is, the faster it appears to be receding from us. This relationship supports the idea that the universe is expanding, leading to the conclusion that galaxies are not only moving away from each other but that the entire universe is experiencing expansion.

The other options do not align with the evidence provided by red-shift. Observing galaxies moving toward each other would result in a blue-shift (decrease in wavelength), suggesting a different interaction entirely. Stationary galaxies would not exhibit red-shift. Moreover, galaxies orbiting stars would not typically result in a consistent red-shift pattern observable across various galaxies on a cosmological scale. Thus, the correct interpretation of red-shift is that it indicates galaxies are indeed moving away from each other.