The spectrum of light from a star that is observed by the Hubble Space Telescope is not exactly the same as that star's spectrum observed by a telescope on Earth. Explain why this is so.

The differences in the observed spectrum of light from a star observed by the Hubble Space Telescope and a telescope on Earth can be attributed to two main factors: the Earth's atmosphere and the Doppler effect. The Earth's atmosphere absorbs and scatters light, altering the observed spectrum for ground-based telescopes. Furthermore, differences in the relative motions between the star, Earth, and the Hubble Space Telescope can result in Doppler shifts, leading to different observed spectra. The Hubble Space Telescope, being outside of Earth's atmosphere and having a different relative motion, observes a spectrum of light that is closer to the star's actual spectrum compared to ground-based telescopes on Earth.