One way to distinguish a star from a planet, particularly when they appear near the horizon, is that stars appear to twinkle and planets shine steadily. Which of these statements is a reasonable explanation for this phenomenon?
A) Stars actually do twinkle-shine with a light that flickers bright and dim-whereas planets shine with a steady, unwavering light.
B) The light from planets is so much brighter than the light from stars (when they are observed from Earth) that it is unaffected by air movement in Earth's atmosphere.
C) The disk of a planet, as observed from Earth, appears larger than the disk of a star. Thus, if refraction through moving air in Earth's atmosphere makes the planet's disk appear to move about slightly, there will normally be a central part of the disk that shines steadily and does not appear to twinkle.
D) Because light from planets is reflected, it is unaffected by the refraction in Earth's atmosphere.

Question

Quizplus · Accepted Answer

The explanation for why stars appear to twinkle and planets shine steadily is due to the apparent size of their disks from Earth. Stars, being much farther away, appear as point sources of light, making them more susceptible to atmospheric turbulence, which causes the twinkling effect. Planets, being closer, present a larger disk size, which means that even though parts of their light might be refracted by the atmosphere, there's always a portion of the disk that remains steady to the observer, leading to a steadier appearance.

One Way to Distinguish a Star from a Planet, Particularly