What is the term used for the bending of light from a celestial body as it passes through the atmosphere?

The bending of light from a celestial body as it passes through the atmosphere is known as refraction. Refraction occurs because light travels at different speeds in different mediums. When light enters the Earth's atmosphere from space, it moves from the vacuum of space (where it travels faster) into the denser air (where it slows down), which causes the light to change direction slightly. This bending effect can influence how we perceive the position of celestial bodies, making them appear slightly displaced from their true position in the sky.

In contrast, diffraction involves the spreading out of waves when they encounter an obstacle or pass through a narrow aperture. This phenomenon is more relevant in the context of sound waves or light waves bending around objects rather than the bending caused by entering a different medium.

Reflection pertains to the bouncing back of light when it hits a reflective surface, such as a mirror or water. This is not the process that occurs when light moves through Earth's atmosphere.

Parallax is the apparent shift in position of objects when viewed from different angles. It plays a role in determining distances in astronomy but does not involve the bending of light due to atmospheric effects.

Thus, refraction is the correct term for the bending of light occurring when it travels through the Earth's atmosphere.