Which of the following best describes the temperature in outer space (far from stars and planets)?

• A. It is exactly 0 K, the absolute zero.
• B. It is approximately 273 K, the freezing point of water.
• C. It is close to absolute zero, around 2.7 K due to the cosmic microwave background.
• D. It is about 1000 K because of solar radiation.

Answer: (C)

Verified step by step guidance

1. Understand that temperature is a measure of the average kinetic energy of particles in a substance or environment.
2. Recognize that outer space, far from stars and planets, is nearly a vacuum with very few particles to have kinetic energy, so its temperature is extremely low.
3. Recall that the cosmic microwave background radiation permeates all of space and has a temperature of about 2.7 K, which sets a baseline temperature for the universe.
4. Note that absolute zero (0 K) is the theoretical lowest temperature where particles have minimal motion, but space is not exactly 0 K because of this background radiation.
5. Conclude that the temperature in outer space is close to absolute zero, approximately 2.7 K, due to the cosmic microwave background, rather than being exactly 0 K or much higher.