Question

In describing his upcoming trip to the moon, and as portrayed in the movie Apollo 13 (Universal, 1995), astronaut Jim Lovell said, “I’ll be walking in a place where there’s a 400-degree difference between sunlight and shadow.” Suppose an astronaut standing on the Moon holds a thermometer in his gloved hand. (a) Is the thermometer reading the temperature of the vacuum at the Moon’s surface? (b) Does it read any temperature? If so, what object or substance has that temperature?

Answer 1

Hint: A thermometer is a device which is used to measure temperature of an object or a substance. A vacuum cannot absorb, conduct or radiate heat which means vacuum has no temperature but the objects inside a vacuum have temperature.

Complete answer:
By the definition, a vacuum has no heat since heat is the average kinetic energy of the molecules in the substance. A vacuum doesn't have any molecules or atoms or anything else, as compared to their surroundings. Now, we know that temperature is a measure of that heat using a scale whether it is Fahrenheit, Celsius or Kelvin.
(a) What the thermometer measures largely depends upon the type of thermometer but most of the thermometers measure their own temperature. The reading we get is the temperature of the thermometer itself. To find out the reading of the temperature of an object the thermometer needs to be in thermal contact with the object and time is needed for the thermometer to reach the same temperature as the object whose temperature we wish to measure.
Thus, the thermometer would not measure the reading of the temperature of the vacuum at the Moon’s surface. It will only measure the temperature of whatever is in contact with the thermometer.
(b) From the above-mentioned reason that, the thermometer will only measure the temperature of whatever is in contact with it. So, it would read the temperature of the glove, since it is in contact with the glove.
Hence, (a) No, the thermometer would not be reading the temperature of the vacuum at the Moon’s surface.
(b) It will only measure the temperature of whatever is in contact with the thermometer.

Note:
Space is defined as a continuous area or expanse which is free, available, or unoccupied. So, we know that in space there is no atmosphere or any other object like on earth. Due to the absence of atmosphere in space, the phenomena of scattering of light does not take place. Due to the following reasons the sky appears darker to an astronaut in space.