It was two hours for sunrise. Ben looked at his watch impatiently, “How much more time till it appears?”
“At least an hour” Alex replied. “It’ll be visible in the Eastern sky just before sunrise.”
They rested on the Mojave Desert ground, with their heads rested on their knapsacks. They were atleast fifty kilometres from the nearest urban settlement and the sky was glinting with thousands of stars.
Alex and Ben were avid star gazers who frequently visited the desert to watch the motion of the stars and the planets in the sky. Tonight however was special. It was going to be the first time since 2005 that all the five planets which are visible by the naked eye would be in the sky at the same time.
They had already spotted Venus, Mars, Jupiter and Saturn. Only Mercury remained and it was expected to rise just before the sun rose and the sky got illuminated.
Alex thought it would be better to talk of something so as to pass the time.
“Did you know, that although Mercury is the closest planet to the Sun, during night, it reaches temperatures of -180°C. While during daytime temperatures soar up to 430°C?” Alex remarked.
“Oh how come it fluctuates so much?” Ben asked curiously.
“Well it all has to do with the fact that Mercury does not have an atmosphere unlike Earth. Due to its small size, gravity isn’t strong enough to hold air and it has a very thin layer of atmosphere which again is constantly blown away by solar winds.”
“But what does the atmosphere have to do with the temperature of the planet?”
“Well, during the daytime, the land gets heated. This causes all the molecules on the surface of the planet to get excited and they gain a lot of kinetic energy. During the night, these ground atoms or molecules pass on the energy to the nearby layer of atmosphere by colliding with the air molecules. This layer then gets more energetic and it in turn passes the energy to the next layer of atmosphere. In this way the energy is transferred all the way to the last layer of the atmosphere and is finally lost to space. So the heat energy gained by the planet’s surface is slowly lost through the atmosphere.”
“Oh I see. So in the case of Earth, this takes place over the entire night and by the
time the energy is lost, it is daytime again. However for Mercury, due to its very thin atmosphere it easily loses its energy and becomes cool in a very short period of time.” Ben said.
“Bingo! Moreover since one year on Mercury which is 88 Earth days is shorter than its one day which is 118 Earth days, one face of the planet’s surface faces the Sun for an entire year and gets heated to a high temperature which is further assisted due to its close proximity to the Sun. Therefore this causes such a large variation in the temperature of Mercury.” Alex explained further.
“Oh this is interesting.” Ben remarked. “People often get fascinated by black holes and other such deep sky objects. But they fail to realise that there is much more to understand of what’s closer to us.”
“Indeed. By the way, what would be your reaction if I told you that on Venus, unlike most of the other planets, sun rises in the west and sets in the east?” Alex grinned.
Does the way the universe work, amaze you? Have you ever looked up at the night sky and wondered how does something happen? Keep your eye out for the next article which releases in the following month where Alex and Ben take one step closer to home and they talk about Venus. The planet which is called Earth’s twin but is nowhere similar to Earth when looked closely.