Have you ever had a cup of coffee? Now if you had a mind as empty as mine, you might have pondered over the varying temperature of your cup of coffee. When it’s just poured into the cup, it’s too warm to drink without having to regret doing so for a couple of days. In a few minutes, the coffee gets a little colder and good for drinking. This is due to the fact that heat flows from a hot body to a cold body whenever it can. Heat flows from the cup of coffee to the air around the cup. But I never observed the room getting hotter when the cup cools down … the reason being that the room is so big that the change in its temperature is not observable.
But we have all gone through that “Oops” moment when you forget the cup of coffee and it gets too cold. Have you ever thought about it? Why doesn’t it cool to the point of freezing in a room? Why does the cooling stop? The answer is thermal equilibrium (nope, this blog won’t be boring just because it talks about thermodynamics) which means that heat naturally flows from a hot body to a cold body until both bodies achieve the same temperature.
How irrelevant to the topic. What’s this thermal equilibrium shit got to do with the universe. Let’s make sense out of everything explained above. Our Sun is just like a cup of coffee cooling down on a table in a room. And just like any another room, the room in which the Sun is cooling down (the Milky Way) is too big compared to the size of the sun which is why we don’t observe extremely big changes in the temperature everyday. If the Sun were to lose all of its heat suddenly, every planet around it would fry. So the gradual cooling process of the Sun is a blessing for us, the slower it cools down, the more time we get under the sun.
But every cup of coffee ultimately does cool down in an environment colder than itself. So will the Sun, and so will every other star in the Universe and every other thing that’s hotter than the rest of the Universe. At this point, a Universal thermal equilibrium will be established and every inch of the entire universe will have the same temperature; there will be no engines capable of working and flow of heat will stop throughout the universe. Such a point is called Heat Death – the ultimate death of the Universe while its lifeless corpse lies there for eternity or perhaps until the beginning of the big crunch(let’s save that for another blog). Anyway, it would take zillions of years until that point is reached, so worry not, we would most probably have killed each other before nature kills us.
Now, to link the predicted death of the Universe in the future to its past; we have to get back to our cup of coffee. What if someone told you that they’re waiting for their cup to cool down for a day and it just won’t change? What if the told you that they tried putting the cup in a fridge for hours and made sure that it wasn’t insulated, but it just won’t cool down? You would probably not believe them or consider it a miraculous creation of an infinite heat source – the cure to the problem of energy crisis.
Just like it is impossible for a cup of coffee to stay warm after continuing to lose heat for a day, it is impossible for billions of stars with temperatures ranging from thousands to hundreds of thousands of Centigrade to keep losing heat for an infinite amount of time and still stay extremely hot. It takes a finite amount of time for a star to cool down and die out. Given an infinite amount of time for the Universe to exist until now, all stars in the Universe should have died out and the should have been in the state of heat death right now and I would not have been here writing this and you would not have been there reading this.
The fact that the temperature of the Universe varies from place to place, the fact that we have seasons to enjoy and hate, the fact that we are alive is the proof that the Universe did not exist forever and that it was created at a certain time. It had a beginning and it would definitely have a death. For whatever begins to exist has a death. Anyway, my cup of coffee has cooled down writing this blog. So I’ll leave it here. Thanks for reading.