2. Entropy
What is it? Entropy is a basic principle in thermodynamics. It is a function in physics that we combat on a daily basis in a variety of situations. A simple explanation of this would be: You lose a lot of the energy by your car to entropy. Energy in your fuel is converted from the explosions in the pistons into mechanical energy, but the heat being produced by the explosions is not stored for later use (closed system), it transfers to the surrounding material and dissipates. The most common loss of this heat energy is in the wheels through the brakes. All of the energy it takes to keep your wheels spinning is lost to that heat energy transferring to the surrounding material and dissipating as you hit those brakes. Everything in the universe is subject to the laws of thermodynamics. Where energy in an area of high concentration moves to areas of low concentration. Stars by the process of gravity compress and fuse their mass generating enormous amounts of energy that radiate away from its core, as the heaviest mass condenses and compresses deeper to the center. Eventually "Burning out" all of it's energy and light until any number of events occur. The complete and eventual certainty of Entropy is referred to as the "Big Chill" where all the energy, heat, and light of the universe will dissipate away into infinity, leaving the universe lacking in energy, cold, and dark.
Is this common? Can I hide under a table to survive? Yes: it effects everyone, and everything, everywhere. So it doesn't matter if our descendants can travel the stars in Star Trek -like ships for the next few billion years. Eventually Entropy will reach a point theorized as "The End of Time". However entropy is not the only reason this will occur, there is another set of forces affecting this inevitable result.
Has this happened before? Can it happen again? Physicists have recently made some predictions that the universe will end in about 5 billion years (roughly the same time our Sun will die out), as mentioned above, the end of time. Where Entropy is a factor, but coincidentally it is not necessarily the main reason. It will simply be part of the general effect of a theory called Eternal Inflation. However, we each have our own personal factors of entropy. While Entropy (itself) isn't necessarily killing us, our rate of decay is. What most people don't normally think about, in terms of entropy, is that we begin the process of death from the moment we are conceived. Depressing, yet, an unfortunate aspect of all systems in the universe. Whether the rate of decay is at an atomic level, or something more complex breaking down into simpler parts, it's true. It's essentially synonymous to Chaos. It takes energy being put back into a system to essentially maintain it. Chaos is simply a part of disordering said system into a reduced state of being and function. Technically speaking, entropy began at the same moment the Big Bang occurred, ever since, all things have been in a constant state of Entropy.