Now that December 21, 2012, is done and over with, perhaps it should be explained how we are really all going to die. Don’t fret, though, you may well have to wait billions of years.
When will humanity become extinct? Most likely, our species will go extinct in the next five or ten million years–perhaps even far sooner. It could be because an asteroid or comet will hit the Earth, or perhaps we will kill ourselves in nuclear annihilation. The speculations could go on forever until they reach ad absurdum, for which is why I shall refrain from going on about all of the possibilities.
However, scientists are much more certain about the extinction of life on Earth and ultimately the Earth itself. Our sun gives us light, and without it, we wouldn’t be around. However, just as it gave us the right to live, it can take it away. Our sun generates its massive energy from nuclear fusion, the process in which two hydrogen nuclei combine to form a new element–helium. That means that the sun’s vast reserves of hydrogen are turning into helium. All of this helium means that the sun is getting brighter, or that its solar luminosity is increasing. In the next billion years, the sun will grow about ten percent brighter. In the years following that, it will get even brighter (Sackmann et al. 1993).
The increasing luminosity of the sun is bad news for the biota living on Earth at this time. The brightness of the sun causes the planet’s temperature to increase, drying up the oceans and making the Earth’s average temperature more than one hundred degrees hotter than it is today (Kasting 1988). Such high temperatures reduce carbon dioxide levels, not allowing photosynthesis to occur–killing all plants on Earth in the next billion years (Britt 2000). Scientists believe that by two billion years in the future, Earth will become completely uninhabitable and all life will go extinct (Britt 2000).
In about five billion years, the Earth will end. Although, by this time, all life will have died out. The sun will become larger and larger, becoming a red giant. Models predict that the sun will expand into space as far out as 150 million miles away (about 1-2 AU), well past where the Earth orbits (Sackmann et al. 1993, Schröder et al. 2008). Most likely, it will swallow up the Earth by 7.6 billion years in the future (Schröder et al. 2008).
Not far after the Earth is destroyed, the galaxy, as we know it, will cease to exist. The collision of the Milky Way and the Andromeda Galaxy by six billion years from now (“The end of the galaxy as we know it?” 31 May 2012) will make it the largest galaxy–which scientists call “Milkomeda”–in the Local Group. In the far future, the entire Local Group will just become one big galaxy.
The end of the universe is a little more guesswork for scientists. There are three main hypotheses concerning the death of our universe–the Big Crunch, the Big Rip and the heat death of the universe. According to the Big Rip, the constant expansion of the universe causes matter to tear itself apart. If this hypothesis is correct, the universe would end in about twenty billion years (Caldwell et al. 2003). The Big Crunch hypothesis states that the expansion of the universe will reverse and it will start diminishing, ending the universe in a singularity and possibly starting a new big bang. The heat death of the universe says the universe will eventually reach absolute zero (-459.67º F.), making work impossible.
Britt, Robert. “Freeze, Fry or Dry: How Long Has the Earth Got?” SPACE.com. 25 Feb. 2000. 24 Dec. 2012. <http://web.archive.org/web/20090605231345/http://www.space.com/scienceastronomy/solarsystem/death_of_earth_000224.html>
Caldwell, R.R., Marc Kamionkowski, Weinberg Kamionkowski, N. Nevin. “Phantom Energy and Cosmic Doomsday”. Physical Review Letters, 91 (7): 071301, 2003. 02 Jan. 2013. <http://prl.aps.org/abstract/PRL/v91/i7/e071301>
Kasting, J.F. “Runaway and Moist Greenhouse Atmospheres and the Evolution of Earth and Venus.” Icarus, 74(3): 472-494, 1988. 24 Dec. 2012. <http://adsabs.harvard.edu/abs/1988Icar…74..472K>
Sackmann, I.-J., A.I. Boothroyd, K.E. Kraemer. “Our Sun. III. Present and Future.” Astrophysical Journal, 418: 457-468, 1993. 24 Dec. 2012. <http://adsabs.harvard.edu/doi/10.1086/173407>
Schröder, K.-P., R. Connon Smith. “Distant future of the Sun and Earth revisited.” Monthly Notices of the Royal Astronomical Society, 386(1): 155. arXiv:0801.4031, 2008. 02 Jan. 2013. <http://dx.doi.org/10.1111%2Fj.1365-2966.2008.13022.x>
“The end of the galaxy as we know it?” Light Years. CNN.com Blogs. 31 May 2012. 02 Jan. 2013. <http://lightyears.blogs.cnn.com/2012/05/31/the-end-of-the-galaxy-as-we-know-it/>
In addition to this article, I have prepared a narrated video saying everything this article just did: