On March 14, 2016 one of the smartest men alive passed away. During his life, he contributed to many theories in the science field and even discovered a few of his own. He was diagnosed with ASL at the age of 21 and was given two years to live. When he died, he was 76 years old. This man, Stephen Hawking, is one of the most famous physicists of all time. One of his most famous quotes goes, “Remember to look up at the stars, not down at your feet.” So, that's what we'll be doing today. Looking into the cosmos at theories on how the universe will end. We’ll be looking at The Big Rip, which, besides its name, is actually the smaller theory here, the Big Freeze that will give you chills, and the Big Crunch that will eat you up.
The Big Rip Theory is the lesser known ending. This theory states that the critical density in the universe will drop and expansion will speed up so fast that everything will rip apart at an atomic level. That was a lot, I know. So now, let’s break that down. The critical density in the universe, according to Swinburne University, is “10 hydrogen atoms per cubic meter. This keeps expansion at a constant rate.” When this density falls below this ratio, that’s when things go haywire. How low this drops is how fast expansion will go. The lower the density the faster the expansion. This theory suggests that the universe is on a flat plane, and that it will just rip like paper. It will start with galaxies, then black holes, stars and planets, chemical compounds, and then atoms themselves. Cosmologists have started to try and mathematically figure out when the universe will rip. George Dvorsky, a futurist who dabbles in cosmology, wrote that “cosmologists found that it all has to do with Dark Matter.” No one really knows what this matter is. Some suppose it could come from nothing, but it is the foundation of our whole universe. 70 percent of our universe is dark matter, 25 percent is dark energy, and 5 percent is normal matter. When solving the Big Rip equation, cosmologists found that if dark matter has a value less than negative one, then this matter will grow to infinity. This concerned them, because it is believed that dark matter right now has a value less of that. This means that in less than 16.7 billion years our universe as we know it, could be gone in a matter of minutes. This may seem like a long period of time, but this next theory will take its time destroying our universe.
The Heat Death, or its other name the Big Freeze, is the most liked theory by astrophysicists. It scientifically makes the most sense with the laws of science we know today. In this theory our universe expands at a constant rate, and will keep going until it is so big and spread out that nothing can be made or destroyed. It’ll be like everything is frozen in time. This theory happens on a spherical plane. Which means you could look at our universal expansion like airing up a basketball. It is all based on the last two laws of thermodynamics. First, isolated systems evolve towards thermal equilibrium, which is when their heat is evenly distributed among the system. Second, the entropy, or ultimate space, of a system will reach a constant value as it approaches absolute zero. Which is zero degrees Kelvin, or about -460 degrees Fahrenheit. Scientists believe right now that our universe is rather set in this constant expansion, or patiently slowing down. Which means that that critical density of the universe is at or close to its equilibrium. According to Dr. Michio Kaku, an astrophysicist, “in a trillion years all of the stars will have been burned up, then a trillion years after that the black holes will have been burned up, and then even protons, subatomic particles, will begin to decay.” This will give us that frozen in time sensation. Right now we are in the Stelliferous Age, or the period where there are still stars dying and being made. This is why Dr. Kaku says it will take trillions of years for everything, down to that subatomic particle, to freeze and die. The polar opposite of this theory is the last one we’re going to talk about today.
The Big Crush is probably the most interesting theory. This also takes place on a spherical plane. Our universe will continue to expand until it hits its maximum value and condenses back in on itself. This is because of that critical density of the universe. That 10:1 ratio. If the density is high then the universe will condense back in on itself. At first scientists thought it was just gravity and attraction between galaxies that helped the expansion, but they’ve now realized they were wrong. According to Universe Today, “any body that goes against gravity will eventually give in and come back down.” Just like when you toss a ball up into the air. So the universe will get so big that its gravity will overpower it and make it condense back in. Like a pastry. It expands with heat and then condenses back down. This theory came from Einstein's Theory of General Relativity, which is basically cause and effect. Because the universe started with the Big Bang, it will end in the Big Crunch. According to Nasa, “the universe is now expanding faster than ever.” Scientists believe the dark matter in our universe is helping speed up expansion and push everything to its ultimate room. Since dark matter is already 70 percent of our universe it won’t take a lot for it to take over. Especially if it has already been expanding for awhile. This would throw off that balance and cause chaos. That chaos will inevitably be the end of this universe. Just like how the Big Bang started from a singular point, the Big Crunch will end that same way. In a super hot, super dense singularity, but this won’t be for billions of years.
Now in this I threw a lot of stuff at you. Trust me, I know. The theory of the Big Rip and how everything could tear apart like paper. The Big Freeze that could freeze everything as we know it in time, and the Big Crunch that is really just the opposite of the Big Bang. We can see that even though we have lived in this universe since the dawn of time, we really don’t know much about it. Hopefully by looking up at the stars and not at our feet, we can someday unlock these mysteries of the cosmos. But let's not rush. We don't have worry about our universe disappearing for millions or billions of years.
- Cosmos, "Critical Density,"Swinborne University of Technology, http://astronomy.swin.edu.au/cosmos/C/Critical+Density
- George Dvorsky, "The Universe Could Tear Itself Apart Sooner Than Anyone Believed," io9, 23 Jul. 2012, https://io9.gizmodo.com/5928274/the-universe-could-tear-itself-apart-sooner-than-anyone-believed
- Kaku, Michio. “The Big Freeze.” Big Think, The Big Think Inc, 13 May 2010, bigthink.com/dr-kakus-universe/the-big-freeze
- Villanueva, John Carl. “Big Freeze.” Universe Today, Universe Today, 8 Aug. 2009, www.universetoday.com/36917/big-freeze/.
- Nasa, "HubbleSite," Nasa, http://hubblesite.org/hubble_discoveries/dark_energy/de-fate_of_the_universe.php