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Fate of the Universe Foldable


1. Fold a piece of light colored paper in half hot dog style.

2. Cut upwards on one side so that you have three evenly spaced flaps.

    Need help making this foldable? Watch the video here:

3. Write a title on each flap-

        Big Crunch

        Big Freeze

        Big Rip

4. Under the flaps, write information about each possible end to the universe using the article below.

5. On the back of your foldable, write your name and class period and answer the following questions in complete sentences.

  1. What two physical characteristics will determine the fate of the universe?
  2. What force makes space curve and slow down?
  3. What force makes space expand?
  4. How does density play a role in the fate of the universe?
  5. How is research changing the way the universe is viewed?
  6. Do you think it is worth it to spend money studying the shape of the universe? Why or why not?
  7. If you knew the fate of the universe, would it change the way you live your life? Explain.


The Fate of the Universe

"Some say the world will end in fire, others say in ice" -Robert Frost


The evolution of the universe is determined by a struggle between the momentum of expansion and the pull (or push!) of gravity. The current rate of expansion is measured by the Hubble Constant, while the strength of gravity depends on the density and pressure of the matter in the universe. If the pressure of the matter is low, as is the case with most forms of matter we know of, then the fate of the universe is governed by the density.

There are three possible futures of the universe. The first is that the universe will collapse in on itself in a Big Bang in reverse. This process is called The Big Crunch. An ending such as this would result if there is enough matter in the universe to counteract the force of expansion. If the process repeats itself, it would be called an oscillating universe.

The second possible end is where the universe would continue to expand until it just slows to a stop over time. Everything will eventually disappear and the temperature of the universe would continue to decease down to absolute zero. This process has many names but the most common is The Big Freeze or The Big Chill. If the universe does not have enough matter to stop the expansion of the universe, this scenario would occur.

The third scenario is that the universe continues to expand forever at an increasing rate. This process is generally called Accelerating Universe or The Big Rip.

A Geometry Lesson

The future of the universe ultimately depends upon its overall geometry: Flat, Spherical, or Hyperbolic. The universe's geometry is determined by the average density of everything in it - a function of the mass. There is one magic number, called the "critical density" which is represented by ρc, that determines which fate the universe will take.

Big Crunch

The Big Crunch is one scenario for the end of the universe, and it will result if the universe has a spherical geometry. This "spherical geometry" is not an abstract idea: It actually relates to what the shape of the universe would be if one could observe it from the "outside." Due to the spherical shape, we call this a “closed universe”.

In this case, the universe contains enough mass - it is above the critical density - to stop its expansion. Once it stops expanding, it will start to contract. Slowly at first, and then faster and faster, the universe will contract and galaxies will come closer to each other. Eventually, everything will merge, for the universe will no longer be large enough for separate galaxies or stars. As it continues to shrink, the universe will heat to huge temperatures, and everything will be compacted into a black hole. Finally, at the end, the universe will be as it began - an infinitely small, infinitely dense, and infinitely hot point. No one knows what, if anything, would happen after that. A popular idea is that the universe would be reborn and it would continue to oscillate between Big bangs and Big Crunches.

An easy way to think of this is by throwing a ball; you throw a ball up into the air. Your release is like the Big Bang, and starts the ball's acceleration. As the ball climbs skyward, it slows its ascent because the Earth has enough gravity to slow it down and pull it back to it. This is like the mass of the universe being enough to overcome its expansion. As the ball reaches its maximum height, it stops, which is what the universe will do if it is over the critical density. Then, ever so slowly, the ball begins to fall back down, faster and faster, until it reaches your hand again (unless you miss). This is the end of the ball's throw, and is like the end of the universe.

The Big Freeze

This scenario for the universe's future will result from either hyperbolic (open) or flat geometry. As with spherical geometry discussed in the above section on the Big Crunch, these geometries are not abstract terms that only weird astrophysicists with thick glasses and poofy white hair use, but rather they are real shapes.

A flat geometry is like a sheet of paper: It is flat; there is no curvature. If the universe is flat, the density is exactly the critical density. This is the Big Freeze scenario.

The Big Rip

Hyperbolic geometry is usually pictured with a saddle, and is depicted below to the right. If the universe is hyperbolic then the density is lower than the critical density and it will continue to expand forver. This is called the Big Rip.

Both of these pose the future of a never-ending universe. After enough time, all galaxies beyond our Local Group will have disappeared beyond the edge of the observable universe.  We can only know a small bit of what the universe contains due to the finite speed of light (300,000 kmps; 186,000 miles per second). Because the universe is a certain age, we can only see that many light-years out; for any part of the universe beyond that, the light has not had enough time to reach us.

After a longer time, all the stars in all the galaxies will have died, and there will be nothing left to make new ones. The universe will be a dark and cold place. Eventually, there will be nothing left but a vast, frozen emptiness.

Early and Current Research

Recent observations of supernova have suggested that the expansion oif the universe is accelerating or speeding up. This implies the existence of a form of matter that is counteracting gravity. We call this “dark energy’ although we have no real idea if it is dark or energy.


Since 1992, there have been many different projects to determine the overall geometry of the universe. The only successful way to determine this so far has been to study the cosmic microwave background radiation (CMB). This is radiation that is left over from the early universe - from the time when atomic nuclei first combined with electrons which made the universe transparent. This happened at the ripe ol' age of 380,000 years, based upon WMAP results. To learn more about the cosmic microwave background radiation, see the History page of this section.

The first such was COBE, which stands for COsmic Background Explorer. It presented the first all-sky picture of the CMB, but its resolution was too poor to accurately determine the geometry (temperature resolution was about 0.002 K; angular resolution was 7° - 14 times the size of the full moon). It did show that the actual density of the universe is very close to the critical density.



The most recent and complete research is from the Wilkinson Microwave Anisotropy Probe (WMAP for short), sponsored mainly by NASA. The WMAP results show that the universe is flat, meaning that the universe will expand forever at an ever decelerating rate. This evidence has ruled out the Big Crunch.


Adapted from:

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