Unit 1:  Our place in the Universe                                          1   2   3   4  

2.5. The future of the Universe

Not too much time ago, cosmologists thought that the future of the Universe only depended on its density of mass-energy and they admitted two possible destinies: the Big Chill and the Big Crunch.

But recently the discovery of the dark energy, responsible for the acceleration in the expansion of the Universe, has presented a third possible scenario: The Big Rip.

• Big Chill

        It is an open universe, where the amount of mass-energy is insufficient

        and it does not reach the critical density required for gravity to slow down

        the expansion.

        In such universe the space would expand endlessly although at slow rhythm,

        braked by gravity. All, the content of the Universe would be condemned

        to a cold and slow death in the middle of the most absolute darkness.

• Big Crunch

       It is a closed universe where the amount of mass-energy is enough to exceed

       the critical density.

       Gravity will be so strong that the expansion will be first slowed down and then

       will begin an accelerated contraction until to reach the initial point of

       the singularity.

       This hypothesis opens the possibility of a “pulsating” universe that undergoes

       infinite cycles of expansion and contraction.

• Big Rip

        It is a universe close to the critical density, but in which the repulsive force

        of the dark energy exceeds gravity.

        This would provoke such an accelerated expansion than in a determinate

        moment the universe would burst and would rip. Matter will be destroyed

        and time will stop.

2.8. The graph on the left represents the possible futures of our universe.

a.   Identify each one.

b.   Which of them seems to be the most probable according to the recent discoveries about dark energy?

c. Which of them is related to the Pulsating Universe hypothesis?