The universe began with a turbulently charged explosion from a minuscule core, thrusting rap­idly toward its outside limits; thus, the life cycle of the cosmos commenced. This cycle continues today. The three possibilities of this expanding universe are that the universe is “open,” “flat,” or “closed.” An open universe means that the uni­verse will continue to expand at an ever-increasing rate forever. If the universe is flat, then the expan­sion rate will slow down, but the universe will never collapse. Instead, all movement will end in an eternal frozen waste. If the universe is closed, then it will expand only until it reaches a certain point, at which the process will be reversed and the universe will shrink until it collapses.

In the universe, dark energy overwhelms every­day gravity and outweighs the visible universe by a factor of 10 to 1. If the big bang model of the uni­verse is right, the universe is expanding, and if there is enough mass in the universe, at some point the expansion will halt and gravitational forces will cause the universe to collapse on itself. However, if there is insufficient matter, the universe will expand forever and will eventually cool off completely to die a slow death. This would be the end point of a closed universe. If, and only if, there is sufficient mass to halt the expansion, or Hubble flow, move­ment will be reversed. Instead of galaxies moving rapidly outward, they would move back toward the center. If the existing diffusion velocity of the universe, in units of kilometers per second per mega parsec, slows in relation to the apparent velocity of recession of a galaxy to its distance from the Milky Way, this would mean the universe is aging. If this end result occurs, the big crunch would create the conditions for a new big bang.

It had been postulated that the universe began about 15 billion years ago with a big bang, starting from an infinitesimally small point of “not anything at all” in the empty space of “nothing” in which matter and time did not exist. A very small point of matter appeared and then exploded and began expanding outward at an ever-increasing tempo. This was only the beginning, and it is still expand­ing today. As the universe expands, more and more matter is shaped into more complex forms. If the universe is a flat universe, then everything will stop and die in cold empty darkness. If it is a closed universe, then it will collapse in on itself.

The big crunch theory, as outlined by Alexander Friedmann (1888-1925), states that if the density of matter in the universe is sufficiently large, gravita­tional forces between the matter will eventually cause the universe to stop expanding; then it will start falling back in. It will eventually end in a second cataclysmic event such as the big bang. The big crunch theory is completely dependent upon whether or not matter is dense enough in the universe. If astronomers correctly calculated the quantity of mat­ter in all visible stars and galaxies, this would be too little to stop expansion, let alone start contraction.

According to the theory, if there is enough mat­ter in the universe, then the gravitational forces of all this matter will stop expanding and begin to collapse. Ultimately, this will lead to a new big bang after enough energy is trapped in an infini­tesimally small point. This theory requires that enough dense matter exists in the universe. Unless a very large amount of dark matter is discovered, the big crunch will not happen.

It appears that the light from stars is in fact bending around what may be blackbodies. These might be the dark matter necessary for contrac­tion. There may also be billions of loose stars between galaxies. There are billions of galaxies in galaxy clusters and billions of these clusters in strings of clusters, all in a tiny envelope in empty space. Each galaxy has not only visible matter but dark matter as well. The question is, in what quan­tity? Dark matter may also comprise most of the universe, but all we can detect is the light matter.

When the expansion of the universe ceases, many strange things will happen. Because of grav­ity, galaxies will begin crashing into one another. The red shifts of expansion, first noted by astrono­mer Edwin Hubble, will be replaced by blue shifts of contraction. The spaces between photons will be condensed. Wavelengths will also be shortened. The result will be an overall increase in tempera­tures of radiation fields.

Temperatures will average at least 300 Kelvin (K). Galaxies will increasingly crowd the night sky until there is no difference between night and day. Temperatures will continue to rise until the aver­age temperatures will reach 1010 K, just seconds before the big crunch. All the matter in the uni­verse will be concentrated into a point of singular­ity so tiny that a new big bang will soon follow.

The countdown is on for this phenomenon. If the big crunch theory is correct, the universe will come to a standstill in about 750 quadrillion (7.5 x 10¹⁷) years. About the same amount of time will pass, maybe a little longer, before the final collapse.

Wild as it may seem, it is no more outrageous a theory than the other two major competing theo­ries of the end of the universe. With all the com­bined matter of the universe, the expansion would tend to slow down considerably. If the drag on this expansion is sufficiently powerful, expansion will stop and all motion will cease. If there is enough mass, then the expansion will reverse itself and will collapse. Only if mass is insufficient will the cos­mos continue getting bigger, exactly for an eternity, if not longer.

See also Big Bang Theory; Cosmology, Cyclic; Singularities; Closed or Open Universe; Contracting or Expanding Universe; End of Universe,

Further Readings

Castelvecchi, D. (2006). A view of the universe before the big bang. New Scientist, 190, 15.

Corwin, M., & Wachowiak, D. (1985). Discovering the expanding universe. Astronomy, 13, 18-22.

Craps, B. (2006). Big bang models in string theory. Philadelphia: Institute of Physics Publishing.

Gallmeier, J., Grilley, D., & Oston, D. W. (1996). How old is the universe? Sky and Telescope, 91, 92-95.

Goodstein, D. (1994, September 19). The big crunch. Paper presented at the 48th NCAR (National Center for Atmospheric Research) Symposium, Portland, OR. Retrieved September 1, 2008, from www .its.caltech.edu/~dg/crunch_art.html

Ikin, K., Sietzen, F., & Smith, P. (2003). Crunch time for runaway universe. Ad Astra, 15(1), 10. Retrieved June 24, 2008, from www.nss.org/adastra/ volume15/v15n1/contents/miscv15n1.htm.htm

Maddox, J. (1995) Virtue in now-antiquated textbooks: Tolman’s relativity, thermodynamics and cosmology. Nature, 375(653), 445.

Martinec, E. J., Robbins, D., & Savdeep, S. (2006). Toward the end of time. Journal of High Energy Physics, 8, 25.

Tolman, R. C. (1987). Relativity, thermodynamics and cosmology. New York: Dover.

Trefil, J., & Kruesi, L. (2006). Where is the universe heading? Astronomy, 34(7), 36-43.