Will stars ever get together? If they do will, an
explosion happen which will start the universe all over again?
The theory of the "Big Crunch" has been proposed before and is a very attractive
theory - it would mean that the universe is inherently infinite (it goes through a
continuous series of birth, death and rebirth).
However, we currently do not have data to support this theory. In order for the Big
Crunch to occur, there must be sufficient mass in the universe to produce the
gravitational attraction to get galaxies and stars moving toward each other. Right now,
we are missing about 2/3 of the required mass to start the Big Crunch.
Also, there is some evidence that not only is the universe expanding, but it is
expanding at an accelerating rate. This surprising data makes the Big Crunch more
of an improbability.
We may yet find the needed mass in dark matter or singularities, but for now we have
to go by what the data says and say that the Big Crunch is unlikely.
Greg (Roberto Gregorius)
Thanks so much for your good question. Your student has a point, although he or she
is confusing stars with superclusters of galaxies, which are several orders of
magnitude bigger and more powerful. IF (there is evidence to the contrary) the
pulsating theory of the Universe is correct, then at some point in the far off in
the future, the expansion will slow, stop, then reverse itself to a "big crunch."
Within a galaxy, stars do not move towards each other, just orbit the center of the
David H. Levy
First of all, it is not entirely certain that the Universe will NOT eventually come
together into a "Big Crunch." That is one possible end for the Universe.
That said, his premise is incorrect. Most of the galaxies are moving AWAY from each
other right now. For them to start moving together, they first must slow down, stop,
and then reverse direction. Current observations make cosmologists doubt that there
is enough gravity for that to ever happen.
I am not a cosmologist myself, so I cannot comment on what would happen to the universe
after a Big Crunch.
Richard Barrans, Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming
First, a short lecture to your student. What you are proposing is NOT a "theory". It
is a "conjecture", or a "speculation". A "theory" is a set of principles (the fewer,
the better the theory) that explains a wide variety of experimental past observations
and makes predictions about what will be observed by experiments, not yet done,
regardless of the topic of the "theory". Two "classic" examples are Maxwell's equations
of electromagnetism, and Darwin's treatment of the evolution of species. A "theory" is
the highest form of recognition scientists give to the treatment of a topic.
Note however, "conjectures" are not bad. They are the "stuff" that laws and theories
are made of. The "conjecture" or "speculation" makes no promises. They just say, "Let
us run this up the flag pole and see if anyone salutes."
Two recent examples:
"Faster Than the Speed of Light" by Joao Magueijo. He poses the question: "What if the
speed of light (in a vacuum) is not constant, but can travel faster/slower than its
traditional value, which in traditional physics is a "fixed" number. Be aware that
the author is not some "off the wall" nut. He is professor of theoretical physics
at Imperial College, London. He has been visiting scientist at the University of
California, Berkeley, and received his doctorate in theoretical physics at Cambridge
University. So his credentials are impeccable. When someone of that stature asks the
question, "What if???" scientists (sometimes not very friendly scientists) take notice.
The conjecture remains neither supported or rejected at the present time, but the
point is that it challenges thinking.
"The Deep Hot Biosphere" by Thomas Gold is another example. He was an acclaimed
astrogeologist, cosmologist, astronomer, among other fields -- a member of the National
Academy of Sciences (U.S.). He taught at Cambridge (U.K.), Harvard, and Cornell. He
died a few years ago.
He speculates that traditional models for the generation of "fossil" fuel (oil, coal)
are incorrect, and deep within the Earth's surface there is methane (CH4) in large
Why have I gone into this detail on an example that is not "on target"? The reason is
"What are the data?" The data to date, is that the Universe is expanding. This is pretty
well established by raw experimental data -- look up Doppler shift -- for details. But
there is a problem.
When the distance between galaxies, which in current theory is age, is not expanding as
fast as current models (note I did not use the term "theory") of the Universe predict.
So your student's conjecture that stars, and therefore collections of stars (i.e.)
galaxies, are getting closer, is not supported by the best current data. What appears
to be happening is that the RATE of expansion at long distances (i.e.) older time is
not as fast as the "Standard Model" predicts.
That is not a small problem!! I think it would be more productive to help explore your
student's conjecture. I know that means a lot of work for you.
"I know it is not possible but I do not have a point to argue back to his theory and
prove him wrong. Please give me a point that I can argue back with." I cannot give you
such a point to "prove" him wrong. His data, stars approaching one another, does not
seem to fit our best present data, but do not make it a contest between your student
and you, right or wrong. Rather, make it an opportunity to explore.
For example: What stars are colliding -- there have to be many to support your student's
conjecture. How does his conjecture address the experimentally well established
expanding Universe? If stars collide, their composite mass is of the order of the sum
of the two. Can the "lost" mass be observed? The collided stars have a mass that is
roughly the sum of the two. Are there any effects on neighboring stars? My point,
possibly too detailed, is to turn the problem into an exploration, not a confrontation.
Our view of the Universe is on rather debatable grounds right now, so don't become
too dogmatic. The "answer" is not on the table just yet. Your student may be right!!
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Update: June 2012