1998 Bonestell Lecture presented by Dr. Kai Woehler 1998 Bonestell Lecture presented by Dr. Kai Woehler
HOW DOES NATURE CHOOSE BETWEEN ALTERNATIVE UNIVERSES? |
| EINSTEIN'S
UNIVERSE About the Big Bang and Black Holes THE DEEP STRUCTURE OF MATTER AND FORCES About Elementary Particles and Forces SYMMETRIES - PRINCIPLES OF DESIGN About the Search for the Holy Grail--The Theory of Everything STRINGS AND STRINGY SPACE About Hidden Dimensions OUR UNIVERSE--A VERY SPECIAL PLACE About Worlds Hospitable to Life THE MULTIVERSE About the Origin by Natural Selection CONCLUSION |
| In 1687 Isaac Newton's great work
"Mathematical Principles of Natural Philosophy" was published. In this work
Newton gives the "Law of Universal Gravitation". This discovery really launched
modern science. The applications of this law to the description of planetary motion in a
heliocentric solar system were enormously successful. The accuracy of predictions made
with these laws is extremely high and gives answers completely sufficient in most
practical problems when the velocities of the moving objects are relatively small compared
to the velocity of light. According to this model, planets are kept in their orbits around the sun by an invisible gravitational "tether", somewhat like a stone is kept swinging around your hand holding the stone by a string What Newton's law does not explain is, what this invisible tether is and how it can act instantaneously over such large distances. |
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| Nearly 220 years later, in 1905 Einstein
published his SPECIAL THEORY OF RELATIVITY. Most of modern physics rests now on this
theory. The content of this theory has been confirmed in many thousends of observations in
electromagnetic, atomic and nuclear phenomena. The theory's main statement is: NO ACTION
CAN BE TRANSMITTED FASTER THAN THE SPEED OF LIGHT. Given this restriction Newton's law of
gravitation cannot be complete because it makes no allowance for the time it takes for the
gravitational action, whatever it is to propagate from the sun to the planet to influence
its motion. In 1916 Einstein published his GENERAL THEORY OF RELATIVITY. In this theory Einstein gives a totally new description of gravitation, which at the same time corrects the problem about transmission of the force and the question about the nature of the force. In this theory in fact the gravitational action is not due to some mysterious force acting invisibly over a large distance. Instead, large masses, like the sun and other stars CURVE THE SPACE in their vicinity. Planets, then, move in closed orbits around the central sun due to that curvature of space, like marbles moving in orbits in a punch bowl. Einstein's Theory makes two major predictions that have shaped the new view of our universe. THE FIRST MAJOR PREDICTION OF EINSTEIN'S GENERAL THEORY OF
RELATIVITY In Einstein's theory however, SPACE ITSELF EVOLVES IN TIME. SPACE IS DYNAMIC. The space that constitutes our universe changes in time. The theory gives models of evolving universes. The simplest class of such models are the so called BIG BANG MODELS. |
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| In these models space evolves, starting
from a pointlike entity, around 15 billion years ago and is expanding in size. This expansion can :
Which of these outcomes is realized in our universe depends on the mass-energy concentration in the universe. The present accumulated observational facts are not conclusive in that respect. Recent data appear to favor an open ever expanding universe. Very recently there has been some evidence that might point toward a universe the expansion of which is even accelerating, perhaps driven by a so called cosmological constant in the model, which in modern interpretation is due to a peculiar form of "tension" of space which has its origin in quantum fluctuations, a concept to which we will return later. There arose many questions about the nature of this BIG BANG. If the universe with all the mass we see now started 15 billion years ago from a point like entity then, how did it get that way? What was before that? Was the universe perhaps expanded before, recontracted like the recontracting model, down to very small size and then bounced back out ward like a tennis ball that is collapsing with the earth bounces back outward? And if so, how is such bounce possible? Will the laws of physics and Einstein's theory allow such bounce? An answer was given by STEVEN HAWKING. He is one of the great minds of the second half of this century. Severely crippled physically by ALS his mind has been a major force in our understanding of the implications of Einstein's theory. |
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| In the late 1960's, together with the
equally brilliant ROGER PENROSE, he proved the so-called SINGULARITY THEOREMS. These
theorems say in essence: if the universe indeed follows the laws formulated by Einstein's
theory of GENERAL RELATIVITY then, a configuration of a large mass concentrated in a small
volume of space as suggested by the BIG BANG models MUST HAVE SINGULARITY AT THE
BEGINNING. A SINGULARITY means density of mass and curvature of space become infinite.
There is no before. There is no possibility in the theory a bounce from an earlier
contraction. There is no way that mass from a previous contraction could have whipped past
each other and bounce back outward. That means: THE UNIVERSE HAD A DEFINITE BEGINNING. In physics it is generally believed that, when a theory predicts singularities the theory is somehow incomplete. It needs modifications in those description of events that lead to singularities. We will see later where that belief leads to. THE SECOND KEY PREDICTION FROM EINSTEIN'S THEORY OF GENERAL
RELATIVITY Black holes were conjectured first in 1783 by John Mitchel of Cambridge. In 1916, immediately after the publication of Einstein's theory Karl Schwarzschild applied the theory to the structure of the space near massive stars. He found that a mass sufficiently compacted would have such a large gravitational pull at its surface, or in Einstein's language, the curvature of space would be so large that every object, however large a velocity given initially would have its trajectory curved back onto the surface of that object. Nothing can ever escape from it, NOT EVEN LIGHT. The relevant quantity on which to decide whether a massive object of a given size is a Black Hole or not is the "ESCAPE VELOCITY." |
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| This escape velocity depends on the
mass and the size of the object. When this velocity is larger than the velocity of light
then the object is a Black Hole. Another way of saying this is: when an object of a given
mass is compacted to a size smaller than the so called "EVENT HORIZON", then the
object is a Black Hole. If the solar mass were compacted to less than 3. 6 miles across,
it would be a Black Hole. If the earth were compacted to a size less than 2/3 of an inch
across, it would be a Black Hole. Until the 1960's it was believed that such extreme mass
concentrations would not occur in nature. Since then it is known, that stars in their final stages of nuclear burning, when the nuclear fuel in their interior is exhausted must contract and become small objects. They become White Dwarfs or Neutron Stars, depending on their mass. If the contracting star remnant has a mass larger than 2. 3 solar masses then the contraction will continue. There is no known physical principle that would indicate that this contraction would ever stop at some small size. From all we know at this time contraction would continue. TO WHAT ? |
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| In 1970 Steven Hawking made his second
major discovery. He investigated the Black Hole solutions that had emerged from Einstein's
Theory to see what these say about collapsing large masses. The result was that based on
Einstein's theory the final state of a mass contracting down to inside that Event Horizon
is that of a SINGULARITY, of a point with infinite mass concentration and curvature of
space, a knot in the fabric of space and time. At the Singularity space and time loose
their usual classical meaning. There is no path beyond the singularity. *All these findings connected with Einstein's Theory of General Relativity raised many questions.
|
THE DEEP STRUCTURE OF MATTER AND FORCES
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