Page 146 - Encyclopedia Of World History Vol V

universe, origins of 1923

second of its existence, the universe expanded faster these elements that newer and more complex structures,
than the speed of light. From the size of an atom it blew such as planets and living organisms, can eventually be
up to many times the size of our solar system. Soon after constructed, using the energy of gravity and the heat
this phase of rapid expansion (known as “inflation”), par- energy pouring out of stars.
ticles of matter and antimatter collided and annihilated Is this story true? It is by far the best story available at
each other, leaving a huge amount of energy and a tiny present, but it is far from complete. Cosmologists wres-
residue of matter. As the universe expanded, it cooled, tle with the problem of the very earliest moments, frus-
and as it cooled different forms of energy and matter sep- trated that they seem to have no way of even testing
arated out from the initial flux. Gravity appeared, then hypotheses about the moment of origin. And even the
electromagnetism, together with the strong and weak tiny fraction of a second after the beginning of the uni-
forces that shape the behavior of atomic nuclei. Quarks verse presents some complex puzzles. Above all, physi-
appeared and, within two or three minutes, the first pro- cists and cosmologists wrestle with the problem of the
tons and electrons. relationship between gravity and the other fundamental
For almost 400,000 years, the universe was still too forces of modern physics.The relationship between elec-
hot for protons and electrons to combine into atoms, so tromagnetism and the “strong” and “weak” nuclear forces
that the entire universe crackled with electrical energy. is now largely understood, but how gravity fits in remains
Then, about 380,000 years after the big bang, the uni- unclear. New observational techniques (including the
verse cooled sufficiently for protons and electrons to use of satellite-based observatories) and new computa-
come together to form the first atoms, of hydrogen and tional techniques have generated a mass of new data
helium. Matter became electrically neutral, and energy about the early universe, and some of this torrent of new
and matter went their separate ways, releasing the flash information has forced cosmologists to rethink parts of
of energy that is detected today as cosmic background the story. In the late 1990s, for example, evidence from
radiation. The next significant event occurred some the study of very remote galaxies showed that the rate of
200 million years after the big bang, when clouds of expansion of the universe is not slowing under the grav-
hydrogen and helium began to collapse, drawn together itational pull of the matter in the universe, as most cos-
by gravity, until their centers heated up to about 10 mil- mologists had assumed. On the contrary, it is speeding
lion° C. At that point hydrogen atoms started fusing to up.What this means remains uncertain, though most cos-
form helium atoms, releasing a colossal amount of energy mologists believe it may be evidence for the existence of
in the process (in nuclear reactions identical to those an antigravitational force that had already been antici-
within a hydrogen bomb).The first stars were born.The pated in some of Einstein’s work. Even more disturbing
release of energy at the center of a star checks the gravi- is the slow realization, from studies of the movement of
tational collapse of the cloud of matter from which it is galaxies, that there exists a lot more “stuff” out there than
formed and creates a more or less stable structure that we can detect. Currently, it seems likely that the matter we
can pump out huge amounts of energy for billions of can observe accounts for no more than about 5 percent
years. Stars play a vital role within the modern creation of the mass of the universe, while some 25 percent of its
story because they supply the energy that sustains life on mass probably consists of matter (known, appropriately,
earth. Furthermore, in their dying stages some of them, as “dark matter”) that we cannot yet detect or explain, and
particularly the very largest, can generate temperatures perhaps as much as 70 percent is accounted for by forms
high enough to fuse nuclei together into more and more of energy (known as “dark energy”) that we cannot yet
complicated elements.When the very largest stars die in detect or fully explain.To be uncertain about almost 95
violent explosions known as supernovae, all the remain- percent of the contents of the universe is a serious embar-
ing elements of the periodic table are created. It is from rassment to modern cosmology.