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Unicamp Newspaper - May 2000

page 10

SEMINAR
Discovery news
of the Universe

What would have happened zero seconds into the history of the world? Professor Steiner, from USP, talks about the fascinating frontiers of astrophysics

AEven before science fiction books and cinema populated our imagination with stories about interplanetary travel, extraterrestrial beings and collisions of gigantic meteors with the Earth, the mysteries of cosmos arouse man's curiosity and lead him to seek, in the immensity of space, the answers to his own terrestrial existence. From celestial observations with the naked eye in Antiquity to research with gigantic telescopes at the beginning of the new millennium, the development of science has allowed man to unravel the mystery that still challenges him: the moment of the creation of the Universe, in the form of a great explosion (the Big Bang), 15 billion years ago. More than that: with the scientific tools available today, it is even possible to predict how everything could end.

"We can already know with certainty that in the three minutes of the Universe's life, gases such as helium and hydrogen were formed, resulting from the recombination of particles of energy generated at the moment of creation ", explained professor João Steiner, to a dazzled audience at Unicamp.

Before that, in a measure of time that scientists call "10-43 seconds" – something compared to microseconds after the Big Bang, time, space and energy emerged. "The key to discovering what the Universe is like is in understanding what happened at zero seconds, at the beginning of evolution."

Professor at the Department of Astronomy at IAG (Astronomical and Geophysical Institute) at USP and Secretary of Monitoring and Evaluation at the Ministry of Science and Technology, Steiner addressed the origin of the Universe in his lecture opening of the CGU (University General Coordination) seminars.

According to him, the extraordinary development of astrophysics in the last 100 years has allowed us to overturn theories and myths, helping to locate our planet in time and space, as well as helping to expand the ability to scientifically explain the origin and structure of the Universe.

Eternal expansion or collapse? – The paradigm that astronomers and astrophysicists are currently focusing on is that of the expanding Universe. What they want to know is the extent of this phenomenon.

Until 1917, scientists believed in the Steady State Theory, that is, in a Universe that was similar in all directions and unchanging in time. However, in the 30s, astronomer Edwin Powell Hubble demonstrated that galaxies - such as the Milky Way, where the Earth is located - are moving away from each other. If this occurs, it is because in the past, perhaps 10 billion years ago, they should have been closer and closer, concentrated in a single point, and expanded with the Big Bang.

The accidental discovery of microwave radiation from the bottom of the Universe, in 1964, also contributed to giving credence to the theory of the birth and expansion of the Universe from the Big Bang. According to the radio astronomers who discovered it, the radiation – captured by domestic television sets when tuned channels go off the air – can be interpreted as the electromagnetic signal remaining from the moment of creation.

"What produced the Big Bang is a question we probably won't be able to answer", ponders Steiner. But science risks two possibilities for the fate of the Universe based on the expansion that the great explosion caused: either it will continue expanding forever or it will stop, if the gravitational attraction between the celestial bodies becomes weaker. make it strong enough to stop the expansion. In this hypothesis, the Universe will contract and collapse, in a process opposite to that of its creation.

Time travel – When science is certain of the expansion or collapse of matter, it will also have foundations to finally explain what the Universe is like. There are two most likely models: if the Universe's tendency is to continue expanding forever, it is because it is open and infinite; If the process is a reversal, scientists say, the Universe is closed, in the shape of a sphere, which would allow a spacecraft, which always traveled in a straight line, to return to the starting point, in a kind of of time travel.

"We will never rest in advancing the frontier of knowledge. This is the scientist's vice", said Steiner, when commenting on astrophysics' efforts to unravel the mysteries of the cosmos.

One of the fronts of science in the search for new information is the tracking of increasingly distant galaxies using large telescopes, with mirrors eight meters in diameter.

Brazil, as revealed, participates in two international projects, Gemini and Soar, which will use this type of equipment to study galaxies up to 14 billion light years away from Earth. There are three telescopes, one in Hawaii and the other in the Chilean Andes, which required investments of US$ 184 million and have image quality ten times higher than that of the Hubble space telescope.

The results that could be obtained excite researchers: to date 100 thousand galaxies have been mapped. With the new telescopes they hope to be able to map up to a million of them. (PCN)

The Earth, a peppercorn
The origin of astronomy is practically confused with that of human civilization itself. From observation of the stars, the Chinese were able to draw up the calendar of a complete year several centuries before the birth of Christ. They also recorded in reliable notes the passage of comets, meteors and meteorites. Babylonians, Assyrians and Egyptians were other people endowed with astronomical knowledge in the Pre-Christian Era, capable of predicting the order of movements of celestial bodies.

From the first theories in Antiquity to sending space probes to find life forms on other planets, man believed in different models of the Universe. For example: the initial belief that pointed to the Earth as the center of the Universe, Geocentrism, changed when Nicolaus Copernicus proposed a heliocentric cosmological model, based on the centralization of the Universe around the Sun.

The invention of large telescopes and advances in the field of photography were decisive allies in the formulation of theories that made man definitively abandon the central position he imagined he would occupy in the Universe.

In fact, our location is insignificant. A simple analogy allows us to understand how microscopic our planet is. If the Sun could be compared to the size of a football, the Earth would be the size of a peppercorn.