University of Barcelona

Are we alone?

Source: Investigación y Ciencia
Published on 01.12.2017


This month of December, the Spanish version of Scientific American (Investigation y Ciencia) features the research of ICREA-ICCUB professor Raul Jimenez in its front page with an article about cosmic explosions and the habitability of other planets in the Universe.

Cosmic Explosions, life and the multiverse

Raul Jiménez
Investigación y Ciencia, December 2017, Nº 495

Apparently, the existence of complex life in the cosmos is strongly threatened by a certain type of stellar explosions. This could explain the Fermi Paradox, and it suggests we could be living in a very special universe.

In 1950, the great Italian physicist Enrico Fermi posed the following question. If our galaxy has about 100,000 million stars, and supposing our Solar System is not an exception, the number of planets in the Milky Way containing life should be exorbitant. In such a case, in some of these planets intelligent life should have developed and sooner or later, it should have spread all over the Galaxy. Why have not we detected any extraterrestrial civilization, then? Why have they not had contacted us? ¿Where are they?

This reasoning is known as “Fermi Paradox” and, although it has been a source of all kind of hypotheses, to date we lack a satisfactory explanation. In recent years, however, we have learnt that complex life in the universe could be much less common that it was thought, due to a particular type of cosmic cataclysm: gamma ray bursts. These stellar explosions are among the most violent phenomena in the universe, and their devastating effects can be felt at distances of thousands of light years. Although they were observed for the first time in the last century 60’s, only recently have we started to discern up to which point its proliferation can compromise the existence of life in whole galaxies.

By themselves, gamma ray bursts could help to explain the Fermi Paradox. However, the consequences seem to go beyond. A thorough analysis reveals that both the number and the distribution of these stellar explosions appear to be closely related to the fundamental laws of our universe. A slightly different cosmos from the one we observe would either lack galaxies (and thus, planets and life) or it would be rich in them, but they would be hostile to complex life due to, precisely, an excess of gamma ray bursts.

This result plausibly confirms, by means of an astrophysical phenomenon unexplored so far, that we are living in a universe too refined for complex life to exist, at least in the form we know it on Earth. All this, coupled to some statistical arguments, could be telling us something about one of the more controversial ideas in today’s science: the hypothesis of a multiverse. The reasoning that urges us to link the presence of life in the cosmos with gamma ray outbursts and the existence of many universes connects Physics at a wide variety of scales, from quantum laws and Chemistry to astrophysical processes and the structure of the Universe as a whole.

Read complete article (in Spanish)