Mankind ‘shortening the universe’s life’

November 30, 2007 at 4:40 pm (ΔΙΑΦΟΡΑ) ()

http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/11/21/scicosmos121.xml&CMP=ILCmostviewedbox

Forget about the threat that mankind poses to the Earth: our very ability to study the heavens may have shortened the inferred lifetime of the cosmos.That does not mean the field of astronomy does direct harm. A universe with a truncated lifespan may come hand in hand with the ability of astronomers to make cosmological measurements, according to two American scientists who have studied the strange, subtle and cosmic implications of quantum mechanics, the most successful theory we have. Over the past few years, cosmologists have taken this powerful theory of what happens at the level of subatomic particles and tried to extend it to understand the universe, since it began in the subatomic realm during the Big Bang.But there is an odd feature of the theory that philosophers and scientists still argue about. In a nutshell, the theory suggests that quantum systems can exist in many different physical configurations at the same time. By observing the system, however, we may pick out one single ‘quantum state’, and therefore force the system to change its configuration. They often illustrate their concerns about what the theory means in this respect with mind-boggling experiments, notably Schrodinger’s cat in which, thanks to a fancy experimental set up, the moggy is both alive and dead until someone decides to look, when it either carries on living, or dies. That is, by one interpretation (by another, the universe splits into two, one with a live cat and one with a dead one.) If we are part of the system, however, things get a bit trickier. Our observations do not change the system so much as help determine what state we find ourselves a part of. This latter facet, related to treating the universe as a quantum state, has puzzled theorists for some time. New Scientist reports a worrying new variant as the cosmologists claim that astronomers may have provided evidence that the universe may ultimately decay by observing dark energy, a mysterious anti gravity force which is thought to be speeding up the expansion of the cosmos. The damaging allegations are made by Profs Lawrence Krauss of Case Western Reserve University in Cleveland, Ohio, and James Dent of Vanderbilt University, Nashville, who suggest that by making this observation in 1998 we may have determined that the cosmos is in a state when it was more likely to end. “Incredible as it seems, our detection of the dark energy may provide evidence that the universe will ultimately decay,” says Prof Krauss. The team came to this depressing conclusion by calculating how the energy state of our universe – a kind of summation of all its particles and all their energies – has evolved since the big bang of creation 13.7 billion years ago. Some mathematical theories suggest that, in the very beginning, there was a void that possessed energy but was devoid of substance. Then the void changed, converting energy into the hot matter of the big bang. But the team suggests that the void did not convert as much energy to matter as it could, retaining some, in the form of what we now call dark energy, which now accelerates the expansion of the cosmos. Like the decay of a radioactive atom, such shifts in energy state happen at random and it is possible that this could trigger a new big bang. The good news is that theory suggests that the universe should remain in its current state. But the bad is that quantum theory says that whenever we observe or measure something, we can select out a specific quantum state from what otherwise would have been a multitude of states, each of which could have been selected out with varying probabilities. In this case however, it turns out that quantum mechanics implies that if an unstable system has survived for far longer than the average such system should, then the probability that it will continue to survive decreases more slowly than it otherwise would. Thus, as a result of making cosmological observations of dark energy, we may have confirmed that we are in a state where the probability of its survival may fall exponentially. “The intriguing question is this,” Prof Krauss told the Telegraph. “If we attempt to apply quantum mechanics to the universe as a whole, and if our present state is unstable, then what sets the clock that governs decay? “Once we determine our current state by observations, have we effectively determined that the clock is not running at late times? If so, as incredible as it may seem, our detection of dark energy may imply both an unstable universe and a short life expectancy.” Prof Krauss says that the measurement of the light from supernovae in 1998, which provided evidence of dark energy, may imply that the likelihood of its surviving is falling rapidly. “In short, cosmological observations may suggest that the quantum state of our universe is such that the probability of long-term survival is limited,” says Prof Krauss. And Prof Krauss stresses that resetting the cosmic clock was not something we have done to the universe but rather what our cosmologically observations may imply about our knowledge of the cosmic clock: “I did not mean to imply causality – namely that our measurement itself reduces the lifetime of the universe – but rather that by being able to make our measurement we may thus conclude that we may not be in the late decay stage.” This is not the only damage to the heavens that astronomers may have caused. Our cosmos is now significantly lighter than scientists had thought after an analysis of the amount of light given out by galaxies concluded that some shone from lightweight electrons, not heavyweight atoms. In all, the new analysis suggests that the universe has lost about one fifth of its overall mass. The discovery was made while trying to analyze clusters of galaxies – the largest cosmological structures in the universe – and is not the result of a cosmological diet but a major rethink of how to interpret x-rays produced by the clusters. Five years ago, a team at the University of Alabama in Huntsville lead by Prof Richard Lieu reported finding large amounts of extra “soft” (relatively low-energy) x-rays coming from the vast space in the middle of galaxy clusters. Although the atoms that emitted them were thought to be spread thinly through space (less than one atom per cubit metre), they would have filled billions of billions of cubic light years. Their cumulative mass was thought to account for as much as ten percent of the mass and gravity needed to hold together galaxies, galaxy clusters and perhaps the universe itself. But now the team has taken a closer look at data gathered by several satellite instruments, including the Chandra X-ray Observatory and have had a major rethink about these soft X-rays, the bottom line being that this chunk of the universe should now be discounted. The reason is that the soft x-rays thought to come from intergalactic clouds of atomic gas probably emanated from lightweight electrons instead. If the source of so much x-ray energy is tiny electrons instead of hefty atoms, it is says the team as if billions of lights thought to come from billions of aircraft carriers were found instead to come from billions of extremely bright fireflies. “This means the mass of these x-ray emitting clouds is much less than we initially thought it was,” said Dr. Max Bonamente. Instead, they are produced by electrons travelling almost the speed of light (and therefore “relativistic”). The discovery may also change what we think is the mix of elements in the universe because these soft x rays mask the tell tale x ray emissions of iron and other metals. “This is also telling us there is fractionally more iron and other metals than we previously thought,” said Bonamente. “Less mass but more metals.” Results of this research by Bonamente, Jukka Nevalainen of Finland’s Helsinki Observatory and Prof Lieu have been published in the Astrophysical Journal. The calculated mass of the universe ranges anywhere from 10 to the power of 53 kg to 10 to the power of 60 kg and is complicated by the fact that there is invisible matter we cannot see, called dark matter.

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