By Roger Highfield, Science Editor
Last Updated: 12:01am GMT 21/11/2007
Forget about the threat that mankind poses to the Earth: our activities may be shortening the life of the universe too.
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The startling claim is made by a pair of American cosmologists investigating the consequences for the cosmos of quantum theory, 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 we change things simply by looking at them and theorists have puzzled over the implications for years.
They often illustrate their concerns about what the theory means 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.)
New Scientist reports a worrying new variant as the cosmologists claim that astronomers may have accidentally nudged the universe closer to its death 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 caused the cosmos to revert to an earlier state when it was more likely to end. "Incredible as it seems, our detection of the dark energy may have reduced the life-expectancy of the universe," Prof Krauss tells New Scientist.
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.
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But the bad is that quantum theory says that whenever we observe or measure something, we could stop it decaying due what is what is called the "quantum Zeno effect," which suggests that if an "observer" makes repeated, quick observations of a microscopic object undergoing change, the object can stop changing - just as a watched kettle never boils.
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. By resetting the clock, the survival probability would now once again 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 reset the clock? If so, as incredible as it may seem, our detection of dark energy may have reduced the life expectancy of our universe."
Prof Krauss says that the measurement of the light from supernovae in 1998, which provided evidence of dark energy, may have reset the decay of the void to zero - back to a point when the likelihood of its surviving was falling rapidly. "In short, we may have snatched away the possibility of long-term survival for our universe and made it more likely it will decay," says Prof Krauss. Not all agree, since his interpretation hinges on one of the issues at the heart of quantum theory - do you need people to do the observing?
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.
