Mystery of `Mass' remains, amongst many others. The European Organization for Nuclear Research (Cern), based at Geneva in Switzerland, is the world's largest lab dedicated to particle physics. It has a massive underground complex in which matter - atoms and their parts - can be smashed together at high speed. Wednesday's celebrations will be marked by a 27km-long ring of light. The floodlights in this circle will draw the circumference of the tunnel to be used for the Large Hadron Collider (LHC), a new experimental tool that will collide protons and other particles at very high energies. Scientists believe this machine, due to come online in 2007, will enable them finally to understand why all the things we can see and touch have mass. This is a big gap in our description of the Universe - and it is not the only one. At the moment, the so-called Standard Model of particles and their interactions gives us only a glimpse into the true nature of what one might call "normal matter" and the forces that hold it together. Measurements of far-distant exploding stars, for example, have led physicists to the knowledge that the cosmos is actually dominated by a mysterious "dark matter" and "dark energy". A full explanation for these phenomena may be many decades away. Last Updated: Wednesday, 29 September, 2004, 08:27 GMT 09:27 UK http://news.bbc.co.uk/1/hi/technology/3698578.stm ---------------- Hubble's deepest shot is a puzzle Scientists studying the deepest picture of the Universe, taken by the Hubble Space Telescope, have been left with a big poser: where are all the stars? The picture shows faint galaxies whose stars were shining just a few hundred million years after the Big Bang. But the image's revelation that fewer stars than expected were being born at this time brings into question current ideas on cosmic evolution. "Our results based on the Ultra Deep Field are very intriguing and quite a puzzle," says Dr Andrew Bunker, of Exeter University, UK, who led a team studying the new data. "They're certainly not what I expected, nor what most of the theorists in astrophysics expected." At issue is the timing of key events in the earliest stages of the Universe. Scientists believe the super-hot conditions that existed after the Big Bang eventually cooled sufficiently to allow protons, neutrons and electrons to form neutral atoms of hydrogen and helium. The transition also saw the cosmos plunge into darkness - the stars that could provide the light had yet to ignite. When they did, from infalling clouds of hydrogen and helium, the "dark ages" gave way to what has been dubbed the "cosmic renaissance". What is more, these hot, young stars produced intense ultraviolet radiation which "fried" the gas in the Universe - to produce the diffuse intergalactic plasma detectable today. But the Hubble Ultra Deep Field presents a problem for this story. When Bunker and colleagues measured the rate of star formation in the image's earliest galaxies, they found it was insufficient to create the levels of radiation needed to produce the intergalactic plasma. "There is not enough activity to explain the re-ionisation of the Universe," Dr Bunker told the BBC. "Perhaps there was more action in terms of star formation even earlier in the history of the Universe - that's one possibility. "Another exciting possibility is that physics was very different in the early Universe; our understanding of the recipe stars obey when they form is flawed." The Hubble data was supported by observations with the Keck telescope in Hawaii and the Gemini telescope in Chile. It has to be said, the Bunker assessment is not totally shared by all groups working in this area. Four other teams investigating the UDF data have put their own very different interpretations on what they see in the historic image. For example, the team headed by Dr Massimo Stiavelli, from the Space Telescope Science Institute, in Baltimore, US, believes the populations seen may well have been able to re-ionise the Universe, provided the stars were bigger and possessed much fewer heavier elements than those we see today. But what all astronomers believe is that to solve this puzzle, they need enhanced space-borne detectors that can better describe the long-wavelength light seen in the most distant stars. "For the first time, we at last have real data to address this final frontier - but we need more observations," said Dr Richard Ellis, of the California Institute of Technology. Last Updated: Thursday, 23 September, 2004, 13:04 GMT 14:04 UK http://news.bbc.co.uk/1/hi/sci/tech/3680944.stm -------------------------------------------------- To see if they're telling the _whole_ truth check "blind science" in Google (and links) -------------------------------------------------- FURTHER REFERENCES GO - "search perceptions" - in SEARCH-ENGINE file-ID www.perceptions.couk.com/uef/lack.txt