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Scientists have peered further back in time than ever before using instruments designed to search for a phenomenon predicted by Albert Einstein almost a century ago but not yet proven to exist.
An American observatory hunting for ripples in space and time called gravitational waves has produced its most significant results yet, despite not having directly detected any.
The “non-discovery” offers insights into the state of the Universe just 60 seconds into its existence. Previous research has been unable to look back in time further than about 380,000 years after the big bang.
Tycho's Supernova
The new window on the dawn of time has been opened by the Laser Interferometer Gravitational-Wave Observatory (LIGO), a network of three detectors that have been seeking evidence of gravitational waves since 2005.
These waves, which are believed to stretch and squeeze space and time as they pass, were predicted by Einstein in his theory of relativity. Violent events, such as a supernova explosion or the collision of two black holes, should make the biggest and most detectable waves. While their existence is accepted by astrophysicists, they have never been directly detected. LIGO has not yet found any gravitational waves either, and this has important implications for astrophysics and cosmology.
Certain theoretical models of what happened in the first moments of the cosmos predict that gravitational waves should be visible in LIGO’s data. As none have been detected, the “non-findings” narrow down possible explanations for the growth of the Universe.
The research, which is published in the journal Nature , also offers proof that gravitational-wave observatories will open up new horizons for astronomy, allowing scientists to examine aspects of the cosmos that have previously been hidden from view, such as supernovas and black holes. The first 380,000 years after the big bang are opaque to conventional telescopes that use the electromagnetic spectrum.
Professor David Reitze, of the University of Florida, the spokesman for the LIGO scientific collaboration, said: “Gravitational waves are the only way to directly probe the Universe at the moment of its birth; they’re absolutely unique in that regard. We simply can’t get this information from any other type of astronomy.”
According to standard theories, the big bang generated a flood of gravitational waves during the first moments of time, which still fill the Universe. The strength of these background ripples in space and time will have been determined by the structure of the young Universe.
LIGO’s failure to detect any signals from these waves in the particular frequencies that it can observe shows the maximum strength that this background can possibly have. The results, therefore, rule out several hypotheses about the early Universe that predict a stronger gravitational-wave background.
The findings should help to explain why and how the Universe acquired its “lumpy” structure, in which matter is concentrated into galaxies with huge areas of empty space in between.
They appear most consistent with the idea that this lumpiness evolved from random fluctuations in the temperature of the Universe when it was microscopic in size. These then became magnified as the Universe inflated.
Professor Jim Hough, of the University of Glasgow, who contributed to the research, said that there was about a one in eight chance that LIGO would detect gravitational waves directly in the next 18 months. If it does not, upgrades to the instruments, which should be ready in 2014, are almost guaranteed to pick them up.
The waves are difficult to detect because the ripples are extraordinarily small. Over the distance between Earth and the star Alpha Centauri — 4.3 light years — a gravitational wave would warp space by as little as the thickness of a human hair.
The LIGO detectors are designed to pick up such tiny perturbations using vast L-shaped instruments. There are two detectors in Hanford, Washington, one with arms two kilometers (1.2 miles) long and one with arms of four kilometers, and a four-kilometer facility in Livingston, Louisiana.
When a gravitational wave passes it will cause one arm to shrink while the other lengthens — by a distance of just one ten thousandth of the diameter of an atomic nucleus.
For a wave to be confirmed it must be observed by at least two detectors. Europe also has two detectors — the Virgo facility in Italy and the GEO600 facility in Germany.
By Mark Henderson, Science Editor
'Non-discovery' of space-time ripples opens door to birth of the Universe - Times Online
Scientists have peered further back in time than ever before using instruments designed to search for a phenomenon predicted by Albert Einstein almost a century ago but not yet proven to exist.
An American observatory hunting for ripples in space and time called gravitational waves has produced its most significant results yet, despite not having directly detected any.
The “non-discovery” offers insights into the state of the Universe just 60 seconds into its existence. Previous research has been unable to look back in time further than about 380,000 years after the big bang.
Tycho's Supernova
The new window on the dawn of time has been opened by the Laser Interferometer Gravitational-Wave Observatory (LIGO), a network of three detectors that have been seeking evidence of gravitational waves since 2005.
These waves, which are believed to stretch and squeeze space and time as they pass, were predicted by Einstein in his theory of relativity. Violent events, such as a supernova explosion or the collision of two black holes, should make the biggest and most detectable waves. While their existence is accepted by astrophysicists, they have never been directly detected. LIGO has not yet found any gravitational waves either, and this has important implications for astrophysics and cosmology.
Certain theoretical models of what happened in the first moments of the cosmos predict that gravitational waves should be visible in LIGO’s data. As none have been detected, the “non-findings” narrow down possible explanations for the growth of the Universe.
The research, which is published in the journal Nature , also offers proof that gravitational-wave observatories will open up new horizons for astronomy, allowing scientists to examine aspects of the cosmos that have previously been hidden from view, such as supernovas and black holes. The first 380,000 years after the big bang are opaque to conventional telescopes that use the electromagnetic spectrum.
Professor David Reitze, of the University of Florida, the spokesman for the LIGO scientific collaboration, said: “Gravitational waves are the only way to directly probe the Universe at the moment of its birth; they’re absolutely unique in that regard. We simply can’t get this information from any other type of astronomy.”
According to standard theories, the big bang generated a flood of gravitational waves during the first moments of time, which still fill the Universe. The strength of these background ripples in space and time will have been determined by the structure of the young Universe.
LIGO’s failure to detect any signals from these waves in the particular frequencies that it can observe shows the maximum strength that this background can possibly have. The results, therefore, rule out several hypotheses about the early Universe that predict a stronger gravitational-wave background.
The findings should help to explain why and how the Universe acquired its “lumpy” structure, in which matter is concentrated into galaxies with huge areas of empty space in between.
They appear most consistent with the idea that this lumpiness evolved from random fluctuations in the temperature of the Universe when it was microscopic in size. These then became magnified as the Universe inflated.
Professor Jim Hough, of the University of Glasgow, who contributed to the research, said that there was about a one in eight chance that LIGO would detect gravitational waves directly in the next 18 months. If it does not, upgrades to the instruments, which should be ready in 2014, are almost guaranteed to pick them up.
The waves are difficult to detect because the ripples are extraordinarily small. Over the distance between Earth and the star Alpha Centauri — 4.3 light years — a gravitational wave would warp space by as little as the thickness of a human hair.
The LIGO detectors are designed to pick up such tiny perturbations using vast L-shaped instruments. There are two detectors in Hanford, Washington, one with arms two kilometers (1.2 miles) long and one with arms of four kilometers, and a four-kilometer facility in Livingston, Louisiana.
When a gravitational wave passes it will cause one arm to shrink while the other lengthens — by a distance of just one ten thousandth of the diameter of an atomic nucleus.
For a wave to be confirmed it must be observed by at least two detectors. Europe also has two detectors — the Virgo facility in Italy and the GEO600 facility in Germany.
By Mark Henderson, Science Editor
'Non-discovery' of space-time ripples opens door to birth of the Universe - Times Online
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