Each mile of Earth's surface is compressed by one-thousandth the diameter of an atom by the strongest waves created by black holes. It is hard to imagine how small the ripples are in space-time. Physicists spent decades building and fine- tuning an instrument called the Laser Interferometer Gravitational-Wave Observatory (LIGO), which they got in 2016
The landscape of invisible black holes is being unfurled. That is only part of the story.
Some wave detectors are getting some work.
Rana Adhikari is a physicist at the California.
Researchers are looking for ways to use the detectors to search for dark matter, the nonluminous stuff that holds galaxies together.
In December, a team led by Hartmut Grote of Cardiff University reported in Nature that they had used a gravitational wave detector to look for dark matter, a lesser-known candidate for the missing mass in and around galaxies. A large class of dark matter models were ruled out by the team. If it affects normal matter very weakly, the stuff can only exist.
The result is a very nice one, according to a University of Michigan astronomer who wasn't involved in the research.
The leading candidate for dark matter until a few years ago was a weakly interacting particle similar to other elementary particles. Experiments for the so-called WIMPs keep coming up empty-handed, making room for other alternatives.
We have reached the stage in dark matter searches where we are looking everywhere, according to a theoretical physicist at Caltech.
Three physicists proposed in 1999 that dark matter might be made of particles that are so light and numerous that they are best thought of as a field of energy. The scalar field has a value at each point in space, and the value varies with a characteristic Frequency.
I woke up one morning and thought the beam splitter was what we needed.
Hartmut Grote.
The properties of other particles and fundamental forces would be subtly altered by scur-field dark matter. The electron's mass and strength would change with the field.
Physicists have wondered if the detectors could spot a wobble. Interferometry is the approach used by these detectors. The beams reflect off mirrors at the ends of both arms after the laser light enters a beam splitter. If the returning laser beams have been pushed out of sync by a passing wave, there will be a pattern of dark and light fringes.
The common thought was that if the beams were pushed out of sync, they would cancel out. The idea of the beam splitter came to him one morning.
The beam splitter is a block of glass that acts like a mirror, reflecting half of the light that hits it and the other half passing through. If dark matter is present, the strength of the force of the field will be weakened, causing atoms in the glass block to shrink. The glass block will expand when the field drops. The interference pattern will appear because this wobble will subtly shift the distance traveled by the reflected light without affecting the transmitted light.
With the aid of computers, the graduate student of Grote searched through the data from the GEO600 detector in Germany looking for interference patterns resulting from millions of different frequencies of dark matter. If you find dark matter, that would be the discovery of decades.
Zurek said the search was only a fishing expedition. The strength of the field's effect on other particles could be anything. Only a specific range of frequencies can be detected.
The failure to find dark matter with the GEO600 detector doesn't rule it out.
Riles and his colleagues have been looking for signs of dark photons in the data from LIGO, which has detectors in Livingston, Louisiana, and Hanford, Washington. Dark particles are light-like particles that interact with other dark particles but occasionally strike normal atoms. If they are all around us, they will push on one mirror more than the other, changing the relative lengths of the arms.
The effects of random fluctuations on the mirrors of the interferometer in Hanford would be the same as the effects on the Livingston detector in Pisa. The researchers did not find correlations in the data. The result they reported last year means that the dark photon must be at least 100 times weaker than before.
Dark matter particles weighing hundreds of kilograms could be found by the detectors. As the heavy particles flew through the detector, they attracted LIGO's mirrors and laser beams.
What else could these instruments catch? The dream of physicists is to find signs that space-time is small. Conventional wisdom says that a detector capable of probing such tiny distances would collapse into a black hole under its own weight. Zurek has been working on an idea that could make quantum gravity visible.
Space-time is a 3D hologram that comes out of a 2D system of quantum particles. Zurek thinks this could be detected by the detectors. Small quantum fluctuations in the 2D space would be amplified when projected into 3D, potentially making waves in space-time big enough for an interferometer to pick up.
When we started working on this, people asked what we were talking about. Zurek said that you are completely nuts.
All Rights Reserved © 2024
