When black holes collide, they produce gravitational waves detectable on Earth. Although theorized by Einstein in 1916, they were not directly observed until 2015. Modern research contrasts older models with new data, revealing that these waves do interact. This knowledge refines our models and challenges the full scope of general relativity in explaining black hole properties.
When two black holes collide, the impact is so big that we can detect it all the way here on Earth. These objects are so immense that their collisions send ripples through spacetime itself. Scientists call these ripples gravitational wavesGravitational waves are distortions or ripples in the fabric of space and time. They were first detected in 2015 by the Advanced LIGO detectors and are produced by catastrophic events such as colliding black holes, supernovae, or merging neutron stars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>gravitational waves. Although Albert Einstein predicted the idea of gravitational waves all the way back in 1916, physicists didn’t directly detect them until 2015 at LIGOThe Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory supported by the National Science Foundation and operated by Caltech and MIT. It's designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. It's multi-kilometer-scale gravitational wave detectors use laser interferometry to measure the minute ripples in space-time caused by passing gravitational waves. It consists of two widely separated interferometers within the United States—one in Hanford, Washington and the other in Livingston, Louisiana.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>LIGO (the Laser Interferometer Gravitational-Wave Observatory). Now, scientists supported by the Department of Energy’s Office of Science along with several other federal agencies are working to better understand these gravitational waves and what they can tell us about black holes.
The Complexity of Black Hole Collisions
Along with being very powerful, these collisions have incredibly complex physics. To be accurate, the computer simulations of them must be complex as well. The simulations need to include every step of the process: black holes spiraling towards each other, merging, becoming a distorted black holeA black hole is a place in space where the gravitational field is so strong that not even light can escape it. Astronomers classify black holes into three categories by size: miniature, stellar, and supermassive black holes. Miniature black holes could have a mass smaller than our Sun and supermassive black holes could have a mass equivalent to billions of our Sun.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>black hole, and then settling down into a single black hole. This process is so complex that scientists need supercomputers to run the simulations.
Two black holes are about to merge in this still from a simulation produced by the Simulating eXtreme Spacetimes, or SXS, collaboration using supercomputers. As the black holes spiral together, they produce ripples in space and time called gravitational waves. Credit: SXS Lensing/Simulating eXtreme Spacetimes Collaboration
The physicists then compare the numerical data from these simulations to models of the process. Older versions of the models showed the gravitational waves not influencing or interacting with each other. However, scientists suspected this wasn’t accurate. Think about two people standing next to each other in a pool, making waves. If each one of them is making very small waves, it’s possible the waves won’t interfere with each other. They’ll die out before they interact. But, if both people are making large waves, the waves will crash into each other and create new waves. Knowing that the collisions produce strong gravitational waves, scientists thought that they would interact with each other – it just wasn’t showing up.
New Insights into Gravitational Wave Interactions
A team of researchers from the California Institute of Technology (Caltech), Columbia University, University of Mississippi, Cornell University, and the Max Planck Institute for Gravitational Physics ran a new, more detailed analysis of these numerical outputs. This analysis showed evidence of gravitational waves interacting with each other, as expected. Each wave causes the others to change slightly. The interactions create new types of waves with their own independent frequencies. These new waves are smaller, more chaotic, and more unpredictable than the original ones. By including this feature in the models, the scientists can more accurately describe what the numerical outputs are telling them.
LIGO Livingston Laboratory. Credit: LIGO Laboratory
Adding these interactions into the models of colliding black holes will make the models more accurate. In turn, these models will help us better interpret real-world observations. The more accurate the models are, the more useful they are for interpreting data from LIGO.
In addition, better models can help scientists figure out if general relativity is the right theory to explain what actually happens in black holes. While general relativity – the famous theory developed by Einstein – broadly explains how gravity affects spacetime, how well this theory applies to the strange properties of black holes is still to be determined.
Implications for Our Understanding of the Universe
Black hole collisions are unimaginably far from Earth and our everyday lives. While we can’t feel gravitational waves ourselves, the data and models scientists make are expanding our knowledge of these incredible phenomena every day.
Source: SciTechDaily
