What happens when three black holes share the same region of space, all orbiting each other? As Science News reports, it remains a mystery. Their orbits can be so unpredictable that even if their movements were measured as theoretically as precisely as possible, their orbital trajectories would still elude us.
Computer simulation of a black hole’s orbit can demonstrate some fundamental characteristics of time. And, according to astrophysicist Nathan Leigh, the results show that “quantum mechanics is imprinted on the chaos of the universe on a fundamental level.”
There is no harmony of the spheres
The very idea of science is based on our experience that the world around us can be quite predictable. If you drop an apple, it will probably fall directly down, not sideways or up. On the grand scale of astronomical events, this predictability or regularity of nature is particularly strong, like the sun rising in the east every morning.
Science’s first great triumph was the ability to build an accurate calendar and predict events like a solar eclipse. These achievements were based on the regularity of the celestial orbits. Today, this same predictability of orbits allows NASA to send spacecraft to outer planets and measure the orbits of exoplanets many light-years away. If the orbit of a black hole is not predictable, even in theory, that shakes things up.
Run the time tape backwards
Orbital simulations and similar scientific models, Interesting Engineering explains, are based on a principle known as time symmetry. That is, if you simulate an orbit and then run the simulation backwards, it will work just as well. The simulated object will orbit in the opposite direction, but will not fly into space in an unexpected way.
The real universe, as Interesting Engineering points out, is not so good. If you drop a cup, it will break and won’t come together.
Astronomers and mathematicians have long known that orbits involving three objects cannot be calculated with the precision that can be obtained for two objects that orbit each other. This is commonly known as the three-body problem. The normal solution to this problem is to simulate the orbit step by step, as precisely as the available programming and computing power allow.
The researchers have discovered that these simulated orbits cannot always be executed in reverse, that attempts to do so do not always end up reproducing the initial starting conditions, as they should, according to the principle of time symmetry.
What they did not know was whether these failures were due to the nature of the universe, or only to the technical limitations of a particular simulation, such as how many decimal places it could calculate.
Black Holes, Gravity and Quantum Mechanics
Now, a team led by astronomer Tjarda Boekholt has built a simulation model so precise that the precision limit of the simulation is set not by the available computing power, but by the structure of the universe itself. It is specifically set by a distance known as the Planck length, which according to the theory of quantum mechanics is the shortest length that can be measured in the universe, according to Science Alert.
(How long is Planck’s length? Approximately 0.000000000000000000000000000000000016 meters. Aren’t you glad you asked?)
The researchers tested their model by simulating the process of predicting the behavior of one black hole, or indeed three black holes. Why black holes? Because its gravitational fields, which are so intense that not even light can escape, they magnify quantum effects, usually only noticeable on the subatomic scale, to the point where they can have large-scale effects.
The simulation research team found that, even with Planck’s length precision, your model was unable to reproduce approximately 5% of simulation runs in reverse to return to the initial model conditions. These runs break the symmetry of time because it is impossible to predict the behavior of a black hole in these runs.
Also, there is no way to know beforehand which one 5% of runs will break time symmetry, which means time symmetry cannot be fully counted.
A touch of chaos
Physicists and mathematicians use the term chaos for systems in which small changes in the initial conditions can produce dramatic changes in the final result. The study results, Science News says, confirm that orbital systems involving three black holes are fundamentally chaotic and can never be reliably predicted over long periods of time.
According to Science Alert, quoting team member Portegies Zwart, “Not being able to turn back time is no longer just a statistical argument … It is already hidden in the basic laws of nature.”
By strange coincidence, reports Universe Today, astronomers recently discovered three supermassive black holes orbiting each other in a galaxy a billion light-years away. But they can’t provide direct proof of orbital chaos, because as Science News points out, we can’t measure real black holes with the precision necessary to model their orbits with the precision of Planck’s length.
We can also rejoice, perhaps, that the chaotic orbits of black holes are 1 billion light-years from Earth.
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