The expansion rate of the universe can be discovered using black holes by scientists

A strange ruler - black holes - is believed to be capable of measuring how fast the universe is expanding.In a new study, University of Chicago physicists have used colliding black holes to measure how fast our universe is expanding.

It has been debated since 1929 that the Hubble constant, the rate at which the universe expands, was discovered by Edwin Hubble. Despite nearly a century of measuring and calculating growth, the constant does not fit real-world observations.

The fundamental physics of the universe suggest that the universe should expand by 68 kilometres per second measuring a galaxy one megaparsec away from Earth – but unfortunately, that does not match up with the observations of actual stars, which appear to be moving at a much faster rate and suggest that we do not understand a significant portion of our universe.

The rate of expansion is therefore a subject of intense interest among scientists. The test uses black holes merging together, an event so powerful that it creates ripples in space-time across the universe. The Laser Interferometer Gravitational-Wave Observatory and the Virgo Observatory can be used to detect these ripples - also called gravitational waves - on Earth.

A study of over 100 colliding black holes has enabled scientists to see how the waves change as they travel. The signal from a black hole would change if it was placed earlier in the universe, causing it to appear bigger than it is, says Daniel Holz of the University of Chicago.

As a result, the challenge becomes calculating the expansion rate from the original signal. Currently, the masses of most detected black holes range from five to 40 times greater than the mass of the Sun.

So we measure the masses of the nearby black holes and understand their features, and then we look further away and see how much further those ones appear to have shifted,” Jose Mar*a Ezquiaga, also a Nasa Einstein Postdoctoral Fellow and a Kavli Institute for Cosmology Physics Fellow, explains. “This gives you an idea of how far the universe has expanded.

This method may provide scientists with more information about the universe, which is only 10 billion years old - a period that is difficult to study with other methods.

The universe switched from dark matter dominating to dark energy around that time, and we are very interested in studying this critical transition,” said Dr Ezquiaga.A second advantage of this method is that gaps in our scientific knowledge create fewer uncertainties.

The method calibrates itself based on the population of black holes, directly identifying and correcting any errors,' Dr Holz said. Alternatively, we can use methods based on our current understanding .

the physics of stars and galaxies, but if there are aspects of the universe that we do not understand, it could severely impact the measurements. In contrast, this method largely relies on Einstein's principle of gravity, which is more consistent.

The more data collected from black holes, the more accurate future calculations will be. In a few years, we should have thousands of these signals, and even more in the next decade or two,' explained Dr Holz. 'At that point, it would be an incredibly powerful way of learning about the universe.'