Astrophysicists have developed a neural network that predicts cosmological parameters from the properties of individual galaxies. Credit; DepositPhotos

There Might be a Fundamental Problem With Our Understanding of the Universe

The measurements of galaxy distances either have a systemic error or there is a fundamental problem with our understanding of the physics of the universe.


Scientists at the University of Hawaii at Manoa have created the largest-ever collection of highly accurate galaxy distances called Cosmicflows-4. A total of 56,000 galaxies were measured using eight different methods. In the universe, galaxies, such as the Milky Way, are composed of hundreds of billions of stars. In the aftermath of the Big Bang, galaxies beyond our immediate neighborhood are accelerating away, faster if they are farther away, due to the expanding universe. By determining distances between galaxies and velocities away from us, we can determine the size of the universe and the amount of time that has passed since its birth.

The Hubble Constant

Astronomers have been attempting to determine galaxies’ distances since they were spotted one hundred years ago, said astronomer Brent Tully. The accuracy of our tools is now so high that we can measure the distance between galaxies and the universe’s expansion rate, as well as the universe’s age, with a few percent precision. Using the newly obtained measurements, researchers determined the Hubble Constant, or H0, the rate at which the universe expands. With a statistical uncertainty of about 1.5%, the team determined the value of H0 to be 75 km per second per megaparsec or Mpc (1 megaparsec = 3.26 million light-years).


To measure galaxy distances, there are several methods available. However, research usually focuses on a specific method. Tully and Ehsan Kourkchi’s Cosmicflows program combines original data from two methods with data from many previous studies. Intercomparisons should mitigate against the possibility of systematic error as Cosmicflows-4 uses a number of different, independent distance estimators. It is estimated that the universe is some 13 billion years old, but a paradox of great significance has arisen regarding the details.

A fundamental problem?

Using the standard model of cosmology, H0=67.5 km/s/Mpc with an uncertainty of 1 km/s/Mpc is predicted. There is a 7.5 km/s/Mpc difference between measured and predicted values for the Hubble Constant, which is much higher than expected, given statistical uncertainties. The measurements of galaxy distances either have a systemic error, or there is a fundamental problem with our understanding of the universe’s physics.

The Cosmicflows-4 experiment also studies individual galaxies and how they flow with the universe’s expansion. As a result of gravitational influences, clumps of matter can deviate from this smooth expansion on a scale ranging from our Sun and Earth to gatherings of galaxies on a scale of a half billion light years. A large proportion of the universe is composed of mysterious dark matter. To better understand how the vast, dark-matter-dominated structures of the universe were formed over eons of time, we can recreate the orbits that galaxies have followed since they were formed by knowing how their motions were influenced by their surrounding mass. The study was published in The Astrophysical Journal.


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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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