The universe was born about 14 billion years ago as a result of the Big Bang. Since then it has grown continuously. But we learned about it less than a hundred years ago. In 1920, American astronomer Edwin Hubble invented what was then the largest telescope in the world, and his colleague Vesto Slifer noticed the red glow of the nebula – what we call galaxies today – and found that the nebulae appear red on our planet because of this , This effect is called redshift – the radiation that is observed for all of the Earth's distant sources (quasars, galaxies), indicating that all sources are separated. In other words, redshift means that the universe expands. Recently, scientists wanted to calculate the exact expansion rate. It turned out that there can be fundamental inaccuracies in our understanding of the universe.
What is the Hubble constant?
Edwin Hubble watched the Andromeda Nebula and classified it as a star system. The discovery of the astronomer expanded our understanding of the universe – now we know that it is filled with galaxies. So Edwin Hubble discovered the cosmological law that characterizes the expansion of the universe. To calculate the speed at which the universe expands, the proportionality coefficient must be used – the Hubble constant.
With the Hubble constant we can determine the average speed of galaxies. The scientifically derived value of the coefficient of proportionality is approximately 500 km / s per 1 Mpc. Remember that the distances in space are measured in parsec: 1 parsec equals 3.0857 x 1019 kilometers. And one megaparsec is the distance of one million parsecs.
However, from the moment Hubble derives its constant, astronomers watching the expansion of the universe come to different values of the Hubble constant each time. And these values do not match. Such a discrepancy casts doubt on our ability to determine the exact age of the universe and even to question our understanding of its fundamental laws.
How fast does the universe expand?
A research team headed by the University of Chicago astronomer Wendy Friedman measured the brightness of red giants in distant galaxies. The study found that the distance from the earth to the red giants was easier to calculate than the distance to other stars. According to calculations by astronomers, the universe expands at a speed of 69.8 km / s per 1 Mpc. Note that the results of the study will be published shortly in the journal Astrophysical Journal.
This is interesting: Can gravitational waves show how fast our universe expands?
As you may have noticed, the results differ from those calculated by Hubble. According to Friedman and her team, the rate of expansion of the universe is slower than the speed calculated by another team of scientists in a recent study – experts focused on a different star type. However, the results obtained by Friedman exceed the expansion rate of the universe, which was calculated in another study in which astronomers measured the remnant after the Big Bang, also known as microwave background radiation.
Thus, the Hubble constant is the biggest problem in modern cosmology. Experts do not rule out that, once we have determined the expansion speed of the universe, we can come closer to the mysteries of dark matter and dark energy.
By the way, you can find out about the latest research results in the field of cosmology on our channel in Yandex.Zen.
Do we know the exact rate of expansion of the universe?
In the middle of the next decade, NASA experts want to bring the Wide Field Infrared Survey Telescope (WFIRST), an infrared wide-field telescope, into orbit. Scientists believe astronomers can more accurately measure the distance between space objects. This in turn may lead us to agree on the values of the Hubble constant.
And what do you think, what are the different values of the Hubble constant? Share your opinion in the comments and with the participants of our telegram chat.