It was in the early 1990-ies. The Carnegie Observatory in Pasadena, California, was empty for the Christmas holidays. Wendy Freedman, one in the library worked on the huge and thorny problem: the rate of expansion of the Universe. Carnegie was fertile ground for such work. It was here, in 1929, Edwin Hubble first saw the distant galaxies flying away from the milky Way, Bouncing in the external thread of the expanding space. The speed of this flow was called the Hubble constant.
Quiet operation Friedman was soon interrupted when the library was broken by fellow astronomer Allan of Sendic, the scientific successor to the Hubble, which decades of rules and refined the Hubble constant, consistently defending the slow pace of expansion. Friedman was one of the last defended the higher rates, and Sandig saw her heretical research.
"He was so angry," says Friedman, now working at the University of Chicago in Illinois, "that was the moment I realized that we were alone in the whole building. I took a step back and think that we are not the most friendly of areas of science".
This opposition subsided, but not quite. Sendic died in 2010, and by that time most astronomers agreed on the Hubble constant in a narrow range. However, the latest data probably would have liked Sandigo, point to the fact that the Hubble constant is 8% lower than the guide number. Almost a hundred years astronomers have calculated it, carefully measuring the distance to the nearest part of the universe and moving further and further. But recently astrophysicists have measured the constant outside, based on the maps of the cosmic microwave background (CMB), spotted the afterglow of the Big Bang, which became the background for the visible Universe. Making assumptions about how push-tacica of energy and matter in the Universe changed the pace of space expansion since formed the cosmic microwave background, astrophysicists can take their cards and adjust the Hubble constant to the modern local Universe. The numbers must match. But they are not the same.
Maybe one of the approaches is something wrong. Both sides looking for weaknesses in their own and other methods, and senior figures such as Friedman, in a hurry to submit their own suggestions. "We don't know in what direction all this will lead," says Friedman.
But if agreement is not reached, it will be a crack in the firmament of modern cosmology. This may mean that existing theories are missing a certain ingredient, which intervened between the present and the ancient past, weaving in a chain of interactions of the CMB with the present Hubble constant. If so, then history will be repeated. In the 1990's, Adam Riess, now an astrophysicist at Johns Hopkins University in Baltimore, Maryland, headed by one of the groups that discovered dark energy, repulsive force that accelerates the expansion of the Universe. This is one of the factors that the CMB calculations should take into account.
Now a team of RISS leads the search for the Hubble constant in the nearby space, and beyond. Its purpose is not only to clarify the number, but also to catch, does it change over time, so that even dark energy can explain it to. Yet he understands little of what may be the missing factor. And he wonders what is happening.
In 1927, Hubble has gone beyond the milky Way, armed with the largest at the time with the telescope in the world, the 2.5-meter hooker telescope, which was standing on mount Wilson above Pasadena. He took a picture of the spiral of weak spots, which are now known as galaxies, and measured the redness of their light as the Doppler shift toward the long wavelengths of light. Comparing the redshift of galaxies from their brightness, Hubble came to interesting conclusions: the dimmer and, presumably, next was a galaxy, the faster it is removed. Therefore, the universe is expanding. And so, the Universe has a finite age, the countdown which started with the Big Bang.the
Debate on the topic of the Hubble constant and of the rate of expansion of the Universe began to play with renewed vigor. Astronomers have come to a certain number, using the classical technique of the "ladder distance", or astronomical observations of the local universe. But these values conflict with the cosmological estimates made on the basis of the maps of the early universe and tied to the present day. From this dispute, it follows that the growth of the universe can feed the missing ingredient.
To determine the rate of expansion and the corresponding constant — the Hubble needed a real distance to the galaxies, and not only relative based on their apparent brightness. So he began the laborious process of building a remote ladder — from the milky Way to nearby galaxies and beyond, to the very edge of the expanding space. Each rung of the ladder needs to be calibrated "standard candles": objects that move, pulsate, flash or rotate in such a way that it is possible to determine exactly how far away they are.
The First step seemed quite robust: variable stars, called Cepheids, which increase and reduce the brightness after a few days or weeks. The length of this cycle indicates an internal brightness of the stars. Comparing the observed brightness of Cepheids with a brightness emanating from her hesitation, Hubble could calculate the distance to it. Telescope at the mount Wilson could see several of the Cepheids in nearby galaxies. For distant galaxies, he assumed that the brightest stars in them will have the same internal brightness. Even in the most distant galaxies, Hubble was supposed to be standard candles with a uniform luminosity.
Obviously, these assumptions were not the best. First published Hubble constant was 500 kilometers per second per megaparsec — that is, for every 3.25 million light years that he was looking into space, the expanding universe is pushing galaxies at 500 kilometers per second faster. This number was incorrect and implied that the Universe just 2 billion years, nearly seven times less than it is considered today. But this was only the beginning.
In 1949, completed the construction of a 5.1-meter telescope at Palomar in southern California — just to the time when Hubble caught a heart attack. He handed over the mantle of Sandigo, trump the observers, who spent the following decades, showing photographic plates during the night sessions, working with a giant camera telescope, shivering and needing breaks.
With higher resolution and high Palomar svetomuzykalny force, Sandig been able to get from Cepheids in more distant galaxies. He also realized that the bright stars are Hubble was, in fact, the whole clusters. They were brighter by nature and therefore much farther away than Hubble thought that, in addition to other amendments, meant much lower the Hubble constant. In 1980-m to years of Sendig stopped at the value of 50, which is fiercely defended. One of his most famous opponents, the French astronomer Gerard de Ocular, proposed a value of 50. One of the most important parameters in cosmology ran literally twice.
In the late 1990-ies of the Freedman, having gone through the verbal abuse of Candidia, has set a goal to solve the puzzle with the new tool, as if deliberately created to work: the Hubble space telescope. His clear glance over the top of the atmosphere allowed the team Friedman to identify individual Cepheid 10 times further than Sandigo managed with Palamara. Sometimes in these galaxies was like Cepheids and bright beacons — Ia sne. These exploding white dwarf stars are visible through the space and break out with a constant and a maximum brightness. Calibrated by Cepheids, supernovae can be used by themselves to probe the most distant reaches of space. In 2001, the team of Friedman narrowed down the Hubble constant to 72 plus or minus 8, that put an end to the conflict Sandidge and de wokulira. "I was exhausted," she says. "I thought I was never going back to work on the Hubble constant".the
But then came the physicist who found the independent method of calculation of the Hubble constant with the most distant and shifted to the red part of the spectrum of the microwave background. In 2003, the WMAP probe published his first map, which showed the spectra of temperature fluctuations in the CMB. This map provided is not a standard candle and a standard criterion: the pattern of hot and cold spots in the primary soup, the generated sound waves, which are ripples swept across the newborn Universe.
Making a few assumptions about the ingredients in this soup — in the form of familiar particles, atoms and photons, some additional invisible substances like dark matter and dark energy — WMAP team were able to calculate the physical size of these primary acoustic waves. It can be compared with the apparent size of the sound waves recorded in the CMB spots. This comparison gave the distance to the microwave background and the value of the expansion rate of the Universe at the initial moment. Making assumptions about how ordinary particles, dark energy and dark matter since then changed the extension, the WMAP team was able to give a constant value in accordance with its current rate of increase. Initially, they derived a value of 72, in accordance with what found Friedman.
But since the astronomical measurements of the Hubble constant showed higher values, although the error decreased. In recent publications Riess went ahead using an infrared camera, installed in 2009 on Hubble space telescope, which may determine distances to Cepheids in the milky Way and allocate them to the most distant, more red relatives among the more blue stars that are surrounded by normal Cepheids. The latter result, which gave the team RISSA — 73,24.
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