These different places could be expanding at different rates, include other types of matter, and have different physical laws than our own universe. (Image credit: Getty Images)Īs the early universe inflated, there are some theories that say that different "pockets" broke away and formed different universes. Scientists speculate that our universe is not the only one. They would probably not be able to tell there was a Big Bang." What about other universes? "Civilizations started then, they would have no evidence that there was a universe with 100 billion galaxies," he said. Residents of that future galaxy would have a much darker universe to observe, Livio said. Later on, other galaxies in our Local Group - the galaxies closest to us - will eventually combine. The Milky Way is on a collision course with the nearby Andromeda Galaxy, and both will merge in about 4 billion years. Hence, the definition of the observable universe." "It doesn't mean that that's all there is in the universe. "We can only see light from galaxies whose light had enough time to reach us," Livio said. In 1 trillion to 2 trillion years, Livio said, this means that there will be galaxies that are beyond what we can see from Earth. This is where the concept of the " observable universe" - the universe that we can see - comes into play. Also, the universe is accelerating in its expansion. The universe is expanding faster than the speed of light (which does not violate Einstein's speed limit because the expansion is of the universe itself, rather than of objects traveling through the universe). This will make them more difficult to see in telescopes. As the universe gets older and bigger, however, galaxies will recede farther and farther from Earth. Measurements of the universe's expansion - through watching galaxies race away from us - show that it is about 13.82 billion years old. (Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images) Would the number of galaxies change?Īs the universe expands, galaxies move away from Earth. ![]() Using instruments such as NASA's Wilkinson Microwave Anisotropy Probe, astronomers have found the CMB is virtually identical wherever one looks. One example of the cosmological principle at work is the cosmic microwave background (CMB), radiation that is a remnant of the early stages of the universe after the Big Bang. This is called the cosmological principle." "That is, the matter in the universe is homogeneous and isotropic when averaged over very large scales. "The simplest assumption to make is that if you viewed the contents of the universe with sufficiently poor vision, it would appear roughly the same everywhere and in every direction," NASA stated. With that understanding in hand, several scientists (including Einstein) tried to understand how gravity affected the entire universe. Einstein said that gravity is a distortion of space and time. The principle dates back to Albert Einstein's theory of general relativity. "We have good reasons to suspect that is the case. "This is assuming that there is no large cosmic variance, that the universe is homogenous," Livio said. Then - using the ratio of the sliver of sky to the entire universe - you can determine the number of galaxies in the universe. You take the portion of sky imaged by the telescope (in this case, Hubble). ![]() Whatever instrument is used, the method of estimating the number of galaxies is the same. The Hubble Space Telescope captured this image of the stars in the NGC 5023 galaxy. The James Webb Space Telescope is expected to reveal even more information about early galaxies in the universe, according to The Astrophysical Journal. While estimates among different experts vary, an acceptable range is between 100 billion and 200 billion galaxies, said Mario Livio, an astrophysicist at the Space Telescope Science Institute in Baltimore, Maryland. So if that single small spot contains thousands, imagine how many more galaxies could be found in other spots. By collecting faint light over many hours of observation, the XDF revealed thousands of galaxies, both nearby and very distant, making it the deepest image of the universe ever taken at that time. If you held your thumb at arm's length to cover the moon, the XDF area would be about the size of the head of a pin. ![]() The telescope watched a small patch of sky in repeat visits for a total of 50 days, according to NASA. Perhaps the most resonant example of this fact is the Hubble eXtreme Deep Field (XDF), an image made by combining 10 years of photographs from the Hubble Space Telescope.
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