Hubble`s law is considered so important because of the value of the Hubble constant H, which is used to determine the exact age of the universe. It also helps to understand dark matter and dark energy. Because the exact value of the Hubble constant H is so important in extragalactic astronomy and cosmology — it leads to an estimate of the age of the universe, helps test theories of dark matter and dark energy, and much more — a lot of effort has gone into finding out. Today, it is estimated at 71 kilometers per second per megaparsec, plus or minus 7; That`s about 21 km/s per million light-years. What does that mean? An object located a million light-years away would move away from us at 21 km/s; an object 10 million light-years away, 210 km/s, etc. There are some important caveats that apply to Hubble`s law. Hubble`s law, which simply states that the speed of a galaxy (or, as is sometimes described, its redshift) is directly proportional to its distance, also tells us something important about the state of the universe. If the universe is static and immutable, there should be no correlation between distance and speed. However, as the universe develops, we expect a correlation between distance and speed. The usual analogy used here is that of an explosion – the shrapnel fragments produced move at a range of speeds, and the objects furthest from the source of the explosion have the highest speeds. Astronomers believe that Hubble`s Law is a direct result of the continued expansion of the universe and that evidence suggests that the universe began in an explosion we call the Big Bang. The Hubble constant is one of the most important numbers in cosmology because it tells us how fast the universe is expanding, which can be used to determine the age of the universe and its history.

It takes its name from UChicago alumnus Edwin Hubble, who was the first to calculate the constant from his star measurements in 1929. In 1927, two years before Hubble published his own paper, Belgian priest and astronomer Georges Lemaître was the first to publish research deriving from what is now Hubble`s law. According to Canadian astronomer Sidney van den Bergh, “Lemaître`s discovery of the expansion of the universe in 1927 was published in French in a journal with little effect. In the influential 1931 English translation of this article, a critical equation was modified by omitting the reference to today`s Hubble constant. [22] It is now known that the changes made to the translated document were made by Lemaître himself. [10] [23] Let`s take a closer look at this idea of an expanding universe. If all objects move outward at a constant speed, the boundaries set by the outermost objects must continually grow. To be more specific about the expansion of the universe, let`s go back to the analogies.

The first is as follows: pixels on a very long elastic. The dots are supposed to represent galaxies. When you pull on the elastic, the distance between the points increases. If the initial distance between each point is 1 cm (point B is 1 cm from point A, point C 2 cm and point D 3 cm) and you pull on the elastic so that the points are now 2 cm apart, point B is 2 cm from point A, Point C will be 4 cm and point D 6 cm. Point C will have moved twice as far from point A as point B at the same time, and point D will have moved three times farther from point A at the same time as point B. From point A perspective, the farthest points seem to have moved faster than the nearest points (remember that the speed of an object is the distance traveled divided by the time it takes to travel that distance). If we were to repeat the previous experiment, but measure the distances between the points from the point of view of point B, we would find that point B would draw the same conclusion as point A. That is, all the points seem to move away from point B and the other points seem to move away faster. The z-redshift is often described as the redshift velocity, which is the recession velocity that would produce the same redshift if caused by a linear Doppler effect (which is not the case, however, because the shift is partly caused by the cosmological expansion of space and because the velocities involved are too large to use a non-relativistic formula). for Doppler offset). This redshift speed can easily exceed the speed of light. [36] In other words, to determine the redshift speed vrs, the relationship: perhaps the most dramatic revision of Hubble`s Law occurred in 1998, when two teams independently announced that they had discovered that the rate of expansion of the universe was accelerating; The abbreviation for this observation is Dark Energy.

The speed of recession can be measured using a phenomenon called the Doppler effect. A classic example of the Doppler effect is how the sound of a siren changes when an ambulance passes by. This is because the sound waves that travel between you and the ambulance are compressed as the ambulance approaches (essentially catching up with its own sound waves) and stretches as it moves away. Any two points moving away from the origin, each along straight lines and at a speed proportional to the distance from the origin, move away from each other at a speed proportional to their distance. Hubble length is defined as the product of the speed of light and Hubble time. It is also known as Hubble removal. The resulting product corresponds to 14.4 billion light-years. cH0-1 is the Hubble length. On the previous page, we attributed the velocities of galaxies and the relationship between their velocities and distances to an explosion. Since all the debris from an explosion comes from the same place, those farther away have to move faster to have traveled farthest in the same amount of time. This is an acceptable analogy, but it is not perfect.

However, it helps us understand that the universe needs to expand. Our best interpretation of the relationship discovered by Hubble is that it implies that the space between galaxies is expanding. Imagine a blueberry muffin. As the muffin cooks and rises, the dough expands and separates all the blueberries. When two blueberries enter the oven half an inch apart and the dough doubles, the distance between them increases to a full inch.