Five questions about the expansion of the universe, that you hesitate to ask
When we look at the distant universe, we see throughout the galaxy - in all directions, to millions and even billions of light years. Because there are two trillion galaxies that we can observe, the sum of all that is behind them, longer and steeper than the boldest of our ideas. One of the most interesting facts is that all the galaxies that we have ever seen, subject to (on average) the same rules: the further they are from us, the faster they are removed from us. This discovery, made by Edwin Hubble and his colleagues back in the 1920s, has led us to a picture of the expanding universe. But what about the fact that it is expanding? Science knows, and now you will learn.
The more we look, the farther back in time we look, not yet seeing the evolution of the universe. But - only if the general theory of relativity applies to the expanding universe
The universe is expanding more than (where)?
At first glance this question may seem common. Because all that extends generally consists of a substance exists in space and time of the universe. But the universe itself - it is space and time containing matter and energy in themselves. When we say that "the universe is expanding," we are referring to the expansion of space itself, in which individual galaxies and clusters of galaxies are moving apart. The easiest way would be to introduce ball of dough with raisins inside, which is baked in the oven, said Ethan Siegel.
Model expanding "buns" universe in which the relative distance increases with the expansion space
This dough - the fabric of space and raisins - related structures (such as galaxies or clusters of galaxies). From the point of view of any raisins, all the other raisins will depart from her, and what they are farther away - the more quickly. Only in the case of the universe furnace and air for tests outside does not exist, there is only dough (space) and raisins (substance).
to Redshift create not just receding galaxies, but rather the space between us,
How do we know that this space expands, galaxies are not?
If you see that in all directions from your deleted items, there is only one reason that can explain this: expanding the space between you and these objects. It was also possible to assume that you are near the center of the explosion, and many facilities are just ahead and removed quickly, because of the explosion got more energy. If this were so, we could prove this in two ways:
- At large distances and high speeds will be less than the galaxies as they would greatly spread over time in the space of
- redshift and distance ratio will take concrete form at large distances that will be different from the form, if the fabric of space expanded
When we are looking at long distances, we find that more in the universe galaxies, the density is higher closer to us. This is consistent with the picture, in which the space expands because look no further - the same thing to look into the past, where there was a smaller expansion. We also find that distant galaxies are related redshift and distance corresponding to the expansion of space, and not at all - if the galaxy just quickly moved away from us. Science can answer this question in two different ways, and both answers support the expansion of the universe.
whether the universe is always expanding at the same rate?
We call it the Hubble constant, but it is constant only in space but not in time. The universe is currently expanding more slowly than in the past. When we talk about the rate of expansion, we are talking about velocity per unit distance: 70 km / c / Mpc today. (Mpc - Mpc is about 3.26 million light years). But the rate of expansion depends on the density of all the different things in the universe, including the matter and radiation. With the expansion of the universe, matter and radiation it becomes less dense, and with the fall of the density decreases and the rate of expansion. The universe is expanding rapidly in the past and slowed down since the Big Bang. Hubble constant - is the wrong name, it should be called the Hubble parameter.
The distant fate of the universe offer different possibilities, but if dark energy actually is constant, as the data show, we will follow the red curve
Will the universe expand forever or ever stop?
Several generations of cosmologists and astrophysicists puzzled over this question and answer it, you can only determine the speed of expansion of the universe and all types (and quantity) of energy that are present in it. We have successfully measured as the number of ordinary matter, radiation, neutrinos, dark matter and dark energy, and the rate of expansion of the universe. Based on the laws of physics and what happened in the past, it seems that the universe will expand forever. Although the probability of this is not 100%; If something like the dark energy will behave differently in the future than in the past and present, all our conclusions should be reconsidered.
Galaxy are moving faster than light? Is not it forbidden?
From our point of view, expanding the space between us and the distant point. The farther it is from us, the faster it seems to us, it will be removed. Even if the rate of expansion would be tiny, distant object once crossed the threshold would be any terminal velocity because the expansion rate (rate per unit of distance) would be multiplied many times when a sufficient distance. GRT approves such a scenario. Law that nothing can travel faster than the speed of light, is applied only to the movement of an object through space and not to the expansion of space. In reality, the galaxies themselves are moving at a speed of only a few thousand kilometers per second, which is far below the limit of 300 000 km / s, set the speed of light. It causes the expansion of the universe and the recession redshift rather than true motion of the galaxy.
In the range of the observable universe (yellow circle) is about 2 trilliona galaxies. Galaxies that are closer than a third of the way up to this limit, we will never be able to catch up because of the expansion of the universe. For the development of people's forces opened only 3% of the volume of the universe
Expansion of the universe is a necessary consequence of the fact that matter and energy fill the space-time that obeys the laws of general relativity. While there is matter, there is a gravitational attraction so that a gravity wins and all will shrink again, or gravity will lose and win an extension. There is no center of expansion and there is nothing outside of the space, which expands; it is the universe itself is expanding fabric. What is most interesting, even if we left Earth at the speed of light today, we have been able to visit only 3% of the galaxies in the observable universe; 97% of them have been out of our reach. The universe is complex.