Cosmologists in the shower time travelers. Looking back billions of years, these scientists are able to follow the evolution of our universe in amazing detail. 13.8 billion years ago, there was a Big Bang. After a fraction of a second the universe expanded exponentially – in a short period of time, called inflation.
During the following periods the space has grown to enormous size, we do not even see the edges. But how can this be possible? If the speed of light marks the cosmic speed limit as there may be regions of space-time, the photons which are beyond our reach? And if they exist, how do we know of their existence? This question is answered with Vanessa Janek Universe Today.
The Expanding Universe
Like everything else in physics, the universe tends to exist in the lowest energy state possible. But after 10 -36 seconds after the Big Bang, according to inflationary cosmology, space was in the false vacuum energy – the lowest point, which really was not the lowest. In search of the true nadir vacuum energy, a split second later, the universe inflated by a factor of 1050. Since the universe continues to expand, but at a slower rate.
Evidence of this expansion in the light of distant objects. As the photons issued a star or galaxy, propagate through the universe, stretching space causes them to lose energy. When photons reach us, their wavelengths show a red shift according to the distance they had gone. That’s why cosmologists speak of red shift as a function of distance in space and time. The light from distant objects traveling so long that when we finally see it, we see the objects as they were billions of years ago.
The red shift of light allows us to see objects like galaxies as they existed in the distant past, but we cannot observe all the events that occurred in our universe during its history. Because our space expands, light some objects it is simply too far away to notice it.
The physics of this boundary is based in particular on a piece surrounding space-time volume entitled Hubble. Here on Earth, we will assess the extent of the Hubble by measuring the so-called Hubble parameter (H0), the value that links the rate of recession of distant objects with their red shift. For the first time it has calculated Edwin Hubble in 1929 to discover that distant galaxies are receding from us at speeds proportional to the red shift of light.
Two sources of red shift:- Doppler and cosmological expansion. Bottom: Detectors capture the light emitted by the central star. This light is stretched or displaced, together with the expansion space By dividing the speed of light on H0, we obtain the amount of the Hubble. This spherical bubble covers an area in which all objects are removed from the main observer at a speed less than the speed of light. Accordingly, all objects outside the Hubble volume removed from the center faster than light.
How is it possible?
The answer to this question has to do with the distinction between special relativity and general relativity. Special relativity requires so-called inertial frame of reference, or, if the simpler background. According to this theory, the speed of light is the same in all inertial systems. If an observer sitting on a bench in the park of the planet Earth or Neptune takes off from the breakneck speed for a speed of light is always the same. Photon always removed from the observer at 300 000 000 meters per second.
General theory of relativity, however, describes the fabric of space-time. In this theory inertial frame there. The space does not expand with respect to anything beyond it, so the limit is the speed of light relative to the observer is not working. Yes, outside the scope of the galaxy Hubble’s moving away from us faster than the speed of light. But galaxies themselves do not overcome space limitations. To an observer in one of these galaxies, nothing violates the special theory of relativity. This space between us and the galaxy stretched and accelerated exponentially.
In the observable universe
Did you include a little surprise: the amount of the Hubble – it is not the same as that of the observable universe. To understand this, consider that when the universe gets older, remote light takes more time to reach our detectors here on Earth. We can see objects that are accelerated beyond our current level of Hubble because the light that we see today, was released by them when they were in the sphere.
Strictly speaking, our observable universe coincides with something called the particle horizon. Horizon particle marks the distance to the farthest light that we can see at this time – from photons have enough time to either remain within, or catch up with gently expands the scope of the Hubble. The observed universe. Technically known as the particle horizon
What is the distance? A little more than 46 billion light-years in any direction – and our observable universe has a diameter of about 93 billion light years, or more than 500 billion trillion kilometers. The particle horizon – is not the same thing as the cosmological event horizon. Horizon particle covered all the events in the past, that we can see at the moment. The cosmological event horizon, on the other hand, determines the distance at which the future observer was able to see at that time the ancient light that is emitted by our little corner of space time today.
In other words, the particle horizon had to do with the distance to objects in the past, the ancient light that we see today, and the cosmological event horizon has to do with the distance, it is able to pass our modern world, as the farthest reaches of the universe will accelerate from us.
Due to the expansion of the universe, there are regions of space that we never see, even if we will wait for infinite time, yet their light reaches us. But what about those areas that lie just outside our current scope of the Hubble? If this sector is also expanding, whether we can see the border facilities?
It depends on which region is expanding rapidly – Hubble volume or part of the universe in the immediate vicinity outside. And the answer to this question depends on two things: 1 increases or decreases H0; 2 The universe is accelerating or decelerating. These two tempos closely linked, but they are not the same. In fact, cosmologists believe that we live in a time when H0 is reduced; but because of dark energy, the rate of expansion is increasing.
It may seem counter intuitive, but as long as H0 decreases at a slower rate than the rate of expansion of the universe, the general movement of galaxies away from us is still going on with acceleration. And at this point in time, according to cosmologists, the expansion of the universe will outperform a more modest growth of Hubble.
Therefore, even though the volume of Hubble’s expanding influence of dark energy sets a hard limit on the growth of the observable universe. Cosmologists are scratching their heads over deep questions like how the observable universe will look like in one day, and how to change the expansion of the cosmos. But ultimately, scientists can only guess the answers to questions about the future, based on today’s understanding of the universe.
The Cosmological time frame is so incredibly high that it will be impossible to say anything specific about the behavior of the universe in the future. Current models are surprisingly responding well to current data, but the truth is that none of us will live long enough to see whether the predictions come true.