Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
Welcome to our Physics lesson on Actual Problems. Horizon Issue. Inflation Phase, this is the fifth lesson of our suite of physics lessons covering the topic of Formation of Galaxies and Solar System. Actual Problems, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
Now, let's conclude the explanation of Big Bang model by discussing some of its actual problematics that are still under observation in order to take a permanent solution. We will begin this part with the horizon issue.
The techniques used in the last century have made possible to detect signals that come from the most remote sections of the observable Universe, billions of light years away from us. From signals coming from remote galaxies, it became clear that physical features, laws and processes in the Universe are the same throughout it. This is true for all directions and distances in which observations are made.
However, the Big Bang theory is insufficient at a certain extent when trying to explain such a perfect order in the Universe. To make this point clear, let's consider the issue of horizon we have dealt with earlier.
We know that it is impossible to see everything on the surface of Earth from a certain position due to its spherical shape. Our eyes can see the light rays that are incident only from a small section determined by the horizon line. (The concept of horizon line is clearer when we are in midst of ocean and the horizon line is visible in all directions. It represents the borderline that separates the ocean and the sky. We also have explained the concept of sky (celestial) horizon in tutorial 22.8.
We can define the horizon of the Universe in the same way. It represents the border that separates the visible Universe and the part of it that extends beyond our actual ability to see or detect signals coming from the remotest galaxies. Thus, since the Universe is about 13.7 billion years old, we can only see or detect EM waves coming from sources that are closer or equal to 13.7 billion light years away from us. This part of Universe is called the Observable Universe.
However, galaxies diverge from each other at lower speeds than the speed of light. This is because gravitational forces acting on the opposite direction to galaxies moving direction. This means the remotest visible galaxies have never been close to our galaxy since we detect signals coming from them. The question that naturally arises at this point is: How it is possible than two objects that have never been in contact with each other manifest share the same characteristics, have the same behaviour and obey the same laws?
Scientists tried to solve this puzzle that obscured the magnificence of the Big Bang theory by introducing the concept of inflation phase, which we will explain through an analogy - the phase change of steam into water.
Thus, when temperature of steam lowers below 373 K (100°C), it must normally turn into water. However, in temperatures lower than that of liquefaction the steam can overcool without turning into water (especially when its degree of purity is very high). As soon as casual fluctuations create water bubbles, they widen at very high speeds, join other similar bubbles and turn the steam into water. The same thing occurs in the Universe as well. Thus, stars are similar to water molecules, galaxies similar to bubbles and so on.
More specifically, the inflation phase in the Universe is believed to have occurred between 10-38 s and 10-30 s after the Big Bang. As we have said earlier, at t = 10-38 s the Universe experienced a symmetry break, where the electroweak and electro-strong interactions separated from each other. This is similar to the phase change from steam to water. At this instant, cosmic bubbles of a new phase began to appear in the cosmos. They enlarged very quickly including a space where much larger regions than those we can observe today were included.
Prior to 10-38 s after the Big Bang, the Universe was chaotic and non-homogenous. The phase change due to this this quick transformation, i.e. through inflation made most heterogeneities disappear and only small fluctuations did remain. They too disappeared with time in the form of cosmic radiation when it separated from matter. We have explained earlier that such fluctuations were responsible for the galaxies formation.
In general terms the inflation phase today is widely accepted as reasonable, but within this context there exist several models that try to explain it scientifically. All these models are still developing and have not obtained yet a definite shape. If one day this is realized, many questions regarding the origin of the Universe will obtain a definitive answer.
You have reached the end of Physics lesson 22.12.5 Actual Problems. Horizon Issue. Inflation Phase. There are 7 lessons in this physics tutorial covering Formation of Galaxies and Solar System. Actual Problems, you can access all the lessons from this tutorial below.
Enjoy the "Actual Problems. Horizon Issue. Inflation Phase" physics lesson? People who liked the "Formation of Galaxies and Solar System. Actual Problems lesson found the following resources useful:
Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
We hope you found this Physics lesson "Formation of Galaxies and Solar System. Actual Problems" useful. If you did it would be great if you could spare the time to rate this physics lesson (simply click on the number of stars that match your assessment of this physics learning aide) and/or share on social media, this helps us identify popular tutorials and calculators and expand our free learning resources to support our users around the world have free access to expand their knowledge of physics and other disciplines.