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In reality, thoughts about how “space” and the universe were created or how the universe will end have always occupied people’s minds..It is from these thoughts, given logical foundations, that modern cosmology has emerged..In recent years, a new branch of scientific knowledge has also taken shape, called astroparticle physics..
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The Universe of the Past
In reality, thoughts about how “space” and the universe were created or how this universe will end have always occupied people’s minds..It is from these thoughts, given logical foundations, that modern cosmology has emerged..In recent years, a new branch of knowledge has also formed, called astroparticle physics..From modern cosmology we learn,that the universe was created through a “Big Bang”..According to the theory,,at the start of creation the intergalactic distances between neighboring nebulae were zero..It was in a completely compressed state from which the Big Bang occurred,that is—
about 15 billion years ago, an extremely hot and infinitely dense point exploded in what is known as the Big Bang, and from this the universe began..Within the first few seconds of this creation process, four forces,some fundamental particles, and atoms originated.
Scientists found through experiment that up until 10^-43 seconds after the Big Bang, the four types of fundamental forces of the universe were merged together as a “super force”..These are: 1) gravitational force, 2) electromagnetic force, 3) weak nuclear force, and 4) strong nuclear force,After the first second, quarks,electrons,protons,and neutrons were created, and after three seconds, protons and neutrons combined to create nuclei,from which hydrogen and helium were formed.Scientists have expressed this entire process in the form of a cosmic calendar.Here, 1 second equals five hundred years (or 475 years)! So it can be said,according to this, the creation of the universe by the Big Bang occurred on January 1, and the galaxies began forming from May 1. Our solar system was born on September 9, and finally, the Earth was born on September 14..
Therefore, it is clear that the universe we see now is not exactly as it is at this moment,this universe was created billions of years ago,and its creation remains unexplained and mysterious to humanity..
The Present Universe
We know the universe is enormous,infinite and boundless, and it was created through a Big Bang..The continuation of this Big Bang led scientists to wonder: how big is our universe??Where are its boundaries,or is it endless??Will the universe exist forever as it is??At the heart of these crucial questions lies the concept of the expanding universe. (expanding universe).Whether the universe is expanding or closed is suggested by Einstein’s general theory of relativity.According to him, the universe was closed.But a few years after his proposal of this closed universe framework, scientists discovered that the universe is expanding.This became evident when they started studying the velocities and distances of galaxies.In 1912, Vesto M. Slipher (1875–1969) discovered the Andromeda galaxy is moving toward us at 170 km per second.By 1928, Slipher had measured the velocities of more than 40 galaxies and saw that most galaxies are moving away from our Milky Way galaxy.’After that, in 1929, Edwin P. Hubble (1889–1953), using the famous 100-inch Hooker reflecting telescope at Mount Wilson Observatory in Southern California, looked at distant galaxies and realized,they are all steadily moving away from each other.He measured the distances to several external galaxies, and earlier, Slipher had determined the spectral redshift of galaxies.Using this information, Hubble calculated the relationship between the “red shift” (z) and their distance (D).This redshift is generally seen as a standard Doppler shift,since distant galaxies are continually moving away from our galaxy.This recession rate is very low.Slipher found Z=0.006.So he wrote a non-relativistic equation for the Doppler shift,v=H.d.Where
v is the velocity of galactic recession and H is a constant.
The Universe of the Future
In the previous section, we got some idea about the expanding universe, that the universe is expanding every moment. Now the question is, will our universe continue expanding like this forever? Or will gravitational attraction eventually slow down the rate at which galaxies are spreading apart, causing expansion to stop and contraction to begin one day? To answer this question, scientists have broadly described three possible fates for the universe. They are—
1) Closed Universe (bounded universe)—If the universe contains matter with high density, it will eventually stop expanding and start contracting, resulting in a closed universe.
2) Open Universe (unbound universe)—If the universe contains matter of low density, it will continue to expand indefinitely, resulting in an open universe.
3) Marginally Bound Universe (marginally bounded universe)—This situation is in between the two mentioned above. In this scenario, the rate of expansion will gradually decrease but the universe will continue to expand as much as possible (flat/marginally).
Now the question is, which possibility will come true? To answer this, we need to know the actual density of the universe as well as the transitional or critical density. The critical density (critical density) is the density required to stop the expansion of the universe. Scientists estimate this value to be about 1.1X10^-26 kilograms per cubic meter. If we try to derive the universe’s critical density, what about finding its actual density? One way is to add the mass of all visible galaxies in the cosmos and divide by the observed volume of space. But calculated this way, the density is extremely low—only 1-2 percent of the critical density. So, it appears that since the value of omega is less than 1 (Ω<1), the universe should be open or infinite (open/unbounded). Yet this cannot be stated with certainty, because the universe also contains dark matter (dark matter). The existence of this invisible matter is inferred only from the gravitational effects observed within galaxies. Physicists today believe that about 99 percent of the universe’s matter may consist of such invisible material! If that’s the case, expansion may halt at some point and contraction may begin. In that case, looking at neighboring galaxies would reveal a blue shift (blue shift), as the objects start to crash into each other. The temperature would then steadily rise. Eventually, after expanding for as long as it had, the universe would contract and return to a singular point (singularity point). This ultimate collapse of the universe has been named the “Big Crunch” (big crunch).
So, two predictions can be made for the universe—it may keep expanding forever, or eventually collapse back into oblivion. Which outcome will occur depends on the current density of the universe. To conclude this discussion, let’s finish with a quote from Stephen Hawking, the renowned physicist of our era:
“In fact, the present density seems to be very close to the
critical density that separates recollapse from indefinite expansion. If the
theory of inflation is correct, the universe actually on the knife edge. So I’m
in the well established tradition of oracles and prophets of hedging my bets by
predicting both ways.”
verry verry fine and tanks.
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