In establishing this new set of assumptions in redefining gravity and our projection of the Universe, there emerged three important hypotheses:
1. Gravity is due to two factors – acceleration and inertia
2. Everything in the Universe is continuously expanding in a three-dimensional pattern.
3. Space-time is expanding similar to a four-dimensional surface of a five-dimensional balloon that being steadily blown up.
MODIFYING THE STEADY-STATE THEORY
In 1948, Bondi, Gold and Hoyle suggested a theory that at that time, gained a popular support. The idea could be summarized this way- the universe expands due to the continual forming of galaxies within the empty spaces (gaps) in-between the already existing galaxies. They even used the word “new matter” that being steadily created within those gaps. This theory was known as the Steady-State Theory. This theory implied that as the Universe expands, this new matter scattered in the gaps between galaxies must influence the total mass of the Universe. The density of the Universe must either be increasing or at least remain. But in 1965, Penzias and Wilson with their discovery of microwave radiation, indicate that the Universe might be denser in the past which was a contradiction to the Steady-State Theory. The theory failed and totally abandoned.
Assuming that everything in the Universe is expanding in a three-dimensional pattern, such as the Earth itself, it implies then, that, its volume is continuously increasing, possibly, in geometrical progression. In Physics, density is defined as the quantitative ratio between mass and volume. If one agrees that the earth’s volume is continuously increasing in a fast rate without taking account of its mass, the Earth’s density would then decrease tremendously, making it so big and yet so light as a feather.
SELF- OPINION
One way to avoid this scenario is to re-examine the Steady State Theory and make some modifications. First, it is not necessary to create or form new galaxies out from the new matter that is continuously created in the Universe, a better proposal would be - this new matter is also continuously created within every bodies and spaces in between them. Therefore, the densities of each body in the Universe, including the Earth, would not fall tremendously as these bodies continue to increase in size. They will maintain their densities, proportionally.
The Penzias-Wilson discovery that the Universe might be denser in the past is not in contradictory to the above proposal. If the rate of the universal three-dimensional expansion of every matter in the Universe is much greater than the rate of the creation of this new matter distributed within the whole Universe, the result would still agree with the observation that the Universe was denser from the past.
HOT BIG BANG THEORY & INFLATIONARY MODELS
The “Hot Big Bang Theory” is today’s most generally accepted theory about the evolution of the Universe. It stated that in the beginning, the Universe was so hot and infinitely small. As it expands, its temperature began to decrease causing the elementary particles of nature to clump together. First, they developed into simple atoms of hydrogen and helium and then into heavier elements. Later on, they formed into complex compounds that created the galaxies, stars, planets and all the existing things we see, big and small, including us, human beings.
But Stephen Hawking made a comment that this Hot Big Bang Theory was insufficient. There are still questions that need to be answered;
First: Why the Universe started so hot?
Second: Why the Universe at large scale, so uniform that all the regions in it look identical whichever direction we look at them?
Third: Why the Universe started so close to a critical rate of expansion that until now, after millions of years of its existence, it’s still close to a critical rate?
Fourth: What is the origin of density fluctuations in the Universe that caused the formations of local irregularities that we commonly known as galaxies and stars?
According to Hawking, Einstein’s General Relativity is not competent enough to answer these questions due to its prediction that the Universe started from an infinite density at a point of singularity that all the laws of Physics would be violated. But he believed that maybe, there is another way to explain the origin of the Universe that will match and answer the questions he enumerated.
One good attempt was the “Inflationary Model” presented by Allan Guth. The Universe began at a very rapid expansion (inflationary mode), not just only in a very intense hot condition but rather, in a chaotic state. Guth also suggested that the accelerating expansion of the Universe was caused by an “extra-special energy” which has an “anti-gravitational effect” (similar to Einstein’s cosmological constant). Light could then have time to travel from one region to another. This could also explain why different regions in the Universe have the same properties- they look identical whichever direction we look at them. He also declared that the total energy in the Universe is exactly at zero consisting of the positive matter energy and the negative gravitational energy. But there is controversy in this idea – why at present observation, the matter energy is going down (the total mass in the Universe is decreasing) as the Universe continues to expand? Hawking also stated that at present, the rate of expansion of the Universe is no longer in an inflationary rate. There could be a mechanism that would eliminate Guth's large anti-gravitational effect that changed the rate of expansion of the Universe in a slow rate. But it could also be possible that some amounts of Guth's extra-special energy still remain in the Universe. This could explain why the Universe retain its critical rate of expansion, this special energy still affects the Universe by sustaining the ability of the Universe to expand although its over-all temperature is going down.
But a group of scientists realized that Guth’s theory had inconsistencies that they abandoned it in its original version. There are other models presented but the third attempt, the Chaotic Inflationary Model by Linde was the most viable but there were still inconsistencies found that at the end, it was not also recognized. Hawking stated that those "inflationary models" were good attempts in initiating ideas dealing with what was really happened on the very moment the Universe was created but in a second thought, maybe, they were making this subject too complicated. There could be a much simpler way to explain the birth of the Universe.
SELF-OPINION
In the Big Bang Theory and the Inflationary models, the Universe started in a very hot or chaotic condition and assumed that the Universe was infinitely small. But according to general relativity, the start of the Universe is from a point of singularity with infinite density. A point in geometry has no dimension - no width, no length nor height, does this means that the Universe started from a zero size? Is there a difference between an “infinitely small size” and a “zero size” Universe? Why the Universe started so hot? Particles having high energies move in high speed preventing them to attract one another. It also causes the temperature of the environment to increase or vice versa, in a very hot environment, particles tend to gain individual energies causing them to move freely without the influence of the force of attraction. The pattern of the over-all temperature of the Universe through observation, suggested that the Universe was hotter from the past but the question of why the Universe started so hot was not clearly been answered but presumed only that it was indeed, started hot.
Applying this new approach in redefining gravity that led to the assumption that the Universe and everything in it are expanding in a three-dimensional pattern, there is no need to find a mechanism that will eliminate the very large anti-gravitational effect that changed the expansion of the Universe from an exponential rate of expansion into a slow rate of expansion – “technically, the Universe is still expanding in an exponential rate and will continue in this pattern”. Guth’s idea that the Universe began in a rapid expansion will agree with this new proposal that all things in the Universe are expanding in a three-dimensional pattern. It is important to emphasize that all the existing matters in the Universe are getting bigger each seconds of a time, possibly, in geometrical or inflationary rate. But appearing that the rate of expansion of the Universe is slowing down is maybe due to a misleading method or projection of observing the Universe. Einstein at one time stated that his space-time has the tendency to expands, indeed it is expanding because of the new matter that is being steadily created within its fabric. Personally, I believe that Stephen Hawking’s mathematical proposal of the quantum gravity and Einstein’s revelation that matter can directly be converted into energy could be the two important aspects to achieve the right approach to a better understanding the of the Universe.
(Note : There are recent scientific studies showing that there is a possibility that the Universe is still expanding in an exponential rate)
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