Expansão cósmica

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A expansão cósmica refere-se à separação constante, ou expansão, de todo o espaço no universo ao longo do tempo. Albert Einstein sugeriu o potencial de expansão cósmica do universo em sua teoria da relatividade, mas os primeiros estudos que essencialmente comprovaram a expansão cósmica foram feitos em 1929 por um homem chamado Edwin Hubble. A partir de suas observações, ele formulou a Lei de Hubble. [1]"A velocidade de recessão aparente de uma galáxia v é proporcional à sua distância d do observador: v=H0d, em que a constante de proporcionalidade H0 é conhecida como a constante de Hubble." [2]

O tema da expansão universal pode enfrentar muita confusão e acusações. Muitas pessoas estão enganadas por aquilo que esta expansão é realmente. Se todo o espaço e matéria no universo expandiu em simultâneo, não só o espaço vazio entre os objetos iria se expandir, mas os objetos se expandiriam, igualmente. As galáxias estariam ainda mais distantes, mas as galáxias e toda a matéria que as compõe também seriam maiores em tamanho. Se isso fosse verdade, ampliando o espaço entre os planetas o dobro da distância também dobraria o tamanho dos planetas e para o observador ficaria como se nada tivesse acontecido. Se o observador se expande tanto quanto qualquer forma de dispositivo de medição, é difícil dizer o que realmente significa expansão. De acordo com a Lei de Hubble, o espaço entre objetos está em constante expansão, mas os próprios objetos, como planetas, pessoas, estrelas, está mantendo sua dimensão essencialmente da matéria e da forma como uma constante.[3]

Efeitos da distância

Na cosmologia, uma unidade de distância é definida como a luz multiplicada pelo tempo. Edwin Hubble, o fundador da Lei de Hubble eo homem que provou que o universo está se expandindo, criou uma unidade de distância conhecida como o comprimento Hubble. Uma unidade de comprimento Hubble é c/H0. Esta medição é igual a cerca de quatorze bilhões de anos luz.[4]

À medida que o universo se expande, o espaço entre os objetos recua e torna-se mais longe na distância. This is the most clear and evident effect caused by cosmic expansion. Although the space between objects expands, the objects, themselves, maintain the same size. There are different analogies to help explain this concept. One example is the raisin bread analogy. If there was a ball of raisin bread dough that consisted of the bread dough with raisins dispersed throughout the dough, the bread would be put in the oven and begin to expand. As the bread expands, the raisins become farther apart from each other. The farther the raisins are from each other, the faster they will recede from each other. This essentially applies to cosmic expansion in how the more distant galaxies are from each other, the faster they recede from one another.[5]

Effects on Light

While the universe continues to expand, not only distance is affected. Light is also greatly affected by the constant expansion of the universe. During this expansion, light waves travel through our universe and, due to the expansion, will get stretched out and create longer wavelengths. When Edwin Hubble was doing his research on galaxies, he realized their light was being redshifted. Due to this, the galaxy clusters are moving away from each other.[6]

Inflation

Visual Rendering of Inflation

Cosmic inflation is essentially a type of cosmic expansion, although the term refers to a specific event at the beginning of time. Inflation is the extreme accelerated expansion of the Universe.[7]

Cosmic inflation is said to be an event that is considered a period of time that took place immediately after the Big Bang event. Cosmic Inflation occurred 10-36 second after the Big Bang expansion. Then it settled into the present expansion we see today. In the cosmic inflation period, a so-called vacuum energy spread across the whole Universe. This vacuum energy later created all the matter in the universe.[8]

Credit for the development of this theory belongs to Alan Guth (See Also: Borde-Guth-Vilenkin singularity theorem), Andrei Linde, Paul Steinhardt, and Andy Albrecht. Prior to their formulated theory, much evidence from previous studies were suggesting this event. Vesto Melvin Slipher used this information to research galaxy movement according to their spectral shift in the early 1920's. Shortly after, in 1922, Alexander Friedmann became the first man to propose that not only did the universe initially expand rapidly, but it is currently expanding. Edwin Hubble, creator of the Hubble's Law, used these previous studies to determine that galaxies tend to be traveling away from us. Hubble used the galaxies' spectral shifts to prove his studies. In his studies, he discovered that the universe is expanding. He noticed that the more distant the galaxy is from us, the faster it seems to be receding. The only apparent solution to this problem is that the space in the universe is in constant expansion.[9]

According to the theory of cosmic expansion, the universe began as a quantum fluctuation that was 1020 times smaller than the size of the proton. Within that rapid amount of time, the universe managed to increase in size by about 1026 times its original size. The speed of this inflation towers over the speed of light, and the force of this inflation was great enough to overcome the force of gravity. Within seconds, the Universe had a diameter of about four inches.[10]

Inflation can be viewed as a hypothesis created to save errors in the big bang theory. Prior to the formulation of the inflation theory, problems began to arise relating to heat. One of the most known and argued problem is known as the horizon problem, which is a light-travel problem. For the heat to have been evenly equalized throughout the Universe, more than ten times the amount of time from the Big Bang would have been necessary. The theory of cosmic inflation was formulated to try and rescue the big bang theory.[11]

Referências

  1. Tests of Big Bang: Expansion Britt Griswold, NASA, Friday, 04-16-2010.
  2. Routledge Companion to the New Cosmology Peter Coles, Routledge, January 14th 2004.
  3. The Expanding Universe Gary Felder, NCSU, 2000.
  4. Hubble Length Multiple Authors, Wikimedia Foundation, Inc., 24 de abril de 2010.
  5. Hubble Expansion Peter Timbie, The University of Wisconsin Madison, 12/04/2009.
  6. Hubble Expansion Peter Timbie, The University of Wisconsin Madison, 12/04/2009.
  7. Cosmic Inflation Joanne Cohn, Unknown Publisher.
  8. Cosmic Inflation Unknown Author, Steadfast Networks, 4 January 2010.
  9. Cosmic Inflation Unknown Author, Steadfast Networks, 4 January 2010.
  10. Cosmic Inflation Unknown Author, Steadfast Networks, 4 January 2010.
  11. Multiverse theory—unknown science or illogical raison d’être? Gary Bates, Creation Ministries International, 30 June 2009.

Ligações externas