Science

  • Issue 115 / January-February 2017



    The Universe A Short History

    Civan Ozturk

    Has the universe existed forever? And how much do we really know about it? Only 4-5 percent of the universe is made up of what we can see today: stars, planets, and galaxies. This means that all of today’s known scientific information is from about just 1/20th of the universe. Scientists cannot detect and comprehend the remaining 95%.



    Dark matter, the mysterious unseen mass, and dark energy, the universe’s mysterious force, comprise the rest of the unknown universe. We still know very little about dark energy and dark matter. Dozens of institutes and thousands of scientists have organized international collaborations in search of both. In fact, scientists hope the biggest energy particle collider [1], the Large Hadron Collider (LHC) in Geneva, will help solve the puzzles of dark energy and dark matter.


           ¬†¬†¬†¬† It is common for people to ask, how did the universe begin? After decades of observing and measuring, today the majority of scientists explain the beginning of the universe via the Big Bang theory. Two astronomers, Arno Penzias and Robert Wilson, established the Big Bang theory of cosmology by observing the cosmic background of radiation [2]. According to their theory, everything in the universe was contained in one single mass and there was no space or time. Everything started with the explosion of this extremely dense and hot mass. This explosion was not like an explosion into an empty space; rather space itself began with this explosion.


    The idea that led scientists to the Big Bang came from observing the universe’s expansion. Edwin P. Hubble found that almost all galaxies are moving away from the center of the universe [3]. He did so by measuring the light from these galaxies to determine their velocities. This proved that the universe was not static, but was instead expanding. After scientists realized that the universe is expanding, they thought that there must be a beginning to this expansion. Then, using the speed of this expansion, they calculated the life of the universe. Through this, they were able to show that the universe has a beginning. Today, almost every scientist agrees with the Big Bang, and they can support it with scientific evidence.


    The idea of the universe, let alone an expanding universe, can be pretty incomprehensible. Let me make it a bit more comprehensible. Think about a balloon. There are two spots marked on this balloon. When you inflate the balloon, you’ll see how these two spots are moving away from each other. The balloon is the universe and the two spots are matter in that universe. This example shows how matter “rides” the expanding universe.


    Until about 20 years ago, most scientists thought that the expansion of the universe was getting slower. In 1998, observations of the Type la supernovae revealed the existence of dark energy. Dark energy, scientists found, was one way to measure the expansion rate of the universe over time. This discovery was proof for the universe expanding at an increasing rate. Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess have been awarded the Shaw Prize in Astronomy in 2006 [4] and Nobel Prize in Physics in 2011 [5] for their breakthrough study on this topic. But though scientists know the universe is expanding faster and faster, no one yet knows why.


    Let’s go back to the beginning of the universe and see how everything was induced into a perfect order. At the beginning, when the Big Bang (BB) occurred, one might think that this came with chaos and disorder. The perfect design of the universe came from that mess.


    If we could get precise information all the way back to the Big Bang, it would help us to solve many outstanding mysteries. Unfortunately, we are unable to gather this information because the cosmos, in its infancy, was foggy and full of light rays. After about 300,000 years, the universe became transparent and many particles fell away; the furthest distance we can see across space is 13.7 billion light years, which is when the universe became transparent.


    Cosmic Microwave Background (CMB) was formed almost 380,000 years after the BB. That is the cosmic background radiation, or thermal radiation, and it is believed to be a leftover from the BB. The CMB is the source of the oldest light in the universe and it represents the kernel of stars and planets.


    In the early stages of this CMB time, elementary particles were formed. These particles acquired mass while passing through the Higgs field and interacting with the Higgs boson [1]. These particles are mainly divided into two categories: fermions and bosons. Fermions are the most fundamental particles, known as quarks and leptons. The quarks and leptons are further divided into six flavors and corresponding antiparticles. Bosons are photon, gluon, W-Z bosons, and graviton. They carry forces, included the four main forces in the universe ‚Äď electromagnetic, strong, weak, and gravitational.


    The basic building blocks of matter are two composite particles, baryons and mesons, which are formed by the combination of quarks. Baryons are made of three quarks, such as protons (two up and one down quarks) and neutrons (two down and one up quarks), of the atomic nuclei. Mesons are usually found in cosmic rays and are composed of quark-antiquark pairs. Today, more than 200 subatomic particles have been discovered at sophisticated particle accelerator laboratories. Most of them are composite particles, composed of other fundamental particles.


    After the creation of these elementary particles, stars, galaxies, and planets were formed, step-by-step.


    First stars: 200,000,000 years after Big Bang

    According to the results of NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), the first stars were formed 200 million years after the BB. The clumps of matter were brought together with the gravitational force and they grew like a growing snowball until they have enough energy to start nuclear fusion process, which is the main process behind the shiny stars up in the sky.

    First Galaxies: 1,000,000,000 years after Big Bang


    1.6 million galaxies have been identified according to the location of the Milky Way Galaxy by The 2 Micron All-Sky Survey (2 MASS). Figure 1.1 is a computer-generated map of our surrounding universe by the 2 MASS, which shows nearly 50,000 galaxies near our galaxy, Milky Way (2 MASS/ J. Carpenter, R. Hurt & T. H. Jarrett).  


    The Milky Way, which includes our solar system, began to form 5 billion years after the BB. There are approximately three hundred billion stars in our galaxy, and there are estimated to be 100 billion galaxies in the universe. Scientists do not know the structure and features of these galaxies. But then, they don’t even know everything about our galaxy.


    How big are objects in the Milky Way? Everyone knows about the moon and the Earth, as well as the other planets in our solar system. The largest star in the Milky Way is VY Canis Majoris, a Red hyper-giant. It has a diameter of 280 million km, which is so big that an airplane flying at 900 km per hour would need 1100 years to circle the star. There are approximately 200 billion stars in Milk Way alone and the sun is only one of them.


    When thinking about all the space in our universe, it makes the order of our own solar system and galaxy seem quite extraordinary.


    A solar system in general consists of a star at the center and rotating astronomical objects (planets, moons, etc.) around that star. In our solar system, the object in the center is the sun and everything orbits around it. There are eight planets including the earth and their natural satellites orbiting the sun. So far, 3946 comets, many asteroids, and thousands of near-earth objects and minor planets have been discovered [6] around the sun. The sun is attracting all these objects with the gravitational force and they counter this attraction by means of their centrifugal force. These forces are balanced and keep the objects in their orbits. All of these are formed and located perfectly with a magnificent balance. How does this kind of order form from a disorder spontaneously?


     


    References:


    [1]       Kara, Cihan, "Will CERN Reveal the Origin of the Universe or Cause the End," The Fountain Magazine, Issue 92, 2013.

    [2]       The Large Horn Antenna and the Discovery of Cosmic Microwave Background Radiation,             https://www.aps.org/programs/outreach/history/historicsites/penziaswilson.cfm

    [3]       Hubble Space Telescope,             https://www.spacetelescope.org/about/history/the_man_behind_the_name/

    [4]       The Shaw Prize in Astronomy in 2006,         http://www.shawprize.org/en/shaw.php?tmp=3&twoid=51

    [5]       The Nobel Prize in Physics 2011,      https://www.nobelprize.org/nobel_prizes/physics/laureates/2011/  

    [6]       The Minor Planet Center: http://www.minorplanetcenter.net/

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