A spiral galaxy is one of three types of galaxies studied and documented by Edwin Hubble. Spiral galaxies are the most common in the universe and have a characteristic spiral contour; that is also the characteristic feature referred to in their name. The spiral shape is usually constituted of arms enfolded around a dense core of galaxy forming matter, and bodies that include dust among others. The most obvious feature that can be seen from the unaided eye; that suggests that the earth’s universe is a spiral galaxy is the Milky Way. The Milky Way is the earths home galaxy; and has the features of a spiral galaxy that include a galactic core, which constitutes of a swelling of extremely old stars that are placed to surround an extensive black hole.
The black hole on the Milky Way is the space between the arrangements of stars, in which the gravitational attraction is so immense it cannot allow the escape of any object. The black hole itself consists of an immense concentration of mass; that results from the death of an expansive star arguably ten times bigger than the sun. This mass gives it the capability of imposing gravitational pull on the objects around it including light that explains the reason as to why the black holes are dark. This is the case because the gravitational pull that results is so immense, that it cannot even let light pass through it.
The other characteristic of the milky way that qualifies it to be a spiral galaxy; is the distinctiveness of the bulge when the milky way is viewed from the side. The Milky Way also has arms surrounding the core; that is constituted of stars much younger than the ones forming the galactic core. The Milky Way has a halo of stars believed to be older than the rest; that is arranged in globular clusters that are the dense packs of stars visible from the earth, though they may appear like single masses.
The bar shape of the milky way also qualifies it to be a barred spiral galaxy; as its core takes a bar-shape that causes the bulge looks like a peanut when viewed from one side. The other fact that distinguishes the Milky Way to be a spiral galaxy is the configuration of the arms that places it within the Sb classification. Apart from the earth’s Milky Way, are other spiral galaxies that have been located within the earth’s universe acting as a proof that the earth is housed by, and in a spiral galaxy.
If the sun and solar were located near the centre of the galaxy; would mean that they would fall close if not within the black hole. Due to the immense gravitational attraction of the black hole that attracts even light; the suns light that is radiated onto the earth would significantly be reduced. The situation would also lead to partial darkness due to the gas and dust that forms a major part of the galaxies; that would block the light and heat radiated by the sun onto the earth.
In the case that the solar system was to be placed in this position; would mean that the earths temperatures would be significantly become lower than the present ones; the light shed on the earth during day time would be very greatly reduced; and the life on earth that relies on the sun’s heat and light, would not exist within the environment. This would also create the need for more sources of lighting and heating; to provide for the lighting needs and provision of temperatures that are homely to the inhabitants.
A globular cluster is a spherical group of stars that move around a galactic core as a satellite. The components of the cluster are usually held very tightly together; by the gravitational force that is resultant therefore giving it the spherical form and high stellar densities. If the earth’s sun and solar were placed near the centre of a large globular cluster; would mean that the earths environment would appear like it is lit by a number of suns, and the shadows formed by the blockage of the sun’s light on the earth would also increase. The effect of this would be; unstable increasing and decreasing of the lighting and temperature conditions; that would be experienced on the earth. These variations would further affect the animal and plant life that is harbored in the environment.
Molecular clouds are composed of clumps, irregular masses, bubbles and filaments that are placed in chemically rich surroundings. An example of molecular clouds is the Taurus and Orion molecular clouds. In the case that the sun was placed at the centre of a dense molecular cloud; the light from the sun reaching the earth would greatly reduce; leading to decreased visibility conditions on the earth. The molecular cloud would also act as a sheltering mass that would reduce the amount of heat and light reaching the earth; which in turn would lead to varied earth temperature which would further result to differing plant and animal life within the environment.
The causes for the redshifts that indicate velocity recession results from the fact that light from moving objects; appears to possess varying wavelengths that are determined by the relative change of position of the source and the observer. In the case when the object is moving further; red waves with a longer wavelength than when the light was emitted show the instance of a redshift. The reverse is a blueshift that is experienced when the source of light is approaching; and this takes place due to the fact that, the wavelength of the light is shifting from longer to shorter measures. In the different cases; the wavelength shifts lead to an apparent variation in the speed of the light in question, and that is why the slow moving galaxies seem to move at massive speeds.
The universe expansion phenomena were discovered by Edwin Hubble in 1929; and in recent discoveries it was documented that if the universe were finite, then the gravitational attraction forces would lead to the collapse of the entire universe. Discoveries identified that the spectra of light from many of the bodies in the universe were increasing acquiring longer wavelengths also referred to as redshifts. Due to the constantly expanding universe function; the universe will eventually after these many years, take the open, flat or closed universe shapes. The result would later be that if the universe expanded forming an open or flat form; it would slow to an expansion rate of zero after a longtime. However if it were to take the closed expansion form, it would later reach the maximum measure and collapse on itself probably leading to another big bang.
The force that slows the expansion in each case is the gravitational pull. The effects of the expanding universe would include reducing temperatures that would later reduce to levels that cannot support life. The distance between different galaxies would increase to the extent that different clusters would not experience each others experience anymore. The supply of gases needed for the formation of stars would get exhausted and the available ones would cease to shine. This means that in a few billion years in the future the habitation of the earth would be impossible, and the universe would turn dark and blank.