Geoff is well known to our Club as he has been a member since November 2005. He has always been interested in Cosmology, and after retiring went back to university to study the subject, achieving a Masters Degree in Astrology.
While Astrology looks at "how stars are formed", or "where they are" and "why do they travel", Cosmology takes a broader view. Cosmology is a study of the Universe as a whole, its beginnings, how it is evolving, and its future developments.
The only really effective force in the universe is gravity. Newton’s Law of Universal Gravitation is used to explain gravitational force. This law states that every massive particle in the universe attracts every other massive particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. When two objects are gravitationally locked, their gravitational force is centred in an area that is not at the centre of either object, but at the "barycentre" of the system; such as the fulcrum being the point of balance for a see-saw. Each system in the galaxy, and presumably, the universe, has a barycentre. The push and pull of the gravitational force of the objects is what keeps everything in space from crashing into one another.
The study of Cosmology began in 1915.
Albert Einstein and his Theory of General Relativity helped define early thoughts. Although Einstein’s early calculations indicated the universe was expanding, he introduced a "fudge factor" to mitigate this apparent anomoly, as his view was that the universe was neither expanding or contracting. Later science indicates that following the formation of the Universe, it initially contracted, before expanding.
The Milky Way we see in the night sky is actually a flat (edge-on) view of "a spiral arm of" our galaxy. Many spiral galaxies similar to ours have been discovered. In 1924 Albert Hubble was able to calculate the distance to some of the discovered Nebulae, and proved they could not be part of our Milky Way. The Milky Way Galaxy has now been estimated to contain 200 billion stars, and it is now thought there are 100,000 billion galaxies!
Geoff showed a picture of Andromeda Galaxy, which is 2.5 million light years away from Planet Earth; that is, the light we see now originated from its source 2.5 million light years ago. (A light year is defined as the distance a particle of light would travel in one Earth year. In one year, light travels about 9,460,000,000,000 kilometers.)
This image, captured with the NASA/ESA Hubble Space Telescope, is the largest and sharpest image ever taken of the Andromeda galaxy — otherwise known as M31. This is a cropped version of the full image and has 1.5 billion pixels. You would need more than 600 HD television screens to display the whole image. Credit: NASA, ESA, J. Dalcanton (University of Washington, USA), B. F. Williams (University of Washington, USA), L. C. Johnson (University of Washington, USA), the PHAT team, and R. Gendler.
In modern study it is important to know if stars are travelling towards us or away. Drawing parallels to the Doppler affect which demonstrates sound waves compressing as they approach us, and stretching as they move away, light waves behave similarly. Science uses the spectrum light creates to compare its movement towards or away from us, and from these calulations, determines the speed of travel of the object being studied.
Using that relationship, Albert Hubble determined the further a galaxy is away from us, the faster it is travelling, and therefore, the Universe is expanding. Indeed, his calculations formed the basis from which scientists have claimed that the Universe is 13.8 billion years old.
Two theories developed concerning the formation of the Universe, these being "Big Bang" and "Steady State". The Big Bang Theory relates to a single point beginning 13.8 billion years ago, while the "Steady State Theory" indicates no beginning and that the Universe remains the same due to "spontaneous creation of matter".
The discovery of constant cosmic background microwaves in radio signals by scientists in US favours the Big Bang theory. These microwaves appear to be the remnants of that initial explosion known as "The Big Bang". It is believed elements developed as the universe cooled following the "Big Bang Event" with sub atomic particles forming atomic clouds of hydrogen, helium and some Lithium. These clouds which were 75% Hydrogen, 25% Helium and minor Lithium, eventually collapsed forming stars.
Atomic Fusion of hydrogen into helium is the source of a star's energy. As a star fades, all the other elements are formed and when the star finally explodes, these are forced back into the universe. These current theories seem to best explain how the formation of current stars, planets and galaxies occured.
Another puzzling question is "what is the future of the universe? Will it keep expanding, or will gravity eventually pull everything back and causing a collapse?" This collapse is referred to as the Big Crunch, but in theory, (and hopefully!!) this event is billions of years off into the future.
When science tried to measure the density of the universe using nearby galaxies, major anomalies appeared. The movement in the studied galaxies using calulations based on gravitational forces with object velocities and direction produced results which were not close to what was actually observed. The only theoretical explanation for the observed condition was that a huge amount of invisible material, now referred to as Dark Matter, exists.
In viewing the extent of this invisible matter, scientists measured the distortion of light which should have travelled in a straight line. The amount of distortion from a known source, helps to determine the extent of this unknown mass. This dark matter is evenly distributed throughout the universe not interacting with anything around it except through gravity. The forces exerted by Dark Matter is known as Dark Energy. In attempting to explain these theories, it is evident how the existence of Dark Energy may be used in trying to explain actual observations. It is believed that the universe comprises of Dark Matter 23%, Dark Energy 73%, and known matter only 4%. There is still much we don’t know about our Universe.
When the size of the Universe is considered, Geoff believes there have to be similar planetary conditions to ours in existance, and many possible planets have been already been identified. Travelling there however, is entirely another matter.
John Smith thanked Geoff for his thought provoking talk on our galaxy and universe.