The Nature of Time, Lead: Marcy Elliot & Sam Meehan

2/27/2007

Summary by Adam Mirando

The Nature of Time

The class held on February 27, 2007 was lead by Sam Meehan and Marcy Elliot on the often simplified idea of time. The discussion began with everyone sharing their current thoughts on the subject. Many of the presented ideas interpreted time as an organization method, only existing as a development of the human mind.

However, the ensuing discussions worked to dispel the idea that time was a made up concept and, instead, portraying it in a whole new complexity. More than just an abstract thought, time is a real phenomenon and an important part of this universe.

Marcy began the presentation introducing the basics of time and its origins. Focus first turns to the question of whether time is real or only a method of organization created in the consciousness. From the perspective of cosmology, time must be real and possesses its own beginning. Once again, attention returned to the Big Bang, which not only seems to have marked the origin of the universe but also of time itself. This conclusion was followed up with a brief description of the development of the current theory of when time started. Ancient cosmology had a cyclical concept of time without a beginning or an end. This idea was later replaced by a more linear theory of time (such as presented in the Bible) in which time progresses from a set origin and is marked by major events. Believers of this concept (which lasted well into the Middle Ages), however, perceived this timeline to be far shorter than now understood. Based on stories and genealogies, these early timelines were measured in the thousands of years. With the integration of geological time this increased to hundreds of millions of years and, later, due to developments in astrophysics, this timeline was finally set to about fourteen billion years.

The discussion then considered some time diagrams consisting of several concentric circles (The Cosmic Spheres of Time). Each of these circles reflected a key event in the history of the universe. As clarified by Professor Möbius, the diagrams demonstrate that as one looks at locations further away from Earth they are looking further back in time. This is because light takes longer to reach Earth the farther away its origin. By looking deep into space one is able to see images of large galaxies forming hundreds of millions of years in the past and, even further, small galaxies that are just visible to us today. This leads to the idea of a cosmic horizon, the furthest distance one is able to see into space, the light from which has been traveling since soon after the beginning of the Big Bang to finally reach Earth now (approximately 14 billion years later). Professor Möbius further explained that it is possible for objects to exist beyond the cosmic horizon but we are unable to see them from Earth. This is because the expansion of the universe displaces these objects at a rate faster than the speed of light, rendering it impossible for light from these areas to reach Earth. If different observers from another location of the universe were to view into space, they would view their own, albeit different, cosmic horizon (perhaps even a sight of ancient Earth). During this discussion, Evan brought up the idea of an x-ray telescope, which Professor Möbius explained could be used to see rays from much more energetic and violent areas within the cosmic horizon, such as the time of the Big Bang, which cannot normally be seen with optical telescopes. A supernova was given as an example, which possesses such colossal amounts of energy that it not only appears as visible light but also x-rays.

Chris Ives followed up by asking if it were possible for anything to be faster than the speed of light. Professor Möbius negated this comment saying that the speed of light could almost be considered the “cosmic speed-limit.” Some objects may appear to move faster than the speed of light even though they are actually moving slower. Professor Möbius gave the example of jets from the poles of black holes from which material is spewed out almost at the speed of light. A blob from one of these poles could appear to be moving faster than the speed of light but it is only an optical illusion caused when these blobs move towards us at an angle. This causes the light to appear as if it were covering more distance than it should. While nothing we know of can travel faster than light through space, the expansion of the universe is a very different concept. Because of the expansion of space within Earth’s cosmic horizon causes this horizon to appear as if it were receding close to the speed of light. As a result, objects beyond this cosmic horizon would seem to be moving faster than the speed of light relative to us and light from these objects will never reach us. This is, however, space expanding and not the objects themselves moving faster than the speed of light.

Sam Meehan brought up the point that some scientists theorize the existence of particles possibly moving faster than light though these particles have yet to be discovered experimentally but are not opposed to by any general theory of relativity. Professor Möbius confirmed the existence of these theories and called the particles tachyons. These particles would have to possess very specific qualities as negative energy particles and would not be able to slow down below the speed of light. Therefore, particles can either be slower than the speed of light or faster, but they than not traverse this boundary.

Mike Dunn continued the discussion on time diagrams by questioning if it were possible for nothing to exist beyond this cosmic horizon. Professor Möbius brought up the idea that all observable data suggests that physics is the same throughout the universe. According to the cosmological principle, if one were to conduct every possible physical observation, everything should turn out to be the same. Therefore, it would not be logical to assume that this one idea of cosmic horizons would be different. To assume otherwise would be to place Earth at the center of the universe.

Professor Davis inquired if there were a way to use our knowledge of the physics of the universe to developed observable evidence opposed to idea of Earth being the center of the universe. Professor Möbius remarked that if the Earth was the center of the universe, then the Big Bang explosion would have had to have occurred in this position. In that case, energy would be randomly distributed and the density should be greater closer to the point of origin and slowly disperse farther away from the center.

Moving away from the idea of time diagrams, Marcy Elliot and Sam Meehan then directed the discussion towards the topic of time perspectives. Sam Meehan began with the idea of time in the form of an arrow heading in the direction of the future. While he said that it was not a perfect representation of time (as will be seen later with the introduction of the Planck time unit) it does show the idea that time only progress forward. This led to the introduction of the seven perspectives of time: thermodynamic, cosmological, radiative, causal, weak, quantum, and psychological/perceptual (though not all were discussed).

Sam explained that, according to the thermodynamic perspective, time progresses into increasing amounts of entropy. A classic example of this, he explained, is of a glass falling off a table and shattering. The resulting pieces would exhibit far more entropy than the glass did when all the pieces were together. He continued with the idea that if the particles were in a different order it would still appear to be the same. But, if one were omniscient and could tell the difference between two particles, they would realize that there is only one configuration. In this case the omniscient being was brought up as being God and would require him to be an active participant in the control of time. Phil Fernandez, however, brought up the point that it is possible for one to observe but not act upon a system. This holds true as long as the observer receives only information radiating from the system and does not input additional energy to acquire this data. In this case, an observer can detect the photons coming from the shards of glass without adding energy to the system.

Chris Ives suggested a possible flaw in the broken glass analogy in that glasses can be rebuilt and, therefore, time could progress against entropy. Sam explained this by saying that while creating a glass my decrease the entropy of the glass, the overall entropy of the universe is increased in the process because of the actions that are required in the glass’s creation, such as the breaking down of glucose for the purpose of energy. Professor Möbius elaborated on this idea by saying that the universe theoretically acquires higher amounts of entropy referred to as the “heat debt” of the universe. This heat debt, however, is alleviated by the expansion of the universe which disperses the entropy across an ever increasing volume of space.

Marcy Elliot continued the discussion on the perspectives of time with the psychological/perceptual perspective. One common idea is to picture the past as behind and the future in front. Sam brought up the idea of the Aymara tribe, which views the past as ahead and the future behind which, as Willie suggests, may be based on the fact that one can see their past but not their future. This also led to the idea that some concepts of time take more the form of organization methods than as a real unit. At this moment, Sam introduced the idea of the Planck Time Unit, 5.4*10-44 seconds, which is the smallest quantification of time, which further discredits the view of time as a constant line. Professor Möbius further explained the Planck Time Unit in that it could not actually be measured but was the smallest division of time according to quantum mechanics. While one can mathematically divide this number into smaller intervals, these results would have no practical use as they do not exist. It is limited by the fact that, in quantum mechanics, the world gets grainy after reducing it to a certain size and cannot be reduced any further. As a result, time is more of a chain of these short intervals rather than a continuous line. Two good analogies were given in order to help understand the concept. The first was given by Chris Ives, who suggested that the idea of the Planck time unit could be thought of like the cosmic horizon. While theoretically things could exist beyond the cosmic horizon, we have no way of looking back beyond this point. The second analogy, suggested by Melissa Russell, was a comparison to the fact that one cannot make measurements smaller than the possible error in finding those measurements. Attempting to do so only results in failure.

The next major discussion, brought up by Andrew, suggested that time could be compared to a sense, such as sight and hearing, and may be habituated to the point where one does not realize the passage of time. Professor Davis suggested that memory could be a sort of sensory organ to fit this analogy to the senses as time is often closely linked to events. Professor deVries, however, contested this idea with the works of Aristotle. Aristotle seems to have categorized different stimuli as sensibles. Color and sound, for instance, were labeled proper stimuli because color is a property of the sense of sight and sound exclusive to hearing. Aristotle also suggested the idea of common sensibles, properties available to more than one sense. Space, for instance, can be detected by both sight and touch. Time appears to be similar to the idea of these common sensibles, in fact the most common sensible, in that all senses seem capable to detect the passage of time. This could include observing movement or even detecting a change in smells. Professor Davis then stated that memory is needed for all those senses to actually detect the passage of time. Professor deVries then argued that the durations of these sensation changes may be even too short to be detected by our sense and then transferred to the short term memory. Instead, this sensation of time could be explained as older stimuli remaining resonant instead of disappearing immediately upon receiving another stimulus. Therefore, this resonance will continue to be integrated in the sensory centers of the brain along with new input instead of being transferred to a memory center. By differentiating between older and newer stimuli a sense of time could be created. Here, Chris Ives suggested the idea of memory as a possible overall sense that works with all your other senses to develop a concept of time. Professor deVries then brought up the idea of virtual motion, where alternating lights may appear as a moving light, but are both actually stationary. Since motion is often depicted as an aspect of time, this may be an example of sight detecting the passage of time on its own.

Focusing away from the idea of time as a sense, Joe Collins suggested that time is the method of how humans organize their sensory data instead of a sense in its own right. As he explained, without time it may appear as if ones life were flashing before their eyes in an instant or, as Sam Meehan suggested, could appear to continue eternally, neither of which actually occur. Professor deVries mentioned that it would be difficult to imagine a world without time since nearly everything is a temporal phenomenon. Joe then questioned whether inanimate objects, such as a hydrogen atom, are affected by time since they do not have a perception of its passage. Sam Meehan suggested that consciousness may be necessary. Professor deVries, however, argued against this idea saying that while consciousness is needed for the concept of time, it is not needed for there to be time. He argued that it seemed illogical to assume that time only occurs because one perceives it does and that everything else is “just there.”

Following this debate, Sam Meehan retook control of the discussion and introduced the topic of relativity. He began with the idea that time is not a constant, though it may appear to be. This fact is more noticeable at speeds approaching that of the speed of light. To better explain this topic, Sam proposed the twin paradox, which Professor Möbius explained as twin (A) remains at the same location while the other (B) is traveling at speeds approaching that of light. When B returns to A, it would appear that A has aged more than B. This is because the acceleration of B bends the space-time lattice. Sam also brought up the idea of other phenomena that cause a bend in space-time. These phenomena include black holes as well as very massive objects (such as a cosmic string). The idea of bending space time also led to the introduction of Alcubierre’s warp drive. This theoretical phenomenon suggests that it may be possible to travel to a destination at speeds apparently faster than the speed of light. However, the object is not actually traveling faster than the speed of light, but is actually riding a space-time wave.

Willie Roda suggested, based on the idea of space-time folding in on itself, the analogy of a book in which all the events are happening simultaneously on different pages. Those on the later pages are aware of what happened on the previous ones and, as time progresses, the occupants of one page continue to the next. Time travel, in this case, would be like jumping to different pages. Professor Davis also debated the idea that this idea of travel would also invoke the idea of time because jumping from one page to another is, itself, a manifestation of movement, and, therefore, time. Professor deVries agreed with this statement, stating that since traveling is distance over time then time must exist in order to travel.

The discussion ended with a debate on the legitimacy of time travel. Sam Meehan began with the questioning of why we do not see people from the future in the present. Morgan O’Neill brought up the idea that traveling in time may only be possible until the time that the first time machine was created. Professor Davis remained skeptical of the idea of time travel and suggested the idea of a time-traveler becoming superimposed on an object that occupied that location in the past. Sam took this time to bring up the grandfather paradox. This suggests that actions done by a time traveler in the past (such as killing one’s grandfather) could cause alterations to the future. In the case of the dead grandfather, the time traveler would never have been born and, therefore, could not exist. Professor Davis suggested that the existence of a paradox suggests error in thought. Professor deVries then brought up the fact that there are real paradoxes, that cannot be solved, and apparent paradoxes, which can be solved eventually. Whether time travel is a real or apparent paradox has yet to be explained.