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Topography of Time February 12, 2009

Posted by greghrinda in Philosophy of physics.
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Much of our life is directly related to the concept of time.   Whether it be  what time class starts or the deadline for an application, we make ourselves slaves to  the clock.   With so much dependent on the notion of time, it is important to dissect our knowledge of it in a scientific manner.

Aristotelian Spacetime

Everyday accounts of time use Aristotelian Spacetime.  In this sense, time is an infinite continuum and an instant in time is defined by the preceding and future time.  This description does not allow for a beginning of time or an end of time because that instant of time cannot be defined.  Aristotle uses a frame independent spacetime that requires the continuous progression of time.

Einstein’s Relativity

Relativity as defined by Einstein has different ramifications to the notion of time.  Each reference body has an individual time, meaning a standard “time” is useless without knowing the reference frame.   Relativity becomes more important as the speed of a reference frame increaes to relativistic speeds (>10% the speed of light).

Time dialtion is the culmination of time difference between reference frames.  Imagine a train passing through the desert.  Michael is centered on the train while Bruce is a distance to the side of the track.  Just as Michael and Bruce are aligned by a line perpindicular to the train track, lightning strikes both the engine and the caboose of the train.  Since both the front and back of the train are equidistant to Bruce and he is stationary, the light from the lightning will reach him at the same time, to Bruce the lightning strikes were simultaneous.   Micheal, on the other hand, travels toward the engine because he is traveling on the train, so he first recieves the light from the frontal lightning strike.  To Michael the two lightning strikes are events seperated by time.

Check out this video for a more detailed analysis of this Train Experiment of Time Dilation.  Here is another video on Time Dilation.  Another thought experiment showing differences in reference frame time is the Twin Paradox.  It is difficult to explain in text, so I am trying to find a good video for it.  Here are some pictures for the twins Pam and Jim.

Twin Paradox

Pam leaves Jim on Earth and travels away from Earth and back in a space ship.  They send each other greetings once a year using light messages.  Even going 60% the speed of light, Pam is eight years older while Jim is 10 years older.

Twin Paradox 2

Consequences of the Big Bang

Our understanding of the universe brings more debate about time.  Through the work of Edwin Hubble in the early 1900s, the universe is predicted to be roughly 13.7 billion years old.  Does this mean that there was a beginning of time?  Not really. The only thing that the current model shows is that time is infinite because the universe is expanding.  As we get closer to the time of the Big Bang, the physics that we use begins to break down, in particular, the Plank Era was the first 10-43 seconds after the big bang and it was not until after this time that the four fundamental forces were formed (Gravity, Electromagnetism, Weak Interaction, and Strong Interaction).  Even Stephen Hawking has noted the quandry of defing time

Time has a finite amount of past, but no beginning.

One new emerging theory relating to time and the Big Bang is the Quantization of Time.  This theory holds that time is comprised of unique quanta of time having a duration of 10-43 seconds.  This theory rebukes the continuum of time, trading in the analog style for a binary code of time related information.  The fact that we are currently incapable of measuring such precise gaps in time is a plus for the theory, but more ground work needs to be done before it is of widespread knowledge throughtout academia.

As was discussed in class, the Big Bang is our universe’s origin, but could we just be the branching of a greater entity above our universe?  This leads to the idea of multiverses.  Our universe could have been forged from the singularity of a black hole in another universe, ripping space and time to start our universe. Likewise, black holes in our universe may be portals to new multiverses.  In this case it would be unclear as to the function of time or the unification of time between multiverses as it is not required that each multiverse follow the same physical principles our universe expresses.

Multiverse

Retrocausality

Electron-Positron Annihilation

The last interesting note on the Topography of Time that I will discuss is retrocausality.  Many people have heard of antimatter, and some have heard of particle annihilation.  In the case of electron-positron annihilation, the preceding matter-antimatter pair meet and are destroyed to produce a gamma photon (ignore the right half of the photo, that depicts information to another phenomena).  In this situation, the only difference between the electron and positron is their charge.  However, if time is not a straight arrow, the suppossed positron particle could just be an electron moving backwards through time.  This is based of the assumption of the right hand rule used to determine direction of charge.  If antimatter is just matter moving backwards through time, what are the ramifications to the physical theories of today?

Sources

Markosian, Ned. “Time.” http://plato.stanford.edu/entries/time/#TopTim

Dowden, Bradely. “Time.” http://www.iep.utm.edu/t/time.htm#H8

Hitchcock, Christopher.  Contemporary debates in the philosophy of science. Maldon, MA: Blackwell publishing, 2004.

Salgado, Rob. “Aristotle’s Spacetime” http://www.phy.syr.edu/courses/modules/LIGHTCONE/aristotle.html

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Comments

1. ebrister - February 12, 2009

Two of Wesley Salmon’s interesting essays on causality can be found in the book Causality and Explanation. One is called “An ‘At-At’ Theory of Causal Influence” and the other is “Causality: Production and Propagation.” He considers the question of whether a signal can travel at speeds faster than time, and what we know about causality from considering that case.

2. Time Travel « Paradigms and Revolutions - February 17, 2009

[…] Traveling at speeds >10% of the speed of light (https://planetparadigm.wordpress.com/2009/02/12/topography-of-time/) […]


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