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Donovan et. al.<BR>
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Jeez, what's got into you? Really! Is this a joke, or what? You're starting to sound like the advocates of teaching creationism as a scientific theory in the public schools who state over and over that evolution is not a "fact" but an unproved theory.<BR>
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I wrote "time travel is not just a possibility, but a verified scientific fact." This means that experiments have been conducted to gather facts to verify the predictions of the equations of time dilation from Relativity. Scientific facts that verify the truth of theories is how science operates: no empirical facts to validate a theory, a theory remains just a theory. Replication of experimental findings that verify theories is the cornerstone of how science connects theory with fact. Any scientist who wishes to demonstrate his theory is more than just a theory conducts experiments to gather facts regarding the predictions of his theory in a manner that documents the arrangement and results of the experiments with such detail and precision that any other scientist who wishes to investigate the predictions of the theory can do so via replicating the experiment. <BR>
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If we find empirical facts that verify the theory of Relativity, it is more than a theory, it has empirical verification. Of course new theories may come along that are more powerful or inclusive, or the universe may change how it operates.<BR>
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But you are spouting nonsense. Theories in science do receive verification with facts.<BR>
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Please educate yourself! The U of I failed. Now go to your room and study the text and equations below:<BR>
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<A HREF="http://www.hcc.hawaii.edu/~pine/book1qts/chapter7qts.html">http://www.hcc.hawaii.edu/~pine/book1qts/chapter7qts.html</A><BR>
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</FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=4 PTSIZE=14 FAMILY="SANSSERIF" FACE="Arial" LANG="0">Time Dilation</FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=3 PTSIZE=12 FAMILY="SANSSERIF" FACE="Arial" LANG="0"> <BR>
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</FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=2 PTSIZE=8 FAMILY="SANSSERIF" FACE="Arial" LANG="0"><SMALL><SMALL><SMALL>The idea that time can vary from place to place is a difficult one, but it is the idea Einstein used, and it is correct -- believe it or not. Richard Feynman<BR>
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Einstein realized that if the laws of nature are the same from every standpoint, then for physicists to be able to continue to do physics in a universe of relative moving objects, they will need to mathematically transform how time will be viewed from different reference frames. Einstein used a mathematical equation called the Lorentz-Fitzgerald transformation. It worked perfectly. The equation is a relatively simple algebraic relationship:<BR>
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T' = T 1-(v/c)2 <BR>
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In this equation, T' is the time of an event in a reference frame moving at a velocity v in relation to an observer whose time is T. The small c is a constant, the speed of light. Let's see how it works. Suppose in our train example that X and Y both possessed clocks that some time ago were synchronized when the train was stationary. Y then moved at a normal speed, very slowly compared to the speed of light, to the point between A and B. Suppose at a prearranged time X departs and that for the last 15 minutes by Y's reckoning the train has left the initial starting point and been moving to the point where Y is at an average speed of three-fifths the speed of light.<A HREF="http://www.hcc.hawaii.edu/~pine/book1qts/#N_5_">(5)</A> What time will the clock of X read according to the Lorentz transformation? If we plug in the data, <BR>
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T = 15 and v/c =3/5, so T' = 15 1-(3/5)2 <BR>
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When X passes Y, X's clock will show that the train has been moving for only 12 minutes! From Y's point of view, X's time has <I>slowed down</I> relative to Y. It would not just seem to slow down; real physical measurable effects would be seen when X and Y compare their clocks. If X and Y both lit cigars at the prearranged time, X would find that his cigar has burned less than Y's as they pass each other.<A HREF="http://www.hcc.hawaii.edu/~pine/book1qts/#N_6_">(6)</A> X will experience nothing unusual. The laws of nature are the same, including that for burning cigars. For X everything will appear normal including the movement of his clock. At no point will X's clock suddenly slow down dramatically. It will appear normal. Likewise, Y will not suddenly see the last few minutes of his experienced 15 minutes fly by at a different rate. His clock will also appear normal. Nor will either notice anything strange about the rate their cigars burn. Time slows down in reference frame X only in relation to reference frame Y. Within their respective reference frames everything is normal. <BR>
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</FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=2 PTSIZE=8 FAMILY="SANSSERIF" FACE="Arial" LANG="0"><SMALL><SMALL><SMALL>If my home and office were separated by many light years, my home (depending on the distance and the speed of my travel) could be many thousands of years in the future when I arrive at work.<BR>
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The testimony of our common sense is suspect at high velocities. Carl Sagan</FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=2 PTSIZE=10 FAMILY="SANSSERIF" FACE="Arial" LANG="0"></SMALL></SMALL><BR>
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This slowing down of time of a reference frame relative to another reference frame is called <I>time dilation</I>. As unbelievable as it may seem, it is one of the most accepted scientific facts of our time.<A HREF="http://www.hcc.hawaii.edu/~pine/book1qts/#N_7_">(7)</A> It has been tested in numerous ways. Very precise atomic clocks have been synchronized and then compared again after one was flown around the world on a jet airplane. The clock on the fast plane slowed down in relation to the clock that stayed on the ground. A similar test was conducted using one of the U.S. space shuttles with the same result. Scientists now apply time dilation routinely in sophisticated laboratory situations. In the billion-dollar particle accelerator laboratories all over the world, physicists can keep special particles of matter "alive" far longer than would normally be expected because of the time dilation effects that result by accelerating particles close to the speed of light. In this way special forms of energy can actually be "stored" for use in crucial experiments. As far as most physicists are concerned, time dilation is a fact of nature. Rather than the large fishbowl of time implied by common sense and Newtonian science, Einstein has revealed to us a "chunky" universe of relative reference frames and times. There is no universal "now"; there are only simultaneous events in relation to local reference frames. Trains, of course, do not move at 111,600 miles per second (three-fifths the speed of light), and hence, it is easy to see why time dilation effects are not noticed by common sense. Theoretically spaceships could. What kind of astronautical scenarios are then possible? Suppose we know twins 20 years of age, one an astronaut who will take a space voyage that will take 20 years by Earth time. Suppose that the astronaut twin averages in his rocketship a speed of three-fifths the speed of light. How old will each twin be when they meet again 20 Earth years from now? Using the time dilation equation we have:<BR>
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T = 20 1- (3/5)2+ 20, which would equal 36. <BR>
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The twin who stays on Earth will be 40 years of age. The twins will no longer be the same age! What applies to time will also apply to space. Just as the twins would discover that there is not one time that marches along in a strict Newtonian fashion, so they would also discover that there is not one large fishbowl of space where the distance between two points is the same for every observer. Just as time slows down, so space contracts. Because of the speed he is travelling, between the points of his departure and arrival the astronaut twin will measure his voyage as 14 trillion miles shorter than his twin would with instruments on Earth. <BR>
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</FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=2 PTSIZE=8 FAMILY="SANSSERIF" FACE="Arial" LANG="0"><SMALL><SMALL><SMALL>Traveling at great speed slows our histories down from one point of view, and allows us to speed to the future from another.</FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=2 PTSIZE=10 FAMILY="SANSSERIF" FACE="Arial" LANG="0"></SMALL></SMALL><BR>
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This example is not science fiction. Time dilation has been shown repeatedly to be a fact of nature; this effect on an astronaut would indeed happen. If it is so hard to believe, it is because we have difficulty realizing that the things we take for granted on Earth do not necessarily apply throughout the cosmos. With Einstein, the cosmos is now our laboratory, and we must adjust to the conditions of this new laboratory. Stranger still, consider this scenario. The star Vega, a star like our Sun and a possible candidate for a planetary system, is approximately 32 light-years away. Suppose in the near future a 30-year old woman astronaut, who has a five year old son, went on a space voyage to explore this star, averaging the colossal speed of 99.5 percent the speed of light. At such a speed it would take her about 64 1/3 years Earth time to make the trip. When she returned, her son, remaining on Earth, would be into his 69th year. Both would be in for a great shock. The 69-year old son would embrace his long-awaited 36 1/2 year old mother! Their personal histories would have seemed to be normal in all other respects, but it would now be clear that traveling at great speed slows our histories down from one point of view, and allows us to speed to the future from another. If such a voyage were undertaken in the year 2000, the mother astronaut could get to the year 2064 in a little under 6 1/2 years. An event that required only 6 1/2 years for the mother, required a little over 64 years for the son. In our train example, an event that happened before another event for one observer (lightning striking point A before point B for X ), happened at the same time for another observer (Y). It would also be possible then for another observer moving in the opposite direction of reference frame X at a great speed to record the lightning striking at point B first. Thus, one person's past could be another's future. Would it then be possible for the mother to return at an age before her son was born? Not according to Einstein's theory, not if the speed of light is a law of nature. Because the speed of light is an absolute that cannot be exceeded, causal connections, such as mothers causing the birth of babies, are preserved in their normal sequences. According to Einstein's theory, the measurement of "before" and "after" may involve a wide latitude, but the order of events will not be changed. The time between the mother's "before" and "after" of her space voyage is much shorter than that experienced by her son, but both would experience her leaving before she came back. If and only if the speed of light is exceeded will the sequencing of causal events be changed, and it is a basic consequence of Einstein's theory that the speed of light cannot be exceeded. According to the theory, it would take an infinite amount of energy to accelerate any object (even an electron) up to the speed of light and thus require more than an infinite amount of energy to exceed the speed of light.<A HREF="http://www.hcc.hawaii.edu/~pine/book1qts/#N_8_">(8)</A> <BR>
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V2020 Post by Ted Moffett<BR>
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