Tuesday, November 20, 2012

Interesting Things to Note from NOVA | The Fabric of the Cosmos: Illusion of Time

This word document created on Friday; October 5, 2012 (8:09 PM)

1.      Lying just beneath everyday reality is a breath taking world where much of what we perceive about the universe is wrong. (0 to 9 sec of intro)
2.      The 3d world is merely a mirage (intro of show)
3.      But time is not what it seems. There may be no distinction between the past, present, and future (intro)
4.      Discoveries over the last century have shown that much of what we think about time may be nothing more than an illusion. Contrary to everyday experience, time may not flow at all. Our past may not be gone, our future may already exist. Time itself can speed up or slow down. Events we think can only unfold in one direction can also unfold in reverse. (2:45)
5.      Use of day and night for time (sundial), to full rotation of earth around the sun, pendulum, to vibration of a quartz crystal (looking for a repetitious cycle), to use of vibration of atoms to use as a clock (vibration of a cesium atom). Clocks can tell us what time it is but what time is.  
6.      What time is exactly is unclear but the passage of time is very familiar to us.
7.      Rise of train travel led to startling discoveries about time: each town had their own time and trains would carry time of the city where the train started. Need for synchronized clocks arose. Time for Issac Newton ticks at the same rate for everyone. As sensible as it may seem, Einstein found that time could run at different rates. Time for me may not be the same as time for you. Time is experienced individually. No universal tick tock. There were times. Einstein found the link between the motion through space and the passage of time. The more you have of one, the less you have of the other. Time and space is linked in much the same way that north and west are. When you are still and not moving through space, all of your passage is through time, but as soon as you start moving through space, some of that previous passage through time has to be diverted and shared with your motion through space resulting in a slower passage through time. Time itself is moving slower for the person that is moving.
8.      At the slow speeds that we move here on earth, motion’s impact on time is too tiny for us to experience it. The effect is real though and can be measured with the use of two atomic clocks and a jet airplane. This experiment carried out in 1971.
9.      Space and time can no longer be considered separate things. Space-time
10.  This idea of space-time led Einstein to realize that this sharp difference we see between past, present, and future may only be an illusion. In our day to day lives we experience time as a continuous flow but it may also be helpful to think of time as a series of snapshots. It is the unfolding of moment, after moment, after moment. Imagine all snapshots lined up. Every moment here on earth as snapshots lined up.  Think of all the snapshots that ever happened and will happen as a loaf of bread. My moment of now may seem to include a cat jumping off the couch, the clock ticking exactly at 12 PM, a pigeon taking off, and a meteor striking the moon. But Einstein said that this now slice would be cut a different angle should we be moving through space. Because motion affects the passage of time, someone who is moving will have a different conception of their “now slice” because it would be cut at a different angle.
11.  Even if the movement is considered slow, because of the vast differences in space, our conception of now can vary by massive amounts in time.  The direction makes a difference too. If the alien is biking towards earth the angle will be angled towards the future. “Once we know that your now can be what I consider the past or your now can be what I consider to be the future, and your now is every bit as valid and my now, then we learn that the past must be real, the future must be real, they could be your now. That means past, present, and future are all equally real. They all exist.” There is just as much reality to the past as there is to this present moment. Just as we think of all of space being out there, we should think of all of time being out there. All that has happened and all that will happen, it all exists. This realization convinced Einstein that the distinction between past, present, and future is only an illusion, however persistent. There is nothing in the laws of physics that picks out one now over another now. It is just our own subjective experience that it feels like things are changing. 
12.   The arrow of time. This is not true with space- we can go back and forth. What can’t time do this? Why don’t we see things flow in reverse order? There is nothing in the laws of physics, that states that events have to flow through what we call “forward” in time. Most equations work equally well for moving forward and backward in time. No arrow of time attached to these equations. Contradiction between physics that seems reversible and so much of our lives that seems irreversible. What’s responsible for the arrow of time?
13.  Entropy. The arrow of time seems to come from the tendency of nature to move towards disorder. “a measure of disorder tends to increase with the passage of time and that propulsion seems to create an arc of time” One problem with this reasoning though. Because the laws of physics don’t distinguish between the future and the past, entropy should increase towards the future but also the past, and that makes no sense. “that’s like saying entropy should increase in either direction that we look. We should look backwards in time and it should increase. “We should look forward in time and it should increase.” The big bang set the arrow of time on its path. Universe started out in a very ordered state and is ultimately responsible for the fact that time seems to have a direction.
14.   Because the expansion of our universe is accelerating, in the far future, after 100 billion years or so, all of the other distant galaxies will have hurdled out of sight from us. It will appear as if our galaxy were in the middle of nothing. Light from distant galaxies have to travel so far to reach us that when we look out at them, we actually are looking back in time. So in the far future where the distant galaxies are no longer visible, astronomers will find the past, in cosmic terms is out of reach. And as for the end of time, one theory says that black holes will eventually dominate the cosmos. Then they too will evaporate leaving nothing but random particles drifting through space. “In the far future where everything has decayed and there is no change, there will be clear notion of the past or the passage of time.” “if you don’t have events happening, then it’s hard to see how you would even imagine that there was time.” “you can’t even tell which direction of time is forward or backwards. In a very real sense, time one day will lose its meaningless.”
15.  “In comparing our everyday experience of time with the true nature of time, we’ve been forced to challenge some of our most deeply held beliefs. We now know that for every event that goes from order to disorder, there’s a link to the big bang itself, giving us the arrow of time. The common sense notion that one true time governs the universe has given way to a picture in which time is different for each and every one of us, and the flow of time, which seems to us as real as the flow of a river, may be nothing more than an illusion. Past, present, and future may all exist on equal footings. Our everyday experience of time will always exert a powerful influence. We will continue to imagine that time is universal, that the past is gone, that the future is yet to be, but because of our scientific discoveries, we can also look beyond experience and recognize that we are part of a far richer and stranger reality.”    

Key Points:

-          There is no distinction between the past, present, and future. They all exist and there is no precedence for one moment in time over another.

-          There is no one, universal time that governs the lives of all of us. We all have our own slices of now. Each and every one of us experience time separately because motion slows the passage of time and although with the speeds humans can achieve, this effect is not noticeable, it is real and over vast distances in space, motion through space can have a vast impact in time and gives us our own individual now slices.

-          There seems to be an arrow of time in our lives that results from an increase in entropy that started since the big bang, even though no laws in physics says that events cannot unfold in reverse order.

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