Lesson 20: Relativity Revisited

Relativity Revisited

In the previous lessons on Special Relativity, we learned the faster you move, the slower time moves for you.  We know this is called time dilation.  We are now going to delve even deeper into that fact to show you just how amazingly crazy Special Relativity is and what that means for you.  As we continue, constantly remind yourself that as crazy as it sounds, this stuff has been proven to be true over and over and over again.  As we mentioned before, if not for the mathematics of Special Relativity, we would not have GPS and many other advances we have today.

Don’t make the mistake of thinking the effects of Special Relativity take effect only when you are moving super fast.  If your friend is sitting down and you just casually walk by, you are moving faster, and time is moving slower for you.  At a walking pace, time is moving about a billionth of one second slower.  It is pretty safe to say time dilation is not going to be very noticeable.  You would have to take a billion steps for a difference in age of one second to occur.  That’s quite a bit different than the difference of years you would see when zooming off to other planets close to the speed of light and coming back to Earth to find everyone older than you or even long passed on, depending on how long your trip was.

Consider this.  When you see someone standing next to you in a room, you are seeing light waves from that person. It took those light waves about a nanosecond to reach your eyes, so the best you can say is you know what that person was doing a billionth of a second ago.  You are truly not seeing what that person is doing “now.”  Granted, it is only a billionth of a second, so for all intents and purposes, you can say “now.”

But what if that person was on a planet 5 light years away from Earth?  Let’s say you could look at that person through a telescope. It would take the light waves 5 years to reach you.  All you can ever know is what she was doing 5 years ago.

Here is where it gets super weird.  Don’t think that just because you can only see what she is doing 5 years ago that she is right “now” doing something on that planet which coincides with your “now” at this moment on Earth.  Don’t think you just can’t see it yet.  Don’t think in the next five years you will be able to see what she is doing right “now.”  Get ready for this next statement. It may be a little shocking.  According to Special Relativity, it is quite possible that she is already back on Earth and probably ten or more years in her future.  So you were just seeing that person on another planet who is already back on Earth.  Freaky!!!

We could go over the math, and I could show you how that is possible, but to be honest, that would be long and tedious. Another way to show you is by using graphs which I think makes the concept a lot easier to see, plus it is pretty cool.  I think you will like this.

First, let me remind you what an event is.  In the earlier lessons on Special Relativity, we defined an event as something that happens in time and space.  It must be described using both.  For example, to just say her wedding is not an event.  To say her wedding at The Anytown Church is not an event.  To say her wedding at The Anytown Church, July 15, 2020, is an event.  You have to have a time and a location in space for it to be an event.

Second, let’s take another look at a cartesian coordinate system like we saw when we did the calculus lesson.

Looking at the image above, you will notice we have a timeline running vertically and a space line running horizontally.  The time line runs from past to present.  Our space line is represented by x.  Technically we should also have a y and z line with the x because space has three dimensions.  But we are only going to use x for simplicity.  It all works out the same.

We put three circles in the coordinate system representing three events.  Let’s say event one is your graduation from school. Event two is meeting your true love.  Event three is the two of you getting married.  If you haven’t done all these things, let’s just pretend you did.

See yourself walking across the line in the image above from past to future. Looking to your right, what would you see?

You would see event one (your graduation) first.  You would see event two (meeting your true love) second.  You would see event three (your wedding) third.

Looking at the image above, let’s overlay another cartesian coordinate system (red) on top of the first but let’s tilt this one to the left 45 degrees.  This will represent another person in a different time frame relative to you.

Now let’s have this person walk the red line from past to future and look to their right.  What will they see?  They will see the events of your life in the order of event two, then one, then three.  What?

They will see you meeting your true love (2) before you graduated (1).  No way!  That’s not what happened.  How can that be?

We gave you the answer in the last supplement.

There is only now. Past and future are an illusion created by our brain.

That is so hard to grasp, isn’t it?  Everything around us seems to support the notion of time constantly marching forward.  Clocks tick.  We move from one place to another.  Our heart beats.  That all points to a real time, doesn’t it?