Wednesday, November 23, 2005

Relative Rant

Todays relativity Rant is about the Twins Paradox.

(Updated 3/1/2014, added illustrations and corrected some typos. Updated example years to match illustrations)

If we placed a living organism in a box ... one could arrange that the organism, after any arbitrary lengthy flight, could be returned to its original spot in a scarcely altered condition, while corresponding organisms which had remained in their original positions had already long since given way to new generations. For the moving organism the lengthy time of the journey was a mere instant, provided the motion took place with approximately the speed of light. (in Resnick and Halliday, 1992)

-Einstien

In short one twin gets in a ship and travels at the speed of light returning to find his twin left behind older due to time dilation during the trip. For the sake of simplicity we will say that acceleration and deceleration from light speed took 1 day each and that the trip covered 1 light year, so essentially 365 days. From the perspective of the twin that made the trip the journey would take two days, or the time at which he was not at light speed where time stopped. For the other twin it would be a year before his twin returned. Thus the Twins parradox.

My problem is that from the perspective of the twin making the trip he covered 1 light year in only 2 days. This means according to the standard equation of S = D/T he covered one light year at a speed faster than light. At least according to his clock and earths perspective. He physically covered the distance it takes light to cover in 365.25 days, but from his perspective it only took two days time... or roughly 182 times the speed of light. The equations of relativity explain this fine from one perspective or the other. What they do not do well is mix the perspectives. For example here we have the Distance covered from Earth's point of view, or Relative Frame of Refference (RFR), and time from the space ships RFR.

So from earths RFR. He traveled at the speed of light and took a little over a year to make the trip. From the Ships RFR, to make a long story short, distance between the points he traveled shortend so that D/T works out to the speed of light. My question then boils down to something practical. What did the traveling twin take to eat ? Did he take meals for 365 days of travel ? Or did he take meals for 2 days of travel. If he needs 365 days worth then he becomes a human version of Schrödinger's cat if he only takes enough for 2.

This problem is worse if you don't bother with accelration. Because for something travelling at the speed of light any S = D/T solution would be S = D/0. Division by zero. Infinity. Infinite speed. Thus according to relativity Distance must also go to 0 else speed exceeds that of light. So while you cannot exceed the speed of light, you can get anywhere in no time at all if you can reach that speed. At least according to relativity. And there is much experimentation to back this up. For example, GPS sats work on the principles of time dilation. But no matter how it is explained to me I still cannot get over the question of what you would take with you to eat on a voyage at the speed of light to the nearest star.

For the time being I think the twins parradox is not real. I think if you could travel at the speed of light and you traveled for one year you would return a year older and still be of an age with your twin. Here is my reasoning.

Take two earths, call them alpha and beta. Lets place them one light year apart. Light leaving one earth reaches the other one year later and vice versa. So lets say each receives TV signals from the other. It is presently the year 2014 on each of our identical earths. Yet due to the set limit of the speed of light each would receive signals from the other that are a year old. Thus TV signals received at either end would be from the year 2013.



Now lets take Two space ships, Two pairs of twins, Two TV sets and Two TIVO's split evenly among the two planets. One of the twins from the two pairs leaves their respecitve planet the same day on a ship traveling at the speed of light. Lets follow ship one.



Ship one launches from alpha in the year 2014 with a TV set watching the signals recieved from the second earth 1 ly distant. He accelerates to the speed of light. He is now encountering the TV signals from beta at twice the speed of light. IE they are comming towards alpha at the speed of light and he is headed to beta at the speed of light. Thus by the time he reaches beta he will see two years of programming and land there in 2015. If he then tuned into TV from his origin planet he would see programming from 2014 showing his launch. He then gets back into his ship and goes back. Again he sees two years of programming and lands back home on alpha in 2016 where he is greeted by his twin, and if he tuned back into the other earth he would see programming from 2015 showing his departure.

Ship two has the exact same experience only in reverse.



Now if they actually sat there and watched their TV sets I think it would be hard to argue they did not spend two years traveling. IE they left in 2014, and returned in 2016. I think time dilation is an artifact of observation of something at high speed. IE the clock is ticking by at the same rate on the ship itself, but you simply can't observe it to tick at the same rate. GPS works on the basis of that observation. So breaking the twins parradox according to my reasoning does not break GPS. If you like try and consider how communications with the ships in transit would work. While the signals comming from the destination planet would be encountered at twice the usual speed (including, just for S&G's, a timming pulse) , no signals could be encountered from the planet being traveled away from cause they could not overtake the ship (provided it was traveling at the speed of light).

However when you start to consider the ships communications things get very interesting indeed. Think of it in terms of observation. The ship leaves in 2014. Lands on Beta in 2015. But you can't observe the landing at Beta till 2016 at Alpha. So it would seem accordingly that once the ship went to light speed it would dissapear. In 2015 you would start to see it leaving earth and watch it progress over the course of the year till it landed on Beta in 2016 (observed 2015 from Beta). As you were observing the landing at beta in 2015 the ship would then arrive back at alpha in 2016. Then you would observe the ship leaving Beta and watch its progress back to Alpha and complete your observations in 2017 even though the ship arrived in 2016.

As you can see the observation of the ship is very out of whack with the ships actual location. The actual location is how GPS works thus you must adjust for it as relativity dictates. What relativity does is allow for the prediction of observance of things traveling at high relatively different velocities. However I hold that is as far as it goes. Time does not dilate. Else traveling at the speed of light is traveling at infinte speed and from your perspective you would pass through all points of the universe simultaneously... and that as far as a beam of light is concerned the universe has no deminsion... IE it is still just a point.

1 comment:

Stuart Westley said...

Great Article with some interesting points. Bit confusing in some points but you get the general idea.