RainmanTime
Super Moderator
Disclaimer: Those who know me from my posts know full well that I often explain that the concepts we typically have of "Time" as an independent dimension through which we can travel is scientifically incorrect. Rather, space-time is an integrated set of dimensions. But despite that I have devised the following analogy to help people understand just how difficult achieving time travel would be.
As both an engineer and an engineering educator, I often like to devise scientifically accurate analogies that help my students get their minds around difficult concepts. While driving home from work Thursday on Interstate 405 here in Los Angeles, I hit upon a good way to help people understand just how much energy it would take to "travel through time." (were that even possible, which of course I do not believe is so)
As we all know, traveling through space requires an expenditure of energy. And since space is really just one part of the overall dimensions of space-time, then we can also surmise (correctly) that it would also require an expenditure of energy to travel through time. So then, is there a way we can begin to estimate how much energy would be required to travel through time? The answer is yes. All it requires is two pieces of common knowledge:
1) That ALL measures of time used by mankind are a result of measuring MATTER in MOTION. For example, a sundial tells the time of day by the motion of the earth's matter about its axis with respect to the sun. All other forms of measuring the passage of time can likewise be shown to be based upon measurements of MATTER in MOTION.
2) That a simple equation for energy expenditure (i.e. Work) is a force required to move some body through a distance. Or, spelled out in equation format, the scalar equation for Energy (Work) is:
Work = Energy = Force x Distance (work done on an object is equal to the net energy gained by that object)
Now let's apply this to the desire for me to travel backwards in time. Let's say when I get home (Huntington Beach) from work (at LAX airport) I decide that I want to go BACK IN TIME only to the point where I left work. Despite LA's notorious rush hour traffic on I-405, I am only wishing to go back in time about 1.5 hours. But how much energy must be expended to make that jump to the past?
Well, I can begin to understand this by computing the work to merely move myself and my car the distance I traveled to get home from work. Since the non-payload driving weight of my 2003 Corvette is on the order of 3250 pounds, and I am just about 200 pounds, and the distance between work and home is right around 35 miles (184,800 feet), we can do this calculation:
Work = Energy = Force x distance = 3450 pounds x 184,800 feet
Work = Energy = 637,560,000 pound-feet = 240.12 Kilowatt-Hours
Is that all? Sheeeesh! That ain't all that much energy to travel through time! Hold on, pardner! That is just the energy to return myself and my car to that point in time! In order to truly achieve time travel, I am also going to have to expend enough energy to move ALL OF THOSE OTHER CARS on the I-405 (whether they were going north or south) back to the place they were located at the time I left work! Because quite literally, if I am going to travel through time, and I want to be at that moment when I left work, then ALL of those other people and their cars would have been in a different place. So multiply the energy required for just myself by all those cars on the I-405 (and some cars may be lighter and may have gone a shorter distance, but some may have been heavier and traveled a longer distance).
But it doesn't end there, does it? In order for me to actually travel back in time, then ALL of the matter that was in motion around the world during that hour and a half would also have to be moved back to its original position...because as we established, time is measured via MATTER IN MOTION. And even if we moved every single bit of matter in the world back to the place it was at the start of my time travel segment, that still is not enough, right? Because the earth and all the heavenly bodies had also moved some distance during that time, right?
Now, I suppose someone could make the (unsubstantiated) argument that all those bodies really far away do not impact time here on this planet, and that I really would not need ALL that energy equivalent to the motion of all the matter in the known universe just to travel back an hour and a half here in time on this planet. And because I am an engineer, then I might even accept that limiting simplification (as we engineers do that all the time). But because bodies in motion around the world influence events every single day, I am still going to insist that we must account for ALL of the motion of ALL bodies on the face of the planet, in order for me to achieve going back in time just 1.5 hours.
When you start to think about all the airplanes, trains, automobiles, and even just the motion of all the masses of the earth's water in motion for that 1.5 hours it took me to drive home, you start to see just what a MASSIVE expenditure of energy it would take just for one little old guy to travel back in time for just 1.5 hours.
And....the further you go back in time, the MORE motion of all that matter you have to account for, and reverse. And let's not also forget the practicality of physics which tells us there are no truly, 100% reversible processes. In other words, it always takes more energy input to reverse a process than it took for that process to naturally unfold.
So....now....do all you time travel believers really believe you can muster the kinds of energy necessary to reverse the flow of time so you can achieve your romantic notions of time travel to the past? Sorry....but time travel is a one-way street. Forward....at the pace you are moving!
RMT
As both an engineer and an engineering educator, I often like to devise scientifically accurate analogies that help my students get their minds around difficult concepts. While driving home from work Thursday on Interstate 405 here in Los Angeles, I hit upon a good way to help people understand just how much energy it would take to "travel through time." (were that even possible, which of course I do not believe is so)
As we all know, traveling through space requires an expenditure of energy. And since space is really just one part of the overall dimensions of space-time, then we can also surmise (correctly) that it would also require an expenditure of energy to travel through time. So then, is there a way we can begin to estimate how much energy would be required to travel through time? The answer is yes. All it requires is two pieces of common knowledge:
1) That ALL measures of time used by mankind are a result of measuring MATTER in MOTION. For example, a sundial tells the time of day by the motion of the earth's matter about its axis with respect to the sun. All other forms of measuring the passage of time can likewise be shown to be based upon measurements of MATTER in MOTION.
2) That a simple equation for energy expenditure (i.e. Work) is a force required to move some body through a distance. Or, spelled out in equation format, the scalar equation for Energy (Work) is:
Work = Energy = Force x Distance (work done on an object is equal to the net energy gained by that object)
Now let's apply this to the desire for me to travel backwards in time. Let's say when I get home (Huntington Beach) from work (at LAX airport) I decide that I want to go BACK IN TIME only to the point where I left work. Despite LA's notorious rush hour traffic on I-405, I am only wishing to go back in time about 1.5 hours. But how much energy must be expended to make that jump to the past?
Well, I can begin to understand this by computing the work to merely move myself and my car the distance I traveled to get home from work. Since the non-payload driving weight of my 2003 Corvette is on the order of 3250 pounds, and I am just about 200 pounds, and the distance between work and home is right around 35 miles (184,800 feet), we can do this calculation:
Work = Energy = Force x distance = 3450 pounds x 184,800 feet
Work = Energy = 637,560,000 pound-feet = 240.12 Kilowatt-Hours
Is that all? Sheeeesh! That ain't all that much energy to travel through time! Hold on, pardner! That is just the energy to return myself and my car to that point in time! In order to truly achieve time travel, I am also going to have to expend enough energy to move ALL OF THOSE OTHER CARS on the I-405 (whether they were going north or south) back to the place they were located at the time I left work! Because quite literally, if I am going to travel through time, and I want to be at that moment when I left work, then ALL of those other people and their cars would have been in a different place. So multiply the energy required for just myself by all those cars on the I-405 (and some cars may be lighter and may have gone a shorter distance, but some may have been heavier and traveled a longer distance).
But it doesn't end there, does it? In order for me to actually travel back in time, then ALL of the matter that was in motion around the world during that hour and a half would also have to be moved back to its original position...because as we established, time is measured via MATTER IN MOTION. And even if we moved every single bit of matter in the world back to the place it was at the start of my time travel segment, that still is not enough, right? Because the earth and all the heavenly bodies had also moved some distance during that time, right?
Now, I suppose someone could make the (unsubstantiated) argument that all those bodies really far away do not impact time here on this planet, and that I really would not need ALL that energy equivalent to the motion of all the matter in the known universe just to travel back an hour and a half here in time on this planet. And because I am an engineer, then I might even accept that limiting simplification (as we engineers do that all the time). But because bodies in motion around the world influence events every single day, I am still going to insist that we must account for ALL of the motion of ALL bodies on the face of the planet, in order for me to achieve going back in time just 1.5 hours.
When you start to think about all the airplanes, trains, automobiles, and even just the motion of all the masses of the earth's water in motion for that 1.5 hours it took me to drive home, you start to see just what a MASSIVE expenditure of energy it would take just for one little old guy to travel back in time for just 1.5 hours.
And....the further you go back in time, the MORE motion of all that matter you have to account for, and reverse. And let's not also forget the practicality of physics which tells us there are no truly, 100% reversible processes. In other words, it always takes more energy input to reverse a process than it took for that process to naturally unfold.
So....now....do all you time travel believers really believe you can muster the kinds of energy necessary to reverse the flow of time so you can achieve your romantic notions of time travel to the past? Sorry....but time travel is a one-way street. Forward....at the pace you are moving!
RMT