Why We Will Never Travel To The Past
by CS Wagner
From "Technopedia", a weekly Tech Q&A newspaper column I used to write.
See further updates below the original article.
Q: You made the comment in one of your columns that it is impossible to travel into the past. Is there any scientific basis for your answer? -EM2
A: I have spent many years answering one technical question after another and this is, strangely enough, one of the easiest. To put it plainly, we as humans will never be able to travel into the past through some sort of time machine because we cannot do it already.
That may seem like a strange answer, but it is logically sound. Simply consider what would happen if a time machine were ever to be invented. There are two problems. First, if the inventor travels back in time, he cannot return to his present to announce his invention. If he travels back only a few days, he could announce his invention without trouble, but what keeps someone from stealing it?
Theft of the time machine is the main reason that we know one will never be invented. Assume someone named Joe invents a time machine in the year 3000. He travels back to the year 2999 successfully and announces his invention. Then someone, say Tom, decides that he wants the publicity for the invention. So, he gets his own model of the time machine and travels back to 2998 (before Joe announced his invention) and then announces that he invented it. Well, Jane gets the same idea. She gets a model and travels back to 2997 to tell everyone that she invented it first.
It is important to understand what would happen each time that someone travels back a year earlier and claims the invention for himself. When Tom went back to 2998 and claimed the invention, it would have been chronologically during the time when Joe was still inventing the original time machine. So, Joe would have ceased work on his model, he wouldn't have tested it, and he would never have traveled back to 2999 to announce his invention. There would not be two claims of the invention. There would only be Tom's claim. We understand what is going on because in this story we are omnipotent. Humans can only see backwards in time. They cannot see into the future, so they cannot see that Joe really made the invention and Tom stole it.
Continuing, when Jane jumps back to 2997 and claims the invention for herself, it would stop any and all development at that time. Neither Joe nor Tom would later decide to claim the invention without traveling back before 2997. So, each time someone travels back a year earlier and claims the invention, they become the sole inventor. There is no evidence of wrongdoing.
Does it even have to be theft? Not really. If a time machine were invented, it would eventually become commonplace. Anyone could get one. Then, someone could travel back to a time before it was invented and claim to be the real inventor.
Now, consider humanity. There are over six billion people in the world. If a time machine were invented, what is the chance that someone would steal the plans for one, make it, and travel back in time to get all the fame for being the inventor of it? Assume that happens. What is the chance that someone else would do it? All it takes is two people, like a bidding war at an auction. One travels back to 2998, the other to 2997. The first then travels back to 2996. The second answers with 2995. When would it end? There is no reason to believe it would. It was already pointed out that there would never be evidence that the machine was stolen repeatedly, so each time it is stolen the person doing the stealing will think that they are the only person to do so. So, someone will eventually travel to our time and claim to have invented the time machine.
There is one flaw in this argument, but it is based on complete fiction. It is Merlin. What if the original inventor travels back in time and doesn't tell anyone about it? Merlin, from the King Arthur stories, was a magician who claimed to live backwards in time. He could tell the future like it was yesterday, but he knew nothing of the past. In this case, a person could repeatedly travel back in time and sort of vacation through history. Certainly, this person would influence whole cultures. It would explain a lot of mysteries. How was Stonehenge invented? If a modern scientist traveled back to the time it was built, the invention would be simple. There are many short periods in history where marvels of science and logic suddenly appear. Of course, the explanation is only mysterious to those who don't realize that there has always been and there will always be those who understand the world more than others. Their numbers may be small, but they are out there and they are performing miracles every day. But, they will never invent a time machine.
Short note on traveling to the future:
Humans naturally travel forward in time. The speed at which we travel is rather constant. However, it is possible to slow down that rate by traveling at or near the speed of light. While traveling at extremely high speeds the world continues at the normal pace but you move through time slower. When you return to the normal world, you will have been gone a short time, but the world will have advanced many years. The effect is that of traveling into the future. It isn't really a time machine, it is just a way of moving really fast. Of course, it is impossible to get that sort of speed with modern technology. This would only be possible by changing mass to energy and then changing it back to mass without altering the mass much. We have the changing mass to energy part down (nuclear bombs), but we can't put it back together yet.
Since writing this article, I have received at least one email each week telling me that I have it all wrong. Why? One person feels that if Superman can travel back in time, so can we. A few others feel that Star Trek proves reverse time travel. Of course, those people are nuts. The ones who are somewhat sane have pointed out a semantic error in this article.
I stated that we will never be able to travel into the "past". What do I mean by "past"? I mean any time that occurred before now. What do I mean by "now"? I wrote the article in 1998 and meant "now" to be 1998. As of 2007, it still stands.
The deal is that it may be possible, and it is probable, that a machine may be built that creates a sort of hole in the future. From the future, you can send information through the hole into the past. I state "information" because I do not know if you will be able to send radio waves, particles, or whole humans through the hole. The limit is that you can only send information to the point in time that the machine was turned on, not any time before it. So, if this sort of reverse time travel was ever invented, it would not allow us to travel into our past - any time before 2003 (or the invention of the machine).
One more note: I get a lot of emails telling me that I misread Einstein's theory about traveling near the speed of light. I did not. When the phrase "travel near the speed of light" is used, it does not always mean traveling in a straight line. You can spin at extremely high speeds. You can also have the atoms in your body spin at extremely high speeds - making you appear to be sitting still. It really isn't a "speed" issue. It is an energy issue. Light (and all electro-magnetic waves) is nearly pure energy. We are mostly mass - very little energy. The higher the ratio of energy to mass, the slower time progresses. When we speed up, we add energy to our body, increasing the ratio. Because adding energy will never work (that has been proven), we must alter the ratio another way. The most logical method is to convert mass to energy, then convert the energy back to the same mass. As of this writing, there has never been any successful attempt to convert even an atom to energy and back into the same atom. It is like breaking a plate and then trying to put it back together so it looks unbroken.
Don't get me wrong. I'm not saying it is impossible, I am only saying that it hasn't been done. If those glowing UFOs ever turn out to be real, I have a sneaky suspicion that they spin at extremely high speeds and then convert the mass to energy (which appears as a glowing streak of light). Then, they must be able to switch the energy back. I simply don't know what anal probes have to do with it all.
Recently, I received a message that asked if I considered multiple timelines. While we can't travel into the past, perhaps someone on another timeline can. Sure. Why not? This article states clearly that we cannot travel into the past in our timeline. Someone else in another timeline may be able to - and they would know it because of the rule that I explained in the article. You know you can travel back in time when a time machine exists. If one doesn't exist in your timeline, it will likely never exist in your timeline.
I received another email. Apparently Stephen Hawking has said nearly the same thing in his Chronology Protection Conjecture. I read his conjecture. Basically, he claims that we won't travel to the past because we haven't seen tons of time tourists. That is nearly identical to my claim that we won't travel to the past because we haven't seen any time machines. Of course, his conjecture was published three years before mine.