To describe in detail the full scope of special (and general) relativity requires careful and extensive mathematical examination, none of which I’m prepared to give here. You could really gain full appreciation the delights of relativity some by sitting in on some kooky physics lectures (or enrolling in them); you may even be able to string together some of the basics as explained in important movies and TV shows such as Back to the Future stringing together some of the basics as explained in some important films, like Back to the Future. Relativity is important because it suggests the exciting possibility of time travel (and perhaps the boring realities of it-sigh).
Relativity involve using frames of reference to describe motion of objects and the constancy of the speed of light. A frame of reference describes some position that encompasses a particular object or event we wish to measure – the frame may be the space I am sitting in now or it may describe me moving through a space described as a separate frame. Note that depending on whether I observe myself as I move, or whether I observe the frame I move through changes the viewpoint of what is moving and how it can be measured.
In my own frame, from my own observation, I am stationary and the frame moves relative to myself. From the point of view of the frame that I am moving through, the frame sees itself as stationary and sees me moving relative to it. Motion is observed between relative frames. This is relativity, and its consequences are grand. Getting your head around the idea of observation by relative viewpoints you are on the way to understanding the connections between space and time.
Oh and the other important thing is the speed of light – that is 300 000 000 metres per second (approximately) a reference point/number/ constant that seems to govern our universe as we learn in the study of physics. Relative observation lead to the notions of length contraction and time dilation, (in no way relating to pregnancy and giving birth) and provides us with the framework to consider ‘time travelling’.
In your frame of motion the time you experience moving relative to another frame is more than the time experienced in the frame that you are moving relative to (because you consider yourself stationary inside your own frame). This is time dilation. There is always that universal experience that time seems to pass us by when we are busy or enjoying ourselves and seems painfully slow when we are bored and idle. Having nothing to do equates to having more time to think about how time is passing.
Also moving faster than the speed of light (going through the maths) leads to the possibility of traveling forwards through time – by experiencing less time in your moving frame compared to everything around you. Generating speeds that exceed the speed of light is where the problem lies – Doctor Emmet Brown managed this with a plutonium fuel source in a Delorean traveling at 88 miles per hour.
The idea of traveling backwards through time as in the Back to the Future movies is rendered paradoxical – the paradox being explored in depth as follows:
if you go backwards in time and change one small thing it leads to a set of consequences, chain reactions that evolve into a different time that you seemingly traveled from. Marty Mcfly stops his dad getting hit by a car in 1956, incidentally it was getting hit by a car that led him to meet Lorraine, his mother who instead of falling for Marty’s father, falls for Marty…this alteration of chain of events means that in turn Marty will not exist because his parents never hooked up because of his mother’s newfound incestuous attraction to her own son.
If he doesn’t exist anymore in 1985, how did he travel from there to the situation he is in now? ‘Causality’ is this idea that everything that occurs follows some cause and effect relation – an event occurring results from some cause that occurred at an earlier time. Backwards time travel violates causality as explored in these movies.
The concept of time travel in fiction would have to be my favorite plot device. I think what makes it so successful is partly its ability to create pertinent social commentary by juxtaposing past and present. A comparatively quaint past reveals the grim outlook that a particular society is bound for some kind of downward spiral. The future may hold improvement and hope. It may also simply reveal that humanity does not change regardless of the moment in history in which people are placed.
We think about traveling backwards in time and changing things in our past and imagining what the memory of a different life experience would mean for the way we think in the present. Unfortunately, the feeling of REGRET about things you experienced in your past is fact of life for us all, an inevitable part of the human condition- part and parcel of cause and effect, and the laws of the universe as referred to earlier.
In the recent TV show, Life on Mars’s protagonist, Sam Tyler, thinks he has gone back in time to 1973 from 2007 and somehow resumes his job as a detective inspector for local policing authority. He is able to interact with his family and events that occurred in the past without having effect on himself (arriving from the future). The brilliance in this series was the concept of bringing policing techniques and technologies of the present (2006-2007) including forensics, education in psychology and very bureaucratic methods via Sam to a team of detectives in 1973 who use instinct, whims and brutal force to put the baddies behind bars.
In the recent bestseller, The Time Traveller’s Wife, the time traveler of the book- Henry, travels back and forth through time uncontrollably due to some pseudo scientific description of a disorder (‘chromo-genetic disorder’ they call it). Like the terminator, time travel is only possible in his birthday suit so for survival when entering a new ‘present’, Henry must run, steal, pick locks, i.e. become some sort of petty criminal to survive. Henry discovers somewhere along the way that the only activity allowing him to stay in the present for prolonged periods of time is with the comfort of romantic time spent with his wife.
It does sometimes disappoints me to see some bogus methods of time travel –like that time traveling scene in the 1978 Superman movie – we are encouraged to believe that Superman can reverse time by using his superhuman strength by flying around the earth with enough force to reverse the direction of spin on its axis.
There is so much time travel in books and films- the idea of time travelers existing way before the physical possibilities of it were considered. I think there is enough fodder in that for some PhD’s in literary studies (don’t steal my idea!). Forward and backward time travel unfortunately is incorrectly represented as though time were some linear chain you could pick any point along to go visit and observe.
I haven’t provided thorough reason as to why backwards time travel is impossible but offer the following ‘thought experiment’ – if there are backwards time travelers why do we know of none? Surely if there were time travelers from the future, somebody would know about them. Perhaps they simply don’t present themselves because of that whole paradox of stuffing up something in the past causing disastrous consequences in their own future. On May 7th, 2005, MIT held a ‘time travelers convention’ – time travelers were invited along to present themselves publicly. No time travelers however were confirmed in attendance- but may have attended incognito.
Youtube has some awesome stuff on time travel that I highly recommend you check out!