The peer assessment for this course was optional and didn’t effect the overall grade for the course. The options were:-
Week 1 — Philosophy is often classified as a purely reflective method of inquiry into reality and our place in it. But science also investigates reality and our place in it, with impressive success. Why (if at all) should we engage in philosophical inquiry into these matters?
Week 2 — If we can’t rule out sceptical hypotheses, can we know anything about the world?
Week 3 — Could a computer have a mind?
Week 5 — Was Hume right to think that one should never believe that a miracle has taken place on the basis of testimony?
Here is my essay.
Is time travel logically possible?
I believe time travel is logically possible. Defined as internal time and external time moving differently so that a human could be ‘x’ older whilst the rest of the world is ‘y’ older or younger.
“People like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion.” ( Albert Einstein). Einstein extended Galileo’s principle of relativity, accounting for the speed of light, to create his ‘special theory of relativity’. This theory linked time and space into a ‘space-time continuum’ of four dimensions. If you move fast enough through space then you can travel forward in time. Einstein died trying to figure out how he could unify electromagnetism and the general theory of relativity.
Einstein’s theory was developed by Paul Langevin and later Max von Laue to become the ‘Twin Paradox’. An example of this (Wikipedia) illustrates how if a ship travelling at 80% the speed of light (671 million mph) took one twin to our nearest star it would take six of his years but ten earth years. On return to earth he would be four years younger than his twin. A logical possibility except that we can’t yet travel that fast. According to Aerospaceweb the fastest manmade object was Helios 2 (1976) which travelled ad 150,000 mph, more than six times faster than Apollo 10 (1969).
“Time travel, I maintain, is possible. The paradoxes of time travel are oddities, not impossibilities.” (David Lewis – The Paradoxes of Time Travel). All the paradoxes and objections to time travel appear to suggest that we would be travelling in the same dimension as we already are, were and will be. The arguments are that a person cannot be in two places at the same time, nor could you effect a past that already exists. Much of Lewis’ argument rests upon the paradoxes of time travel and how they can be overcome. His theory relies on space and time being in four dimensions so that you can be in different time planes from different view points.
Theodor Kaluza’s (1919) idea of a fourth ‘curled up’ dimension was refined by Oskar Klein. ‘String theorists’ have used those theories and Einstein’s ‘special theory’ to posit that there might be more than ten dimensions. The string and superstring (M) theories are in their infancy but the confirmed existence of the Higgs boson has progressed their understanding of quantum physics. The machine that produced this can move particles at nearly the speed of light. They can get to 99.9% the speed of light but never exceed it although only 80% is needed for the Twin Paradox.
“I have experimental evidence that time travel is not possible. I gave a party for time-travellers, but I didn’t send out the invitations until after the party. I sat there a long time, but no one came.” Stephen Hawking, despite his scepticism also spent a long time working on the theories of time travel. His work revolved around using worm holes and black holes as a medium for crossing from one time plane to another. He describes black holes as ‘time machines’. The disadvantages are that they are far away and don’t take us very far in time. Worm holes that are around us are too small although Professor Hawking believes we may one day be able to expand them to a size big enough for a human or a space ship to travel through. He has not, however, come up with a way to maintain the expanded wormhole in place long enough before it is destroyed by radiation feedback.
In conclusion: Scientific theories determine that if we can travel fast enough we can time travel. The speed at which we can make particles move has reached a stage where it would be fast enough to do this. The amount of energy needed to move anything that fast is enormous but we are creating new forms of energy all the time. Professor Stephen Hawking said that if time travel existed we would see time travellers. If time travel existed but travel was only possible to a different dimension, then we wouldn’t be able to see them. String theory offers us many more dimension. I believe that one day we will be able to travel fast enough and have enough energy to do this. In order to save the paradoxes we would only be able to travel to a different dimension.
Primary source of information – Wikipedia, course notes and howstuffworks website.
My overall result for this essay was 17 out of a possible twenty-one. Here are the remarks from my three peer assessors.