The Reality of Time Travel
September 18, 2012 § Leave a comment
Theoretical physics is surprisingly poetic. In his book Black Holes & Time Warps, Kip Thorne describes it as the study of what an infinitely advanced society would be able to do, if they were only constricted by the laws of physics. It verges on the edge of science fiction in its use of metaphors and models. If the universe is idealized into a two-dimensional state, theoretically it could be folded, bringing two points in the fabric of space time that are laterally lightyears apart close together in hyperspace. Thorne seriously considers the scientific possibilities of time travel from the perspective of relativity through a wormhole, like we could time travel through a tunnel burrowed blindly in the rich loam of the universe. In 1916, before the television was even invented, Ludwig Flamm used mathematics – which always seemed so boring and static to me in high school – to prove the possibility of wormholes. Their predicted lifespan is short, to say the least – they open briefly, two spherical openings at each end, and then pinch off and disappear. Anything caught in the middle is destroyed.
So much of the idea of time travel through wormholes relies on highly idealized ifs – if the universe acts two-dimensionally, if the mouth of the wormhole is a perfect sphere, if a never before seen “exotic” matter (like undiscovered forms of matter can be compared to something as mundane as starfruit) exists can hold the wormhole open, if space time can survive being “twisted in reference frames” – then a wormhole could bridge the gap between two distant points in space. Thorne continues to imagine the implications of this in romantic ideals – he and his wife, Carolee, holding hands from lightyears away, across the vacuum of time.
Thorne offers two possible perspectives for approaching the reality of time travel. The quantum strategy involves delving into “quantum foam” – in small regions the size of a Planck-Wheeler length, gravitational fluctuations are higher, causing space itself to “writhe” and creating the “negative energy density” required to hold open a wormhole. The author posits that maybe a much more advanced society will one day be able to pull a wormhole out of this foam like the Birth of Venus and enlarge it for classical use, somehow quoting that it would be effective in .4% of attempts.
The classical strategy involves much more literal effort. Thorne describes creating an indentation in space time on one side of the wormhole, creating a “sock.” To build a wormhole scientists would only have to tear a hole in the tip of the sock and resew it onto the other side of space time. However, this strategy is still affected by the highly complex consequences of quantum physics, so the practical implications are hard to consider.
In reality, you and I will never see the existence of time time machines. According to Thorne, we are further from time travel than cavemen were from moon landings. Thorne echoes Stephen Hawking and claims that time machines are most likely to self-destruct at the moment of activation. So Carolee and Kip will not be able to reach out to hold each other from distant stars, across the blank expanse of outer space. And the only wormholes I will ever see are eaten in the dirt by annelids.