Great Scott! Time Travel and Rights of Passage


What if I told you I’d never seen ‘80s sci-fi adventure classic “Back to the Future”?

(Gasps) Are you serious?!

Yes. I didn’t initially avoid my first spin in Doc Brown’s DeLorean for any pointed purpose. I’d been raised on "2001: A Space Odyssey," the original "Star Wars" trilogy and "Bladerunner," all of which were good enough for me. I ignored my critics. But over time I received ever more grief and began stubbornly opposing the film just for the hell of it. My critics could buzz off. Then I started covering physics, which since my undergrad I’ve taken sideline interests in.

I’m no expert (and won’t ever be) on any of this, yet I feel my brain sort of, almost, maybe beginning to wrap itself around the idea of warping space-time enough to allow for travel forward or back in time. So, in light of a recent re-release, I figure now’s the time to finally take a trip with Marty McFly and the good Doctor.

It was a fun trip despite the sketchy science.

In the event I get anything here wrong (which is probable as I’m no physicist and have seen the film only once) or if you are in fact from the future and want to hang out then by all means, get at me. Stephen Hawking and Leonard Mlodinow say examinations of both the cosmic microwave background radiation, which you can think of as the Big Bang’s fingerprint, and of copious amounts of light matter suggest the infant universe had nothing to do with the type of space-time curvature that would permit time travel. So how do we go about warping local regions of the now more adolescent universe to escape the present?

We know Einstein’s (the man, not Doc’s dog) relativity allows for temporal leaps forward, only we pitifully underdeveloped humans don’t yet have the engineering capabilities to make it happen. Doc’s DeLorean would either have to surpass the speed of light, which is about 182,282 miles-per-second (a bit more than his 88 mph threshold), or wiggle its way into a wormhole, which Hawking and Mlowdinow describe as a “thin tube of space-time connecting distant regions of the universe.” Wormholes are mathematically possible with positive energy density (think of a sphere) but exploiting one to traverse time would demand a negative density (think of saddle). We can’t yet create these saddles, either.

The film also exploits the alternative histories hypothesis. When Marty steps back into 1955 he can act freely without adhering to the consistency of past events because he hasn’t even been born yet. But Richard Feynman’s well-tested “sum over histories” theory (definite locations or histories don’t exist because all histories are not only equally probable, but occur simultaneously) seems rather to support the consistent series hypothesis (even if space-time is warped to allow travel into the past, “what happens in space-time must be a consistent solution of the laws of physics”), according to Hawking and Mlodinow.

Nice try, Zemeckis.

- blog by Brian Anderson, graduate student reporter, Medill School of Journalism, Northwestern University



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