They have to go and try to spoil everything and declare that time travel is more than likely impossible. "There are a handful of scenarios that theorists have suggested for how one might travel to the past, said Brian Greene, author of the bestseller, The Elegant Universe and a physicist at Columbia University. “And almost all of them, if you look at them closely, brush up right at the edge of physics as we understand it. Most of us think that almost all of them can be ruled out.”"
Lest a dream be lost - I think that next to last sentence is the key here: "brush up right at the edge of physics AS WE UNDERSTAND IT." Our minds are so infintesimally small compared to the Universe and the Mighty God who created it. The fact that we can conceptualize a tesseract now, at this time in our feeble mental development, should give us hope in the future of somehow understanding ways to use that concept. Imagination is the key to exploration - as long as we can imagine that there are possibilities too big for our little minds to grasp - and yet reach beyond limitation anyway - we may find that the impossible turns out not to be so impossible after all.
(Einstein was so far ahead of his time with his unified field theory - believing that the two forces he understood at that time, Magnetism and Gravity, were not separate at all but part of a grander underlying principle - that he felt lonely and isolated from his colleagues. And yet, whose concepts does String Theory substantiate decades later? Einstein's, of course).
Until them, we can continue to dream, can't we? My favorite time travel books are: The Doomsday Book by Connie Willis, Outlander & Dragonfly in Amber by Dianna Gabaldon (the rest of the books in the series suck), Time's Last Gift by Philip Jose Farmer, Timeline by Michael Crichton, Enchantment by Orson Scott Card (love this because it is also an updated fairy tale), and of course, Mark Twain's A Connecticut Yankee in King Arthur's Court.
Just for fun: Who wouldn't love to have a "time turner" like Hermione uses in one of the Harry Potter books? Think of everything we could get done by being in two places at the same time!
I could lump The Chronicles of Narnia in the list above because the children *are* able to pass into another world where time is traveling at a different rate than it does in our own world. Perhaps via a tesseract? Nah, Aslan doesn't have to explain anything with science - after all He's not a tame lion.
As far as books about passing into another world where time is traveling at a different pace than our own: The Chronicles of Thomas Covenant by Stephen R. Donaldson are INCREDIBLE. Six books in the first two chronicles, another one in a third chronicle written and one being published in October. Donaldson's Mordant's Need is also great - two books The Mirror of Her Dreams and A Man Rides Through. The Song of Albion triology by Stephen R. Lawhead is wonderful, I read it again and again and again.
Regardless - today is today and it has enough troubles of its own. To quote a great line from Star Trek: TNG
"Seize the time, Meribor. Live now; make now always the most precious time. Now will never come again" -- Picard (The Inner Light)
That NOVA program on String Theory is fascinating. Here's the opener - the rest (all three hours worth) can be viewed here.