1. Time can(‘t) be rewritten.
Sorry. If time travel can happen at all, it’s likely that we can only go forward. Which means anything that’s happened already is set, because we can’t go back in time to change it. (Otherwise we’d have met some time travellers from the future, surely?)
Unless you have a traversable wormhole. That would allow you to get around not being able to travel faster than light by taking a shortcut through space-time. Good luck finding one though — we’re not even sure if they exist yet.
2. Scientists have designed a Tardis.
“Time and Relative Dimension in Space” sounds very impressive and physics-y but it doesn’t actually mean much. Benjamin Tippet, who recently wrote a scientific paper with colleague David Tsang about how a real-life TARDIS would work, thinks “Transversable Achronal Retrograde Domain in Spacetime” is a better name for the blue box. It means something that can go backward in time and move faster than the speed of light. Which is handy, because that’s what the Tardis does.
But they’re not going back home to their planet Melissa Majoria. The disappearance seems to have been caused by the more earthly combination of parasites, agricultural chemicals, and poor nutrition.
4. And there really are cracks in the skin of the universe.
Theoretically, at least. And on an extremely small scale. But cosmologists have said there might be “defects in spacetime” called cosmic strings that are, for all intents and purposes, tiny cracks in the universe. Luckily, there’s no chance of us getting caught up in them and erased from history.
Oh, and on a bigger scale, there’s this familiar-looking nebula 11,000 light-years away. Those dark patches are actually clouds of dust absorbing light from behind them. If you could stand in the middle of the sooty dust cloud, you wouldn’t be able to see any stars at all.
5. We’ve not quite invented the Tardis translation circuit… yet.
The Doctor’s Tardis can instantly translate (most) languages using a telepathic field that gets into the head of anyone that enters it. That’s not something that any real-world object can do yet. But don’t worry, some people are on the case.
One developer has made augmented reality glasses that can translate spoken Spanish and display English subtitles to the wearer. And there’s a phone app that can translate text in several languages in real time, and a pair of glasses that does the same thing for Japanese writing, displaying subtitles.
Not quite the Tardis telepathic field yet, though.
6. The scale of the universe means that surely there is some other life out there…
Without aliens, the Doctor wouldn’t have much to do (well, given that he’s an alien, technically he wouldn’t exist at all). In the real world, we’ve found over a thousand planets outside our solar system in just the last 20 years. But in the few years we’ve been listening out for extraterrestrial lifeforms, we haven’t heard a peep. That doesn’t mean there is no other life in the universe. When you think about the vast scale of the cosmos, surely there is?
7. …but we have no idea if we’ll ever make contact.
Sadly, without a Tardis, we only have a small slice of space and time to explore. Our nearest star is a few light-years away, and we’re nowhere near having light-speed travel yet, so we can’t even get that far. If alien life is not close by, we might never encounter it.
But look on the bright side: Would you ever want to meet the Weeping Angels?
8. Some people do have two hearts.
Not everyone with two hearts is from Gallifrey. Very few humans have ever been born with two hearts, but sometimes when someone needs a transplant the new heart is grafted directly onto the original. Eeeek.
And some octopuses have three hearts: one main one to pump blood around its body and two additional ones to pump blood over each of its gills.
9. The stars are going out.
But much more slowly than they do in “Turn Left”. And we’re already at the beginning of the end in terms of star-forming in our universe. Which means it’s all downhill from here until we reach heat death in several billion years where one by one all the stars explode and, eventually, go out. Yikes.
But it would never happen how it does in the show, where Donna and Wilfred see the constellation Orion blink out before their eyes.
If a star 10 light-years from us disappeared, it’d take us 10 years to find out. That’s because light travels at a finite speed and the universe is really, really big. All the stars are different distances away, so we’d see them go out at really different times, probably spread over thousands of years.
Unless Davros managed to set the Reality Bomb so everything happened at once from Earth’s point of view…