Know It All

He's got an answer for everything, week 4

1) How does the Terminator film actually work? How does Kyle Reese come back from time and create someone who already existed in his lifetime? - Stu, Email
For those who haven't seen the film in years: John Connor sends Kyle Reese back in time to protect his mother, Sarah. Although they're being chased by the Terminator, she and Kyle find time to have sex and conceive John. Kyle then dies before he gets to fight alongside John, and before he gets an opportunity to be sent back in time. The short answer is that it doesn't work. It's tantalisingly close, but it doesn't sit right with the rest of the plot. Kyle's timeline itself is very simple: he's born, he gets sent back in time, he has a child, he dies. In time travel fiction, everything doesn't have to connect up to be a perfect loop. Kyle doesn't need to go back in time again, because he already did it. He couldn't live in an unending loop, going back in time over and over, because he'd eventually be too old to conceive, or die of old age. His lifetime is linear. Where this falls down is that the plot does require a perfect loop. If Kyle can die because he doesn't need to time travel a second time, then he doesn't need to time travel the first time. John Connor doesn't need to send Kyle to protect Sarah and conceive John, because John is already alive in the future. If Kyle's lifetime is linear, then so is John's. They can either change what happens or they can't. It can't be both. If you want paradox-free time travel, you'll have to watch Bill and Ted instead.

2) Why do bubbles come from the bottom of a pint of lager when there's no air pockets? - DeZZie, Snodland
The carbon dioxide (CO2) bubbles come from the lager itself. Some of the CO2 occurs as part of the natural brewing process. Traditional brewers add wort (beer before it's fermented) and yeast, which creates additional CO2. Alternatively, they can add fermenting beer and yeast, in a process called kreusening. For your standard pint of lager, CO2 is artificially dissolved into it at pressure. When it's poured into a glass, the CO2 gathers around any tiny scratches or imperfections in the glass, forming bubbles, which then float upwards. A good head is a sign of a good pub: if the glass hasn't been washed well, any greasiness will gloss over these scratches, stopping the bubbles from forming, and making the beer seem flat. If the glass hasn't been properly dried, the water will have the same effect.


3) What¹s the stickiest thing in the world? - Roy, Hove
A stick. Actually, the stickiest natural substance is secreted by the Caulobacter crescentus bacteria. This harmless bacteria, which lives in rivers and water pipes, uses a chain of sugar molecules when attaching itself to objects. These chains are 3 times stronger than superglue, and can withstand forces of 5 tons per sq inch. The sugar molecules are being studied to see if it can be man-made. If it can, it'll be great for using as sutures, as it's incredibly strong and biodegradable. Although not as strong as the bacteria, the most interesting glue is also based on a substance found in nature. So-called dry glues are based on the microscopic branched elastic hairs on gecko feet, enabling the geckos to grip to surfaces. Scientists have made a version using carbon nanotubes; it's 10 times stronger, with 1 sq inch able to support 100kg. These carbon nanotubes are incredibly adhesive under perpendicular shear forces, but can simply be lifted away in another direction, or in simple terms, if you wore shoes and gloves covered with them, you could climb walls.


4) Is “magic” total bollocks? - PK, email
In the sense that there aren't any mystical forces making the rabbit appear in the hat, yes it's total bollocks. There's lots to like about magic though. Grab a tennis ball, stick it in your armpit, and gently squeeze. It'll stop the blood flow through your brachial artery, and thus stop the pulse in your wrist. Obviously, that's not something you should be doing for long periods of time, just like you shouldn't tie a rubber band around your finger for ages. The tennis ball makes for a quick and hugely effective trick though. Showmanship is where it's at. Simply saying "Look, I can stop my pulse" isn't going to impress anyone. This is where the bollocks comes in. Tell your audience of mildly disinterested friends that you've been reading a book about meditation. Spin them some silly tale of being able to control the flow of blood around your body just by using your mind. A chant will really build the mood. They know it's bollocks and you know it's bollocks, but they want to believe. They want to play along. Magicians often say you should never reveal your tricks. This isn't quite right. You should never reveal your tricks to someone who wants to pretend to believe. The few people who truly want to know how it's done will appreciate it more by understanding it. By revealing the secrets to a few choice people (like the readers of a Know It All column) you save yourself from falling into the most common trap of any magician: of being a bit of a smug git.

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