Christmas: how to cheat at pulling crackers
Ever wanted to make the perfect snowball, win the Christmas cracker novelty every time, and impress your festive guests by creating snowflakes indoors? Science correspondent Richard Gray asks the experts who can show you how...
How to win when pulling a cracker – without fail
As demonstrated by the weapons experts at QinetiQ, the defence agency which, when they’re not developing technology for the MoD, like to experiment with Christmas table decorations.
- Hold your end lower than the other person’s, so the cracker tilts downwards towards you.
- To prevent the cracker tearing, use a firm, two-handed grip.
- Apply a slow, steady pull, rather than a swift tug, which will only compromise the integrity of your section of the cracker.
- Avoid twisting, as this will add stress to the cracker wrapping. For the same reason, avoid laughing too hard at Uncle Bob’s annual ‘joke’ about ‘pulling a cracker’.
How to make the perfect snowball
To create frozen missiles that produce a satisfying splatter when they hit Auntie Gladys requires a working knowledge of physics and the right weather conditions. Professor Peter Main, Director of Education and Science at the Institute of Physics and erstwhile “snowballologist”, notes: “You don’t want it to disintegrate mid-flight, but it should splatter on impact without causing damage.”
Step 1. Check the weather. Outdoor temperatures around 32F (0C) will ensure the snow has the correct moisture content, a key component of the perfect snowball. At lower temperatures, the snow may be too powdery, containing more air and therefore less water, making it harder to pack tightly into a ball.
Step 2. Wear gloves, not mittens. The individual fingers give gloves a larger surface area and allow more heat to escape, thereby slightly melting the snow as it is squeezed into a ball.
Step 3. Scoop up the snow with cupped hands. Typically, fresh, uncompacted snow is between 90 and 95 per cent trapped air. To reduce the air content and create a ball, slowly close your hands together while rotating the trapped snow.
Step 4. Squeeze with increasing pressure: the snow should make muffled cracking noises as the last of the air is squeezed from between the snowflakes as they compress. Avoid excessive pressure or your snowball might disintegrate under the stress. “The trick,” says Prof Main, “is to compress it enough to enable it to stick together, but not enough to form lumps of ice”.
Step 5. Make a small pile of snowballs, ensuring plenty of ammunition in case of retaliation. Setting snowballs aside will also improve them, as they recover from the melting caused by your body heat. As your missiles slowly refreeze, they will become firmer still – deep and crisp and even.
Step 6. Throw first snowball. Fire at will, or until Auntie Gladys calls Uncle Bob.
How to make your own snowflake
By Professor Kenneth Libbrecht, an expert in atomic and optical physics based at the California Institute of Technology, who – despite his pioneering work on ice crystals – has probably never been snowed in. Warning: this experiment is best avoided with family members who have braved the blizzards to make it for Christmas lunch.
Step 1. Cut half an inch off the bottom of an empty 500ml plastic soft drinks bottle.
Poke a hole in the centre of the cutaway section using a needle, then poke four holes around the side. Fill with a small, round piece of sponge, and use four pins inserted through the side holes to hold it in place.
Step 2. Thread some fishing line through the central hole and push it through the sponge. Hold it in place using some sticky tape on the bottom of the bottle.
Step 3. Trim the length so it will hang freely inside the bottle when put back together and balanced upside down. Attach a paper clip to the end of the line.
Step 4. Place the upturned bottle inside three stacked polystyrene cups so the bottle’s label is at the same height as the top of the cups. Wet the sponge and reassemble the apparatus so that the fishing line hangs down inside the bottle.
Step 5. Fill the cups with crushed ice so the bottle is packed tight. After five minutes, small ice crystals should start to form along the fishing line.
Step 6. Use a magnifying glass to examine the crystals. “They can be beautiful,” says Prof Libbrecht. “Snowflakes are complicated crystals, but it is hard to say with certainty that no two are the same.”
How to calculate the calories in your lunch
An at-a-glance analysis of all your favourite festive trimmings, courtesy of scientists at the British Nutrition Foundation – plus tips on how to serve up a healthier meal.
Two slices of roast turkey 225 calories
Stuffing 231 calories
Pork sausage and bacon 197 calories
Four small roast potatoes 400 calories
Cranberry sauce 45 calories
Boiled carrots 14 calories
Roast parsnips 102 calories
Boiled Brussels 32 calories
Gravy 17 calories
Bread sauce 50 calories
1 portion Christmas pudding 273 calories
3 tablespoons of custard 119 calories
1 tablespoon of brandy butter 195 calories
2 tablespoons double cream 269 calories
1 slice of Christmas cake 249 calories
1 portion of chocolate log 101 calories
1 portion cheese and buscuits 394 calories
1 portion of mixed nuts 243 calories
1 mince pie 200 calories
1 glass of mulled wine 245 calories
2 glasses of wine 170 calories
Total 3,771 calories
However, to make it a healthier lunch:
- Use chestnuts, not sausage meat, for the stuffing
- Eat your turkey without the skin: it contains most of the fat from the bird
- To roast, cut potatoes and parsnips lengthways. Large pieces absorb less fat than smaller ones
- Convince children to eat Brussels sprouts by telling them: “They are a good source of vitamin C, folate and other bioactive substances.” Never fails.
How to shed those festive extra pounds
It will take a mere 14 hours to walk off your Christmas lunch. At an average walking speed of 3mph, that means walking 42 miles.
How to follow the christmas star
The Star of Bethlehem which, according to the Bible, guided the Three Wise Men to Jesus’ birthplace, could have a solid basis in science.
Using historical records and computer simulations that allow the position of the stars and planets to be charted back more than 2,000 years, Mark Thompson, fellow of the Royal Astronomical Society, claims that between 3BC and 2BC, there was a series of unusual astronomical events called conjunctions, involving the planet Jupiter and one of the brightest stars, Regulus. The planet passed the star travelling first in its usual easterly movement, before it then appeared to reverse and pass again in a westerly direction, before changing direction again to pass the star a third time.
Mr Thompson said: “Jupiter, the king of planets, passing so close to the king of stars on three occasions could have been interpreted as the birth of a new king.”
These three conjunctions, which took place on September 14 3BC, February 17 2BC and May 8 2BC, were caused by an astronomical phenomenon called retrograde motion, in which a planet will appear to drift west for a period of several weeks. This happens when outer planets which orbit the sun at a slower rate than the Earth appear to “overtake” our planet.
“The retrograde motion meant Jupiter was travelling in a westerly direction in the sky and so the Three Wise Men may have followed it from Persia,” Mr Thompson said. “By camel, it would have taken about three months, roughly the same time the planet was travelling in this westward direction.”