48 Fun Facts About Christmas Science

Reindeer are unique among deer in what way?

Females may grow antlers in reindeer, the only deer where both sexes do, and pregnant cows usually keep theirs until their calves are born.

When do adult male reindeer shed their antlers?

Adult bulls cast their antlers after the autumn rut, by early to mid-winter, while young bulls often keep theirs until April.

A 2011 University College London study found reindeer can see which kind of light that humans cannot?

Reindeer see ultraviolet light down to about 320 nm; snow reflects most UV while urine and wolf fur absorb it, so they stand out as dark shapes.

The reflective layer in an Arctic reindeer's eye changes from gold in summer to what colour in winter?

In winter the tapetum turns deep blue and reflects less light back out of the eye, raising sensitivity in the long darkness at the cost of sharper vision.

What causes the clicking sound reindeer make as they walk?

Tendons slipping over bones in their feet make the click; eland antelope make a similar knee-click, which in their case tells rivals how big a bull is.

Two reindeer in A Visit from St. Nicholas are named for Dutch words meaning what?

'Donder en bliksem' is Dutch for 'thunder and lightning'; the 1823 printing had Dunder and Blixem, later Germanised to Donner and Blitzen.

Roughly how many water molecules make up a typical snowflake?

10 quintillion is the high estimate: counts run from 10^18 to 10^19 water molecules, so two identical complex flakes are very unlikely.

Ice is clear, so why does snow look white?

Crystal facets scatter all wavelengths of light, and after countless reflections within a snowpack the whole spectrum bounces back together, which we see as white.

Who was the first person known to take detailed photographs of snowflakes, starting in 1885?

Wilson Bentley, a Vermont farmer, photographed his first snow crystal on January 15, 1885, and shot well over 5,000 more without finding two alike.

Snowflake physicist Kenneth Libbrecht was a scientific consultant on which 2013 film?

Frozen: Libbrecht grows designer snow crystals in his lab, shaping each one by changing the temperature and humidity as it grows.

Mistletoe is what kind of plant?

Mistletoe is an obligate hemiparasite: it photosynthesises with its own green leaves but cannot live without a host, driving a haustorium into the branch to take water and minerals.

How are most mistletoe seeds spread to new host trees?

Birds such as the mistle thrush eat the berries, then wipe the sticky seeds off their beaks onto branches or pass them in their droppings.

The red 'petals' of a poinsettia are actually what?

Leaves called bracts supply the colour, while the true flowers are the tiny yellow cyathia clustered at the centre.

What does a poinsettia need to turn red for Christmas?

Poinsettias are short-day plants: long periods of darkness, at least fourteen hours a night for weeks on end, trigger the colour change.

The idea that turkey makes you sleepy blames which amino acid?

Tryptophan gets the blame, but turkey holds about as much as chicken or beef, so the rest of the big meal is the likelier cause of the doze.

Which two chemicals did Hans van Doorn identify in the 1990s as the source of Brussels sprouts' bitterness?

Hans van Doorn showed sinigrin and progoitrin drove the bitterness, so seed companies crossed old low-bitterness varieties with modern ones and sprouts got milder.

How are cranberries harvested from flooded bogs?

They float and are corralled after the beds are flooded for the autumn harvest, and the same beds are flooded again in winter to protect the vines.

Which chemical is used on the friction strip that makes a Christmas cracker bang?

Silver fulminate, a friction-sensitive explosive, is painted on one card strip and an abrasive on the other, so pulling the cracker apart sets it off.

Edward H. Johnson, who made the first known electrically lit Christmas tree, worked with which inventor?

Edward H. Johnson, vice president of Thomas Edison's Electric Light Company, had walnut-sized bulbs specially made, and a Detroit reporter publicised his 1882 tree.

Which Christmas decoration was invented in Nuremberg around 1610, originally made with silver?

Tinsel was first made of silver or silver-plated metal, and because silver tarnishes quickly, lead and aluminium versions later took over.

Candy canes get their cooling taste from which compound in peppermint oil?

Menthol, the main component of peppermint oil, binds the TRPM8 cold receptor on nerve endings, so the mouth registers cold without any drop in temperature.

The Nordmann fir, a favourite Christmas tree, is prized because its soft needles do what?

Its needles do not drop readily when it dries, which makes this fir from the mountains south and east of the Black Sea a favourite cut tree.

Old Tjikko, a Swedish tree whose root system is about 9,550 years old, belongs to which species?

Norway spruce is Old Tjikko's species: its trunks live only centuries but keep regrowing from the ancient roots, and Oslo sends one to Trafalgar Square each Christmas.

What is the botanical term for a species like holly with separate male and female plants?

Holly is dioecious, with male and female flowers on separate plants, so only females bear berries and need a male nearby; monoecious species carry both sexes on one plant.

Frankincense is an aromatic resin tapped from trees of which genus?

Boswellia trees are tapped by scoring the bark, and the milky resin that oozes out hardens into tear-shaped drops that are collected by hand.

Johannes Kepler linked the Star of Bethlehem to a triple conjunction of Saturn and which planet?

Jupiter: Kepler reasoned that the Star of Bethlehem, like the new star he saw in 1604, came with a great conjunction of Jupiter and Saturn.

In the Northern Hemisphere, the winter solstice, the shortest day, falls on which dates?

The solstice falls on December 21 or 22, occasionally December 20, when the North Pole tilts furthest from the Sun and the north has its longest night.

Which great scientist was born on Christmas Day 1642 by the Julian calendar then used in England?

Isaac Newton was born at Woolsthorpe on 25 December 1642 by the Julian calendar, which England kept until 1752; by the Gregorian calendar that is 4 January 1643.

'Christmas disease' is another name for which condition?

Haemophilia B, a deficiency of clotting factor IX, was named Christmas disease after Stephen Christmas, the first patient described, in a paper published in the BMJ's 27 December 1952 issue.

Swarms of Australia's Christmas beetles can strip and even kill which kind of tree?

Gum trees, or eucalypts, can be stripped of leaves by dense Christmas beetle swarms, and several beetle species are implicated in eucalypt dieback.

The Christmas tree worm, Spirobranchus giganteus, lives where?

Coral reefs: when threatened, the worm pulls its two spiral crowns back into its tube and plugs the opening with a trapdoor-like lid.

Which animals migrate from forest to sea by the millions each year on Christmas Island?

Red crabs set off with the first rains of the wet season, and roads close so the swarms can reach the shore to breed.

Eggnog may have developed from which medieval hot milk drink curdled with wine or ale?

Posset, hot milk curdled with wine or ale and spiced, was drunk in medieval England as a cold and flu remedy; eggnog likely descends from it, with eggs and later rum added.

Which spirit is traditionally warmed and set alight over a Christmas pudding?

Brandy: in A Christmas Carol, Mrs Cratchit carries in her pudding 'blazing in half of half-a-quartern of ignited brandy', and the family hails it a triumph.

An ancient Roman forerunner of fruitcake mixed raisins, pine nuts and which seeds into barley?

Pomegranate seeds went into that Roman mix; from the 16th century, cheap sugar from the colonies let Europeans candy fruit, making fruitcake affordable.

Reindeer noses have specialised turbinate bones that do what?

Scroll-like turbinate bones greatly increase surface area inside the nostrils, so, as in a moose, incoming air is warmed and moistened before it reaches the lungs and heat is recovered on the way out.

Ukichiro Nakaya discovered that a snow crystal's shape depends on temperature and on what else?

Nakaya showed shape depends on temperature and whether the air is above or below saturation, and in 1936 he grew the first artificial snow crystal.

Reindeer moss, a staple food of reindeer, is not a true moss; what is it?

A lichen: reindeer live mainly on it in winter, sometimes digging under the snow to reach it.

The poinsettia is named after Joel Roberts Poinsett, the first US minister to which country?

Mexico's government asked for Poinsett's recall after he became embroiled in the country's politics, and he left the post in 1830.

Which Irish passage tomb was built with a 'roof-box' that lets in the winter solstice sunrise?

Newgrange's roof-box lets the winter solstice sunrise light the inner chamber for about 17 minutes, and demand to watch from inside is so great that places are drawn by lottery.

Early German artificial Christmas trees, a response to deforestation, were made from what?

Dyed goose feathers were wired into branches for trees from about 5 cm to 2.5 m tall, and red berry tips often doubled as candle holders.

Which president sponsored the first electrically lit Christmas tree in the White House, in 1895?

Grover Cleveland's 1895 tree carried more than a hundred multicoloured electric bulbs; General Electric's first commercial light strings came in multiples of eight sockets.

Which caffeinated South American drink is brewed from a species of holly, Ilex paraguariensis?

Yerba mate was drunk by the Guaraní before Europeans arrived, and Jesuit missions later domesticated the holly and grew it on plantations.

In which US city were aluminum Christmas trees first manufactured?

Modern Coatings of Chicago made the first aluminum trees; Manitowoc's Aluminum Specialty Company then mass-produced the Evergleam, and A Charlie Brown Christmas (1965) mocked the shiny trees.

What were the 15-inch snowflakes reported at Fort Keogh, Montana, in 1887 made of?

Clumped ice crystals make big flakes, as crystals collide and stick together while falling, and Guinness lists the Fort Keogh flakes as the largest on record.

What is the sticky coating on mistletoe seeds that glues them to a branch called?

Viscin makes the seed so sticky that it glues to bark and holds until the seedling's haustorium penetrates the branch.

Which Roman emperor dedicated a temple to the 'Invincible Sun' on 25 December 274?

Aurelian made Sol Invictus the empire's chief god, and some scholars think he also began a 25 December festival of the Sun's birthday, just after Saturnalia.

In Turkey, the poinsettia is popularly named after which national figure?

Mustafa Kemal Atatürk: a popular story traces the name to 1935 reports of a US professor naming a new flower after him, but that flower was yellow.