50 Fun Facts About Christmas Science

Reindeer are unique among deer in what way?

Since males shed theirs in early winter, the antlered team on Santa's sleigh is most likely all female.

When do male reindeer shed their antlers?

Once the bulls are bare-headed, the antlered cows take the top ranks at the best feeding spots.

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

Urine and fur, invisible against snow to us, stand out sharply to a reindeer in the Arctic gloom.

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

The shift in the tapetum lucidum improves vision during months of continuous darkness.

What causes the clicking sound reindeer make as they walk?

Loud knee-clicking turns out to be an honest signal of body size, a rare case of non-vocal acoustic communication in mammals.

In the 1823 poem A Visit from St. Nicholas, Dunder and Blixem take their names from a Dutch oath meaning what?

They were later Germanised to Donner and Blitzen; Rudolph did not arrive until 1939.

Why do most snowflakes show six-fold symmetry?

Rarely, at around -2 °C, triangular snowflakes with three-fold symmetry can form instead.

Roughly how many water molecules make up a typical snowflake?

That is 10 to the power 19, which is why it is so unlikely that any two flakes are alike.

Ice is clear, so why does snow look white?

Diffuse reflection of the whole spectrum from countless tiny facets does the trick.

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

The Vermont farmer captured more than 5,000 crystals and died of pneumonia after walking home through a snowstorm.

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

Four of his snowflake photos also became US postage stamps in 2006, with about 3 billion printed.

Mistletoe is what kind of plant?

It photosynthesises but drives a structure called a haustorium into its host to steal water and nutrients.

How are most mistletoe seeds spread to new host trees?

The name itself descends from Old English 'mistel', long linked to bird droppings on branches.

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

The true flowers are the tiny yellow structures at the centre.

What does a poinsettia need to turn its bracts red?

At least fourteen hours of dark a night for six to eight weeks, thanks to photoperiodism.

Poinsettias are often said to be highly toxic. What does the evidence say?

The plant is native to Mexico and Central America and named for the first US minister to Mexico.

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

Turkey actually contains no more of it than other meats; the big meal and the wine do the real work.

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

Seed companies then bred low-bitterness varieties, which is why sprouts taste milder than they did.

How are cranberries harvested from flooded bogs?

Beds are flooded in autumn for harvest and again in winter to protect the plants from cold.

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

Tom Smith added the 'crackle' in the 1840s after hearing a log spit on the fire.

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

Grover Cleveland sponsored the first electrically lit White House tree in 1895.

Modern tinsel was invented in Nuremberg in 1610 and originally made of what?

Lead foil took over for decades in the 20th century because, unlike silver, it did not tarnish.

Why were candy canes reportedly first hung on Christmas trees?

Straight striped peppermint sticks appear in an 1844 confectioner's manual; 'candy-canes' at Christmas are recorded by 1874.

The Nordmann fir, a favourite Christmas tree, is prized because its needles are not sharp and do what?

It is native to the mountains around the Black Sea and grows to over 60 metres in the wild.

Old Tjikko, a Norway spruce clone in Sweden, has a root system carbon-dated to roughly what age?

Norway spruce is the original Christmas tree species and the one Oslo sends to Trafalgar Square each year.

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

Holly leaves can carry six to eight spines a side, though some trees have none at all.

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

Myrrh, its companion gift, comes from thorny trees of the genus Commiphora in the same plant family.

Astronomers have tried to explain the Star of Bethlehem as a conjunction of which planets?

Kepler wrongly argued a conjunction could spark a nova; modern calculations show the planets never merged into one light.

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

It happens when the pole reaches its maximum tilt away from the Sun.

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

By today's Gregorian calendar his birthday is 4 January 1643.

'Christmas disease' is another name for which condition?

It is named after Stephen Christmas, the first patient described with the factor IX deficiency.

'Christmas beetle' is the common name for beetles of which genus, seen in Australian summers?

The Australian Museum calls the Argentine lawn beetle, also out in December, an 'impostor'.

The Christmas tree worm, Spirobranchus giganteus, lives where?

Its two colourful spirals, which give it the name, are used for feeding and breathing.

In which year did Captain William Mynors sail past and name Christmas Island on Christmas Day?

Its annual red crab migration to the sea has been called one of the wonders of the natural world.

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

In the Middle Ages it was taken as a cold and flu remedy.

A Christmas pudding is traditionally served flaming. Which spirit is warmed and set alight?

The pudding is steamed a second time before serving and often eaten with brandy or rum butter.

The earliest known fruitcake recipe, from ancient Rome, mixed raisins, pine nuts and which seeds into barley?

Later English fruitcakes used rum and dried fruit to extend shelf life, which is why yours may still be edible.

Reindeer noses have specialised turbinate bones that do what?

Like a moose's, the reindeer nose warms and moistens frigid air before it reaches the lungs.

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

Supersaturated air produces lacy, ornate crystals; drier air makes them solid and compact.

Reindeer are described as osteophagous, meaning they do what?

In extreme cases they will chew each other's antlers before they are even shed.

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

Poinsett, also a botanist, began shipping the plants to his South Carolina greenhouses possibly as early as 1826; before that it was the 'Mexican flame flower'.

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

Stonehenge's main axis points the other way, toward the solstice sunset, while Cahokia Woodhenge in Illinois is also solstice-aligned.

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

Feather trees ranged from 5 cm to 2.5 m tall, and their branch tips often carried artificial red berries that doubled as candle holders.

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

It carried over a hundred multicoloured lights; General Electric's first commercial strings came in multiples of eight sockets.

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

Ilex has over 570 species, more than any other woody dioecious flowering-plant genus; yaupon holly in the southeastern US is caffeinated too.

In which city were aluminum Christmas trees first manufactured, in 1958?

Production later moved to Manitowoc, Wisconsin, and A Charlie Brown Christmas (1965) mocked the shiny trees as commercialism.

Guinness lists the widest snowflakes ever, seen at Fort Keogh, Montana in 1887. How wide?

Normal aggregated flakes top out around 3 or 4 inches; single crystals the size of a dime have been observed.

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

Birds wipe the sticky seeds off their bills onto branches; it is a mix of cellulose strands and mucopolysaccharides.

In AD 274, which emperor made 25 December the birthday festival of the 'Invincible Sun'?

In the old Roman calendar 25 December was the solstice itself, and the feast followed hard on Saturnalia, held 17 to 23 December.

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

The name traces to a spurious newspaper report about a professor's visit, and it stuck: 'Atatürk çiçeği', the Atatürk flower.