Christmas Science Trivia
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48 free Christmas Science trivia questions with answers — science & nature quiz, new questions added Sep 2026.
40 free Christmas Science trivia questions with answers. There is a surprising amount of real science hiding in the Christmas season, and this quiz collects the best of it. Forty questions cover reindeer biology (why Santa's team is probably female, and what colour their eyes turn in winter), why snowflakes have six arms and whether two are ever alike, how mistletoe steals from its host, why poinsettias turn red, and whether turkey really makes you sleepy. There is chemistry in the Christmas cracker, botany in the tree on your floor, astronomy in the star of Bethlehem and the solstice, a bit of medicine in Christmas disease, and some natural history in Christmas beetles, Christmas tree worms and the red crabs of Christmas Island. Easy questions ask what makes snow look white; hard ones want the compound that makes a cracker bang and the year the first electric tree lights were lit. Every answer was checked against Wikipedia's articles on the topics, and each question carries the sentence that supports it.
30 of 48 questions with answers and explanations. Play the quiz
Q 01Reindeer are unique among deer in what way?
Females may grow antlers
Females may grow antlers in reindeer, the only deer where both sexes do, and pregnant cows usually keep theirs until their calves are born.
Q 02When do adult male reindeer shed their antlers?
Early to mid-winter
Adult bulls cast their antlers after the autumn rut, by early to mid-winter, while young bulls often keep theirs until April.
Q 03A 2011 University College London study found reindeer can see which kind of light that humans cannot?
Ultraviolet
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.
Q 04The reflective layer in an Arctic reindeer's eye changes from gold in summer to what colour in winter?
Blue
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.
Q 05What causes the clicking sound reindeer make as they walk?
Tendons slipping over bones in their feet
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.
Q 06Two reindeer in A Visit from St. Nicholas are named for Dutch words meaning what?
Thunder and lightning
'Donder en bliksem' is Dutch for 'thunder and lightning'; the 1823 printing had Dunder and Blixem, later Germanised to Donner and Blitzen.
Q 07Roughly how many water molecules make up a typical snowflake?
10 quintillion
10 quintillion is the high estimate: counts run from 10^18 to 10^19 water molecules, so two identical complex flakes are very unlikely.
Q 08Ice is clear, so why does snow look white?
Crystal facets scatter all wavelengths of light
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.
Q 09Who was the first person known to take detailed photographs of snowflakes, starting in 1885?
Wilson Bentley
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.
Q 10Snowflake physicist Kenneth Libbrecht was a scientific consultant on which 2013 film?
Frozen
Frozen: Libbrecht grows designer snow crystals in his lab, shaping each one by changing the temperature and humidity as it grows.
Q 11Mistletoe is what kind of plant?
An obligate hemiparasite
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.
Q 12How are most mistletoe seeds spread to new host trees?
Birds eat the berries
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.
Q 13The red 'petals' of a poinsettia are actually what?
Leaves called bracts
Q 21Candy canes get their cooling taste from which compound in peppermint oil?
Menthol
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.
Q 22The Nordmann fir, a favourite Christmas tree, is prized because its soft needles do what?
Do not drop readily when it dries
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.
Q 23Old Tjikko, a Swedish tree whose root system is about 9,550 years old, belongs to which species?
Norway spruce
Leaves called bracts supply the colour, while the true flowers are the tiny yellow cyathia clustered at the centre.
Q 14What does a poinsettia need to turn red for Christmas?
Long periods of darkness
Poinsettias are short-day plants: long periods of darkness, at least fourteen hours a night for weeks on end, trigger the colour change.
Q 15The idea that turkey makes you sleepy blames which amino acid?
Tryptophan
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.
Q 16Which two chemicals did Hans van Doorn identify in the 1990s as the source of Brussels sprouts' bitterness?
Sinigrin and progoitrin
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.
Q 17How are cranberries harvested from flooded bogs?
They float and are corralled
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.
Q 18Which chemical is used on the friction strip that makes a Christmas cracker bang?
Silver fulminate
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.
Q 19Edward H. Johnson, who made the first known electrically lit Christmas tree, worked with which inventor?
Thomas Edison
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.
Q 20Which Christmas decoration was invented in Nuremberg around 1610, originally made with silver?
Tinsel
Tinsel was first made of silver or silver-plated metal, and because silver tarnishes quickly, lead and aluminium versions later took over.
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.
Q 24What is the botanical term for a species like holly with separate male and female plants?
Dioecious
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.
Q 25Frankincense is an aromatic resin tapped from trees of which genus?
Boswellia
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.
Q 26Johannes Kepler linked the Star of Bethlehem to a triple conjunction of Saturn and which planet?
Jupiter
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.
Q 27In the Northern Hemisphere, the winter solstice, the shortest day, falls on which dates?
December 21 or 22
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.
Q 28Which great scientist was born on Christmas Day 1642 by the Julian calendar then used in England?
Isaac Newton
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.
Q 29'Christmas disease' is another name for which condition?
Haemophilia B
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.
Q 30Swarms of Australia's Christmas beetles can strip and even kill which kind of tree?
Gum trees
Gum trees, or eucalypts, can be stripped of leaves by dense Christmas beetle swarms, and several beetle species are implicated in eucalypt dieback.