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49 free Christmas Science trivia questions with answers — science & nature quiz, new questions added Aug 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.
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Q 01Reindeer are unique among deer in what way?
Females may grow antlers
Since males shed theirs in early winter, the antlered team on Santa's sleigh is most likely all female.
Q 02When do male reindeer shed their antlers?
Early to mid-winter
Mature bulls drop their antlers in early to mid-winter, soon after the autumn rut, so the biggest males are bare-headed by December; younger bulls may keep theirs until early spring.
Q 03A 2011 University College London study found reindeer can see which kind of light that humans cannot?
Ultraviolet
A 2011 UCL team led by Glen Jeffery showed reindeer eyes admit ultraviolet light down to about 320 nm; urine and lichen, invisible against snow to us, stand out sharply in UV.
Q 04The reflective layer in an Arctic reindeer's eye changes from gold in summer to what colour in winter?
Blue
The tapetum lucidum turns blue in winter as pressure in the eye compresses its collagen, scattering light so less escapes and sensitivity rises during months of darkness; in summer it is golden.
Q 05What causes the clicking sound reindeer make as they walk?
Tendons slipping over bones in their feet
Loud knee-clicking turns out to be an honest signal of body size, a rare case of non-vocal acoustic communication in mammals.
Q 06Two reindeer in A Visit from St. Nicholas are named for a Dutch oath 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. Rudolph did not arrive until 1939.
Q 07Why do most snowflakes show six-fold symmetry?
Ice crystals have a hexagonal structure
Rarely, at around -2 °C, triangular snowflakes with three-fold symmetry can form instead.
Q 08Roughly how many water molecules make up a typical snowflake?
Ten quintillion
A typical snowflake holds about ten quintillion (10^19) water molecules, and with so many ways to arrange them two identical complex flakes are vanishingly unlikely.
Q 09Ice is clear, so why does snow look white?
Crystal facets scatter all wavelengths of light
Each ice crystal's facets scatter all wavelengths of light, and after countless reflections within a snowpack the whole spectrum bounces back together, which we see as white; pure ice itself is clear.
Q 10Who was the first person known to take detailed photographs of snowflakes, starting in 1885?
Wilson Bentley
Wilson 'Snowflake' Bentley, a Vermont farmer, took the first photomicrograph of a snow crystal in 1885 and captured more than 5,000; he died of pneumonia in 1931 after walking home through a blizzard.
Q 11Snowflake physicist Kenneth Libbrecht was a scientific consultant on which 2013 film?
Frozen
Libbrecht advised Disney's animators on snow-crystal shapes for Frozen (2013); four of his snowflake photographs had already become US postage stamps in 2006, with about 3 billion printed.
Q 12Mistletoe 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 13How are most mistletoe seeds spread to new host trees?
Birds eat the berries
Q 21Modern tinsel was invented in Nuremberg in 1610 and originally made of what?
Shredded silver
Nuremberg's 1610 tinsel was shredded silver, hammered thin and cut into strips; because silver tarnished, lead foil took over in the 20th century until it was phased out over toxicity in the 1970s.
Q 22Candy 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 23The Nordmann fir, a favourite Christmas tree, is prized because its needles are not sharp and do what?
Do not drop readily when it dries
Birds such as the mistle thrush eat the sticky berries and wipe or excrete the seeds onto branches; the name is often traced to Germanic 'mist', dung, plus 'tan', twig.
Q 14The red 'petals' of a poinsettia are actually what?
Leaves called bracts
The true flowers are the tiny yellow structures at the centre.
Q 15What does a poinsettia need to turn its bracts red?
Long periods of darkness
Poinsettias are short-day plants: long periods of darkness, about fourteen hours a night for six to eight weeks, trigger the bracts to turn red through photoperiodism.
Q 16The idea that turkey makes you sleepy blames which amino acid?
Tryptophan
Tryptophan, a precursor of serotonin and melatonin, gets the blame, yet turkey has no more of it than chicken or beef; the big meal and the wine do the real work.
Q 17Which two chemicals did Hans van Doorn identify in the 1990s as the source of Brussels sprouts' bitterness?
Sinigrin and progoitrin
Dutch scientist Hans van Doorn found the glucosinolates sinigrin and progoitrin drove the bitterness; seed companies then bred low-level varieties, so sprouts taste milder than they did in the 1980s.
Q 18How are cranberries harvested from flooded bogs?
They float and are corralled
Beds are flooded in autumn for harvest and again in winter to protect the plants from cold.
Q 19Which chemical is used on the friction strip that makes a Christmas cracker bang?
Silver fulminate
A trace of silver fulminate, a friction-sensitive explosive, coats one strip and an abrasive the other; London confectioner Tom Smith added the bang to his bon-bons after hearing a log crackle on the fire.
Q 20Edward H. Johnson, who made the first electrically lit Christmas tree, worked with which inventor?
Thomas Edison
Edward H. Johnson, a vice-president of Thomas Edison's Electric Light Company, lit a tree with 80 hand-wired red, white and blue bulbs at his New York home in December 1882.
It is native to the mountains around the Black Sea and grows to over 60 metres in the wild.
Q 24Old Tjikko, a Norway spruce clone in Sweden, has a root system carbon-dated to roughly what age?
9,550 years
Old Tjikko's root system was carbon-dated to about 9,550 years in 2008 by Leif Kullman of Umeå University; the visible trunk is young, as the clone keeps regrowing. Norway spruce is the tree Oslo sends to Trafalgar Square.
Q 25What 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 26Frankincense is an aromatic resin tapped from trees of which genus?
Boswellia
Frankincense is tapped from Boswellia trees of Arabia and the Horn of Africa, notably Boswellia sacra; myrrh comes from thorny Commiphora trees in the same family, Burseraceae.
Q 27Astronomers have tried to explain the Star of Bethlehem as a conjunction of which planets?
Jupiter and Saturn or Jupiter and Venus
Kepler linked it to the triple conjunction of Jupiter and Saturn in 7 BC; others prefer the very close pairing of Jupiter and Venus in June 2 BC, though neither fits the Gospel's moving star.
Q 28In the Northern Hemisphere, the winter solstice, the shortest day, falls on which dates?
December 21 or 22
The December solstice falls on 21 or 22 December (rarely 20 or 23), when the North Pole is tilted furthest from the Sun, giving the Northern Hemisphere its shortest day.
Q 29Which 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 30'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.