how deep is the sea? Why is the sky blue? And what is the point of boys? Six out of 10 adults struggle to answer the philosophical and scientific questions posed by curious children, says a survey.
Adults' ability to handle such questions is made worse by their lack of general knowledge, which is only slightly above that of the average 11-year old. More than 1,500 adults and primary pupils were interviewed by children's publisher Dorling Kindersley to coincide with the launch of their Eyewitness Guides for youngsters.
Most adults admitted to being regularly stymied by the questions children asked them.
Dorling Kindersley have released a list of the 15 most common questions, many of which require a detailed knowledge of the natural world. For example, children will ask why clouds stay in the sky, how long it takes a tadpole to turn into a frog and why pebbles on the beach are different colours.
Di Christopher, head of Sandown primary on the Isle of Wight, said: "Children ask questions simply, honestly and innocently, in an open-minded way.
"Questions about the world around them need to be answered. It's an opportunity to resolve misunderstanding. And it can lead to a network of enquiries. It feeds their inquisitiveness."
Adults have also submitted some of the more idiosyncratic questions asked by children.
Many reveal a metaphysical streak that would challenge the bravest of philosophers: Who created God? Am I real or is this just a dream? If a leaf is alive, does it have feelings?
Nicholas Tucker, a senior lecturer in culture at Sussex university, said: "Very often, children want answers adults can't give. For them, everything potentially has meaning at the level of feelings, rather than on a scientific level."
He added that adults should not fear revealing their ignorance. "Often, children's questions aren't about wanting an answer at all, but about making contact with adults," he said.
Nonetheless, many adults are ill-equipped to answer children's questions.
The survey reveals that parents, like their offspring, are more likely to recognise X Factor judge Simon Cowell than new Prime Minister Gordon Brown.
And, like footballing icon David Beckham, who famously admitted to being baffled by his six-year-old son's homework, more than half of parents have difficulty understanding their children's school work.
Maths is the subject most likely to confuse adults, while one in 20 admitted to being defeated by every subject on the school timetable.
But Lyn Allcock, a gifted-child consultant for Mensa, believes that lack of knowledge need not prevent teachers and parents from tackling a never-ending stream of prepubescent questions.
"Teach them how to fail," she said. "It's all right not to know everything and it's all right to get things wrong. If people were born knowing everything, we wouldn't need schools.
"If you don't know something, say so. But then follow it up with, 'I know how to find out'. Make learning fun."
Tricky questions and answers.
Well some of them...
Q Why is the sky blue?
A Clear skies look blue, because gases in the air bounce mostly blue light towards our eyes.
Q How do birds know which nests are theirs?
A Bird nests are immensely variable structures. Despite their similarity in overall shape, the fine details of these nests identify their makers as surely as a fingerprint, so a bird will never get lost.
Q How deep is the sea?
A 19,800ft (approx 6,000m)
Q Do insects have brains?
A Yes. An ant brain, for example, has about 250,000 cells. A human brain has 10,000 million cells, so a colony of 40,000 ants has collectively the same size brain-power as a human being.
Q How do clouds stay in the sky?
A Clouds form when there is enough moisture in the air, and when moist air is lifted high enough in the air to cool and condense. On a clear day, the sun heats the ground, sending up bubbles of rising warm air. Fleecy cumulus clouds will appear in the sky, and disappear again when these bubbles no longer form.
And questions without
Q Why are people bad to each other?
Q How did the first person get chicken pox?
Q Why do baby dolphins not have to wear armbands?
Q How many crumbs are there in Weetabix?
Q Why do teachers hand out so much homework?