Helix @ CSIRO

For kids who love science

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River crossings

You will need

six pieces of paper - a river, a boat, a man, a chicken, a fox and a bag of corn.

Cut out all the pieces.

What to do

  1. Cut out the farmer, the fox, the chicken, the boat and the bag of corn along the black lines.
  2. Fold along each dotted line
  3. Use sticky tape to make the pieces and the boat.

The puzzle

A paper boat shape.

You’ll need two pieces of sticky tape to make the boat – one for the front and one for the back.

A farmer needs to get a fox, a chicken and some corn across the river. He can only carry one of these things at a time. The animals are well behaved when the farmer is around, but when he goes to the other side of the river they are not very well behaved.

If he leaves the fox with the chicken then the chicken will get eaten. If he leaves the chicken with the corn, the corn will get eaten. How does he get all three across the river without anything getting eaten?

What’s happening?

A strip of paper with a farmer on it, folded into a triangle.

Use sticky tape to make the other pieces stand up.

This is a very old puzzle called ‘the river crossing puzzle’. These sorts of puzzles have been around for over 1000 years. It might seem impossible, until you realise the farmer can take things back from the far shore, to stop them from getting eaten (or eating something).

Here’s a slightly harder puzzle:

A family of a mother, a father and two children want to cross a river, and they meet a fisherman with a small boat. The fisherman will let the family borrow his boat, but only if they give it back afterwards. The boat is very small, and it can only just carry one adult without sinking, so no other people can be in the boat when there’s an adult on board. The two kids are a lot lighter, and can both go in the boat at the same time. Can the family cross the river, and still give the fisherman back his boat?

The farmer and corn are in the boat, the fox and chicken are on the bank.

Try to get all the pieces across the river without anything getting eaten!

This puzzle is also possible (as long as the children are strong enough to row the boat) but it takes quite a lot of going back and forth across the river, and some of the people would get very tired.


There’s a very powerful way of solving these sorts of puzzles, by drawing a network. Different circles represent all the possible positions of people and the boat, and each line represents a boat trip. If you cross off every possibility that isn’t allowed, like when something got eaten in the original puzzle, then any path from the starting spot to the ending spot is a solution.

This technique is hard to do by hand, but with help from a computer it is reasonably quick, and the patterns make it easy to see the most efficient solutions. Networks like this are also used to design production lines, and chemical production techniques. This sort of diagram is also used to help predict the effects of genetically engineering bacteria.

More information

A collection of river crossing puzzles
The history of river crossing puzzles

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Recycling on the reef

Written by Michele Weber

Tube sponges in water

If it weren’t for the diet of the humble marine sponge, reefs might be rather boring places.
Image: Thinkstock

Coral reefs have much in common with rainforests: both are full of life, but are low in nutrients. How is that possible? As far as a coral reef goes, it’s because marine sponges produce waste that contains food that other reef animals can eat. Continue reading

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Moth mimic

A man wearing sunglasses. There is a zoom box indicating the sunglasses are covered in tiny cones.

These sunglasses are coated with a new material invented to reduce glare. The material was inspired by the eyes of moths!
Image: Gabriel Loget / UC Irvine

Written by Sarah Kellett

The way a moth’s eyes have adapted to darkness may help us stop glare from the Sun.

Despite their tendency to circle light bulbs, moths have eyes that are designed for darkness. Each eye has a bumpy pattern that stops light reflecting off the surface, possibly helping the moth see in the dark and hide from predators.

For years, scientists have been trying to replicate the effect. Continue reading

Antarctic poem winner

Congratulations to David from QLD who won the Antarctic Territory Series Coin for the poem below.

Icebergs formed when pieces of ice break away from the Antarctic ice sheet by CSIRO

Icebergs formed when pieces of ice break away from the Antarctic ice sheet by CSIRO

The land truly down under, it’s plains of ice and snow.

Hide a sight of wonder, where few are blessed to go.

Above the desolate landscape, atop a thousand whites.

Nature’s ultimate canvas, for the amazing Aurora lights.


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Jumping puzzle

You will need

pritout, scissors, tape, pencils.

You will need these items.

Assembling the pieces

  1. First make the playing pieces. Cut along the thick black lines to get three boy strips and three girl strips
  2. Fold each strip along the dotted lines to make a triangle and hold it together with a piece of sticky tape.
  3. The remaining piece of paper has a line of seven circles – this is the board.

Continue reading

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Turtles in trouble

A sea turtle and fishing net on the beach Image - Dhimurru Aboriginal Corporation

A sea turtle and fishing net on the beach
Image – Dhimurru Aboriginal Corporation

When waste isn’t disposed of carefully, it can find its way into rivers and oceans. This human made litter can be very harmful for marine animals, including sea turtles.

There are seven threatened species of marine turtle and we have six of them here in Australia. One of the threats to turtle species is marine debris – waste that humans throw away that has made its way into the ocean. Waste affects turtles in two ways – either they mistake it for food, or they get tangled up in it. Continue reading

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Know your temperatures

Written by Matthew Dunn
Illustrated by Alex Hallatt

−273.15 °C
Absolute zero

Frozen panda.Absolute zero is, unsurprisingly, the lowest temperature possible. When things get colder, their particles slow down. At −273.15 °C, they are motionless and entropy is zero. We can’t cool things down to absolute zero, but Finnish scientists have got very close − even as close as 0.000 000 001 °C above it.

Panda having a mole frozen off by a Dr.−196 °C
Liquid nitrogen boils

While we’re most familiar with nitrogen as a gas in the air around us, when it’s cooled down below −196 °C, it turns into a liquid. Liquid nitrogen isn’t just super cool – it’s also super useful for science. It can be used to store biological samples, freeze off moles that might be cancerous, and cool down superconductors!

Panda meeting penguin. They are complimenting each other on their outfits.−93.2 °C
Coldest temperature on Earth

Continue reading


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