New submarine pilots often have difficulty steering the submarine because of how the plastic pressure hull and the water distort their vision. Over time, they get used to this, but we can’t have a new submarine pilot crash a submersible. Your challenge is to teach your brain how to adjust for this distortion.

Activity steps

1. Fill the glass two thirds full with water. The glass should be clear and without patterns as you will need to look through it.
2. Place it on a table and position the two pens or pencils and yourself as shown in the diagram.
3. Now pick up one pen(cil) in each hand, and looking through the glass, try to get the ends to meet.
4. How did you get on? Look over the glass to see how close you got.
5. Do you need some more practice? Keep on trying to get the ends of the pen(cil)s to meet.
6. As you keep on trying, your brain will adapt to your new way of seeing the world and the task should get easier.
7. Once you think you have got the hang of this, you will need to pass your 'test'.
8. In one minute, touch the ends of the pen(cil)s together five times.

More ideas

If you found this activity too easy, try moving the pencils further away from the glass. Say about 20cm away.

This will mean that the direction of the pen(cil)s reverse, which may pose an even greater challenge!

• Glass (tumbler size)
• Water
• 2 pens or pencils (two different colors if possible)

This challenge involves the principle of refraction. Refraction is the science name for the bending of light. This happens when the light from the pen(cil) to your eye passes through different types of matter, eg the water, the glass and the air.

You can see how the direction of the light travelling between the pencil and your eye changes in the diagram opposite.

The top diagram shows how the refraction of the light confuses your view of the ends of the pen(cil)s. The dark arrows represent what you see, whilst the lighter arrows show where the ends of the pen(cil)s actually are.

If you move the pen(cil)s further away, you can see how the path the light travels will actually reverse the direction of the pen(cil)s as you view them, shown in the bottom diagram.

This bending of the light also occurs when you are looking out of the clear pressure hull in the submersible. We thought this might be tricky to set up in your kitchen and so we came up with the glass idea, just to give you a sense of how difficult it must be to operate the submersible safely.