Perspective

[Sadguitarist]

Can anyone think of an answer to a 5 year old's question:
'Why do things get smaller as they get further away?' Obviously the 5 year old will need to understand - therefore no jargon!

[Hippy]

Such a simple question! First things don't get smaller at their distance from you increases, it only seems that way because of the way your eyes see things. It is all to do with angles, but we are not going to get technical, save to say that it is the angular size that decreases and that is why our eyes see an apparent change in size. Here, try this simple demonstration. Needs a penny, a pencil, a ruler and a piece of paper.

 

Draw a dot near the edge of the paper then place the penny towards the centre of the papaer, about five centimetres from the dot. Take the ruler and join the dot with the outer edges of the penny and draw straight lines; you get two divergent lines. Ok, now move the penny away from the dot in the same direction, but this time stop at about fifteen centimetres. Do the same line drawing and you will see straight away that the angle is much smaller. The penny is just the same, but its angular size with respect to the dot (the observer) reduces with distance.

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[ll_billym]

Hippy is correct, the way to approach the question to establish that things don't get smaller.  This can be demonstrated by holding a coin right up to the eye and moving it away until it is barely visible, then letting the child walk up to it and see that although it appears to get bigger again it has not changed size.  This should teach that it is "us" (our viewpoint / perspective) that makes things seem bigger or smaller not the object itself.  However I cannot think of a way of explaining the technical reason for this to a 5 year old.

[stevie21]

By the time that you figure out how to explain this in a user friendly way, the 5 year old will have lost all interest and will just want to crayon your white living room walls a nice shade of green.

[brachiopod]

Although slightly glib, I did find stevie21's answer quite funny.

(As the 'owner' of a 16 month-old  X-09-03 model, I have these joys to come !)

But since we seem to be using pennies, how about comparing the coin with the moon (wait 'til a good early-evening full-moon).

Close to the eye = bigger (than the moon)

At arm's length = smaller (than the moon)

Same moon, same coin that hasn't left the hand?

[brachiopod]

(don't know how that came out all indented.)

[PatTheRat]

Well some people never grasp this concept. Anyone see the episode of Father Ted where Dougal asks why the cows outside are really small?

[brachiopod]

Father Ted was the first thing I thought of when I read this question !!

[PatTheRat]

Seriously though...try this. Have two adults, say mummy and daddy? Have mummy sit with the child on a park bench and ask the child, 'who is bigger.....you, or your dad'. The kid will say dad. Then have dad walk away, until he appears quite small. Ask the same question now. The child will automatically know that dad should still be bigger, but he's just far away.

[Hammer]

"They're not small - they're far away!"

[Sadguitarist]

Thanks for all the answers. Liked no 9 best!
Sadguitarist

[Sadguitarist]

Sorry I meant Pat the Rat's answer.
Sadguitarist

[stevie21]

Excuse the earlier glibness, I was just thinking to myself "I don't have the mental capacity to explain this to an adult let alone a child" so resorted to saying something silly.

[NetSquirrel]

You can increase your 5-year-old's understanding further if you show by how much objects appear smaller and bigger  compared to how far away they are (from your eye).  Take two similarly sized objects (e.g. two pens) and position one about half a metre away.  Give the other pen to the child and ask her/him to position their pen so that it appears twice as tall as the far away one.  Hopefully they will come up with a distance about halfway between their eye and the other pen.  This shows that when something is twice as close, it looks twice as tall, and twice as wide, and vice versa.  A bit tricky for a 5-year-old to understand but I'm sure he or she will get to grips with it pretty quickly.

[stevie21]

I thought that i had a brainwave but even this might be too technical.
I was walking past a nice old church today & it was so big that it took up my entire field of view (try to use less technical language with the 5 yr old! haha). Similarly, if you hold a 2p coin really close to your face, it appears really big because you can't see anything past it. If you look at a pile of coins a short distance away then there are lots of other things in your view so the coin is relatively smaller.

That's still not a good explanation at all is it? I give in :(