This is a way to visualise the size of the universe, and in particular how much of the sky the amazing ‘Hubble Ultra Deep Field’ picture takes up.
https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field

One of the most majestic images humanity has ever seen.  I stole this copy from Wikipedia:

The Ultra Deep Field is 2.4 arc-minutes wide (0.04 degrees), so it’s a tiny slice of the visible universe. In fact you’d need thirteen million exposures just like it to cover the entire sky.

But, even in that tiny sample you there are over 5,000 galaxies. (I’m not even going to get into how many stars can make up a typical galaxy, but ours contains about 200 billion stars)

But what does that actually look like? I decided to make something to help visualize just how small a slice of sky the picture is:

Here’s how you use it. The string is 5 meters long, and you hold the small piece next to your head, and look at the tiny 3.5mm square target.

I’m super happy with how it turned out, it’s a very immediate way of understanding the true scale of the image.

I got the HUDF image glossy printed at officeworks, for about a dollar a sheet, and lasercut a few boards at the same time. 

Files up here for anyone that wants to make their own:

https://www.thingiverse.com/thing:2413202

I’m happy to give away my spares to any teacher or educator that’d find them useful. If you’re interested, shoot me an email.