A tour of the universe

As I have already said in this post and on Twitter (@scienceontoast), my recent adventures in the world of online science communication have rekindled a childlike enthusiasm for cool science that I have not felt for many years.

The unimaginably vast and mysterious universe is at our fingertips like never before thanks to fast internet, clever web content, and the power of social media and collaborative projects such as Wikipedia.

I've heard it said that the human mind simply cannot comprehend nor imagine the sheer size and scale of our universe. This may be true, but a clever web app by Cary Huang helps us get a little bit closer. (Thanks to Ashley Youett who originally sent me the link. It's been popular since on Twitter).

The Scale of the Universe 2 is a window with a sliding scale bar which the user controls to zoom through the length scales of the universe, starting out on our human scale and then delving down through the realm of the ant, the human ovum, bacteria and viruses, through our own DNA, atoms and molecules and right down to the nucleons, quarks and finally the Planck length, the fundamental quantum unit of length. Each object has a picture showing its relative size and potted info on each item is available with a click. I counted 12 empty orders of magnitude (a factor of 1000000000000) between the smallest elementary particle and the Planck length. To very tenuously paraphrase the great Richard Feynman, "there's plenty of room at the bottom". The universe really is an incredibly empty place.

Zooming back out quickly to the human scale again, we then start pulling back the camera to explore larger and larger objects. We learn that a marathon runner would have a good chance of running from pole to pole on a neutron star without stopping for lunch (but would succumb to some heinous gravity) and that the projected size of the moon is about the same as that of the continental USA (or Australia!).

The most fascinating part for me, though, is the stars. The stars cover sizes only a bit bigger than the Earth (the example is the white dwarf Sirius B), and in relative star sizes, the Sun is not really much bigger. Stars can really be stupendously large, with the largest red giants on the scale 10000 times bigger than the Sun!

We draw back further and swim through planetary nebulae, star clusters and galaxies. It astonishes me to think that in every single galaxy out there in the universe there are hundreds of billions of stars and I feel convinced that our there somewhere, perhaps even in our big sister Andromeda, there is intelligent life gazing out into space with the same sense of unfathomable scale and longing.

As we survey the galactic clusters that make up the larger superclusters and the filamentous structures that are formed by the distribution of matter in our universe, we eventually reach a limit: since light takes time to reach us, each distance further we can see takes us further back in time. We can see so far back in time, in fact, that distant universes are mere embryos, relics from much earlier in the history of the universe than we are in the present day. We can see so far back that we can see the very point at which the opaque soup of the universe first became transparent. Beyond this, we can see no more!! This is the limit of the observable universe, the curtain beyond which we can no longer reach the enquiring power of our telescopes. The nebulous grey beyond this in The Scale of the Universe 2 represents our uncertainty about exactly what comes before (although we have a pretty good idea right up to very, very early times in the formation of the universe, but for that we will have to talk about the Large Hadron Collider).

The Scale of the Universe 2 is by no means the first of its kind I’ve seen (and I assume there was a Scale of the Universe 1) but it is a fascinating tool to help us understand, in some small way, the true scale of the universe. It is also useful for one of my favourite pastimes... making my mind boggle, on purpose!