Strongly Celestial

Looking outward; looking backward in time...


About | Launchpad | Gallery | Contact

Fun Facts

This is my place to store tidbits I have found interesting on my journey. Whenever possible, I will include references and in some cases links to more detailed documents and/or websites. If you spot some inaccuracies, please let me know! As with the rest of my website, I grant permission to use any of these documents; all I ask is that you drop me a note to let me know.

The Scale of Things
It is very difficult for us to grasp the scale of things when they are far outside our normal frame of reference. Here are some Fun Facts to help visual the scale of things in the universe:

  • How big is a hydrogen atom?
    Applying the classic Bohr orbital atomic model and a few basic simplifications, you can calculate...

    If a proton (hydrogen's nucleus) were the size of a basketball, then its electron would be about the size of a golf ball and at ground state it would be flying "in orbit" approximately 5 miles (~8 km) away! Stop for a moment and think about the incredible emptiness this represents at the atomic level!

    P.S. Why we care: hydrogen makes up ~75% of all chemical elemental mass in the universe!

    P.P.S. Yes, I know most quantum physicists would take me to task for over simplifying an outdated atomic model. Please view this in the light it is intended: a fun fact to provide a rough frame of reference we can easily comprehend.
Click here for a pdf
  • What if a star was a grain of sand?
    In his lecture series on Cosmology (see my Education page), Professor Mark Whittle helps people visual how many stars are in the galaxy by describing how big a box you would need to hold them, if each star was the size of a grain of sand. He did not provide the underlying math, so I attempted to derive the result and found the following:

    If you assume that the Milky Way has 300 billion stars in it (current estimates are 200-400 billion), and you make each of them the size of an average grain of sand (0.25mm in diameter), and throw them into a box, you would need a box that is almost 4 cubic meters in volume. That is a cube having dimensions of 1.6 meters (5.2 feet) on a side...filled to the top with our "sand stars"!

    Let's expand this model to the entire universe and assume that there are approximately 300 billion galaxies out there (probably in the right order of magnitude), with an average star population of our Milky Way (which is considered fairly average). If you turned all those stars into sand, you would need a box with a volume of just under 1,200 cubic kilometers to hold all those stars. That translates to a cube having dimension of ~10.6 kilometers (~6.6 miles) on a side!

    P.S. In his lecture, Professor Whittle said our galaxy - filled with "sand stars" - would fit in a cube that is 1 meter on a side. As to why my calculation is a bit larger, my guess is he may - more accurately - not have assumed uniformly sized spheres (since actual stars vary in size), allowing the smaller stars to pack a bit more neatly among the voids of the bigger stars and improving volume efficiency in his model. Still, we're in the same ballpark!
Click here for a pdf