The size of our universe (from "The Evidential Power of Beauty" by Thomas Dubay)

Next we move out into our home galaxy, the Milky Way, our spiral of 2 or 3 billion stars like our sun ... You and I are spinning at an immense rate of speed in this wild cosmic joy ride, with our galaxy being from edge to edge approximately 100,000 light years across. It would take our jumbo jet 100,000 million years to make the trip once around. The other star closest to us, Alpha Centauri, is four light years away, and it would take a persevering pilot 5.5 million years to make a one-way trip to this, our celestial neighbor. To stretch our minds a bit further: our known universe is approximately 12 to 15 billion light-years to its edges, and it is continually getting larger at a tremendous rate of speed.
...
[A]stronomically speaking our own galaxy is very small indeed. Astronomers have recently discovered the largest galaxy thus far known. In a cluster of galaxies known as Abell 2029 there is one that is sixty times the size of our own. Possessing more than 100 trillion stars, it is about 1 billion light years from us. Beyond Abell 2029 there are billions of additional galaxies and stars in all directions.
...
In an effort to aid our imagination someone has estimated that there are about ten thousand grains of sand in a handful, and further, that there are more stars in the universe than grains of sand found on all beaches of the earth. When one considers that America has approximately eighty-four thousand miles of shore line ... and when we add to that the far longer beaches in other countries, and the thousands upon thousands of lakes over the globe, we arrive at a considerable amount of visible matter--not to mention the far greater amount of "dark matter" we cannot see.