A Simple Question
In all seriousness, I’m curious. And I have a question that I invite astronomers, physicists, or mathematicians, none of which I am — beyond that of a lay person’s dabbling, — to answer. By way of preface, I watched a number of you tube explanations of an expanding universe in hopes of finding an answer to the question I’m about to ask. Some were fascinating, some were boring. But two different approaches to explaining what scientists think we know, while effectively demonstrating expansion, clearly illustrated the nature of the problem the question addresses.
The expansion of the universe is at the heart of the inquiry. One of the explanations invites us to consider the universe as a balloon. Dots on the balloon represent the galaxies. As the air fills the balloon, it expands and the dots move farther and farther apart. The other explanation, which I like better because it illustrates the same principle in a more realistic, complex way, compares the universe to a loaf of raisin bread baking in the oven. As the bread rises, the raisins separate and move farther apart throughout the loaf.
So now to the question. We know for a fact that galaxies collide. The Hubble Space Telescope, named for the astronomer who gave us the concept of an expanding universe, has captured images of it happening.
The collisions are dramatic, chaotic, beautiful, frightening, and at the heart of both endings and beginnings. We also know by witnessing the phenomenon of the red shift that the universe is not only expanding but doing so at a continuously increasing rate. All of which brings us to the question.
If the universe is expanding and that expansion pushes galaxies away from one another, How do galaxies collide?
While we wait for the answer, we can pass the time (ah — another potential question) by traveling through both space and time in the simulation of our universe below.