Every day we are faced with compression in one form or another. When we squeeze water out of a sponge, pack a suitcase before vacation, trying to fill all the empty space with the necessary things, compress the files before sending them by e-mail. The idea of removing “empty” space is very familiar.
Both on the cosmic and atomic scales, scientists have repeatedly confirmed that emptiness occupies the main space. And yet it is extremely surprising how true this statement is! When Dr. Caleb A. Sharf of Columbia University (USA) wrote his new book, “The Zoomable Universe,” he, by his own admission, planned to use it for some kind of dramatic effect.
What if we somehow manage to collect all the stars of the Milky Way and place them next to each other, like apples tightly packed in a large box? Of course, nature will never allow man to subjugate gravity, and stars will most likely merge into one colossal black hole. But, as a thought experiment, this is a great way to illustrate the amount of space in the Galaxy.
The result is shocking. If we assume that the Milky Way can have about 200 billion stars, and we generously believe that they are all the diameter of the Sun (which is overestimated, since the vast majority of stars are less massive and smaller in size), we could still assemble them into a cube, the length of the faces of which corresponds to two distances from Neptune to the Sun.
“There is a huge amount of empty space in space. And that brings me to the next level of craziness,” Dr. Scarf writes. According to the observable Universe, defined by the cosmic horizon of light movement since the Big Bang, current estimates suggest that there are between 200 billion and 2 trillion galaxies. Although this large number includes all the small “protogalaxies”, which will eventually merge into large galaxies.
Let’s be brave and take the largest number of them, after which we will pack all the stars in all these galaxies. Impressively generous, suppose they are all the size of the Milky Way (although most are actually much smaller than our Galaxy). We will get 2 trillion cubes, the faces of which will be 10 ^ 13 meters. We place these cubes in a larger cube, and we will remain with a megacube with a side length of approximately 10 ^ 17 meters.
Pretty big, right? But not on a cosmic scale. The diameter of the Milky Way is about 10 ^ 21 meters, so a cube of 10 ^ 17 meters in size still occupies only 1/10 000 of the size of the Galaxy. In fact, 10 ^ 17 meters is about 10 light years!
Naturally, this is just a little trick. But it effectively indicates how small the volume of the Universe actually occupied by dense matter, compared with the emptiness of space, perfectly characterized by Douglas Adams: “The cosmos is great. Really great. You simply won’t believe how vast, enormous, breathtakingly large the cosmos is. Here’s what we mean: you might think that the nearest diner is far away, but for space it means nothing.” (“The Hitchhiker’s Guide to the Galaxy ”).