How Big Is Space?
How Big is Space and the Universe?
How Big Is Space? – Once upon a time there was an extremely clever Englishman named Douglas Noel Adams who wrote a series of books called The Hitchhiker’s Guide to the Galaxy, which provided instructions for visiting all the galactic hotspots for only fifty Altarian dollars per day. This fictional book went on to describe the size of the Universe which I’ll paraphrase as “Big. Really big… In fact you won’t believe just how mind-bogglingly huge it really is if you happen to think it’s a long walk to the local drugstore…”
Aside from being a very amusing series, the truth is that he was absolutely correct. The scale of the Universe it literally incomprehensible, but there is something called the Sloan Digital Sky Survey (SDSS) that does just barely scratch the surface and begin to give an inkling of the size of the Universe. Before you click the video link in the next section for this two minute tour, there are a few things you ought to know.
Scale Is Important
First, the blobs of light you’ll see are actually galaxies, not individual stars; even those dots in the far background are entire galaxies. Stars are far too small to be seen on this scale.
Second, each blob/dot contains 100 and 500 billion stars, and measures between 30 and 60 thousand light-years from one edge to the other. That means it would take 667 human lifetimes to cross just one galaxy.
In order to see this in reality, the camera filming it would have to travel at 375 trillion times the speed of light. Another way to think about it is that travelling at the speed of light it would take 37,500,000,000,000 years to film it.
Scope Is Important
Next, the SDSS is an accurate depiction composed of only the closest 400,000 galaxies to our own Milky Way galaxy. According to our current understanding of physics and the Universe itself, there are about 100,000,000,000 galaxies, so what you see in the video represents only 1/250000th of the Universe.
Taken all together, with our current understanding of stellar formation, there are 70,000,000,000,000,000,000,000 stars (70 sextillions) in the Universe, most of which have planets. Even if the odds of a life-sustaining planet was one in a million, that means there are 70 quadrillion possibilities, and if the odds of advanced civilization arising were also one in a million, that means there are 70 billion planets with civilizations, or 10 civilized planets for each person currently alive on our world.
Finally, it is completely silent (as is the galactic void) and is best viewed on the largest monitor you have, in a darkened room. Have a look at it now, and I’ll wait here until you’re done…
Back already? In the vernacular of the 1970s, “Is your mind blown?” You can watch that again and again and it never seems to get boring when you understand even a fraction of the scope of the Universe and the answer to the question, “how big is space?”.
Our Tiny Star
For some additional perspective on “how big is space”, let’s look at another size comparison. Above, stars were noted as being “too small” to be seen on that scale. But just how small is a star?
Our Sun (depending on what you call the “edge” and how you measure it) is up to 875,000 miles (1,400,000 kilometres) across. In comparison, Earth is about 7,900 mi/12,700 km across (shown by the tiny dot in the center of the image, surrounded by the arrows) or >1% of the Sun’s width.
Our Tiny World
But Earth is so big, isn’t it? The last time you saw a video of the Earth taken from the observation cupola on the international space station, you probably noticed that our planet was so big that you could never see all of it at a glance. You would have to move your head or eyes to take it all in.
To put that in perspective, consider a tiny mote of dust, dancing in a sunbeam. Remember the tiniest dust-speck you ever saw—the one where you almost weren’t sure it was actually there… In comparison, that is almost exactly halfway between the sizes of an atom compared to Earth.
How Big is Space?
So, how big is space and the Universe? Well, in ancient times it was thought to be just a few miles, with a black sphere surrounding us. The stars were thought to be tiny holes that let the magical light of some deity shine through. After Copernicus and Galileo started hypothesizing and using primitive telescope, it was thought that the Solar system was the Universe, while the notion that everything beyond “the planets” was essentially a painted backdrop.
In the last Century we believed that our Galaxy was the extent of the Universe until Henrietta Leavitt (1868–1921), inventoried 1,777 of the variable stars in the Large and Small Magellanic Clouds. Though we didn’t know it at the time, these are a pair of small companion galaxies of our Milky Way. She was particularly interested in 47 stars called Cepheid Variables (sef-ee-id) which are very bright but change intensities over time because they’re out of balance. They continuously expand and contract, and they die young because they use their nuclear fuel very quickly.
Another astronomer named Ejnar Hertzsprung (1873-1967) studied much closer Cepheids in our galaxy and figured out how to calculate distances to them through parallax. At opposite seasons of the year our planet about 186,000,000 miles away from its previous position and so by looking at something far away, compared to something slightly closer you can determine an angle.
That measurement, taken six months later, gives you the opposite angle. Using the Law of Sines we can then calculate the distance to the object.
Hertzsprung then classified them by brightness (apparent magnitude) and period (how long it took to go from brightest to dimmest) which allowed people to calculate their distance. Suddenly we knew that the Magellanic Clouds were a lot further away than we ever imagined.
Using Leavitt’s observations he thought the clouds were 37,000 light years away. It wasn’t until Harlow Shapely (1885–1972) came along that we finally got the more accurate 95,000 lightyear figure we now use.
Other astronomers started to measure the distance to even more distant Cepheid variables, and we knew then that these distant objects were actual galaxies. Edwin Hubble (from the eponymously named Hubble Space Telescope) measured Cepheids, too, and showed that some faint smudges (called nebulae M31 and M33) were other galaxies that were 900,000 and 850,000 light years away, respectively. Now, with better tools, we know these are actually 2.5 million light years away.
Nicolaus Copernicus revealed that the Earth wasn’t the center of the universe in the 16th century. Galileo Galilei had a 9x telescope (the most powerful up to that time had been marine navigators’ telescopes at 3x). and championed the cause of Heliocentrism, where the Earth moved about the Sun.
Just by observing the four (eponymously named) Galilean moons of Jupiter orbiting Jupiter and going through phases, just like our own Moon, he proved that everything didn’t orbit the Earth or the Sun.
Shapely showed us that the Universe was at least 10 times bigger than previously thought.
Hubble proved it was 1,000 times bigger than that.
Now, utilizing blue and red shifting of the spectrum by distant objects, we can see that the Universe is constantly expanding. More specifically, the further the object is, the faster it is receding. This give a little insight into the question, “how big is space?”
What is truly interesting about this phenomenon is that we now know that “space” itself is expanding. By putting two dots on a balloon and inflating it, the dots appear to be moving away from each other, even though they are experiencing no motion compared to their actual location on the balloon.
The Universe works in the same way, but the actual galaxies are truly moving away from each other from the initial impetus given by the Big Bang. When their motion is “added” to the expansion of the Universe, the furthest galaxies are actually receding at a rate of speed greater than that speed of light (but without breaking any laws of physics).
What this means to “how big is space” is that there is an event horizon, or an “edge of the Universe” and any object whose cumulative speed-plus-expansion exceeds the speed of light simply vanishes because the photons can never travel fast enough to reach us here. Those distant galaxies appear to vanish—they still exist—but we will never see them again.
The ultimate irony is that those people that believed we were at the center of the Universe were right! No matter what direction you look, the Edge of the Universe is equally far in all directions. As far as the Visible Universe is concerned, we are right dead center. So take heart… No matter where you are, who you are, or how much wealth you possess, you are the center of the Universe!
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