The Scale of The Universe

Powers of ten are pretty cool. They're actually pretty powerful, if you know what I'm saying. But what is the power of ten in math? A power of ten is any integer power of the number ten, basically ten multiplied by itself a certain number of times, any number of times. For example, 10 to the power of one is just 10. 10 squared is 100. 10 cubed is 1000. You get the idea.

The powers of 10 help us compare the relative size of things here and represent any number you want. It's called the order of magnitude. Positive order of magnitude will make X bigger, while a negative number will make X smaller. The effect of adding one extra zero to the beginning or end of any number may seem irrelevant, but what happens if we take these numbers to the extremes? What might these numbers represent?

Believe it or not, the powers of 10 actually put our universe into perspective quite nicely. Let's start with a really small power of 10. At ten to the negative 35 meters, we come to what is known as the Planck length. The Planck length is the smallest measurable distance in the entire universe, much like at the center of a black hole. At a scale this tiny, the laws of physics break down and cease to be valid. The amount of time it takes a photon of light to travel one Planck length is known as the Planck time and is equal to 10 to the negative 43 seconds, meaning that this is the shortest measurable time possible.

Any time children--this physically has no meaning at all. This is why, at the moment, scientists can only say that the universe came into being after it was already 10 to the negative 43 seconds old. Getting larger, at 10 to the negative 18 meters, we reach quarks. These are the subatomic particles that compose protons and neutrons. At 10 to the negative 7 meters, we reach the smallest forms of life, single-celled organisms.

At one tenth of a meter, you'll find things that you can see, like eggs, birds, and toilet paper. At one meter, we have everyday life: humans, dogs. Blue whales come in at a solid 30 meters. Next, we come across the meaning of life, or 42, whatever you decide it is. At 270 meters, we reach the length of the Titanic. Triple that, and we get the relation of Vatican City, the smallest country in the world.

It's kind of funny because Central Park in New York City is actually four kilometers long and is eight times larger than Vatican City, which is an entire country. Clocking in at 11,000 meters is Phobos, Mars's largest moon. Fun fact: one day, it's gonna crash into Mars, so if we're gonna colonize it, we should probably find a way to deal with it. With an order of magnitude of 5, we have Hydra, one of Pluto's moons.

Even though it's a moon, it's only a hundred kilometers across. The state of West Virginia in the United States is actually four times as large. There's also about ten to the five hairs on the average human head. At 2,300 kilometers in diameter, we have everyone's favorite planet, Pluto. Oh, anyway, moving on with the order of magnitude of seven, we have Earth at 12,700 kilometers.

And at a diameter of 200,000 kilometers, we have Proxima Centauri, the closest star to our Sun. It's also home to Proxima b, an exoplanet with features much like Earth. If there were to be a manned mission to any other star systems or planets, Proxima b would probably be the first choice. With an order of magnitude of 9, the Sun clocks in at about 1.4 million kilometers wide. It accounts for more than ninety-nine point eight percent of the mass in our solar system.

At ten powers of 10, we come across the orbits of Mercury, Venus, and Earth, ranging from 36 billion kilometers from the Sun all the way to 93 million kilometers. Although these orbits seem pretty big, they're dwarfed by one of the most luminous stars in the sky, the Pistol Star, at 470 million kilometers wide. It radiates as much energy in 20 seconds as our Sun does in one whole year. But the Pistol Star is nothing when compared to the largest star ever discovered, UY Scuti. It is over two billion kilometers wide, and if it were to replace our Sun, it would completely swallow the planets of Mercury, Venus, Earth, Mars, Jupiter, and Saturn.

At 26 billion kilometers, we reach what is known as a light-day. It is exactly how far light travels in 24 hours. This distance is currently farther than any human or spacecraft has ever traveled. At 10 to the 14 meters away from Earth, our solar system appears only as a small point of light in the sky, just like every other star that we see in the night sky.

At 10 to the 15 meters, we have the Cat's Eye Nebula, one of the most complex nebulae ever discovered. The entire nebula is nearly half a light-year in diameter. At 2 light-years away from Earth, we reach the Oort Cloud, a region of space filled with water and methane ice. At this far distance, the Sun's gravity no longer has an effect on objects past this point; other stars are stronger.

At 10 to the 17 meters, we have a familiar sight: the Pillars of Creation. Each pillar is over 5 light-years long—that's about 48 trillion kilometers each. Everyone has seen these before; however, they won't last forever. They're actually already gone. The Pillars of Creation are located at about 7,000 light-years from Earth, but about 6,000 years ago, they were destroyed by a nearby supernova, meaning that in 1,000 years they'll fade away from our view and disappear into the darkness of space.

Skipping forward to 10 to the 21 meters away from Earth, we can finally see the Milky Way galaxy in its entirety. Every star in the night sky that you can see lies within our galaxy; however, at 10 to the 22 meters, we've reached the distance to our nearest neighboring galaxy, Andromeda. You can actually see Andromeda in the night sky with a simple pair of binoculars or a normal telescope.

At 10 to the 23 meters, we reach what is known as the Local Group. Its name pretty much tells you what it is; it's the Local Group of galaxies that are near the Milky Way. We're actually the second largest just behind Andromeda. The Local Group is a part of the Virgo Cluster, a group of galaxies just like the Local Group, except much larger. The Virgo Cluster contains about 1,500 galaxies and is over 15 million light-years long.

At 10 to the 24 meters away from Earth, we come across the anomaly known as the Great Attractor. See, objects with a lot of mass have a stronger gravitational pull; that's why planets have moons, and you don't— they're a lot more massive than you are. However, the Great Attractor is a bit different. It's pulling clusters of galaxies towards it, but we can't observe or see what it is. It's an object with mass tens of thousands of times larger than the Milky Way's, but we don't even know what it is.

At 10 billion light-years from Earth, we come across the largest known object in the universe, the Hercules Corona Borealis Great Wall. It's a bit of a mouthful, but rightfully so. Why? Because it physically should not exist. It is 10 billion light-years long, 7 billion light-years wide, and nearly 1 billion light-years deep. This means that light will take 10 billion years to cross the entire wall.

Only once, to put it into perspective: the universe is only 13.8 billion years old, and the time that Earth has been a planet is about four-and-a-half billion years. The light that has left from one end of the Great Wall hasn't even made it halfway to the other side yet. The structure is so big that it breaks laws of physics.

There is something in the world of science known as the cosmological principle. To put it simply, it says no matter where you are in the universe, if you look in any direction, you should see an even distribution of matter. This, in turn, creates a limit for the sizes of objects. It's about 1.2 billion light-years, meaning that this structure is eight times the supposedly maximum size of the largest object possible.

At ten to the twenty-seven meters away from Earth, we reach the outer limits of the observable universe. This is as far as we can go, and most likely we'll ever be able to. And thus, our journey ends. Just 27 steps ago, we were back at Earth, back at life as we know it. But the most amazing thing to me is that we traveled to the outer limits of our universe as we know it, reaching the largest structures known in the entire universe, and it only took us 27 steps—27 orders of magnitude.

But in order to travel to the tiniest limits known to man at the Planck length, we have to take 35 steps backward from the human level. This means that we are eight orders of magnitude, or about 100 million times larger, compared to the smallest thing there is that the universe is compared to us. And that, I find, is the most interesting thing of them all.

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