One thing you should know about space: it's huge. Mind-bogglingly huge. If you were to think of the biggest thing you could possibly image, it would still be more than a billion times bigger than that (and don't say you imagined infinity, because you can't. And stop being clever). The problem with just saying "the universe is huge" is that it doesn't really convey the distances involved. We can talk all we want about light-years and parsecs (unit of distance, not time, sorry George Lucas), but it doesn't really mean much. They're just words. And, as wonderfully evolved as language is, a lot of scientific terms fail to covey conceptual content with them, because our brains simply didn't evolve to deal with this sort of stuff. So today, I'm going to try to take a stab at this comprehension, let's see if you can follow.
How far away is the Sun? Well, you could say it's one Astronomical Unit (AU), or that it's about 150 million kilometers, or about 93 million miles. Well, those are big numbers, but they really don't paint much of a picture. Even saying that the Sun is actually 860,000 miles across, but only appears to be about the size of a quarter because we're so far away doesn't help. So let's undergo a gedankenexperiment (a thought experiment): Let's say that you have decided to go on a vacation with your family to the sun, because you operate on the principle that the ideas you have at 2 am are completely reasonable. Lucky for you, the highway committee also operates on the same principle, and just recently built, at great expense and headaches, a highway straight to the sun. The toll's outrageous, but you can still drive there. Let's assume that the highway is the same boring sort of highway we see normally in America, with a speed limit of 65 mph. Let's also assume that you drive on it much like you drive on a normal highway, at about 80 mph. Now, how long would it take you, without taking breaks, to drive to the sun on this highway? You could do out the math, or I could just tell you the answer: 132 years (and you thought the commute to work was bad). Let's say that you're more sane than that, and take a plane instead. The average velocity of a commercial airliner is about 550 mph. At that speed, your flight would only take 19 years. Let's hope the pilot had his coffee that morning. Finally, let's say you really broke the bank, because you didn't want to endure the 19-year flight, and were still dead-set on making a vacation spot out of the sun. So you managed to get a spot on one of NASA's rockets destined to break solar orbit (which you proceed to redirect toward the sun). This rocket goes at a whopping speed of 36,500 mph. Still, even in your cozy rocket, it would take you 106 days to reach the sun. Of course, once you finally get there, you realize that it might not be the idyllic vacation spot you had thought it to be, and have to turn around and go home again. Bummer.
Hopefully that illustrates a bit exactly how far away the Sun really is from us, and that's the nearest star. In fact, it would take even longer than that to go to the outer planets—Jupiter alone is closest to us at 390,682,810 miles (that's about four times farther away from us than the sun). Image trying to get to Pluto, at about 270 million miles away at its closet point (that's almost a year in our rocket, and over 55 years in our airplane). And that's all just our own neighborhood. Let's take a look outward.
The next closest star to us is Proxmia Centuri, at 4.2 light-years away. Oh, well that doesn't seem too bad, right? Only 4.2. How much is a light-year anyway? Well, it's the distance light travels in a year. And light is fast. Really freaking fast. 186,282 miles per second fast. That's a little under 12 million miles a minute, and about 670 million miles per hour. As I said, really freaking fast. And, since we know how fast light goes, how far does it make it in a year? Well, it goes about 16 billion miles per day, which puts a light-year at about 5.878x1012 miles—5,878,000,000,000 miles: about 5.8 trillion miles. So how far would it take our rocket, which made it to the sun in only 106 days, to go a light-year? Only about seventeen and a half thousand years. To make it to Proxima Centuri, it would take it 74 thousand years. If that kind of a distance isn't ridiculous, I don't know what is.
But wait! It gets even better. The brightest star in the sky is Sirius, which is about 2.6 parsecs from Earth. Well, 2.6 isn't a bad number. Obviously, it's farther than Proxima Centuri, but it can't be that bad. Well, it isn't, relatively speaking. A parsec is about 3.26 light-years. So that's about 19 trillion miles. That puts Sirius at about 50 trillion miles away from earth. That would mean that our rocket would take over 155,000 years to reach it. For reference, humans only evolved about 200,000 years ago. And when you look at Sirius, it might be fun to realize that, not only is it 50 trillion miles away, but that it's also about 1.5 million miles across. That's pretty enormous.
But the fun doesn't stop there. The distance from us to the galactic core is (conservatively) about 25,000 light-years, or about 150,000,000,000,000,000 miles (150 quadrillion miles), which is about 450 million years in our rocket (that's before life even made it out of the ocean). The distance from us the the next nearest (non-dwarf—the nearest dwarf galaxy is Canis Majoris, which is about as far away from us as the galactic center is) galaxy, Andromeda, is 778,000 parsecs, or about 2.5 million light-years. That's 1,500,000,000,000,000,000 miles—1.5 sextillion miles, which is about 46,000,000,000 (46 billion years) in our rocket—that's longer by far than the universe itself has existed (it's only about 13.7 billion years old). And that's only the beginning. Take a look at the Hubble Deep Field (warning—crazy large image). That's a look at a small, seemingly blank, portion of the night sky. Every point of light in that picture is a galaxy. The universe is beyond enormous. Words cannot describe it. It's magnificent and terrifying. It's something for which one should feel the deepest sense of awe at its vastness.