Rocket equations and such are hard enough. But that's the real world.

What I am talking about is writing space fiction or running a space themed role-playing game; like Traveller.

Space kicks your ass. The closer you stick to reality the more difficult it gets.

The first thing that hits you is distances. To quote Douglas Adams, "Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the drug store, but that's just peanuts to space."

Let's talk about that for a bit.

Most of us can internalize how far 250 miles is. You've probably even driven that far without stopping. Just a bit more than three and half hours on the interstate. You might even think of that as a long trip.

That's all the further away that the International Space Station gets. In space terms it's practically TOUCHING the earth.

By way of comparison, the moon is about 233,000 miles from here; give or take since it's in an elliptical orbit and will get closer and farther away. Yes, the moon is about 1,000 times as far away as the space station. Think about that road trip; 3,500 hours at interstate speed. Light takes a whole second to make the trip, and light is FAST.

When you get past the moon we stop using miles and kilometers and start using astronomical units. 1 AU is the average distance from the earth to the sun; it's about 93,000,000 miles. 151

__YEARS__ at interstate speed. It's also just a bit over eight minutes for light to make the trip. The moon is 0.00257AU from Earth.

Jupiter is about 5.2AU from the sun. Do that math. Long ways isn't it?

Let's take a bit of a side trip. Hauling three men from the earth to the moon and back took a 300 foot tall rocket and only the very tippy top came back with them. That part would easily fit in your garage. It went a bit faster than interstate speeds and makes the trip in about a week. And that's the way it had to be done. Going farther will require much larger rockets or much slower trips. 0.00257 AU in a week is 31

__YEARS__ to Jupiter and that assumes the shortest the trip can be.

Well before we leave the solar system we start thinking in terms of how long it takes light to get there. The recent Mars landing took place 7 light minutes from here. That means it takes light seven minutes to make the trip. If you try to have a conversation there will be 14 minute gaps in the replies.

Pluto is 39.264 AU, 3,649,934,370 miles or 5.45 light hours.

On this scale our sun is a teeny little dot. 865,373.71 miles in diameter seems very small now doesn't it?

Most of you have heard of a light year? That's how far light goes in a year. 5,878,600,000,000 miles. It's a unit of distance, not time. A parsec is similar, 3.26 light years. 19,174,000,000,000 miles. Han Solo is an idiot.

Notice how these zeros are adding up?

Alpha Centauri is our closest neighbor. It's 4.366 light years away. 25,665,967,600,000 miles. Just 41,855,784.41 years on the interstate. Hominids have not been around that long!

A gaming note, lots of the stock Traveller ships have a "jump-1" drive. A jump 1 drive can go a parsec in a week but no farther. You may notice that Alpha Centauri is farther than a jump-1 ship can travel.

Now the mind-fuck. Remember how big the solar system seems? Scale the sun down to the size of a grain of sand. Now, let's build a scale model of the galaxy with a grain of sand for each star. Guess how big our model is.

It just barely fits inside the solar system!

Space is FUCKING HUGE.

I am not even going to get into how far Andromeda is from here, and it's a bigger galaxy than our home one.