Why it Shouldn't Happen in a Galaxy Far, Far Away

I've noticed a trend in SFR where the setting is another galaxy. In spite of the poetic Star Wars opener, this disturbs me on many levels. The "fiction" in Science Fiction Romance allows for a universe of ideas and imaginative settings, but there's also that "science" part to consider.

Let me explain why this has become my #1 pet peeve with the subgenre:

Why go there?

The Milky Way Galaxy

Our home galaxy is made up of some 200,000,000,000 stars. That's 200 billion suns. Let me say that again. Two hundred billion. We can be pretty sure a good number of those 200 billion suns have multiple planets and moons and asteroids orbiting them. That's a whole lot of real estate. Why set a story outside those parameters?  Does it make it any more exotic? Or alien? I think not. If anything, it only makes it more implausible.

Why? Time. Distance. And Physics. 

Let's take it in increments.

Distance from the Earth to our Sun

The average distance between the Earth and the Sun is 93 million miles or roughly 149 million kilometers. Because the distances in space are so enormous, this is a standard of measurement refered to as an AU or International Astronomical Unit. Note that this is the "average" distance. Objects in space do not stay in one place so there is no constant point A to point B distance.

So looking down the street in our immediate solar neighborhood:

Distances within our solar system (the planetary system revolving around our single sun):
Earth to Mars:  0.5 AU or 48,600,000 miles
Earth to Jupiter:  4.2 AU or 390,500,000 miles
Earth to Saturn:  8.4 AU or 793,800,000 miles
Earth to Uranus: 18.4 AU or 1,689,800,000 miles
Earth to Nepture: 30.0 AU or 2,701,400,000 miles
Earth to Pluto: 38.53 AU or 3,573,200,000 miles
Earth to the Kiuper Belt:  5,000 to 100,000 AU or 465,000,000,000 to 9,300,000,000,000 mi.

Whew!  Okey-dokey. We're already covering a lot of ground and we've hardly made it off the block. Let's think about a trip to the "next town."

Distance to the Nearest Star

Proxima Centauri, the closest (actually part of a triple sun system called Alpha Centauri), is 39,900,000,000,000 km away or about 26,200,000,000,000 miles. That's about 4.22 light years. We're definitely going to have to pack a lunch.

How Long Would It Take to Get There?

The distance of 4.22 light years means it would take 4.22 years traveling at 186,282 miles per second (mps not mph) to reach it.

Let's get some real space/time perspective on that.

The Galileo probe currently holds the record as the fastest spacecraft to travel through space at 106,000 mph. Using Jupiter's gravity to create a slingshot effect, we might possibly have a spacecraft achieve a velocity of 150,000 mph. (And that's to the nth times slower than 186,000 miles per second.)

Our Voyager I spacecraft, launched in 1977, has been traveling outbound for almost 35 years. It reached Jupiter in 1979, Saturn in 1980 and flew beyond the orbit of Pluto in 1989. It has now been traveling for almost 35 years and hasn't yet reached the Kuiper Belt or the heliosphere that marks the outer bounds of our own solar system, much less interstellar space--the space between solar systems.

Some scientists believe Voyager 1 (and Voyager 2, which is traveling on a different trajectory) will leave our solar system sometime in 2016. Voyager is traveling at about at about 57,600 kph or 35,790 mph. If it took almost 40 years just to reach the edge of our own solar system, much less cover the space to the closest star, think how vast that distance truly is!

So let's pretend we could develop an ion drive that could approach light speed. Just getting to that speed takes time. In fact, it could take about 4,900 years to accelerate to half the speed of light and another 4,900 years to begin decelerating to normal speed when we reach the halfway point to Proxima Centauri. (It takes a lot of time to slow down, too.) That would be 9,800 years or more time than all of recorded human history to get to the nearest star.

Even if we could instantly accelerate to and from light speed, it would still take well over four years just to reach Proxima Centauri traveling at the rate of 186,282 miles per second.

There are about 26 stars that are considered near our own sun (neighboring towns, relatively speaking). Bernard's Star, at 6 light years distant, is the closest star that is thought to have planets of its own.  Procyan B, the farthest of the "near" stars is about 11.5 light years distant. One of the brightest stars, Vega, is about 27 light years away or 6.5 times further than Proxima Centauri.

Whew! And that's only to reach the closest stars. We're nowhere near talking about other galaxies yet.

Distance across the Milky Way Galaxy

Our own galaxy is about 1,000,000,000,000,000,000 km (or about 100,000 light years) across.

Our Sun, which is on one of the arms of our spiral galaxy, takes over 200 million years to circle the Milky Way Galaxy just once. 

So, if we could instantly achieve light speed coming and going, it would take over four years just to reach the closest star and 100,000 years (5,000 generations!) to fly across our own galaxy.

And we're supposed to go where?

Distance to the Nearest Galaxy--Hello, Andromeda

The distance to the nearest galaxy, Andromeda (also called Messier 31 or M31), is estimated to be between 2 to 2.2 million light years away.

What? You want mile markers?

2.2 million light years
= 186,000 miles per second (rounded)
x 60 seconds/minute x 60 minutes/hour x 24 hours/day
x 365 days/year
= 12,904,531,200,000,000,000 miles distant

By the time we get there--provided we can even attain that proverbial "instant" light speed--chances are we've evolved into something that isn't even human. After all, how old is the human species--scientifically speaking? And that's assuming there are no mechanical failures or accidents along those 2.2 million years since we're beyond the help of the nearest spacecraft repair shop. In fact, since we're aiming for light generated over 2 million years ago and then adding the time for our trip, the galaxy may not even be there when we arrive over 4 million years after the light was generated. Sobering, yes?

And once we arrive, how do we let anyone know? Even sending messages via light, it will take 2.2 million years to reach the folks back home--who have by then probably also evolved or gone extinct.

Other Implausibles

In addition to the problem of spanning unfathomable time and distance, there's also problems with the fabric of intergalactic space.

Galaxies are connected by a denser plasma than the empty spaces of the universe. Galactic medium is mostly composed of ionized hydrogen. It may be up to 100 times denser than that of intergalactic space. Atoms may not behave the same way in intergalactic space due to the absence of energy in the void.

There could also be mysterious forces at play, such as dark matter and dark energy, that work differently outside the influence of a galaxy. No one is sure if propulsion systems, or matter in general (such as that making up the hull of the spacecraft), would behave in the same way if intergalactic space doesn't have the same physical laws.

Wait, What About Warp Drive?

Clearly, if we're going to jaunt about space, we're going to need some sort of Warp Drive (Star Trek), space bending (Dune), or jump gates (Dock Five series--Linnea Sinclair). Even so, the distances we'd have to bridge within our own galaxy are so incredibly vast, why oh why would we ever need or want to cross eternity to another galaxy? What could there possibly be over there that we don't have right here? (Right here, give or take 50,000 light years, that is.)

So why go there indeed? It seems staying within the bounds of our own galaxy makes the science in the Science Fiction Romance much more within the realm of "suspension of disbelief." 

Me? Believe I'll stick around the ol' hometown.