Friday, June 11, 2021

When you look at the night sky, you're seeing an illusion

The Andromeda Galaxy

 I write science fiction – with an emphasis on the fiction bit. However, mindful of the 'science' bit, I try to adhere to the basic tenets of physics and what knowledge I have of astronomy. But let's face it, if you're writing fast-paced space opera, you need to have things like faster than light travel (FTL). And it has to be really advanced FTL, too. I think we tend to gloss over the facts about how vast space really is, in much the same way that politicians say 'one billion dollars' without batting an eye.

One billion looks like this in dollars. $1,000,000,000. Or put it another way, one thousand million. That's eye-watering money.  But it pales when you start talking about numbers in space.

Even within our little solar system with its unpretentious sun at the centre, the numbers are large. It takes about eight minutes twenty seconds for a photon from the sun, travelling at light speed, to reach Earth. Light travels at about 300,000 km per second, so that's about 300,000 X 500, therefore 150 million km – which is the average distance of Earth's orbit from the sun. In comparison, light from the moon takes a bit over a second to reach Earth, a distance of about 384,400 km. In this context, it doesn't sound like a huge number – but it took Apollo11 76 hours to reach the Moon. It takes months for (unmanned) spacecraft to reach Mars or Venus, years to reach the outer planets.

Once you start to talk about light years, the numbers are mind boggling. One light year is a distance of 9.5 trillion kilometres. If we wanted to visit Alpha Centauri, one of the closest stars to ours, we would need to travel at the speed of light (which is impossible) for nearly four and half years, so really advanced FTL would be a definite plus, especially if it's a love story. Sexual tension can only go so far 😉

The size of our Milky Way galaxy is hard to determine since we're in it. Numbers vary from 100,000 to 200,000 light years or more in diameter, so if Admiral Piett was right in saying that the Millenium Falcon could be on the other side of the galaxy by now – that's one hell of an FTL drive. (Of course, that galaxy far, far away might be much, much smaller than ours…)

Once we get outside our own galaxy, the numbers become… astronomical?  One of our nearest galactic neighbours, the Andromeda Galaxy, is 2.5 million light years away.

That segues nicely (the distance, not the sexual tension) into another astronomical fact. Whenever we look at any object in space, we're looking into the past. If the sun suddenly exploded, we wouldn't know for about eight minutes. Alpha Centauri may have exploded in a nova three years ago but we wouldn't know about it for another year and a half. Fortunately for us, it's not likely to die a supernova death, which would cause major problems for life on Earth. But Betelgeuse, the red giant star in the Orion constellation, will do just that – if it hasn't gone already. It is 642.5 light years from Earth and has been behaving erratically of late. Whatever that means. It might have exploded centuries ago.

Whenever you look at the night sky, you're seeing an illusion.

And that leads us to constellations. Astrology is fun, but it's hard to imagine how planets and distant stars can have any significance in human lives. It's easy to see the planets move around the night sky. But stars move, too. We just don't see the motion because they are so far away. 

Take Orion as an example. Perhaps Orion would look the same from other planets within our solar system but over time the stars will move in relation to each other. This short video will show how much.

"It all goes to show that while we take the stars as unchanging guides, they are constantly shifting. Right now, if you want to make sure you're headed in the right direction, you find Polaris (the end of the "ladle" of the Big Dipper is helpful here). But in 3,000 BCE, the star Thuban was the north star. And if humanity hangs around for another 13,000 years, we'll get a new North Star: Vega, the most luminescent star in the constellation Lyra, and currently the second brightest star in the in the northern celestial night sky. Which means our descendants 13,000 years from now (or about 500 generations out) will have a much easier time pointing themselves due north. Something to look forward to!" [source]

Outside our solar system, maybe from Alpha Centauri, the constellations we know and love won't be visible.

And all of that gives lots of opportunities for space opera plots – on the understanding that we have super-duper FTL drives, fantastic air and water recycling systems, fabulous radiation shields, and artificial gravity. (My ships have all those, of course.)

Eye of the Mother is based on the premise that an important star in a constellation the alien Yrmak culture views as the mother deity in their religion has gone supernova. Planets in systems closest to the star can actually see it has exploded, while those further away can't see the constellation.

I've written another story which will appear in due course where the changing shape of constellations depending on the viewer's location is an important clue.

As much as I'm a Star Wars fan, I'd be among the first to agree the science in the shows is pretty ordinary. Star Trek is slightly better. Maybe. I'm happy to admit that I write a form of fantasy but I do my best to avoid magic in my books. That 'science' bit is important.


  1. Here, here! Wonderful blog and I'm definitely "on board" with your thoughts. Yes, at our current rate of travel it would take us roughly 50,000 years (give or take) to reach the NEAREST STAR, much less go galloping about the cosmos. How do we achieve that? This science IS important in SFR. Otherwise, we're writing space fantasy or futuristic. I try to employ at least fundamental theories (if entirely fictional) of how my ships get from point A to point 42 light years distant in a hurry, in at least a somewhat believable--in a suspension-of-disbelief--way. But to me, that's what SFR is all about. Exploring romances set in extraordinary times with capabilities far beyond present day. But no technical manual necessary! Just make it feel and read as if it could be some future reality where our science is sufficiently advanced to tackle the enormous distances in space.

  2. As Arthur C Clarke said, “Any sufficiently advanced technology is indistinguishable from magic.” But I try, as you do, to at least make it plausible.


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