Since its beginning, science fiction has taken readers to other worlds through flights of the imagination (manifested as rockets, giant hollow cannon shells, weightless spheres, wormholes through space/time, strange creatures, balloons, flying saucers, transporter beams and more means than I can remember). The challenge has always been to make readers and viewers feel like they’ve actually been there.

We know that being present on the surface of another planet would be very different from standing on Earth, but we will never know just how different until we actually do it, no matter how much scientific research we do. For a long time we only knew of our solar system’s nine planets (back before Pluto got demoted) and imagination sketched Mars as a dry planet criss-crossed with ancient canals, while Venus was a torrid swampy jungle. New information corrected those visions, and now space telescopes like Kepler have discovered planets around other suns as strange as anything we could have imagined.

Still, the key to making those planets come alive to readers of science fiction depends on tapping into how those environments will be perceived by our senses. It’s a daunting task.

Take a so-called super-Earth planet, for example—considered similar to ours in atmosphere and temperature range perhaps, but with stronger gravity. Of course, we’ll feel that extra weight (and immediately look for a quick and easy diet plan) and complain about the extra effort required by every movement. We’ll breathe harder, especially at first, and with the extra gravity will come a denser atmosphere—a higher concentration of oxygen if we’re lucky, but possibly more of the lighter gases that would have escaped from smaller planets. The content of water vapour in the air will be different, and you must have noticed how smells are amplified on hot, humid days. Smells will be much more pungent on planets with denser, wetter air, and since so much of our sense of taste depends on smell, foods will taste different too—possibly more flavourful, which is good, but subtle elements could be much more noticeable as well. If you cook like I do, there won’t be any hiding that burnt taste from the bottom of the pan. Astronauts in space crave spicier food, perhaps because their air is dry, but also because their nasal passages tend to clog a bit in zero gravity. High gravity might mean leaving the sriracha sauce behind on Earth!

Popular Science had a cool article recently about how food would taste on other worlds. Have a look.

I suspect that the diversity of smells will probably be the most pronounced reminder that we’re not on Earth anymore. Close your eyes and recall the very different odours of a pine forest, a muddy marsh, a rose garden, an ocean beach, a field of clover, a city street after a summer rain. There are countless environments on Earth that your nose would immediately identify, and each of those unique scent signatures is made up of hundreds, possibly thousands, of elements, such as the breed of grass (freshly cut or not), the composition of the soil (rich humus or salty sand), flower fragrances (in bloom or not), the temperature of pine needles or mud (in sun or shade). Imagine how utterly different the odour of another world will be where every single living thing is a species never before encountered.

How does a writer even describe that? We usually have to fall back on comparisons to familiar fragrances and proclaim that the new smell is something like them.

The sun will feel different, too. You’ve noticed how, on a hazy summer day you can practically feel the sun crisping your skin, but on a bright spring afternoon you can easily get a sunburn without realizing it at all. Other planets will have suns that are smaller or larger, closer or farther away, redder or bluer, fiercely energetic or calmer than our own sun, with huge differences in their output of  ultraviolet and other radiation. What reaches the surface of the planet will also depend on the composition of the atmosphere, the water vapour (especially clouds), any ozone layer, reflection and refraction from water droplets or dust particles or ice crystals in the air, and the day/night cycle.

Then we come to the realm of sounds. The density, temperature, and moisture content of air all affect the speed that sound travels, to a degree. But remember how hard it is to locate the direction a sound is coming from when you’re in a fog? Snowfall mutes sounds. Rainfall masks sounds. Pressure changes on your ear drum can affect the pitch of a sound you hear (I especially notice this when I’m scuba diving and haven’t equalized the pressure in my ears often enough). And all of that is just how sounds we know are affected by conditions. What about sounds that are all new to us, because they’ve been created by unique environmental factors or bizarre forms of life? Again, we have to fall back on similes (“it made a sound like…”) to give the reader a reference for understanding. Quite a challenge to express something truly alien.

The most common fallback in portraying alien words is to use visual description: a violet sky smeared with golden cloud that sometimes obscures the giant red sun and smaller white sun that glide at different speeds from horizon to horizon. Yet, as authors, we can’t afford to describe anything too far from normal human experience—readers’ minds would rebel or, at the very least, would be badly distracted by trying to imagine the picture we’re painting (like when we’re having to explain how the green-skinned villain disappears into green shadows cast by the red sun but not the black shadows cast by the white sun).

All of this goes to explain why written and filmed depictions of alien worlds probably err on the conservative side. The scene-setting can’t get in the way of the story, and it will always fall short of reality anyway—the universe is a strange and exotic place. That doesn’t mean it isn’t worth taking the journey with us.

We’re a whole lot cheaper than a ride with NASA.