10 Things Writers Should Know About the Universe

The universe is ripe with creative potential. It’s vast, mysterious, and for most of us, something we won’t experience firsthand—and so we turn to stories to take us there.

Here, Dr. Matt Bothwell lays out 10 things writers should know about the universe.

Everything in space is so far apart, on any human scale, that it’s almost impossible to comprehend. The Solar System is often represented in fiction as being made up of a few big planets packed close together, so that traveling between them is a matter of taking a quick jaunt in a spaceship.

The reality is that the planets in our Solar System are more like specks of dust, adrift in an enormous void and separated by a vast gulf of darkness. The artist Josh Worth has created a nice tool called “a tediously accurate map of the solar system.” The Moon is scaled to one pixel. What will strike you, more than anything, is just how big and empty space really is.

We live in an unusually dense part of the Universe, full of (comparatively) packed together objects. Once you head out into interstellar space, the real emptiness begins. The best way to describe this is by using the Voyager probe. Launched in 1977, it was designed to take pictures of the outer planets (and did so spectacularly!).

Its photographic mission complete, Voyager headed off into the void. It is still one of the fastest spacecraft the human race has ever built, flying into the blackness at an astonishing 17 kilometers per second. But even at this speed, it will take nearly 100,000 years to reach the nearest stars—and over a billion years to leave our Milky Way galaxy.

A rather sobering fact is that all the stuff that makes up the familiar Universe—that is, me, you, the objects around you, the air you are breathing, the Sun and all the stars in the sky, represent just 5% of the Universe. The remaining 95% is a total mystery.

We call this strange stuff "dark energy" and "dark matter"—where the word "dark" basically means "we have no idea what is going on here." Dark matter seems to be some mysterious substance that holds the Universe together. Without it, our galaxy would spin itself apart.

Our best guess is that it is some kind of as-yet-undiscovered particle, which just totally ignores light (which makes it invisible). But all our attempts to catch one in action here on Earth have been in vain. So we keep looking!

(Matt Bothwell: On Uncovering the Invisible Universe)

Astronomers around 100 years ago discovered that the Universe is getting bigger all the time. We eventually figured out that this was because the Universe started off really tiny and dense, and has been getting bigger (and colder, and emptier) ever since. We call the Universe’s explosive beginning "the Big Bang."

In the 1990s, astronomers made an unexpected discovery: the expansion of the Universe is actually speeding up. This was totally unexpected; something is pushing the Universe apart faster and faster, and we have no idea what it is.

We call the effect "dark energy" (because we have to call it something). But because we don’t understand Dark Energy, we don’t yet know how the Universe will end. It might simply get bigger and bigger forever—or it might speed up, and tear itself apart. Scientists are working on the answer—watch this space!

Don’t be fooled by the names. Dark energy and dark matter are totally different things (as far as we know). Dark matter pulls stuff together, dark energy pushes stuff apart.

Black holes aren’t just cosmic vacuum cleaners, sucking up and destroying everything around them. Black holes are objects with gravity, just like everything else in space. If our Sun was turned into a black hole tomorrow, Earth wouldn’t get sucked in—we would just happily orbit around the new black hole (the lights would go out, of course, so it wouldn’t be all good news).

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There are many kinds of light we cannot see—from long-wavelength radio waves and microwaves to super high energy gamma rays. What is deeply astonishing (to me, at least) is that the light we can see with our eyes represents only vanishingly tiny part of the total spectrum.

Here’s an analogy. The shortest, bluest wavelengths a human eye can see are around 380 nanometres (where a nanometre is a billionth of a metre), and we can see long-wavelength red light up to around 740 nanometres—after which it crosses the border into invisible infrared light. You can think of a factor of two in wavelength as the "window" through which we see the world. By a nice coincidence, a factor of two in wavelength also has meaning when we talk in terms of sound, rather than light. Two notes, one octave apart (like middle C on a piano, and the C one octave higher), have wavelengths of sound that differ by a factor of ... two.

So, by analogy, we can think of our eyes as being able to see one "octave" of light. On this scale, the full electromagnetic spectrum stretches 65 octaves, side to side. And we can only see one central octave, out of that enormous span. We are totally blind to nearly 99% of all the light the Universe sends our way.

Luckily, modern astronomers can use telescopes to see all that invisible light and paint a complete picture of the Universe in all its glory. Telescopes have another useful feature: they allow us to look back in time. The stars in the night sky can be tens or even hundreds of light years away—so when we look at them, we are receiving signals from decades in the past. The most distant galaxies can lie billions of light years from Earth, and when we see them we are peering back through billions of years of cosmic time. Using telescopes, astronomers have the power to literally see into the past.

One of the most common misconceptions about professional astronomers is that they spend all their time staring through telescopes. The truth is that telescope time is very precious, so professional astronomers count themselves lucky to have a few nights of telescope time in a year. The rest of the time is spent analyzing the data, writing papers, and having spirited debates about what it all means.

People often assume that scientists get very annoyed with movies and books that get scientific details "wrong" somehow. There are endless think-pieces floating around the internet excoriating films for being scientifically inaccurate. My view is that it’s nice to get the details right, but it’s not the most important thing. If you’re making a piece of art, the art should come first. There’s no sound in space, but Star Wars wouldn’t be the same without those explosions, you know?

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