Tag Archives: space

The Cosmic Train Schedule, and Getting Science Right

by Jennifer Willis

During the Q&A following my author reading at Orycon in November, I was asked a question I’d not gotten before:

“What was the coolest thing you learned while researching your Mars books?”

What an awesome question, right? I had to think quickly on my feet and sort through all of the fun stuff I got to dig into while working on these three books. The answer that sprung to mind, though, was the Cosmic Train Schedule. And I promise that’s not something I just made up.

The Cosmic Train Schedule is an online resource that includes real-world transit times between Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. It’s a massive timetable that spans centuries and gives exact dates for departures and arrivals as well as information on aphelion, perihelion, and other fun geekery.

And I did geek out over this. I opened up a new project in Aeon Timeline and mapped out all of the (fictional) manned missions to Mars for my series, including both the government-sponsored trips crewed by trained astronauts and the waves of colony missions that are central to my stories. This helped me get a better sense for the lengths of missions, a reasonable timeline for sending people on interplanetary voyages, and a hard schedule for overlaps between missions and gaps when there would be no human beings on the Red Planet. While I had a lot of nerdy fun pulling that together and inserting more mundane elements like future Super Bowl dates (because I also mapped out a fictional NFL expansion as background material), I also needed this information to construct and drive my stories—particularly for the third book, Mars Heat.

So why go to all this trouble? Because actual science matters in science fiction. This can be tricky for authors, because sometimes real-world limitations and physics can get in the way of what would otherwise be an awesome plot point. But I try not to use handwavium too much if I can help it. This is a big reason I’m still excited that I got to participate in the Launch Pad Astronomy Workshop for Writers at the University of Wyoming in 2011, even though my brain melted as we tried to absorb what amounted to a college course in astrophysics in the space of a single week. It’s no coincidence that Mike Brotherton—founder of Launch Pad, UW physics and astronomy professor, and sci-fi author—is the one who directed me to the Cosmic Train Schedule.

Sci-fi authors have a unique opportunity to promote science literacy through our work. Countless astronauts, scientists, and others credit their early sci-fi reading for inspiring their studies and careers, and scientific understanding is important for everyone. Plus, it’s fun to learn something new while you’re in the middle of a great read. My SFR books aren’t hard science fiction, but I do try to get the science right where possible.


A chronically optimistic nerd, Jennifer Willis writes urban fantasy, sci-fi, and sci-fi romance. She is also the writer behind the Northwest Love Stories feature in The Oregonian and has a byline in the Hugo Award-winning Women Destroy Science Fiction from Lightspeed.

Gravity: Does Size Matter?


by Robert Scanlon

When you think of epic science-fiction, do your thoughts turn to slow-motion zero-gravity scenes, or fancy space stations with complex mechanisms for simulating gravity?

But what do you think of when you imagine a planet several times the size of Earth? A colossus, right? So the gravity would be unbearable, wouldn’t it? I mean a massive planet must need high gravity just to stay together.

This is not the case. It’s possible to have massive planets with lower gravity than Earth, and planets smaller than Earth with high gravity.

It’s all a question of density and mass. And of course, size matters.

For example, Jupiter, a massive planet and the biggest in our solar system, is 31 times the mass of Earth, and 12 times the diameter. But Jupiter’s gravity is only just two and a half times that of Earth.

Mars, is half the diameter of Earth, and one-tenth of the mass, but has one-third of Earth’s gravity.

Mercury, the smallest and least massive planet in our solar system, is quite dense (only slightly less dense than Earth). Its gravity is about 40% of the Earth’s, and higher than Mars.

So what makes a planet dense? (And therefore more likely to have a higher gravitational attraction.)

For the most part, if the planet is solid, it will be down to the composition and distribution of the heavier elements. Metals such as iron — one of the galaxy’s most common metals — will contribute strongly to the planet’s density, and therefore its gravity.

But some planets are not entirely solid!

For example, Jupiter is a “gas giant,” meaning, although it is huge, it’s not that dense (compared to Earth). But because the outer portion of Jupiter is thought to be gas or liquefied gas, it is hypothesized that below all that gas is a solid core. So if you try to stand on Jupiter’s gaseous surface, you’d fall through the gas (and at two and a half times earth gravity, you’d fall fast!), and probably end up on a solid surface somewhere (note: don’t try this at home. It’s probably fatal).

Back to the sci-fi. Just because the intrepid explorers land on a big planet, it doesn’t mean it will be hard to move due to the high gravity. In actual fact, it’s more likely the g-forces will be less.

Which brings to mind an interesting observation. Given the number of extraterrestrial planets visited in sci-fi history, don’t you think it’s incredibly lucky that most of them seem to have a gravitational pull the same as Earth’s?

Makes it easier (and cheaper) to film, I suppose!

Maybe this is one reason I liked the movie, “Gravity” so much – they took the time to make sure the gravitational science was true-to-life, even though it is science-fiction!


Robert Scanlon is the author of Constellation, the first book in the Blood Empire series and a Space Opera Science-Fiction Epic. In which there are two planets and one moon with completely different gravity to that of the Earth’s. And lots of zero-gee floating!

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