Simulating the World of Game of Thrones in Universe Sandbox ²

Universe Sandbox ² - 20150707-140519 UI

An Unpredictably Long Winter is Coming

Fans of George R. R. Martin’s fantasy series A Song of Ice and Fire or the television series, Game of Thrones, know well the often repeated warning, “Winter is coming.” 

For those living on the continent of Westeros in this fantasy world, summers can be long, and so can the winters. But some winters are especially cold and last for several years, while others are relatively mild and short.

What causes this variance in seasons?  Martin doesn’t offer an explanation, so we’re free to speculate.

One research paper (“Winter is coming”) proposes that perhaps there’s a natural explanation: Westeros is on a circumbinary planet, meaning its orbit extends around a binary star system.

Simulating  Westeros in Universe Sandbox ²

The paper may be tongue-in-cheek, but that doesn’t mean we can’t use its parameters to try simulating it in Universe Sandbox ². Like the paper, we were unable to find stable orbital parameters that would create the level of unpredictability discussed in the books or the show.

We could, however, create a system that has variable winter and summer intensities on regular predictable intervals with a large northern polar ice region. Though our results didn’t exactly match those in the paper, we managed to recreate similar seasonal patterns to what the authors describe in their paper.

If you own Universe Sandbox ², you can see this simulation for yourself in Alpha 15: Home -> Open -> Fiction -> Lands of Ice & Fire | Game of Thrones.

To open the temperature graph, open the Westeros planet’s Properties, select the Climate tab, hover over the Surface Temperature icon and click the Graph button.

If you don’t own Universe Sandbox ², you can buy it now to get instant access to the alpha via Steam code:

Universe Sandbox ² Alpha 15.2 | The Pluto Encounter Update

Universe Sandbox ² - New Horizons Pluto 2

If you already own Universe Sandbox ², just run Steam to update to the latest version.

Or you can buy Universe Sandbox ² here:

New Horizons

We’ve just released Alpha 15.2, which features a simulation of NASA’s New Horizons trip past Pluto and its moons. The spacecraft will be closest to the icy dwarf planet next Tuesday, July 14th. You can find the simulation in Home -> Open.

We will be updating Pluto’s and its moons’ textures as data is received from the New Horizons spacecraft.

If you keep the simulation running to 2019, you will see New Horizons approach its second target, 2014 MU69 (or PT1), an object with a diameter of 30-45 km orbiting in the Kuiper belt. New Horizons will likely be closer to PT1 than our simulation reflects, though, as NASA will be using a portion of its remaining fuel to get closer to its target.

You can also check out NASA’s own New Horizons simulation.

Recent Updates & Changes

In this update we’ve also made it possible to draw trails relative to a body and made additional tweaks and fixes.

In Alpha 15.1, released on June 26th, we updated the look of Ceres based on the latest photos from NASA, added a random asteroid feature, new moons of Pluto, pulsar jets, and improved the look of brown dwarfs. We also re-introduced the ability to customize launch bodies: Hover over bodies in the Add panel then press a number key to assign the body to that launch slot.

Full list of What’s New




Alpha 15 Now Available

Universe Sandbox ² - New Collisions Alpha 15

Universe Sandbox ² is now easier to use and explore, faster than ever before, and alive with the sound of music.

This is the biggest update yet for Universe Sandbox ².

Run Steam to update or buy Universe Sandbox ² now for instant access to Alpha 15.


Redesigned User Interface

Universe Sandbox ² - Alpha 15.1 UI

We redesigned the user interface for a cleaner, more intuitive experience. There’s a new layout, a whole new set of icons, cursors, and fonts, a brand new Home menu with generated thumbnails for previewing simulations, and a lot more. The interface is constantly being improved, but we’re very happy with the direction it is now heading. 

Improved Performance

Universe Sandbox ² - Saturn Neptune Alpha 15

We rewrote physics from the bottom-up for much better performance. Physics also now runs asynchronously from other components, which means that even if it is busy with a ton of calculations, the user interface and camera should still be completely responsive.

New Dynamic Soundtrack

Universe Sandbox ² - Soundtrack Alpha 15

Universe Sandbox ² now features a soundtrack which responds to actions and events in the simulation. Collide two planets and listen to the music swell. Music by Ryan Macoubrie.

And A Lot More


Alpha 15 took longer than we expected, but we think it’s well worth the wait. We’re excited to hear what you think:


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New UI Screenshot & Alpha 15 Update

New User Interface

User Interface Improvements

In the screenshot above you can see the improved Open, Add, and Properties panels. (Although you won’t usually have all 3 open simultaneously.)

The design will still change a bit as we continue development, but it’s a good representation of the direction we’re heading: unified icon styles, minimalistic design, better spacing, and a more intuitive organization of controls and settings.

One of our favorite new additions is the thumbnails in the Open panel, which provide a much more representative and inviting preview of the available simulations.

The biggest change? We’ve moved most of the actions you’ll need for exploring and interacting with a sim to a bottom bar. We pride ourselves on the amount of customizable options, but they’re only as useful as they are easy to find and adjust.

What else have we been working on since Alpha 14?

  • Getting our newest team member up to speed
    • A big welcome to astrophysicist Jenn Seiler!
    • Jenn is currently working on improving volatile loss rates and implementing magnetic fields (look for these in future updates)
  • Refactored physics and performance optimizations (see previous post)
  • Transitioning to GIT for our source control
    • This will help us maintain a monthly update schedule, as we can now develop features on the side without affecting the main project, then merge them in when they’re ready
  • Improved graphics settings and options
  • First steps in integrating backend visual improvements
  • New tech which lets users heat up one side of a body (coming post-Alpha 15)

We’re working hard to get everything working again for Alpha 15. Keep your eyes peeled. We look forward to hearing what everyone thinks.

If you don’t own Universe Sandbox ², you can get instant access to the alpha through our website:

Happy Earth Day!

Universe-Sandbox-²-Earth Day

First observed in 1970, Earth Day now gathers over 1 billion people in 192 countries every year on April 22 to celebrate our planet and raise awareness of the issues it faces. According to Earth Day Network, that makes it the largest civic observance in the world.

The growth of this movement toward the care and appreciation for our planet is evident all around us. Environmental awareness is no longer reserved for activists and radicals.  ”Going green” and “reducing your footprint” have become familiar, if not trendy, concepts.

But despite this, human-caused climate change continues to take us further down the road toward inevitable crisis. It’s a bleak forecast, but one that we, as individuals, nations, and a global community, must confront if we want to create the necessary changes.

Earth in Universe Sandbox ²

In Universe Sandbox ², we’ve added a simple climate simulation for Earth. We hope it helps in understanding how our climate works, and how fragile our planet is.

Here are a few things you can try in Universe Sandbox ²:

  1. Simulate Future Climate Scenarios

    • We’ve included the ability to simulate scenarios based on data from the most recent IPCC report
    • We recommend trying the Climate Scenarios activity (Home -> Main tab)
    • You’ll learn how to use the different models and graph Earth’s temperature over time
    • Learn more about simulating these scenarios in our previous blog post
  2. Tidally lock the Earth to the Sun


    • Select Earth (in the default Solar System sim)
    • In Earth’s properties window, click the “Motion” tab
    • Scroll down and click “Tidally Lock”
    • Now one side of the planet will always face the Sun
    • And the other side of the planet will begin to freeze over
    • Tidal locking is why there’s a “dark side of the moon.” From here on Earth, we can only ever see the same side
  3. Turn Earth into a Comet or a SnowballUniverse-Sandbox-²-Earth-Comets

    • Try moving the Earth closer to the sun to turn it into a comet.
    • Or move the Earth out past Mars and watch it freeze over. (Load the sim “Earths Next to Sun” to see multiple Earths at various distances from the Sun)


If you don’t own Universe Sandbox ², you can get instant access to the alpha through our website:

Alpha 15 Preview: Performance Boosts & UI Changes

We’ve been working hard on Alpha 15. It’s coming, slowly but surely.

In our last post, we talked about the upcoming performance improvements. Because of this substantial physics rewrite, it’s taking some time to fully integrate the changes and restore everything to working condition. But the results are worth it; we’re seeing some big performance boosts.

We’ve also made some major changes to the UI. It’s still a work-in-progress, but we’re very excited about its direction.


The changes to the UI have made it easier to control the simulation and explore some features which were previously buried under layers of menus. Realistic physics and data make up the engine that powers Universe Sandbox ², but the key to revealing the wonders of our universe lies within the ability to interact, manipulate, and experiment. For us, this means making it easy to answer the question, “What would happen if I chucked the Earth at the Sun?”

Keep your eyes peeled for Alpha 15.

If you don’t own Universe Sandbox ², you can get instant access to the alpha on our website:

More Performance Improvements in Universe Sandbox ²

Universe Sandbox ² - Saturn Rings
The last few alpha updates of Universe Sandbox ² have each included changes in the physics code to improve performance on a wide range of hardware. But never assume that Thomas, our numerical physics developer, is done with optimization; there’s always more performance that can be squeezed out.

That being said, sometimes it’s not worth trying to squeeze out the last drop; sometimes it’s better to start fresh. Thomas explains in his video description: “The core NBody physics was rewritten from the ground up to give back some of the raw computation speed, which had been lost under layer upon layer of C# sugar coating.”

If all goes well, this could mean that the physics-side of Universe Sandbox ² will run much faster than it does now. In addition, it will be running asynchronously, which essentially means that even if physics is bogged down with thousands of calculations, the user interface should still be responsive.

Check out Thomas’s video below for a demonstration of how powerful the new system is. 50 000 particles around Saturn would normally have brought this simulation to a halt, but now it runs very smoothly:

From the description:

Note that the slight stuttering, primarily at the beginning, is caused by the screen recording.

This demonstration shows the performance on an Intel i7 CPU running the rewritten C# engine on Mono. The rewrite will let us quickly add support for native code using SSE as well as native code running C++AMP on CPU or GPU, plus still OpenCL.

Full implementation may take a bit, but we’re very excited to see it up and running in Universe Sandbox ². When it’s ready, we’ll be sure to let you know.

Get instant access to the alpha and a pre-order of the final Universe Sandbox ²:

Alpha 14 Now Available

Universe Sandbox ² - Explode

A long list of bug fixes, first pass on total fragmentation, re-enabled exploder tool, better performance for slower machines, and further improvements to the user interface.

Run Steam to update or buy Universe Sandbox ² now:


Our last update introduced a lot of new features, and took a bit longer than we expected. So for Alpha 14 we returned to our monthly release schedule and focused on fixing bugs.  Some of these bugs have been around for a few versions, and others were introduced with last update’s big changes.

Total fragmentation is disabled by default as it’s still a work-in-progress, but you can enable it in Simulation settings (gear icon on the left). It can best be seen with the re-enabled exploder tool. Select Powers on the left, then select Exploder, then click on a body to make it instantly explode. This is also a work-in-progress; better transitions are on the way.

We also made improvements to collision and gravity calculations when running CPU mode. This means better performance for older hardware which can’t run OpenCl mode.

We revamped tooltips for smarter placement and increased visibility. We also made the Launch Body toolbar customizable, so now you can set the hotkeys to launch any body you choose.

For a full list of bug fixes and improvements in Alpha 14, check out the What’s New.

And as always, we’d love to hear your feedback:

Future Earth Climate Scenarios

Universe Sandbox ² - Earth Future Climate Scenarios

One of the most important features in Universe Sandbox ² is the ability to simulate Earth’s climate. It’s a relatively simple simulation, but it helps demonstrate exactly how fragile and ever-changing our climate is.

In Alpha 13, you can select possible future scenarios for Earth’s climate. These scenarios simulate the rise in carbon dioxide levels in Earth’s atmosphere caused by human activity up until the year 2100.

To simulate these, we use the same Representative Concentration Pathways used in the latest report from the Intergovernmental Panel on Climate Change (IPCC). These four pathways are projections for the future of greenhouse gas emissions and resulting concentrations in our atmosphere. You can see each pathway’s projections in the graphs below (left: emissions; right: concentration).

Carbon Dioxide emissions and concentration

CO₂ emissions and associated concentrations generated from the RCP Database.

There are many factors we can consider when looking at what changes will affect emissions. Policies, land use, global population, our attitudes toward production and consumption —  these can all have a huge impact on greenhouse gas emissions. Each RCP makes different assumptions about how and when these factors might change.

To stabilize concentrations, decreases in emissions are required, because even when emissions are lowered, CO₂ hangs around in the atmosphere for a long time.

Not only do the scenarios project different outcomes for concentrations, but, importantly, they each follow a unique trajectory based on a range of possible socio-economic changes. One assumes a peak in greenhouse gases in the next decade, while another assumes that there will never be stabilization.  (This is simplified for the sake of this introduction; you can learn more here.)

In Universe Sandbox ², you can enable RCPs by selecting the Climate tab in Earth’s properties and toggling “Select an RCP Scenario.” The default is RCP 8 5. Click the (+) icon to select one of the other 4 scenarios.

Once enabled, the pathway’s concentration level will be tied to the simulation year. The change in net radiative energy balance is also specified by the scenarios, and we put that right into our energy balance as a decrease in outgoing infrared energy. This has the effect of increasing the greenhouse effect and ultimately increases the average temperature of the planet. To see how the different scenarios play out, you can graph Earth’s temperature over the course of several decades. Below is a simulation of RCP6 through 2100.

Universe Sandbox ² - Climate and Graph 2

These pathways are not forecasts. But simulating them in Universe Sandbox ² can help you gain a more intuitive understanding of what is possible for the future of Earth’s climate.

Check out this blog post by Naomi, Universe Sandbox ²’s climate scientist, to learn more about how we simulate climate: Climate in Universe Sandbox ².

You can also check out the climate tutorials right in Universe Sandbox ²: Home -> Main -> Activities.


Physics Changes in Alpha 13

A riddle: This feature is the biggest feature of Alpha 13, but it doesn’t draw a whole lot of attention to itself. In fact, when it’s working perfectly, you won’t even know it’s there. Without it, though, you’d be shaking your fist at the screen as you watch the whole solar system fall apart. What is it?

The physics rewrite of course! (Maybe the title of this post gave that away.)

While the collision overhaul part of the physics rewrite makes for some impressive visuals, perhaps more important is the addition of a new integration mode and the changes made to the way Universe Sandbox ² handles timestepping.

In short, orbits in Alpha 13 are much more stable, and capable of maintaining this stability even at very high timesteps.

An easy way of demonstrating this difference is to compare the behavior between Alpha 13.1 and Alpha 12 when adding Earth in orbit around Sirius B, a white dwarf that is similar in size to Earth.

Open a new simulation, add Sirius B, then add Earth close by. In Alpha 12, unless you drastically lower the timestep from the default of 1.3 hours per second, Earth quickly gets flung out of orbit.

Alpha 12.1 Unstable Orbit

You can see in the last screenshot above that Earth has shot off the screen. Somewhere, it is speeding off into the depths of space. This is certainly not what you expect when trying to put Earth into a simple orbit. But because of the high timestep and the relatively small orbital period, the simulation cannot calculate Earth’s position accurately enough to keep it in orbit.

This was a common problem in the original Universe Sandbox. Many users expressed their frustration when they’d run the standard solar system simulation, turn up the timestep, and watch as Mercury slingshotted out of its orbit and past Pluto. No, this is not what physics says should happen, but rather a computational limitation. In our FAQ for the original Universe Sandbox, we explained it like this:

  • As you turn up the time step you lower the accuracy of the simulation. If the accuracy is too low, bodies will get thrown out of the system.
  • The numbers: Mercury takes about 88 days to make a single orbit around the sun. A time step of 22 days would only be calculating a new position for Mercury 4 times in that period. This isn’t enough accuracy to maintain a stable orbit. The Earth is further out and takes 365 days to orbit the sun. This same time step of 22 days results in about 16 position calculations for the Earth which is enough to maintain an orbit.

Fortunately, Universe Sandbox ²’s numerical physics developer, Thomas, has spent a lot of time finding and implementing a solution to this problem.

Now, in Alpha 13.1, you can put Earth into orbit around Sirius B without worrying what the timestep is:

Alpha 13.1 Stable Orbit

Alpha 13.1 Orbit from Above

The new Global Adaptive integration mode will always take a safe step in order to maintain the accuracy as determined by the “tolerance” setting. Tolerance is the maximum amount of error that is allowed while taking a step when compared to perfect accuracy (which cannot run in realtime).  This number will be much larger for simulations on the galaxy scale than simulations for dice and bowling balls, as the “acceptable” margin of error would be exponentially higher. You wouldn’t want your dice to take a million kilometer leap, but it’s probably okay for them to be off by a centimeter.

Tolerance can be manually adjusted in the settings, or you can let Universe Sandbox ² handle the adjustments. The tolerance is automatically set when loading a simulation to an amount that sufficiently maintains accuracy while also keeping the simulation running smoothly. It is also adjusted whenever a new body is added. We plan to add more automatic adjustments to respond to other simulation changes.

Finally, another large factor in determining stability is the actual numerical integrator that is used, with each having different strengths and weaknesses. For this, we can turn to a video that Thomas has created in order to explain some of the different integrators available in Universe Sandbox ².

While the physics in Universe Sandbox ² is not perfect yet, we’ve made huge strides over the past year. Optimizations in terms of accuracy and performance are an ongoing process, and we look forward to continually improving the simulation.