Mathematicians find 12,000 new solutions to ‘unsolvable’ 3-body problem

https://www.livescience.com/physics-mathematics/mathematicians-find-12000-new-solutions-to-unsolvable-3-body-problem


The three-body problem is a notoriously tricky puzzle in physics and mathematics, and an example of just how complex the natural world is. Two objects orbiting each other, like a lone planet around a star, can be described with just a line or two of mathematical equations. Add a third body, though, and the math becomes much harder. Because each object influences the others with its gravity, calculating a stable orbit where all three objects get along is a complex feat.

Now, an international team of mathematicians claims to have found 12,000 new solutions to the infamous problem — a substantial addition to the hundreds of previously known scenarios. Their work was published as a preprint to the database arXiv, meaning it has not yet undergone peer review.

More than 300 years ago, Isaac Newton wrote down his foundational laws of motion, and mathematicians have been working on solutions to the three-body problem pretty much ever since. There is no single correct answer; instead, there are many orbits that can work within the laws of physics for three orbiting objects. 

Related: The ‘Three-Body Problem’ has perplexed astronomers since Newton formulated it. A.I. cracked it in under a second.

Unlike our planet’s simple loop around the sun, orbits for the three-body problem can look twisted and tangled, like pretzels and scribbles. The 12,000 newly discovered ones are no exception — the three hypothetical objects start at a standstill and, when released, are pulled into various spirals toward one another via gravity. They then fling past one another, moving farther away, until the attraction takes over and they once again come together, repeating this pattern over and over again.

The orbits “have a very beautiful spatial and temporal structure,” lead study author Ivan Hristov, a mathematician at Sofia University in Bulgaria, told  New Scientist. Hristov and colleagues found these orbits using a supercomputer, and he’s confident that with even better tech, he could find “five times more.”

Three-body systems are quite common in the universe; there are plenty of star systems with multiple planets, or even multiple stars orbiting each other. In theory, these new solutions could prove extremely valuable to astronomers trying to explain the cosmos. But they’re only useful if they’re stable, meaning the orbital patterns can repeat over time without breaking apart, flinging one of the component worlds off into space. Just because they’re theoretically stable doesn’t mean they’ll stand up to the many other forces present in a real star system.

“Their physical and astronomical relevance will be better known after the study of stability — it’s very important,” Hristov said.

Juhan Frank, an astronomer at Louisiana State University who wasn’t involved in the work, is skeptical that these orbits will turn out to be stable. They’re “probably never realized in nature,” he told New Scientist. “After a complex and yet predictable orbital interaction, such three-body systems tend to break into a binary and an escaping third body, usually the least massive of the three.”

No matter what, though, these solutions are a mathematical wonder. According to Hristov, “stable or unstable — they are of great theoretical interest.”

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via Space https://www.space.com

September 24, 2023 at 05:11AM

Unity walks back new engine pricing after protests

https://www.pcworld.com/article/2081112/unity-walks-back-new-engine-pricing-after-protests.html

Forget Starfield, Baldur’s Gate 3, or [insert the game that you’re currently playing here]. The big story in the game industry over the last week has been Unity and how the makers of the cross-platform engine have pissed off pretty much everyone. On Friday, Unity issued an update a little over a week after announcing a new per-install fee structure that would have drastically increased costs for developers large and small. Following the near-universal outcry, Unity has scaled back some — but not all — of the planned changes.

Most importantly, the free tier of the Unity engine will not automatically charge game developers a fee for every installation of games developed with it. In addition, the terms applying this fee to games retroactively, possibly setting the bar for the charge impossibly low for thousands of titles already on the market for PCs, consoles, and mobile phones, are now gone. The runtime fee changes will only be applied following the next major release of the Unity game engine. That release won’t come until 2024.

Other controversial aspects of the new fee structure are still in place. Per-installation fees will remain for new games that earn more than $1 million USD in a 12-month period with an option to swap out this revenue model for a rather steep 2.5% revenue share scheme. That fee will be based on the estimated numbers of users engaging with the published game on a per-month basis. And along with the user installation numbers, these will be self-reported. The self-reporting concession sidesteps many of the issues that developers had with how users would be calculated, like re-installations, game streaming, or games offered on multiple platforms.

While per-installation fees for bigger and more profitable games remain, it seems like these changes address most of the issues that developers (and by proxy, gamers) had with the original shocking announcement. The concession that existing games built with Unity will not be subject to retroactive charges, endangering the very existence of some games and their developers’ ability to continue selling them, is a big walk-back. The announcement was made in a post that begins with an apology, and one that’s more sincere than a previous damage control tweet.

Even so, the week-long episode created a deep rift between Unity and the game dev community that won’t be easy to reverse. Many developers began considering a shift to Epic’s similarly cross-platform Unreal Engine, or smaller alternatives like Godot or Defold. With a reprieve of several months at least before the less dramatic changes are set to go into effect, Unity may find that it’s no longer the de facto standard for indie developers.

via PCWorld https://www.pcworld.com

September 25, 2023 at 11:36AM