From The Desk of...The Chief Scientist

"Going Negative"

Written by Paul Sutter on Sunday, 23 April 2017. Posted in From The Desk of...The Chief Scientist

Josh Kessler, COSI's Program Manager, had a quick question for me as we were driving to OSU to talk with the Astronomy Department about solar eclipse plans (more on that later). He heard in the news "something something discovering negative mass", and that seemed like a big deal.

Indeed, discovering negative mass would be a big deal, since it doesn't exist in our universe. Particles with negative mass would repel positive-mass particles, which means you could put one next to a positive-mass particle and watch as they spontaneously accelerate off to infinity. That seems...wrong.

So imagine my surprise when the headlines came rolling in recently about a "breakthrough" that is "turning physics upside down". For once, the blame isn't fully on the press release or the media. The scientists flat-out put it in the title of their paper accepted by Physical Review Letters:

"Negative mass hydrodynamics in a Spin-Orbit--Coupled Bose-Einstein Condensate"

How profound! But the very first sentence of their abstract gives the game away: "A negative effective mass can be realized in quantum systems..."

A negative *effective* mass is an entirely different beast than a negative mass. In fact, the term is really a historical artifact that doesn't mean what you think it means. It means that in ultra-cold quantum systems, there are internal forces that make a fluid move in surprising ways. In this case, when they shut off their trapping laser, the fluid expanded a little bit then stopped. That's it.

It's a totally routine operation in this branch of physics, not at all surprising, and not at all negative.

"The Calendar"

Written by Paul Sutter on Sunday, 16 April 2017. Posted in From The Desk of...The Chief Scientist

For those of you paying attention, Easter came a tad late in the season this year. But what if it got so bad it was celebrated in May?

That was the problem faced by leaders of the Catholic Church in the late 1500's. The calendar they were using, initially proposed as a reform by Julius Caesar a millennium and a half before that, didn't exactly line up with the actual length of the year. Sure, it was good enough for a couple hundred years, but over time errors crept in, and soon enough it was shorts-and-sandals weather during the big Spring party.

Pope Gregory XIII was sick of it, and so - another reform. Every 4 years would be a leap year (a feature of the older Julian calendar), unless the year was divisible by 100 (then no leap year) unless it was divisible by 400 (then leap year anyway). These changes to the leap schedule shortened the average length of the year by almost 11 minutes, meaning only minor corrections need to be made every once in awhile to keep everything synched up.

The Gregorian calendar is a little weird, but it does the job.

"Pluto is (not) a Planet"

Written by Paul Sutter on Monday, 10 April 2017. Posted in From The Desk of...The Chief Scientist

Recently Joe Heimlich, co-director of COSI's Center for Research and Evaluation, fired off a quick question for me: rumors abound that Pluto may be reinstated as a planet. Is it true? What gives? (I'm paraphrasing).

In 2006 the International Astronomical Union adopted the following requirements for planethood: An object must 1) orbit the sun, 2) be large enough that its own self-gravity pulls it into a spherical shape, and 3) clear the neighborhood of its orbit of any debris.

With its large moon Charon, and all the other junk in the outer solar system, Pluto failed requirement 3 and was demoted to "dwarf planet" status.

The decision was met with heavy criticisms within the astronomical community. Why should a definition of an object rely on its environment and not just on properties of the object itself? If the Earth were moved to the orbit of Pluto, we would lose our planet status - how does that make sense? Why weren't all interested parties involved in the vote back in 2006? And so on.

Recently a group of astronomers proposed a new definition of planet: it must be large enough to make it round, and that's it. The new definition covers Pluto and friends, "rogue" planets that aren't bound to any star, and also upgrades some large moons to planetary status.

The debate continues, but one thing is clear: we will never return to a state with exactly 9 planets in the solar system. Either it will continue to be 8 or be around...10,000. We'll see.

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