The Soft Bands Of Saturn

In last week’s episode of It’s Okay To Be Smart, I talked about why the moon orbits the Earth. If you haven’t watched it yet, give it a look. I’ll wait.

There’s some pretty interesting and counterintuitive astrophysics keeping the moon orbiting Earth and not getting gobbled up by the sun. But I left one thing out of that video. The moon doesn’t really orbit the Earth. Strictly speaking, the moon and the Earth orbit each other.  

Just like the Earth exerts a gravitational force on the moon, the moon and its mass are “tugging” right back on us. As a result, the two bodies are actually orbiting a point in between, called the barycenter.

If you’ve ever watched pairs figure skating, you’ve seen this in action. When spinning through this move, called a “death spiral”, the two skaters are actually rotating around a barycenter in between their two centers of mass:

This is true of any two orbiting objects, whether it’s a pair of binary stars, a planet and its star, or a planet and its moon(s). You can think of it just like a playground see-saw, with the masses and distance between the two orbiting objects determining where the “balance” point is. 

The Earth/Moon barycenter is about 1,700 km beneath the crust:

Jupiter, despite being more than five times farther from our central star than Earth is, is so massive that its barycenter lies outside of the Sun:

The Earth-Sun barycenter, on the other hand, is effectively in the center of the sun. Our mass is just peanuts compared to that of that huge burning ball of hot gas:

When two orbiting bodies have similar masses and are relatively close to each other, it can be tough to figure out who’s orbiting whom. This is one reason that some astronomers think Pluto and its moon Charon are more of a double-dwarf-planet system:

Scientists use the see-saw physics of barycenters to study planets in distant solar systems, observing these wobbly waltzes to discover planets that we can’t see with telescopes.

The dig deeper into this cool bit of astrophysics, check out this article from my friend Chris Crockett. And cue the Dead or Alive…

A viewing favorite

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SUNSET IN MARS’ GALE CRATER  

Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at.  It matters that you don’t just give up.

Stephen Hawking, who turns 74 today. Happy birthday! (via astrowhat)

Jupiter as seen in 1879 and 2014. Weve come a long way

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On the care and keeping of your scientist

Congratulations on adopting a scientist! Regardless of their field they will require much coffee, free food, and love. Here are some field specific tips for keeping your scientist happy and healthy!

Biology: make sure they don't get overly invested in their model organism by reminding them about the flaws inherent in their system on a regular basis, but also make sure to join in when they criticize other models in favor of their own

Chemistry: don't let them do that 'just one more reaction' at 10 pm. make sure they get out of the lab and see the sun on a regular basis. try to keep them from partying too hard when they do leave the lab

Geology: humor their rock puns but don't let the lick the rocks (they will tell you they need to lick the rocks to identify them, but don't fall for it)

Astronomy: try not to let them become completely nocturnal. point out nice stars to them and look suitably impressed by their "pictures" of planets that don't look like anything to you

Physics: take them to the park on a regular basis to remind them that things larger than subatomic particles exist. bring a frisbee or a ball to play catch with and be impressed by their ability to calculate trajectories

Math: always make sure to have free batteries for their calculators and a mathmatica user guide on hand. Humor them when they tell you why space without angles is important

Ecology: make sure they remember to wear sunscreen and keep an eye on them in the field. Remind them to come inside and analyze their data occasionally

Psychology: don't mention Freud or ever call them a soft or social science, but make sure you gently remind them that social factors can impact reproducibility and try to keep them from drawing sweeping conclusions about the inherent nature of humanity

Neuroscience: be suitably impressed by their newest experiment and then remind them that people are not mice as often as possible

Computer Science: make sure they take breaks while debugging by limiting their supply of coffee. Nod and smile when they go off on indexing and arrays. Make sure they always have a rubber duck.

Make sure to keep your scientist away from engineers unless they have been properly socialized to interact in a translational household. The most important thing is to remember to hug your scientist on a regular basis and remind them that there is life outside the lab