How Is Ground Coffee Like a Planet? Just Add Zero Gravity.

Bad Astronomy
The entire universe in blog form
Nov. 24 2013 8:00 AM

Planet Espresso

protoplanetary disk
A solar system's baby portrait: A disk of material around a star.

Artwork by Karen L. Teramura / UH IfA

A long time ago — 4.56 billion years ago, give or take an eon or two — the Earth upon which you currently live wasn’t here. Well, not all in one place, at least: It was actually scattered over trillions of cubic kilometers of space, occupying part of a dust-laden disk orbiting the just-forming Sun.

This disk was huge, hundreds of thousands of kilometers thick, and stretching for billions of kilometers out from the Sun. But it wouldn’t stay that way: Over time, pieces of it stuck together, getting bigger, aggregating more and more material. Eventually, those clumps stuck together to form ever-bigger lumps called planetesimals. Once they got big enough that gravity could start actively drawing material in, they grew into proper planets.


Describing this process in general isn’t hard, but nothing beats a good demo. I’ve often wondered if it were possible to do such a thing, and now I know the answer is yes. And of all places, it comes from my old friend Dan Durda, asteroid scientist, who performed a lovely and elegant demonstration of this on the TV show “Richard Hammond Builds a Planet”. The necessary ingredient that never occurred to me? Gravity. Or really, the removal thereof:

Nice. The coffee grounds have a slight charge to them, which makes them stick together into clumps, much like when you rub a balloon on your head and can stick it to a wall. This is actually an annoyance in some coffee grinders, because the electrostatically charged bits stick to the plastic walls of the grinder bucket, making it hard to get them out (and they get all over your hands and clothes).

On the other hand, that same irritating principle is what makes planets, or at least gives them a good start. I’d say that’s good grounds for dismissing the charge.

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  


The World

How Canada’s Shooting Tragedies Have Shaped Its Gun Control Politics

Where Ebola Lives Between Outbreaks

Gunman Killed Inside Canadian Parliament; Soldier Shot at National Monument Dies

Sleater-Kinney Was Once America’s Best Rock Band

Can it be again?

Paul Farmer: Up to 90 Percent of Ebola Patients Should Survive

Is he right?


“I’m Not a Scientist” Is No Excuse

Politicians brag about their ignorance while making ignorant decisions.


Driving in Circles

The autonomous Google car may never actually happen.

In Praise of 13th Grade: Why a Fifth Year of High School Is a Great Idea 

PowerPoint Is the Worst, and Now It’s the Latest Way to Hack Into Your Computer

  News & Politics
Oct. 22 2014 9:42 PM Landslide Landrieu Can the Louisiana Democrat use the powers of incumbency to save herself one more time?
Continuously Operating
Oct. 22 2014 2:38 PM Crack Open an Old One A highly unscientific evaluation of Germany’s oldest breweries.
Gentleman Scholar
Oct. 22 2014 5:54 PM May I Offer to Sharpen My Friends’ Knives? Or would that be rude?
  Double X
The XX Factor
Oct. 22 2014 4:27 PM Three Ways Your Text Messages Change After You Get Married
  Slate Plus
Tv Club
Oct. 22 2014 5:27 PM The Slate Walking Dead Podcast A spoiler-filled discussion of Episodes 1 and 2.
Brow Beat
Oct. 22 2014 10:39 PM Avengers: Age of Ultron Looks Like a Fun, Sprawling, and Extremely Satisfying Sequel
Future Tense
Oct. 22 2014 5:33 PM One More Reason Not to Use PowerPoint: It’s The Gateway for a Serious Windows Vulnerability
  Health & Science
Wild Things
Oct. 22 2014 2:42 PM Orcas, Via Drone, for the First Time Ever
Sports Nut
Oct. 20 2014 5:09 PM Keepaway, on Three. Ready—Break! On his record-breaking touchdown pass, Peyton Manning couldn’t even leave the celebration to chance.