How to Explain Black Holes to Children

stewartleeThe funny thing about having little kids (I’ve got a two year old and a six year old now) is they ask you questions about gravity or the alignment of planets or reproductive cycles or the seasons or weather, and I can’t remember the answers, and I have to go away and look them up, and I find them faintly terrifying. It’s such a massive idea. The great thing about having kids is you don’t want to lie to them and you don’t want to fob them off with some half measure,…so having kids that ask difficult questions reawakens the sort of wonder of science to you on a weekly basis because they ask you things you don’t know about….[He] asks me questions about stars and black holes and suns and light and time, so you do have to reach back into what you remember from school or go and look it up in a kid’s book or like an Idiot’s Guide to Time and to try and find yourself explaining it [as] a child.

These are the words spoken by British comedian Stewart Lee in an issue of The Incomplete Map of the Cosmic Genome. How do you explain a black hole to a child? There are several different ways to go about it.

Personification

You may consider going anthropomorphic. In the new self-published kids book Peter and the Black Hole, Krystyna LaRose, mother of four, likens the state of a black hole to the state of a stressed-out kid who is so upset, his true self is hidden beneath the emotional outpour. The star is so stressed that it is invisible.

peterblackhole2
Peter and the Black Hole is illustrated by Raquel Rodriguez

 

Simile

If you look at something like kidsastronomy.com, you get a lot of analogies. The sucking power of a black hole is likened to the sucking power of a vacuum cleaner. The “squishing” power of a black hole is likened to the squishing power of a sponge–that is, something large that is full of empty space can squish down to take up less space but be denser, in the same way that matter is filled up mostly with empty space. What I like about this site is that in addition to the similes, it uses the real terms like “event horizon” and “singularity.”

 

Plain English

Randall Munroe’s books have exploded in popularity recently. What If? has been co-opted on the front tables of bookstores everywhere. His kids book The Thing Explainer has seen equal success. The premise of The Thing Explainer is that author Randall Munroe has a list of the thousand most commonly used words and is only allowed to use these words to explain how complicated things work–from the international space station to microwaves. Essentially, while its mission is to explain the world in plain English, it is a text that goes out of its way not to call anything by its real name. It’s an interesting experiment Munroe has done here, but while “bridge” may not make the list of top thousand most common words, it is in plain English and does not need to be referred to as “a very tall road.” I question whether using an arbitrary set of words only is really how we should be teaching children. Perhaps it is a good supplement for kids who struggle with jargon, but I was surprised to read in the New York Times this week that parts of this book are being incorporated into high school textbooks starting next year.

Tell them what you find interesting

Chances are, if you find something interesting, so will your child. You don’t have to pick out the most basic elements of an idea and try to make it interesting. There are ideas within black holes that fill you with wonder, so tell those things to your kids. For example, the answer to “What happens if you fall into a black hole?” is fascinating to both children and adults. In The Eye of Harmony, Professor Brian Cox says, “Mass and energy curve space and time.” In Cox’s example, he uses comedian Rufus Hound as a guinea pig to send into a hypothetical black hole. Rufus has a clock strapped to his back, and that clock sends out a burst of light at each tick, which can be seen by observers (us) from a safe distance. As Rufus approaches the black hole’s event horizon, his clock ticks slower and slower. Rufus is perceiving time normally, but to us, the bursts of light are getting farther and farther apart until he’s at the event horizon. At that point, that light burst never reaches us. Cox says,

cox-smallSo time stops, from our perspective. We see that frozen image of Rufus. He never makes it across the horizon from our vantage point. According to him, everything proceeds quite normally (although he’s getting spaghettified, it has to be said) until he gets squashed on the singularity. This image of Rufus frozen forever at the horizon. But here’s the wonderful thing. The same is true for the collapsing star itself.

If you or your child is worried about falling into a black hole, don’t worry. It’s extremely unlikely. In an issue of The Incomplete Map of the Cosmic Genome, Dr. Chiara Mingarelli explains:

Chiara Mingarelli copyThey’re not really holes and they’re not really black and they’re not after anyone! No, there’s no real danger of the Earth falling into a black hole or being gobbled up by one. There are some relatively nearby black holes but they have a few times the mass of the sun and they’re not rogue black holes going through various solar systems, although that could happen at some point but it’s so random and so rare that it’s not really worth worrying about, so that’s one of my childhood fears put to rest! 

 

If you would like to subscribe to The Incomplete Map of the Cosmic Genome, it is an inexpensive web video-based popular science magazine that can be purchased by subscription here.

 

Nelson Noven is Anglonerd magazine’s science and culture correspondent.
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