# Evil Squirrels from Extra Dimensions

It’s been a very long day, so I’m lying on the couch watching
“Pardon the Interruption” on ESPN. They’re having a boring
conversation about baseball, and I’m just drifting off into a pleasant
doze when:

Fear! Fire! Foes! Awake! Fear! Fire! Foes! Awake!

I jolt awake. “What are you barking at?!?” I yell at the dog, who
is standing in the middle of the living room, baying at nothing. She
stops.

“Scary things!”

The room is empty. “There’s nothing here,” I say, and then hear a
car door slam. I look outside, and see the mathematician next door
heading into his house. “Were you barking at Bill? He’s harmless!”

She looks sheepish. “No. There were scary things. Evil squirrels!”

“There were not. If there were squirrels here, where did they go?”

“They were evil squirrels. With goatees. They went back into their
home dimension.”

—-

You can read the rest of the conversation, and a more serious physics explanation with it, at the World Science Festival blog. The Festival is June 2-6 in New York City, and I’ll be there on that Sunday signing books as part of the “Author’s Alley” program in the Street Fair.

The dialogue in question was originally written for How to Teach Physics to Your Dog, but that chapter was dropped for length reasons. I really like the dialogue, though, so I’ve hung onto it (and read it a few times at bookstores and cons), and it might yet appear in a sequel, if there is one.

The physics explanation is new, and radically shorter than the original chapter. The chapter also had some diagrams, and a lot more detail about how extra dimensions work, and how they affect gravity. This gets the basic flavor, though, so if you’ve missed the previous talking-physics-with-the-dog posts and book previews, well, this is the sort of thing you’re missing. You can get a whole lot of it, in either dead-tree or electronic format, wherever books are sold.

(This is the one online thing I mentioned earlier. Now I’m off-line for the rest of the day, barring complete catastrophe of some sort.)

1. #1 Neil B
May 18, 2010

I’ve long teased my friends that squirrels must not be real animals. We don’t see their babies despite presumed nests (I figure some would fall out) so I say they reproduce quantum mechanically. (Well, I recently saw a pic of a dog nursing baby squirrels: Dog nurses baby squirrels who lost their home. So they do exist!)

As for other dimensions: hard to say. Compactified ones are still part of “our universe.” Many of those talking multiverse style variations in laws of physics say it’s really effectively-isolated regions of our space, rather than truly separate space-time regimes not contiguous with our own. (But there’s a need for a multiverse of some sort, since many appreciate the logical absurdity of one model universe (“possible world” in the broad, Tegmarkian sense) being granted reification and not others.

BTW it was claimed in comments on Backreaction that it’s wrong to refer to “other universes” because of the meaning of “uni” but REM “atoms”, “Indians” (of America) etc. Words can be flawed.

2. #2 Mike Olson
May 18, 2010

Your writing style is a real hook. I’ve said it before: I really enjoyed your book. A great presentation of heavy, heavy ideas in a style that made it fun.

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