The dog is standing at the window, wagging her tail excitedly. I look outside, and the back yard is empty. "What are you looking at?" I ask.
"Bunnies made of cheese!," she says. I look again, and the yard is still empty.
"There are no bunnies out there," I say, "and there are certainly not any bunnies made of cheese. The back yard is empty."
"But particles are created out of empty space all the time, right?"
"Have you been reading my quantum physics books again?"
"It's boring here when you're not home. Anyway, answer the question."
"Well, yes, in a sense. They're called 'virtual particles,' and the zero-point energy of the vacuum can occasionally manifest as particle-anti-particle pairs."
"See?" she says, wagging her tail harder, "Bunnies made of cheese!"
"I'm not sure how that helps you," I say. "The virtual particles that are created from vacuum fluctiations have to annihiliate in a very short time, in order to satisfy the energy-time uncertainty relationship. A virtual electron-positron pair lasts something like 10-20 seconds before it disappears. They're not real particles."
"But they can become real, right?" She looks a little concerned. "I mean, what about Hawking radiation?"
"Well, yeah, in a sense. The idea is that a virtual pair created near the event horizon of a black hole can have one of its members sucked into the black hole, at which point, the other particle zips off and becomes real. The energy to account for the mass has to come from somewhere, so the black hole loses a tiny bit of mass."
The tail-wagging picks back up. "Bunnies made of cheese!"
She gives an exasperated sigh. "Look, virtual particles are created all the time, right? Including in our back yard?"
"Yes, that's right."
"Including bunnies, yes?"
"Well, technically, it would have to be a bunny-anti-bunny pair..."
"And these bunnies, they could be made of cheese."
"It's not very likely, but I suppose in a Max Tegmark sort of 'everything possible must exist' kind of universe, then yes, there's a possibility that a bunny-anti-bunny pair made of cheese (and anti-cheese) might be created in the back yard, but..."
"And if I eat one, the other becomes real." She's wagging her tail so hard that her whole rear end is shaking.
"Yeah, but they wouldn't last very long before they annihiliated..."
"I'm very fast."
"Given the mass of a bunny, they'd only last 10-34 seconds. If that."
"In that case, you'd better let me outside. So I can catch the bunnies made of cheese."
I sigh. "If you wanted to go outside, why didn't you just say that?"
"What sort of blog post would that be? Anyway, bunnies made of cheese!"
I look out the window again. "I still don't see any bunnies, but there is a squirrel by the bird feeder."
"Ooooo! Squirrels!" I open the door, and she goes charging outside, in the wrong direction.
She's a very silly dog.
(Update 5/15/07: After another dog post got Digged, the folks at CNET's "Buzz Out Loud" podcast did a dramatic reading of this entry. I don't see a way to permalink individual episodes, but it's the May 11, 2007 podcast, and at least at the time of this writing this is a direct link to the MP3. It's way at the end of the show, and I'm inordinately amused by this. Of course, the dog think it's only her due...)
This post brought to you by Rabbit Hole Day...
That's absolutely hysterical! What a great, simple, engaging presentation of a bit of science most people don't understand—or even know about. Bravo!
Also, thank you for the warning. I'll have to make sure our dog doesn't get into my microbiology books - who knows what'll happen if she notices Lourens Bass-Becking's comment about "Everything is Everywhere"...
Delightful and enlightening. Thank you, Chad.
I am surprised however that Emmy didn't bring up the absolute proof of the existence of bunnies made of cheese -- Welsh Rabbit. ;-)
That was hilarious!
What a wonderful, engaging article. I've bookmarked it as an example of popular science done right (not to mention forwarded it to all my dog-loving friends :)).
Yes but what KIND of cheese were the bunnies made of?? It seems to me that some kinds of cheese bunnies would be more likely than others... in the grand scheme of cheese bunnies... you know...
No discussion regarding bunnies made of cheese would be complete without a link to the following story:
Highly recommended to read aloud to friends.
Hello Dog, my name is Cheese (yes really) and I'm a greyhound. Sometimes I catch bunnies, not very often I grant you mainly because my stupid humans don't like it and stop me given the chance. Anyway, on the basis of "you are what you eat" I suggest that although bunnies made of cheese are a dubious idea, Cheese made of bunnies actually does exist.
Licks and buttsniffs.
Hello Dog, my name is Cheese (yes really) and I'm a greyhound. Sometimes I catch bunnies, not very often I grant you (mainly because my stupid humans don't like it and stop me given the chance). Anyway, on the basis of "you are what you eat" I suggest that although bunnies made of cheese are a dubious idea, Cheese made of bunnies actually does exist.
Licks and buttsniffs.
I've always understood Hawkings radiation as an anti-virtual-particle entering the black hole's event horizon, while the "positive" particle escapes into the universe. The black hole would then be reduced by the anti-particle.
What's confusing is that, given that these virtual particle pairs appear randomluy, wouldn't it work out to about 50% of the time where the positive particle enters the black hole and the anti-particle escapes? That is, wouldn't it work out that the mass of a black hole remains constant? (You would still have radiation, it just wouldn't reduce the black hole's mass because it would consist of a roughly equal amount of particles and anti-particles.)
I'm pretty sure my understanding of this process has a hole somewhere...
What's confusing is that, given that these virtual particle pairs appear randomluy, wouldn't it work out to about 50% of the time where the positive particle enters the black hole and the anti-particle escapes? That is, wouldn't it work out that the mass of a black hole remains constant?
The mistake you're making is in assuming that anti-particles have negative mass. In fact, both particles and anti-particles have positive mass, so whichever one escapes being eaten by the black hole increases the total mass of the larger universe. That mass increase has to come from somewhere, because energy needs to be conserved on longer time scales, and the mass of the black hole is reduced as a result.
Ahh, well there goes the intuitive reason then. Who'd have thought that a black hole gaining a particle would actually reduce it by the mass of two particles?
Strange world, ain't it?
Hi, as soon as I saw the link (below) I remembered this post. I think maybe this advertising company reads your blog? Bunnies of cheese indeed ...
The Buzz Out Loud CNET Podcast hosts are off doing holiday stuff today (7/3/2009) and they did a hilarious mashup using their past episodes. The dramatic reading of this was included, which is how I found this entry. You made me laugh, cry, and look confused at the same time. =) Love the post!
NB: Do not bite the anti-bunny. You can determine the anti-bunny very simply by looking for a coating of nuclear flame.
I come here by sheer chance, I started reading... and I couldn't leave till the end.
Congrats for your blog, for your science knowledge and for your writing capability.
I'll come back to this blog again, for sure. :D