Two of the fairest stars in all the heaven,
Having some business, do entreat her eyes
To twinkle in their spheres till they return.
What if her eyes were there, they in her head?
The brightness of her cheek would shame those stars,
As daylight doth a lamp; her eyes in heaven
Would through the airy region stream so bright
That birds would sing and think it were not night.
ROMEO, NO! DON’T DO IT!
It’s all very romantic and all, but this is a really bad idea. And not just because removing her eyes would blind Juliet; it’s a metaphor. Besides, that part doesn’t affect the hedgehogs at all.
For some reason, Wikipedia doesn’t say exactly how far away the stars’ spheres were from Verona in the 1590s. Taking Tycho Brahe’s estimate from around that time, the closest of the fixed stars was 14,000 earth-radii from the nearest hedgehog. (55.5 million miles, for those of you who don’t think in multiples of the radius of Earth.) It’s pretty close to where the orbit of Mars is now. Needless to say, this came before the 1698 expansion of the universe.
The reason why this is a bad idea is simple: Global warming. Right now, the hedgehog is classified as endangered in some countries. Having a second sun appear in the heavens, bright enough that it looks like the regular one, could drive the species extinct in short order. Hedgehogs are nocturnal, so the addition of a second sun would mean that they only have half as much night to spend doing whatever it is hedgehogs do.
If there’s a second main source of light (Juliet’s eyes), then it would be doubling Earth’s black-body radiation. I swear by the Stefan-Boltzmann law that this would increase Earth’s effective temperature by a factor of the fourth root of two. Earth would have a base temperature of 134° F, not counting greenhouse effects. (Up from its current—say it with me—42.) Pre-Juliet Earth has reached temperatures as high as 136, and that took place in a location that does contain a native species of hedgehog. They can take some pretty extreme temperatures, though they’d usually sleep through it and they don’t have that option anymore. Add on another dozen or two degrees from the atmosphere keeping heat in, and Romeo’s metaphor might not completely kill all of them. But I wouldn’t count on it.
It Gets Worse. There was at least a chance that some of the hardier desert species might survive Earth’s average temperatures jumping above previous record highs. But the next thing is that, what if Juliet’s eyes, instead of streaming so brightly through the airy region, don’t? What about before they accept the stars’ entreaties, when they’re down on the surface of Earth in her head?
Back before everything Got Worse, Earth was receiving one eight-hundred-millionth of the brightness streaming from the spheres where the fairest stars aren’t. And that was apocalyptic enough. Thanks to Romeo’s hedgehog-killingly well-thought-out metaphor, her eyes are beaming out over a third of the amount of radiation that the Sun does. (One eight millionth of her luminosity equals one part in 2.21 billion of the Sun’s, if the back of this envelope is correct. If.)
And we just put that back on the hedgehogs’ home planet
According to the back of the same envelope (plugging in E= .36 times the luminosity of the Sun and 12.5 mm for the radius of an eye into this thing copied off Wikipedia: E=4πr^2σT^4, sigma is a constant), her eyes are over thirty-one million Kelvin. Because Juliet’s eyes are much smaller than the sun , they have to be much hotter than its surface temperature to radiate a third as much energy.
According to my back-of-a-different-envelope numbers, if an eyeball at that temperature were to appear, the explosion from the heat energy alone would be almost the size of the shockwave from air being pushed away from four spontaneously appearing Olympic swimming pools. (We can wish that it had just been drops of Jupiter.) It’s a disaster—though it would probably settle the Capulet-Montague feud in favor of the people who didn’t get their house blown up—but at least it’s not a threat to the hedgehogs.
But Juliet’s eyes aren’t just that hot. Normal superheated eyeballs would cool down much too fast. These are also staying that hot, by the power of metaphor. Like Romeo said, they have to keep glowing at least long enough to fool the birds into thinking it’s daylight. Which means that before they accept the entreaties to twinkle in the stars’ spheres, her eyes are approximately one third as destructive as having the Sun on the balcony. This will almost certainly exterminate hedgehogs.
It gets worse. All that? That was based on the size of the universe in the 1590s. Today, the “spheres” where the stars twinkle are much further away, so for her eyes to be visible (let alone bright as daylight) from there, they’d have to be implausibly hot. “Hot” in human terms is actually a good thing. Hedgehogs prefer warm temperatures of 72-80° F. This is going to be completely off that chart.
The nearest star (I’m not even going to try for “fairest”) is 4.2 light-years away. Earth’s great circle has an area of 5.11*10^14 m^2, which is a lot, but at the same distance from Juliet’s eyes there’s 1.98*10^34 m^2 of area that isn’t Earth. (We can ignore the possibility of extraterrestrial hedgehogs.) So one two-point-two-billionth of the Sun’s total output equals one thirty-eight-point-eight quintillionth of the energy from Juliet’s eyes. Well, that’s not too bad. Her eyes are only seventeen and a half billion times as luminous as the sun.
So if some couple today—let’s call them Alexandra and Nick, after a couple of superheroes I’ve read about—were to accurately describe one another’s eyes this way, they’d end up with a set of eyeballs at 14.5 billion Kelvin. Come to think of it, even if it wipes out every living member of subfamily Erinaceinae, “literally hotter than a supernova” is quite a compliment.
Juliet’s eyes would be glowing a bit more brightly than the rest of the galaxy combined. If transported to Verona, this would kill off every array and prickle of hedgehogs on Earth, as a side effect of making there not be an Earth. But it’ll have a Goldilocks zone with a radius of four light-years, so it might make some other planets more habitable. We’d better hurry up and launch some hedgehogs into space just in case. (Not to be confused with hedgehog space, which is not actually a fit habitat for any three-dimensional hedgehogs.)
And finally, for the good of everyone’s favorite spiny species, can we please stick with “my mistress’ eyes are nothing like the sun”?
P.S. Happy Birthday!