Darkness for Health Scientists have now discovered that only when it's really dark can your body produce the hormone called melatonin. Melatonin fights diseases, including breast and prostate cancer. But if there's even a little light around your bed at night, your melatonin production switches off. Even watching TV turns on other immune system hormones that should be active only in daytime. They get depleted, and you're more likely to get a cold.
Nature needs darkness, too.
The immune systems of animals grow weak if there's artificial light at night. It turns out that's easy to fix. Lights that spill so much glare up into the sky that it even wipes out the stars can be shielded with reflectors to focus on the light and make them more efficient. Or, you can simply switch off the lights. At the Sears Tower in Chicago, they are turning out the lights to save the birds.