At the height of rush hour at 5:28 p.m. on November 9, 1965, 30 million people in about a half-dozen states, including New York and two Canadian provinces, were plunged into darkness.

Dubbed the Great Blackout of 1965, its cause was a faulty relay station in Ontario, Canada, that sent an overloading power surge over transmission lines.

The same sort of thing can happen to someone who's had too much to drink.

According to the director of the National Institute on Alcohol Abuse and Alcoholism (part of the National Institutes of Health), too much alcohol "shuts down the ability of the brain to consolidate memories."

When you've passed the legal driving limit of blood alcohol concentration (0.08) and get up to around 0.16, ethanol — the compound in alcohol that causes drunken symptoms — crosses the blood-brain barrier, targeting receptors in the hippocampus (where memories are kept), and memory-making signals are blocked.

The result is a gap in time, or a “blackout.”

The good news is that the damage isn't permanent, although chronic excess drinking does irreversibly damage the brain. The bad news is you could have gone from a Dr. Jekyll to a Mr. Hyde, done something terrible, as Mr. Hyde did, and not remember it.

The NIH advises that if you want to drink responsibly, know your limit. You can avoid blackouts by not drinking to the point of slurring words, becoming uncoordinated, or vomiting.