Just how frigid is the polar vortex dropping a blast of cold air on the Midwest this week? Depending on who you listen to you, it's colder than Alaska, the North Pole, or even base camp on Mt. Everest. Jimmy Fallon opened his Tonight Show monologue on Tuesday night by saying its colder than Antarctica.

Who's right? They all are, but they're not making up these comparisons on their own. People are repeating analogies they're hearing from scientists and meteorologists--skilled communicators who know how to get information across in a way that you'll remember and share with others.

On Wednesday morning, a host on the Weather Channel warned that in Chicago, the temperature had dropped to 20 degrees below zero. A 20 mile-per-hour wind chill made it 'feel' like 40 to 50 below. "These are numbers that are almost impossible to wrap your brain around," he concluded.

That's right. The numbers are too big. The human brain isn't built to analyze large numbers easily. Instead, our brains have created a mental shortcut--analogy. We process our world in analogy, we speak in analogy, and we like to get information in analogy.

In a dangerous situation where life-saving information must get out quickly, analogies are incredibly powerful. Analogies are also important for any educator or communicator who needs to be put big numbers into perspective. Neuroscientists say analogies can be very powerful teaching teaching tools because they give people a mental framework on which to build new knowledge.  

An analogy, of course, is comparing something abstract or unfamiliar to something concrete or familiar. As far back as ancient Greece, philosophers like Aristotle recommended speaking in analogies because they help your audience understand topics they know little about. Since this week's polar vortex is bringing the coldest air in a generation, millions of people in the U.S. don't have never experienced anything quite as cold.

The coldest day I recall while attending Northwestern University in Chicago was minus 10 degrees. How much colder is 50 below? I'd need an analogy to understand it.

Dave Malkoff, a Weather Channel reporter in Cedar Rapids, Iowa, used visual analogies to explain how dangerously cold it was. He threw a cup of hot water into the air and watched it instantly turn to snow. It came down as a sheet of icy flurries. He then took a cup of hot coffee, turned it upside down and watched a brown chunk of ice drop out. "It's turned into a frozen hockey cup," he said.

Not to be outdone in the world of analogy, an Iowa television station interviewed workers in a freezer plant who couldn't wait to get on the job because it was warmer in the deep freeze cooler than it was outside.

If you want to grab people's attention, find an analogy that gives your listener a mental shortcut. Be careful, though. Analogies are so irresistible, people sometimes go overboard to find one. Is Chicago really colder than Mars today? It seems as though that popular comparison might be a stretch, according to astronomers. But if it's colder than base camp on Everest, that's all I need to know.