Current Weather
The Spy FM

Watts For Lunch? (Or Why Humans Are Like Light Bulbs)

Filed by KOSU News in Science.
June 10, 2013

There’s a new lunch place down the block, so like you do when the menu looks interesting, I walked in and ordered something mysterious, which for me was the “Red Lentil and Edamame Salad,” mostly because I can never remember what edamame is, and because that word suggests doing something slightly frightening, like munching accidentally on one’s mother.

How Much Energy Am I Eating? Enough To Power A Flashlight?

What arrived was a bowl of lentils, roasted carrots, raisins, mint and (I’m guessing) edamame beans. I took the bowl to a window seat, and that’s when my mind began to wander. My mind doesn’t need much to go free. It slips off whenever I let it, when I’m by myself and alone with my thoughts, which, at this moment, were: “So I’m chewing these beans and I’m breaking them into little bits, which will become littler bits in my stomach, (bond-breaking, as the chemists would say) so I’m turning food into energy. But how much energy am I getting? Does a salad produce enough calories or watts or whatever, to light a flashlight? Or run an electric toothbrush for 10 minutes?

(Do you ever do this? I do this all the time.)

After lunch I looked up the answer. I found it in a fine little book by Wayne State Professor Peter Hoffman, called Life’s Ratchet: How Molecular Machines Extract Order from Chaos. In it, he says humans will typically eat roughly 2,500 calories a day.

1.5 Million Joules Is … ?

Professor Hoffman is a physicist. He goes on to make some quick calculations. If one food calorie equals 4,184 joules of energy, at 2,500 calories a day, that means our bodies break down or release 1.5 million joules. Sounds like a lot, no? But if you divide those joules by the number of seconds in a day (86,400), that works out to a rate (where 1 watt = 1 joule per second) of about — 120 watts a day. In other words, that’s all I need to dream, wake, dress, shower, work, walk to a restaurant, order a salad, ask myself how much energy am I using, and then look it up, think about it, and write this essay. I can power all trillion cells (of me) for a day at the same rate that it takes to light one 120-watt light bulb.

That’s it?

That’s it. Peter Hoffman writes, “Humans talk, write, walk and love using the same amount of energy per second as a light bulb.”

I’m humbled. I will now confess that when I got back from the salad place, I diddled, I called friends, yakked with office mates and used up lots of time to avoid writing this, and yet — down deep, at a cellular level, it turns out I’m a mind-boggling display of energy efficiency. You too, of course.

On certain afternoons, this is a nice thing to know. [Copyright 2013 NPR]

Leave a Reply

5AM to 9AM Morning Edition

Morning Edition

For more than two decades, NPR's Morning Edition has prepared listeners for the day ahead with two hours of up-to-the-minute news, background analysis, commentary, and coverage of arts and sports.

Listen Live Now!

9AM to 10AM The Takeaway

The Takeaway

A fresh alternative in morning news, "The Takeaway" provides a breadth and depth of world, national and regional news coverage that is unprecedented in public media.

View the program guide!

10AM to 11PM On Point

On Point

On Point unites distinct and provocative voices with passionate discussion as it confronts the stories that are at the center of what is important in the world today. Leaving no perspective unchallenged, On Point digs past the surface and into the core of a subject, exposing each of its real world implications.

View the program guide!

Upcoming Events in your area (Submit your event today!)

Streaming audio and podcasts

Stream KOSU on your smartphone

Phone Streaming

SmartPhone listening options on this page are intended for many iPhones, Blackberries, etc. with low-cost software applications available to listen to our full-time web streams, both News on KOSU-1 and Classical on KOSU-2.

Learn more about our complete range of streaming services

We're perfecting the patient experience - Stillwater Medical Center