Science & Technology

Those of us trying to lose some pounds after overindulging this holiday season can get help from a slew of smartphone apps that count steps climbed and calories burned. Self-tracking has also become a way for companies to make money using your fitness data. And some experts worry that the data collected could be used against users in the long run.

At a recent Quantified Self Meetup in downtown San Francisco, technology lovers are testing homemade do-it-yourself devices on people eager to measure their mind and body.

Now that the Christmas feast is over, you may be looking at all the extra food you made, or the food that you brought home from the store that never even got opened.

And you may be wondering: How long can I keep this? What if it's past its expiration date? Who even comes up with those dates on food, anyway, and what do they mean?

Here's the short answer: Those "sell by" dates are there to protect the reputation of the food. They have very little to do with food safety. If you're worried whether food is still OK to eat, just smell it.

Transcript

(SOUNDBITE OF MUSIC)

DAVID GREENE, HOST:

It's MORNING EDITION from NPR News. Good morning. I'm David Greene.

Let's begin our show this Christmas Day with a look back at a business development this year that took many investors by surprise. Just over three months ago, Apple's stock hit a record high - for a few days in September a single share was selling for more than $700. But since then, Apple's stock has tanked. In December, it traded briefly below $500 a share.

With billions of children to visit in just one night, how does Santa make it to every house? And how does he fit down the chimney — assuming your house has one. Astrophysicist Neil De Grasse Tyson talks to David Greene about the science of Santa.