CNN 2011-02-07（在线收听）

President Mubarak is the leader of a country that's in the middle of a political uprising. Protests against the government have been going on all across Egypt, and experts think there could be a lot more demonstrations starting today. The Muslim Brotherhood, the largest group of protesters, is speaking out against President Mubarak's government. It's telling its followers to protest in the streets after today's weekly Muslim prayers end.

In some cases, protesters have fought with police officers. They've thrown things at the security forces. And those forces have used tear gas to try to break up the crowds. At least three protesters and one police officer have been killed this week. Social networking is playing a role in all of this, too. A lot of the protests are being organized on blogs and sites like Twitter and Facebook.

Focusing on a single event in our "This Day in History" segment. On January 28th, 1986 -- exactly 25 years ago today -- the space shuttle Challenger exploded less than two minutes after liftoff, killing all seven people on board.

One of those seven people was Christa McAuliffe. She wasn't an official government employee, like most other astronauts. She was a teacher. And she was picked from a group of more than 11,000 people in the field of education to journey into space. John Zarrella shows us how, 25 years after McAuliffe's tragic death, she's still inspiring young people.

The fifth graders at Francis Scott Key Elementary School in Arlington, Virginia know quite a bit about space.

I want to be able to drive rovers on Mars.

I just recently learned from my brother that the constellations have moved, which is very interesting!

There's a good reason. A picture of Christa McAuliffe, the first teacher in space, sits on a cabinet in the classroom. The kids know who she is not so much from history books, but from their teacher.

The woman moaned. This tooth must come out.

You see, their teacher Micaela Pond is connected to McAuliffe in a way that simply cannot fade over time.

I feel very lucky to have known her, and I try very much to inspire my students. Whatever your dream may be, it's possible.

A quarter century ago, Pond babysat Christa's kids and knew McAuliffe from Sunday school. A junior at Concord High in New Hampshire where McAuliffe taught, she sat in the auditorium with other students that January morning.

And then we heard, "Roger, go with throttle up."

Challenger, go with throttle up.

And that phrase, "obviously there's been a major malfunction."

Flight controllers here looking very carefully at the situation, obviously a major malfunction.

I think the realization hit us quite quickly that this isn't good.

Seventy-three seconds into the flight, McAuliffe and the six other astronauts perished when Challenger exploded. The accident was caused by bitter cold combined with a faulty rocket booster seal. But the tears that fell that day soon turned to a river of inspiration, leading Pond and many others to follow Christa's path.

I think Christa would be very proud of the legacy she's left. I think she would be ecstatic to know that her students went on to be teachers and were inspired by her.

McAuliffe called her flight the ultimate field trip.

I don't think any teacher has ever been more ready.

She never got to teach her lessons from space. But today, Pond is one of so many who teach because of Christa McAuliffe. John Zarrella, CNN, at the Kennedy Space Center in Florida.