AMNA NAWAZ: Forty years ago today, the Challenger# space shuttle exploded on live television just 73## seconds after liftoff.

All seven astronauts# aboard died, including Christa McAuliffe,## the first teacher and ordinary citizen to fly# in space, plunging the nation into mourning.

GEOFF BENNETT: I spoke with# our science correspondent,## Miles O'Brien, who has covered# the space program for decades,## about that moment and how it changed the# country for our video podcast "Settle In."

Here's some of that conversation.

Why was this particular launch -- why did it## capture the public's imagination in# a way that previous launches hadn't?

MILES O'BRIEN: It was all# about the teacher, Geoff,## Christa McAuliffe, elementary school# teacher from Concord, New Hampshire,## who had participated in a nationwide contest# to become the first teacher in space.

She was a fabulous, interesting character# and won the rights to fly on the shuttle as## the shuttle program turned toward allowing# civilians to fly in space.

And they were## leaning toward trying to show the world that# the space shuttle system was routine and could## get people to space, everyday people to# space, in a relatively inexpensive way.

1986, they had 15 flights on the manifest, way,## way beyond anything it had attempted in the# past.

It was going to launch spy satellites,## commercial satellites, scientific missions.# And they were really kind of hell-bent to## prove that this system was reliable enough# for a teacher to fly and give lessons.

And so the world was fixated on that after 24# previous flights.

The first flight, of course,## in 1981 got a lot of attention.

Then many of the# flights fell off the front page of the newspapers,## but this one really captured# hearts and minds and pointedly,## sadly, was watched by hundreds of thousands of# schoolkids in their classrooms that morning.

GEOFF BENNETT: You happened to be there that# day.

Set the scene for us.

What was it like?

MILES O'BRIEN: Well, I wasn't quite# there.

I was -- but I was close enough.

You have to remember this was a record cold snap# in Florida, a 100-year record.

I was a 26-year-old## green reporter working in local news in Tampa,# Florida.

And I had spent the entire night in a## citrus grove doing live reports with a grower who# was worried about losing his crops because of the## bitter cold.

It was down in the teens, and, in# Florida, that's something that people remember.

And after a full night of work, I went to# sleep and was awakened by the assignment## editor at my station, saying: "The shuttle has# exploded."

And I couldn't even process that.

And I went outside in my house -- at my# house in Tampa, and I looked up in this## impossibly Bluesky, and I could see the# remnants of the contrail of Challenger,## and it was like a big, giant Y in# the sky.

This is 150 miles away,## and it just kind of hung there like# a pall over the state and the city.

And so I got busy doing the local news assignment,## but it's hard to overstate how much of a shock# this was to the country.

Up until that time,## NASA, despite the fact that it had a terrible# accident in 1967, the Apollo 1 accident, where## three crew members were incinerated on a launchpad# during a test, but that was out of public view.

This was something everyone saw instantly.

It was# broadcast live on CNN.And the world watched it,## and children were connected to it.

And there was# a profound sense of loss of innocence, I think,## for NASA, which at that point really,# in the public's mind, could do no wrong.

GEOFF BENNETT: A loss of innocence for NASA.

I mean, did it feel like the nation and the world## in mourning in real time?

What# was the immediate aftermath like?

MILES O'BRIEN: Yes, it was a pall.

And Ronald Reagan was supposed to deliver his# State of the Union address tha.. for a time, he thought -- they thought they would# press on and actually give that address, but,## eventually, they canceled the State of the Union.

And, instead, he gave an Oval Office speech## that was -- it was authored by his# famous speechwriter Peggy Noonan.

RONALD REAGAN, Former President of the# United States: The crew of the space## shuttle Challenger honored us with the# mann.. We will never forget them, nor the last time# we saw them this morning, as they prepared for## their journey and waved goodbye, and slipped the# surly bonds of Earth to touch the face of God.

MILES O'BRIEN: It was a collective## tragedy that I think at that point# only rivaled the assassination of JFK.

GEOFF BENNETT: And you can find that# full conversation and all episodes of## "Settle In" from PBS News on our YouTube# page and wherever you get your podcasts.