OGDEN -- All this week and last, the Ott Planetarium and Weber State University physics department have been taking phone calls from worried folks.
"People call us and say, 'What's up with this asteroid thing? Is it going to hit us?' " said Stacy Palen, planetarium director and WSU physics associate professor.
"And we say 'No,' then they ask how we know, and we tell them they would have to come up and take some math classes to completely understand, but we really do know the asteroid is not going to hit us."
The asteroid in question is 2012 DA14 and is described by NASA as a small, near-Earth asteroid.
It is due to pass relatively close to Earth today, shortly after noon Mountain Time.
NASA also says there is no chance the asteroid will strike Earth. But 2012 DA14 will pass between the orbit of Earth's communications satellites and the planet's surface.
The asteroid is 150 feet long, about half the length of a football field. At its closest, it will pass 17,000 miles above the planet's surface, Palen said.
For perspective, the asteroid that hit Earth approximately 66 million years ago -- and is believed to be the main factor in the mass extinction of dinosaurs -- is estimated to have been about 6 miles long, said Brad Carroll, WSU physics professor.
"That one had about the same energy as a million nuclear weapons," Carroll said. "It hit off the coast of Mexico, and it dug a huge hole, so there's a crater under water that they've studied and measured.
"This one is only 150 feet, so that's a lot different, and this one is not going to hit the earth. This one is small, and space is pretty big."
Palen said a 330-foot asteroid did hit Earth in 1908, in Siberia. According to historical accounts, it knocked down an estimated 80 million trees over an 830-square-mile area.
"Ones like that, you expect to see every 200 years or so, so we are not technically due for one of those for a while," Palen said. "But it's statistics, so we could also get two every 200 years, then none for 400 years. They're out there, for sure."
Palen said no injuries from the 1908 impact were reported.
"Where it comes down makes a big difference," she said. "It's a bigger problem if it's on top of New York than if it's in the middle of Siberia."
Carroll said 2012 DA14 will approach Earth, passing by our planet's Southern Hemisphere, and will leave passing by the Northern Hemisphere. The asteroid will not reflect much light, so will not be visible to the naked eye.
NASA Television will provide 30 minutes of live commentary about the fly-by today, beginning at noon Mountain Standard Time.
The commentary will incorporate live views from Australia of the asteroid, weather permitting, and related animation. Viewing websites are www.nasa.gov/ntv and www.ustream.tv/nasajpl2. The asteroid will pass closest to Earth at 12:25 p.m. Mountain Standard Time.
Carroll said 2012 DA14's orbit is similar to that of Earth, but tilted. If it were represented by two hula hoops, they would overlap, but one would be slightly raised, he said.
Carroll said scientists may be able to learn about the asteroid's composition based on the way it reflects light.
Palen said some scientists believe there may be seismic activity on 2012 DA14, with vents that release gases.
Earth's gravity will also pull at the asteroid, changing its orbit, Carroll said.
"We won't know how much it will change until after the encounter," he said. "Earth is really going to yank on the asteroid with its gravity. It's going to be deflected, almost as though it is taking a sharp right turn."
Palen said our planet is hit constantly by smaller asteroids.
"There are a lot of these rocks out there, but this one is not a danger to us. We are totally good."