Seeing or hearing Discovery's return to Earth

For those wanting to follow along today, here are some common questions and answers from people wanting to see or hear the space shuttle Discovery's return to Earth. If you have other questions, click "Space Chat" below and we'd be happy to answer them.

Can I look up and see the shuttle fly overhead?
Not likely today. Discovery will come streaking over North America and into Florida during broad daylight. The plasma trail that is created as the shuttle rips through Earth's atmosphere is not distinct enough to be seen with the naked eye against a bright sky. At night, under a clear sky, you'll have a great view. Today, TV and the Internet are your best bets. We'll have live updates on what is happening here in the Flame Trench and we have a link to view the live NASA TV feed (and some other views at KSC) on your computer, so stick with us throughout the day for the latest and greatest information, images and video. If you want alerts sent to your cell phone, log in to floridatoday.com/text and consider signing up for our text messaging service.

Will I hear the sonic booms?
If the shuttle flies overhead, you should be able to hear the famed twin sonic booms. The closer to the landing site (and lower the altitude of the plunging orbiter), the easier it is for you to hear the booms. Today's landing will provide great opportunities for people in parts of Florida to hear the booms in the final minutes of the shuttle's descent. Take at the landing tracks in the latest post in the Flame Trench for the most up to date path.

Where in Florida will I hear the booms?
That depends on the flight path. The first Florida landing chance would bring the shuttle across northern and eastern Florida, crossing into the state west of Jacksonville heading directly toward the Atlantic Coast. The second Florida landing opportunity would bring the shuttle over the Florida panhandle and then cut across the middle of the state well north of Orlando on an eastern track toward the runway. If you're generally living beneath the flight path and you avoid background noise (loud traffic, for instance), you should be able to hear the booms. Historically, you'd hear the booms along Florida's east coast (if you're under the flight path) about 10 minutes before the touchdown time. Along the Space Coast, you should hear the booms about four to five minutes before touchdown.

What causes the booms?
Air pressure. As the shuttle cuts through the atmosphere flying faster than the speed of sound, air molecules get pushed aisde (like water around a fast-moving boat). The air molecules form a shock wave around the nose and the tail of an aircraft. The rapidly increasing air pressure can be heard as a loud boom.

Why two sonic booms?
The space shuttle is big for a supersonic aircraft. A typical aircraft capable of this kind of speed would be a fighter jet, something about 50 feet or so long. For those small fighters, the shock waves generated at the nose and the tail of the aircraft happen less than one-tenth of a second apart. On the ground, people would hear what sounds like one boom. The orbiter is 122 feet long. The time between the nose and tail shock waves is half of a second, just long enough for us to hear both of the booms.