Space Debris
Dear David,
First of all please accept my thanks and regards as you have clarified
many astronomical puzzle for which I was searching the correct answer. I
am writing to you after a long time.
As I know from Internet web site that plenty of space debris is
revolving around the Earth at various altitude and definitely at
different speeds.
Frequently NASA or ESA etc sends an artificial satellite or space shuttle
around Earth's orbit at a distance of more than 200 KM to 40000 KM. Even
in 1994 astronaut Mark Lee was found flying over earth's surface as satellite.
How do they avoid collision and monitor the movement of such unwanted
space debris as the danger appears due very high speed?
Reply
Dear Bishnu
Space debris is gradually being recognized as a serious problem, and
at least one collision has already been reported, involving a French
satellite. The density of spacecraft is still low, so the risk is small,
but it is not zero. The US Navy is monitoring such objects by radar and
yes, the number is increasing.
The solution is uncertain. Low altitude orbits and highly elliptical
ones reenter the atmosphere after a while, but communication satellites
in synchronous orbit, of which hundreds now exist, will stay around for
millions of years unless picked up.
The danger also exists on the space station, even though at its low
altitude debris does not last as long as at higher ones. One helpful
fact is that most satellites are launched towards the east, so when they
overtake their mutual velocity is only part of their total velocity.
Still, collisions between satellites whose orbits have different
inclinations to the equator can be very damaging.
Teaching Nuclear Fusion
As a 7th grade science teacher, I have been looking through many websites, to find activities to teach
sun's fusion reaction "in a nutshell." That is how I came across yours sections S-7 and S-7A.
Actually, I have been looking for a more kinesthetic "hands on"
approach but hopefully I can take your material and "soften the edges"
to make it more middle school friendly (although our population of
students tends to be academically inclined and I hope that I won't have
to take off too many edges). I hope to be able some way to come up with
something like M&M's for them to experience fusion tastefully!