I am confused by a question brought to me by one of my students who has
been reading about the SOHO spacevehicle. It has been inserted in an orbit
about the Sun at a Lagrange point ( defined as a point where Sun's Gravity
and Earth's Gravity fields balance). The press release I just read from the
net say it should be stable there fro 20 years due to wonderful work of
insertion.
Here I have trouble: Is the net force at the Lagrange point zero? If so,
how does it manage to orbit at all? Is it not an unstable equilibrium?
I suspect that there is something rather rudimentary that I am overlooking
and I also know that real world Physics is more complex that high school
physics, but...I could use some help.