From John Doe :
Brian Gaff wrote:
Are you deliberately being pedantic?If you understand gravity, then you are
the only person on this earth who does. Is there in fact anywhere where
there is zero gravity?

From a practical point of view, free falling or being at a LaGrange
point cancels out the obvious aspects of gravity. But it doesn't
generate 0 gravity environment.

Lagrange points are *not* points where gravity is cancelled out. (One
obvious check it the equilateral L4/L5 points, where the gravity
vectors are at 60 degrees to each other, forming the equilateral
triangle.) In the three-body situation, there is only one point where
gravitational forces are in balance. It is a point between the two
primary bodies, and is *not* even the same as the L1 Lagrange point.
The reason why they're different is because to keep the two primaries
at a distance, they need to be rotating around each other (leading to
Coriolis and centrifugal effects in the rotating Lagrange reference
frame).

Consider this possibly flawed analogy:

You are sunbathing outdoors in middle of winter. The cold temperature
may cancel out the heat from the sun, making the sun appear to be
neutral for temperature, but the sun's UV rays are still impacting your
skin.

NASA's misrepresentation of thermal science is another matter! I was
watching a Discovery Channel series over the weekend and *cringed*
when I heard a shuttle commander compare the aero-heating temperature
that the shuttle experiences on deorbit as being "as hot as the Sun".
TOTALLY failing to grasp the conceptual distinction between
temperature and heat. (This too has been discussed at length in past
years here on sci.space)

Until we fully understand gravity, we must consider the possibility that
acceleration of mass may not be the only impact gravity has on objects.

Again, the original criticism addresses the failure to grasp the most
basic effects of gravity that have been thoroughly explained since the
1680's. It is the "what" of gravity that has been confused, let alone
the "how".

And if we ever do unravel the "how", then we can hope for technologies
like anti-gravity. But it is important to learn how to walk before
attempting to run.


~ CT