Measuring distance from the Sun.
I hope this isn't too dumb a question, but when a planet's distance from the
sun is given, should that be assumed to be from the center of the sun to the
center of the planet, or is it a measure of the surface of the sun to the
surface of the planet?
-- and if it's surface to surface, then what is considered the surface of a
Your question isn't dumb, and it has a simple answer: from the center
of the Sun. A spherical mass--Sun, Earth, red giant or whatever--
pulls objects outside it with the same force as it would, if all
its mass were concentrated in its middle. As far as gravity is
concerned, the position of the surface makes no difference.
By the way--the Earth does not orbit the center of the Sun.
If the solar system contained only it and the Sun, the two would
orbit their common center of gravity. Of course, the Sun being
much more massive, that point is very close to the center of the Sun.
With more planets, the system orbits around the common center
of gravity, which I suspect is close to the center of gravity
of its heavyweights--Sun, Jupiter and Saturn. Viewed from some other
solar system, far away, this would make the Sun's position wobble a
bit, in response to the motions of the planets. In recent years,
astronomers have observed such subtle wobbles in the motions of
quite a few nearby stars, and concluded that like the Sun, they
had planets, too--big planets, like Jupiter. It is still too hard
to detect the effects of lightweights such as Earth, but progress
is being made.
Keep up your interest!
Who owns the Moon?
If you be so kind as to reply, please tell me, is it true that the Moon
has a formal proprietor and who is this man?
Thank you in advance for your kindness.
Reply I do not know who told you differently, but the moon belongs
to all of us together, even you, even I. When Neil Armstrong
stepped onto the moon he said "We came in peace in the name
of all of mankind" and that still holds true.
Acceleration of a RocketI've looked at your site and have taken some
information but I need more for my project. In my project I want to
search on the G force on the rockets at launch.
I really do not know. The g-forces on a rocket vary with the design.
Manned rockets stay under about 5g, unmanned scientific satellites may be
launched at up to 10-12g, small sounding rockets with strongly built
instruments sometimes reach 30g, and missiles can also accelerate very
rapidly. The greatest acceleration is usually not at launch but just
before burn-out, because the thrust of the motor changes little
(or not at all), while the mass goes down as fuel is burned.