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Please note!

This is just a selection--

either

or else

Classifications are tentative, and some entries appear under more than one heading.

Additional questions-and-answers:

"The Great Magnet, the Earth"

In "The Exploration of the Earth's Magnetosphere" on the magnetic environment of Earth in space.

Main Divisions

1. Spaceflight
2. Sun and Solar System
(3. Magnetism)

4. Stars and the Universe
5. General Physics

5a Electromagnetic radiation
5b Gravity
5c Other general physics

6. Elementary Astronomy
7 Earth and its motions

7a. Earth and its motion
7b. Earth atmosphere
7c. Calendar and related items
7d. Shape and size of the Earth
7e. Earth -- other motions

8. Questions about space
9. History
10. Moon
11. Orbits
12. Miscellaneous

1. Spaceflight

(1) About asteroids hitting Earth.
(3) Dispensing water at zero-g.
(6) Measuring distance from the Sun.
(8) Acceleration of a rocket.
(24) If light speed sets the limit, why fly into space?
(40) Mission to Mars
(47) Why do Rockets Spin?
(50) The Shapes of Rockets and Spacecraft
(51) Space Debris
(55) Spaceflight Without Escape velocity
(60) Van Allen Belt and Spaceflight
(62) (a) Why are Satellites Launched Eastward?
... and what is a "Sun Synchronous" orbit?
(b) Why are satellites launched from near the equator?
(66) Solar Sails
(80) The De Laval Nozzle
(88) Space Launches by Cannon--A
(89) Space Launches by Cannon--B
(105) History of the use of De Laval's nozzle on rockets
(106) Why don't Space Rockets use Wings?
(114) Why not use a heat shield going up?
(117) Why not use nuclear power for spaceflight?
(125) Re-entry from Space
(139) Operation of Ion Rockets
(141) The De-Laval Nozzle
(142) Why does the space shuttle rotate at take-off?
(160) Holes in a Solar Sail
(168) Fast Trip to Mars (1)
(169) Fast Trip to Mars (2)
(170) Spacecraft Attitude
(179) What would a breach in a space station do?
(187) Launch window of the Space Shuttle
(191) Re-entry from orbit
(192) Effects of weightlessness on one's body
(204) Shuttle orbit and Earth rotation
(210) Removing "Killer Asteroids"

2. Sun and Solar System
(11) Why don't we feel the Sun's gravity pull?
(13) How does the solar wind move?
(15) What if the Earth's axis were tilted 90° to the ecliptic?
(19) What keeps the Sun from blowing up?
(21) Should we fear big solar outbursts?
(22) Planetary line-up and the sunspot cycle
(23) What are comet tails made of?
(33) Distance to the Horizon on an Asteroid
(49) Why are planets in nearly the same plane?
(53) Contribution of different elements to Sunlight
(69) Clockwise or counter-clockwise?
(71) Density of the Sun's corona and the "Scale Height"
(77) Can geocentrist theory still be possible?
(98) High Temperature in Cold Outer Space
(104) How does the upper atmosphere get so hot?
(107) Distance of horizon on Mars
(116) The unusual rotation of the planet Venus
(132) How hot is the Sun?
(144) What if a Neutron Star hit the Sun?
(148) View of Earth and Moon from Mars
(155) Questions about the Solar Corona:
(1) Why don't its particles separate by weight?
(2) What accelerates the solar wind?
(173) How were planets created?
(176) Sun's Temperature and Energy Density of Sunlight
(189) Picturing the Sun from a different distance
(190) What makes the sun shine so brightly?
(193) Blimps on Mars
(196) Does the solar wind have escape velocity
(212) Is the Sun attached to another star?
(213) What if the Sun turned into a black hole?
(233) Is the Sun on fire?

3. Magnetism
Questions about magnetism are answered on the web at
"The Great Magnet, the Earth"
and at
"The Exploration of the Earth's Magnetosphere"

If you are reading this from a compact disk, go to the home pages of the appropriate folder, then search for "Questions and Answers" (at the end of the list of contents). The home pages are

-- For "The Great Magnet, the Earth", go to folder earthmag and open demagint.htm.
-- For "The Exploration of the Earth's Magnetosphere" go to folder Education and open Intro.hrml.

4. Stars and the Universe
(12) How hot are red, white and blue (etc.) stars?
(46) Lightspeed, Hyperspace and Wormholes
(48) Around What does the Sun Revolve?
(61) Nearest Star Outside Our Galaxy
(67) (a) Distance to the Big Dipper
(b) Big Dipper star names
(74) Motion of the Sun through space
(82) What is Gravitational Collapse?
(86) Twinkle, twinkle little star
(112) What if our Sun was a much hotter star?
(129) "Constellation" or "Asterism"?
(135) The Big Bang
(147) What Holds Galaxies Together?
(185) Star positions shifted by the atmosphere
(205) Worrying about Wormholes and Black Holes
(214) Do absorption lines have a Doppler shift?
(228) Does the universe have an axis?
(234) Confusion about the "Big Bang"

5. General Physics

5. General Physics--Electromagnetic Radiation
(101) The effect of the Color of Light on the Output of Solar Cells
(103) What is "radiation"?
(137) The Pressure of Sunlight
(183) How can radio waves carry sound?
(214) Do absorption lines have a Doppler shift?
(215) What are "Electromagnetic Waves"?

5. General Physics--Gravity
(10) Rebounding ping pong balls and gravity-assist
(11) Why don't we feel the Sun's gravity pull?
(29) Gravity at the Earth's Center
(45) Can Gravity Increase with Depth?
(55) Spaceflight Without Escape Velocity?
(93) Why does Gravity Exist?
(124) Acceleration due to gravity
(219) Gravity at the Earth's center (see #29 above, also #180 in (7e))
(221) Third grader asks: how far to zero gravity?

5. General Physics--Misc
(2) The swirling of water in a draining tub.
(8) Acceleration of a rocket.
(9) Rebounding ping pong balls (re. #35)
(10) Rebounding ping pong balls and gravity-assist
(37) Are the Sun's Rays Parallel?
(38) More thrust in reverse than going forward?
(52) Teaching Nuclear Fusion
(70) Isotopes in Center of Earth
(72) Did Tesla extract free energy from thin air?
(98) High Temperature in Cold Outer Space
(118) "Doesn't heat rise?"
(121) Can kinetic energy be reconverted to work?
(123) Speed of toy car rolling off an inclined ramp
(126) Balancing a Bicycle
(143) Cold Fusion
(163) Superposition of Waves
(177) Teaching about energy in 8th grade
(181) Freak waves on the ocean
(202) Three-color vision
(203) Superconductors work, universe expands
--with no energy input. Why?
(218) Any limits to Newton's 2nd Law?
(222) "How does inertia affect a rolling ball?"
(227) Newton's law or Bernoulli's?
(230) Syllabus for catching up on physics

6. Elementary Astronomy
(20) Those glorious Southern Skies!
(90) The Southern Pole of the Sky
(99) Refraction of sunlight and starlight by the atmosphere
(122) Does any location get the same number of sunshine hours per year?
(129) "Constellation" or "Asterism"?
(130) "Position of the Stars when I was Born"
(134) Eclipse of Venus?
(138) How is the instant the seasons change determined?
(151) Altitude of the tail of the Big Dipper
(156) Why does the rising Sun look so big?
(158) Unequal Seasons
(159) Is the Big Dipper visible from Viet Nam?
(175) "Zenial Days" on Hawaii
(194) Planet Mars "huge" in the sky, in August 2005?
(195) Astronomy and telescopes for ones' own children
(198) Portable star finder
(223) What determines the quality of a telescope?

7. Earth and its motion

7a. Earth rotation
(2) The swirling of water in a draining tub.
(15) What if the Earth's axis were tilted 90° to the ecliptic?
(26) Why does the Earth rotate? Why is it a sphere?
(59) Changes of the Polar Axis of Earth
(78) Can Earth's rotation reverse, like its magnetic polarity?
(95) What would happen if Earth rotated faster?
(108) Stopping the rotation of Earth?
(120) Why isn't our atmosphere flung off by the Earth's rotation?
(131) Rotation of the Earth's Core"
(165) If the Earth's Rotation would Stop... (1)
(166) If the Earth's Rotation would Change... (2)
(171) What makes the Earth rotate?
(172) Energy from the Earth's Rotation?

7b. Earth atmosphere
(73) What does "lapse rate" mean?
(94) Atmospheric "Thermals"--Triggered by Electric Forces?
(103) Height of the Atmosphere
(178) (1) About the jetstream
(182) Citation on "Bad Greenhouse" web page
(207) The greenhouse effect
(210) Telling a 3-year old about the atmosphere (2 questions)
(217) Why air gets cold higher up--a wrong explanation

7c. Calendar and related items
(17) Where is the boundary between summer and winter?
(54) Jewish Calendar
(57) Does Precession change the Length of a Year?
(87) Teaching about seasons
(110) When does Jewish Sabbath start in the far north?
(226) Does precession affect the timing of summer?

7d. Shape and size of the Earth
(26) Why does the Earth rotate? Why is it a sphere?
(56) Who first proposed a round Earth?
(76) Distance to the Horizon
(79) Why is the Earth round?
(107) Distance of horizon on Mars
(162) Science Fair Project on the Size of the Earth
(208) Separation between lines of latitude and longitude
(224) Why design maps around curved lines?

7e. Earth and its other motions
(25) Does precession mis-align ancient monuments?
(58) The Analemma
(69) Clockwise or counter-clockwise?
(70) Isotopes in Center of Earth
(75) Teaching about tides
(81) Why 23.5 degrees?
(113) Finding the north direction
(115) Sun's elevation at noon
(128) Why isn't Longitude measured from 0° to 360°?
(133) How much weaker is gravity higher up?
(154) Shape of the Earth's Orbit
(164) The Sun and Seasons
(174) Does Precession of the Equinoxes shift our Seasons?
(175) "Zenial Days" on Hawaii
(180) Gravity at the Earth's center
(186) The equation of time
(216) Why are the two daily tides unequal?

---------------------------------------------------------------------------

8. Questions about space
(1) About asteroids hitting Earth.
(28) Where does space begin?
(30) Radiation hazard in space (3 queries)
(34) "Danger, falling satellites"?
(37) Are the Sun's Rays Parallel?
(103) Height of the Atmosphere
(161) Consequences of no more solar X-rays
(225) "Drag" by the Sun on the Earth's motion?
(232) At what distance does Earth start looking spherical?

9. History
(4) Robert Goddard and World War II.
(41) Kepler's calculation
(54) Jewish Calendar
(56) Who first proposed a round Earth?
(64) Gunpowder and Rockets
(80) The De Laval Nozzle
(105) History of the use of De Laval's nozzle on rockets
(235) How did Tycho calibrate his instruments?

10. Moon
(5) Asymmetry of the Moon's orbit.
(30) Radiation hazard in space (3 queries)
(42) The Appearance (Phase) of the Moon
(68) Was Moon landing a hoax?
(75) Teaching about tides
(83) Can Earth capture a second moon?
(85) How far is the Moon?
(92) Why does the Moon have bigger craters?
(119) Have any changes been observed on the Moon?
(127) Is Absolute Zero reached on the Moon?
(140) Physical Librations of the Moon
(149) Appearance of the Moon (1)
(150) Appearance of the Moon (2): Does it "roll around"?
(188) No "Man in the Moon" from Australia?
(197) Astronomy for cliff-dwellers of New York City
(199) What if the Moon was closer? (2 questions)
(200) Why doesn't the Moon have an atmosphere?

11. Orbits
(5) Asymmetry of the Moon's orbit.
(14) The shape of the orbit of Mars
(27) What's so hard about reaching the Sun?
(32) The Lagrangian L3 point
(34) Overtaking Planets
(35) Falling Towards the Sun
(39) The varying distance between Earth and Sun
(41) Kepler's calculation
(43) Stability of Lagrangian points
(44) Can an Asteroid Impact Change the Earth's Orbit?
(62) (a) Why are Satellites Launched Eastward?
(a) What is a "Sun Synchronous" orbit?
(b) Why are satellites launched from near the equator?
(74) Motion of the Sun through space
(83) Can Earth capture a second moon?
(84) How far does Earth's Gravity Extend?
(96) Where do gravity of Earth and Sun balance?
(167) What if the Earth stopped in its orbit?
(220) Does the Earth follow a "squiggly" orbit?

12. Miscellaneous
(18) The Ozone Hole
(36) The Polar Bear
(63) How Tall Can People Get?
(72) Did Tesla extract free energy from thin air?
(91) Do Astrologers use Wrong Positions for Planets?
(97) The Ultimate Astronomy Tool
(100) Advice to a would-be astronomer
(109) The equation of a parabola
(110) When does Jewish Sabbath start in the far north?
(111) Where is the center of the global landmass?
(136) Thanks for the "Math Refresher" in Spanish
(145) Why did the Moon appear Red?
(146) Centrifuge for Whirling Astronauts
(152) Sudden decompression, 5 miles up
(153) Do Negative Ions make you Feel Good?
(157) Drawing a Perpendicular Line in Rectangular Coordinates
(184) Do Cosmic Rays produce lightning?
(192) Effects of weightlessness on one's body
(206) What should I study?
(211) Strange light seen from Hawaii
(216) Why are the two daily tides unequal?
(224) Why design maps around curved lines?
(229) Frictional electricity
(230) Syllabus for catching up on physics
(231) Parabolic reflector

Go to main listing of questions

Back to the Master List

Author and Curator: Dr. David P. Stern
Mail to Dr.Stern: stargaze("at" symbol)phy6.org .

Last updated 11 November 2003