Listed below are questions submitted over about 14 years by users of "From Stargazers to Starships," posted together with their answers. This is just a selection from the many questions that arrive. They were included because either they are the sort that keeps being asked again and again, or else the answers make a special point, often going into details which might interest many users.
This is a complete list, over 500 items (so far), and because of its length it is given here separately, in the order submitted. A complete list sorted by topic area is in file
Either list is linked to all the messages, collected in 26 separate files to speed up access.
David P. Stern 25 February 2012
- About asteroids hitting Earth.
- The swirling of water in a draining tub.
- Dispensing water at zero-g.
- Robert Goddard and World War II.
- Asymmetry of the Moon's orbit.
- Measuring distance from the Sun.
- Who owns the Moon?
- Acceleration of a rocket.
- Rebounding ping pong balls (re. #35)
- Rebounding ping pong balls and gravity-assist
- Why don't we feel the Sun's gravity pull?
- How hot are red, white and blue (etc.) stars?
- How does the solar wind move?
- The shape of the orbit of Mars
- What if the Earth's axis were tilted 90° to the ecliptic?
- Mars and Venus
- Where is the boundary between summer and winter?
- The Ozone Hole
- What keeps the Sun from blowing up?
- Those glorious Southern Skies!
- Should we fear big solar outbursts?
- Planetary line-up and the sunspot cycle
- What are comet tails made of?
- If light speed sets the limit, why fly into space?
- Does precession mis-align ancient monuments?
- Why does the Earth rotate? Why is it a sphere?
- What's so hard about reaching the Sun?
- Where does space begin?
- Gravity at the Earth's Center
- Radiation hazard in space (3 queries)
- "Danger, falling satellites"?
- The Lagrangian L3 point
- Distance to the Horizon on an Asteroid
- Overtaking Planets
- Falling Towards the Sun
- The Polar Bear
- Are the Sun's Rays Parallel?
- More thrust in reverse than going forward?
- The varying distance between Earth and Sun
- Mission to Mars
- Kepler's calculation
- The Appearance (Phase) of the Moon
- Stability of Lagrangian points
- Can an Asteroid Impact Change the Earth's Orbit?
- Can Gravity Increase with Depth?
- Lightspeed, Hyperspace and Wormholes
- Why do Rockets Spin?
- Around What does the Sun Revolve?
- Why are planets in nearly the same plane?
- The Shapes of Rockets and Spacecraft
- Space Debris
- Teaching Nuclear Fusion
- Contribution of different elements to Sunlight
- Jewish Calendar
- Spaceflight Without Escape Velocity?
- Who first proposed a round Earth?
- Does Precession change the Length of a Year?
- The Analemma
- Changes of the Polar Axis of Earth
- Van Allen Belt and Spaceflight
- Nearest Star Outside Our Galaxy
- (a) Why are Satellites Launched Eastward?
What is a "Sun Synchronous" orbit?
(b) Why are satellites launched from near the equator?
- How Tall Can People Get?
- Gunpowder and Rockets
- Solar Sails
- (a) Distance to the Big Dipper
(b) Big Dipper star names
- Was Moon landing a hoax?
- Clockwise or counter-clockwise?
- Isotopes in Center of Earth
- Density of the Sun's corona and the "Scale Height"
- Did Tesla extract free energy from thin air?
- What does "lapse rate" mean?
- Motion of the Sun through space
- Teaching about tides
- Distance to the Horizon
- Can geocentrist theory still be possible?
- Can Earth's rotation reverse, like its magnetic polarity?
- Why is the Earth round?
- The De Laval Nozzle
- Why 23.5 degrees?
- What is Gravitational Collapse?
- Can Earth capture a second moon?
- How far does the Earth's gravity extend?
- How far is the Moon?
- Twinkle, twinkle little star--
How I wonder, what you are.
- Teaching about seasons
- Space Launches by Cannon--A
- Space Launches by Cannon--B
- The Southern Pole of the Sky
- Do Astrologers use Wrong Positions for Planets?
- Why does the Moon have bigger craters?
- Why does Gravity Exist?
- Atmospheric "Thermals"--Triggered by Electric Forces?
- What would happen if Earth rotated faster?
- Where do gravity of Earth and Sun balance?
- The Ultimate Astronomy Tool
- High Temperature in Cold Outer Space
- Refraction of sunlight and starlight by the atmosphere
- Advice to a would-be astronomer
- The effect of the Color of Light on the Output of Solar Cells
- What is "radiation"?
- Height of the Atmosphere
- How does the upper atmosphere get so hot?
- History of the use of De Laval's nozzle on rockets
- Why don't Space Rockets use Wings?
- Distance of horizon on Mars
- Stopping the rotation of Earth?
- The equation of a parabola
- When does Jewish Sabbath start in the far north?
- Where is the center of the global landmass?
- What if our Sun was a much hotter star?
- Finding the north direction
- Why not use a heat shield going up?
- When and where can rainbows be seen?
- The unusual rotation of the planet Venus
- Why not use nuclear power for spaceflight?
- "Doesn't heat rise?"
- Have any changes been observed on the Moon?
- Why isn't our atmosphere flung off by the Earth's rotation?
- Can kinetic energy be reconverted to work?
- Does any location get the same number of sunshine hours per year?
- Speed of toy car rolling off an inclined ramp
- Acceleration due to gravity
- Re-entry from Space
- Balancing a Bicycle
- Is Absolute Zero reached on the Moon?
- Why isn't Longitude measured from 0° to 360°? "Constellation" or "Asterism"?
- "Position of the Stars when I was Born"
- Rotation of the Earth's Core"
- How hot is the Sun?
- How much weaker is gravity higher up?
- Eclipse of Venus?
- The Big Bang
- Thanks for the "Math Refresher" in Spanish
- The Pressure of Sunlight
- How is the instant the seasons change determined?
- Operation of Ion Rockets
- Physical Librations of the Moon
- The De-Laval Nozzle
- Why does the space shuttle rotate at take-off?
- Cold Fusion
- What if a Neutron Star hit the Sun?
Why did the Moon appear Red?
- Centrifuge for Whirling Astronauts
- What Holds Galaxies Together?
- View of Earth and Moon from Mars
- Appearance of the Moon (1)
- Appearance of the Moon (2): Does it "roll around"?
- Altitude of the tail of the Big Dipper
- Sudden decompression, 5 miles up
- Do Negative Ions make you Feel Good?
- Shape of the Earth's Orbit
- Questions about the Solar Corona:
(1) Why don't its particles separate by weight?
(2) What accelerates the solar wind?
- Why does the rising Sun look so big?
- Drawing a Perpendicular Line in Rectangular Coordinates
- Unequal Seasons
- Is the Big Dipper visible from Viet Nam?
- Holes in a Solar Sail
- Consequences of no more solar X-rays
- Science Fair Project on the Size of the Earth
- Superposition of Waves
- The Sun and Seasons
- If the Earth's Rotation would S t o p... (1)
- If the Earth's Rotation would C h a n g e... (2)
- What if the Earth stopped in its orbit?
- Fast Trip to Mars (1)
- Fast Trip to Mars (2)
- Spacecraft Attitude
- What makes the Earth rotate?
- Energy from the Earth's Rotation?
- How were planets created?
- Does Precession of the Equinoxes shift our Seasons?
- "Zenial Days" on Hawaii
- Sun's Temperature and Energy Density of Sunlight
- Teaching about energy in 8th grade
- About the jetstream
- What would a breach in a space station do?
- Gravity at the Earth's center
- Freak waves on the ocean
- Citation on "Bad Greenhouse" web page
- How can radio waves carry sound?
- Do Cosmic Rays produce lightning?
- Star positions shifted by the atmosphere
- The equation of time
- Launch window of the Space Shuttle
- No "Man in the Moon" from Australia?
- Picturing the Sun from a different distance
- What makes the sun shine so brightly?
- Re-entry from orbit
- Effects of weightlessness on one's body
- Blimps on Mars
- Planet Mars "huge" in the sky, in August 2005?
- Astronomy and telescopes for ones' own children
- Does the solar wind have escape velocity
- Astronomy for cliff-dwellers of New York City
- Portable star finder
- What if the Moon was closer? (2 questions)
- Why doesn't the Moon have an atmosphere?
- Telling a 3-year old about the atmosphere (2 questions)
- Three-color vision
- Superconductors work, universe expands--with no energy input. Why?
- Shuttle orbit and Earth rotation
- Worrying about Wormholes and Black Holes
- What should I study?
- The greenhouse effect
- Separation between lines of latitude and longitude
- Motion of air: hot to cold, or high pressure to low?
- Removing "Killer Asteroids"
- Strange light seen from Hawaii
- Is the Sun attached to another star?
- What if the Sun turned into a black hole?
- Do absorption lines have a Doppler shift?
- What are "Electromagnetic Waves"?
- Why are the two daily tides unequal?
- Why air gets cold higher up--a wrong explanation
- Any limits to Newton's 2nd Law
- Gravity at the Earth's center
- Does the Earth follow a "squiggly" orbit?
- Third grader asks: how far to zero gravity?
- "How does inertia affect a rolling ball"?
- What determines the quality of a telescope?
- Why design maps around curved lines?
- "Drag" by the Sun on the Earth's motion
- Does precession affect the time of summer? (2 questions)
- Newton's law or Bernoulli's?
- Does the universe have an axis?
- Frictional electricity
- Syllabus for catching up on physics
- Parabolic reflector
- At what distance does Earth start looking spherical?
- Is the Sun on fire?
- Confusion about the "Big Bang"
- How did Tycho calibrate his instruments?
- Gases that fill balloons
- Asian tradition on the start of winter
- Why our year starts at January 1
- Sticking a hand out of a window...
- One year of continuous sunlight?
- Shielding out radio waves
- The way gravity changes with depth
- The Sun's Axis
- "Gravity Particles"?
- A "short stay on Mars"
- Weight and mass
- "The Moon Hoax"
- Shuttle re-entry from space
- Energy levels: plus or minus?
- How can such small targets be accurately hit
so far away?
- A teacher asks about compiling lesson plans
- Why the Moon has its phases
- How can a spacecraft self-rotate?
- Stability during a rocket launch
- Boiling point of water in space
- Konstantin Tsiolkovsky
- The Color Indigo
- Electromagnetic Waves and Electromagnetic Induction
- Why do orbits curve?
- The "Sundial Bridge" in Redding
- (a) Temperature in space
(b) Exposure to the space environment: Freeze or burn?
- Remote sensing of Thunderstorms
- What keeps Electrons away from the Atomic Nucleus?
- The Stars on the Winter Solstice of 2012
- Mars Sunset
- Gravity at the Center of Earth
- The Big Bang
- "How Often are Stars Born?"
- The Path of Lightning
- Launching a Rocket from an Airplane
- The Equation of Continuity
- The Four Corners Monument
- Which among the brightest stars is closest to N Pole?
- Gravity Assist
- Is the Centrifugal Force "Real"?
- How do we know Earth is bigger than the Moon?
- Sound Waves on the Sun?
- What if we had to give up use of Satellites?
- Rotation of Venus
- "Proper Motion" of Stars
- Doppler Shift from the Big Bang
- Science Fiction scenario for a Flight to Mars
- Motion of the Moon
- "Iridium" flares
- Discovering Planets outside the Solar System
- Landing speed of airplane
- The Hubble Constant
- Are Summer Nights Darker?
- "Space Elevator"
- Black Holes
396A Posssibility of Asteroid Hitting Earth (1)
- Don't use Diesel fuel in a gasoline car!
- How bright is our Sun when seen from space?
- What is a "field"?
- Outer limits of the Solar System
- Gravitational Energy
- Stresses on a Railroad Bridge
- The constellation of Cassiopeia
- Tracking of radioactivity carried by winds
- Why can't the space shuttle reenter "slowly"?
- "The Standard Model of the Universe"
- About the Maya Calendar
- Are light sabers possible?
- Can the heat of sunshine make the Earth expand?
- About Mountains
- "Will the World end in 2012?" (a,b)
- Advice to graduating High School Student
- Could a (heat resistant!) ship float on the Sun?
- Reducing the fuel weight of the Space Shuttle?
- How do Rockets Land?
- The Earth's Spin reduced by Global Warming
- Circumnavigation of the Sun
- Are nuclear forces merely gravity at very close distance?
- Changing the Earth's Rotation
- Why are planetary orbits eccentric?
- Forces on Comet-dwellers
- Nuclear reactors and bombs
- Why doesn't magnetism affect electro-magnetic waves?
- Is humanity changing the climate, or is it the Sun and the Earth's magnetism?
- Advice to home-schooling parent
- Science of Clothing
- Calculating a Collision
- The Coriolis force and more
- Why isn't the solar system stratified by density?
- Tapping Atmospheric Electricity
- Global Disaster in 2012?
- What's the difference between speed and velocity?
- Effect of Gravity on Electromagnetic Waves
- Why is North the reference, not South?
- The lowest 700 km of our Atmosphere
- Doomsday 2012?
- Where does a Flying Bird get its Support?
- Why does Sun seem to move?
- Why don't waves disturb each other?
- Does the Moon's motion Change?
- Big Dipper and Weather
- What IS the Ecliptic?
- Precession, Greenhouse and more...
- Latest Sunrise, Earliest Sunset
- Falling off the Earth's Bottom?
- Rolling down a slope
- Pelton Wheel Efficiency
- Energy loss rate of our Sun
- The Sun's distance
- Why does sunlight have a continuous spectrum?
- Harry Paul Sprain's perpetual Motion Device
- Can the plasma that fills space help spaceflight?
- Spiral arms of our galaxy
- What powers a glider?
- Maximum speed for propeller-driven airplane?
- The speed at which gravity spreads
- Layers of the Earth
- Why doesn't the sky fall on us?
- Imagine a non-rotating Earth
- Flying east with a 1° error
- US Flag on the Moon
- Rope stretched across a long lake...
- About studying electronics in the USA
- Publish Stargazers as a book?
- Charging of Earth by lightning: + or – ?
- If no stars were seen--could Earth's orbital motion be discovered?
- Local Solar Time in Iceland
- Is orbital motion same as free fall?
- Build a straight tower in warped space?
- The 2011-2 sunspot maximum
- Is Earth adding mass?
- Shape of a "bottle rocket"
- Fantasy spaceflight vs. reality
- Telling a 7-year old about stars "dying"
- (1) Why is lightning jagged? (2) What did Tesla do?
- How can the north wall of my house be in sunlight?
- Heating the inside of Earth
- Dawning of the Age of Aquarius
- Why is hydrogen the fuel of choice?
- Gamma ray bursts
- Counter-clockwise swirling motion in the atmosphere
- Leap years on the Jewish calendar
- Earth axis tilt and climate (1)
- Earth axis tilt and climate (2)
- Does the Sun move?
- Can the Sun interfere with the visibility of the Big Dipper?
- Why can't we feel the Earth's rotation?
- Is our galaxy held together by a central black hole?
- Why don't gas planets just evaporate?
- Source of the Sun's energy
- Point of gravity equilibrium
- Solar system motion through the Galaxy
- Spaceflight by waiting for the Earth to turn?
- Does Earth rotation affect size of creatures?
- The year 2012
- Are our galactic arms winding up or opening up?
- Advice to a home-schooling mother
- Are all stars we see suns?
- Newton's 3rd law
396B Posssibility of Asteroid Hitting Earth (2)
- Author's IQ
- Global Warming caused by Sun getting nearer?
- The year 2012
- Empty space behind North Star?
- The year 2012 and the 26,000 year cycle
- "Quarter Squares"
- Do Rockets need "something to push against"?
- Sunrise-Sunset asymmetry
- Re-entry from orbit
- Earth Axis and Gravity
- The year 2012
- Choosing an Aerospace Career
- Advice for "new" physics teacher
- Paradox of Time Travel
- Is 7th grade Earth science boring?
- Air Resistance
- Experimenting with Microwave Oven
- Is the Sun losing mass?
- Sun's position at noon, south of equator
- Fred Hoyle's theory of the Sun's Corona
- Why don't Protons and Electrons combine?
- Days in a Year
- Position of the Moon in the sky
- Earth crossing Galactic Equator?
- Is the geocentric theory ruled out?
- Does the Southern Sky have a Pole Star?
- What is the fate of starlight energy?
- Double-slit diffraction of particles
- Does the Sun overhead reduce effective weight?
- Evidence for Global Warming ?
- Distances to the Equator
- Weight on the Equator and at the Pole
- Why doesn't gravity overcome buoyancy?
- The Prime Meridian
- Is L2 in the Earth's Shadow?
- In what direction is Israel from NY?
- Is the World Overpopulated?
- Magnetic Energy
- Magnetic Carnot Cycle
- Defining the Equator
- Second Moon for Earth?
- The year 2012 and a distant companion of our Sun
- Distance between two points on a sphere
- Getting sucked n by Gravity
- The work of Nikola Tesla
- Firing a cannon straight up
- Does one see half the sky--or more, or less?
- Why are nights dark?
- The origin of the Solar System
- Flying to other planets
- The heat of the Sun's corona
- Crossing our galaxy's equator
- Newton's 3rd law--in statics and dynamics
- Barycenter of Earth-Moon system
- What if Earth rotated in only 10 hours
- What Book covers material of "Stargazers"?
- Climate Change
- A classroom Demonstration
- Why doesn't the Solar System Collapse?
- A Diamond Core for Jupiter?
- Why no "artificial gravity" on the space station?
- Precession of the axis of Mars
- Does the axis of the Sun precess?
- Can a microwave oven produce 900 deg Celsius?
- Beaming energy through space
- The year 2012
- The Earth's Precession Cycle
- The empty space inside an atom
- Rotation of Galaxies
- Sailplane flight
- How far to the Pole Star?
- Missed Discoveries
- Independent study for bright students
- Double slit interference experiment in space
- Ionizing Radiation and the Origin of Life
- On Earth's spin and Moon's appearance
- Back to the Geocentric Universe?
- Radiation risks from uranium counterweights
- The centrifugal force from Earth's rotation
- Earth's rotation and human lifespan
- Dependence of cosmic redshifts on direction
- Difference between Gravity and Magnetism
- SciFi world with ahort days and long nights
- Celestial Equator and Ecliptic Equator
- Cavendish gravity constant G drops out
- Teacher seeks material
- Solar Sails
- Life under stronger gravity
- Message from Kansas
- Finding true north in an underground mine
- Calculation of Gravity
- Message from Michigan
- Confused about "Temperature"
- "Negative work" and energy
- The Coriolis force on a moving air mass
- Recent change in sunset?
- Space and Dark Matter
- Newton's 3rd law
- Shift of Earth Axis in 2012?
- Ptolemaic Theory of Planet Motion
- Electricity from Earth's Rotation?
- Change in Earth's gravity after Tsunamis
- Science fair expt. on light output of CFLs
- Does iron 56Fe have the most stable nucleus?
- "Black Light Telescope"
- Message from New Jersey
Go to main list of questions (by topic)