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Astronomy---earth

Balance point:  At what point between the Earth and the Moon will their gravitational fields cancel each other
Day-night:  Why does Earth have day and night? Do all planets have the same?
Distance to the Sun:  Concerning your question & answer on Rrmer's determining the speed of light in 1672, how did he know the diameter of Earth's orbit? Even today, without using sophisticated equipment, it would be difficult.
Earth, full-circle: How high do you have to be to view Earth as a full circle?
Eclipse:  Why isn’t there a solar eclipse every month?
Ending:  When is the end of the world?
Equator twilight: why so short?
Equinoxes and solstices:  Please explain an equinox and a solstice.
Halo:  Last night around 11:15 pm, there was a wonderful ring around the moon. It was a hazy sky, not many stars to be seen.  Is there a name for this? What causes it? Thanks for any (moon) light you can shed.
Horizon:   I noticed at sunset that I can see jet trails at a very far distance and, if the sun is just right, I can see the jet sparkling in the setting sun. How far away is the horizon from the jet if it is flying at 36,000 feet? Is it 50 miles, 100 miles, 200 miles?
Leap Year: I heard on the radio that it will be 400 years before we have another leap year like 2000. Is this true?
Navigation:  When men first sought to reach the north and south poles, with the instruments they had at the time — a sextant, a compass and knowledge of the sun and stars — how did they know when they had reached the poles?
Orbit beginnings: How did the Earth start rotating around the sun and how did the Moon begin rotating around Earth?
Spin:  How fast does the world spin on its axis?
Spin:  As we know, the Earth is spinning from west to east at approximately 500 mph (800 km/h).  Why can't I go up in a helicopter in Tallahassee, FL; hover for four hours and descend in Los Angeles?
Spin:  Two identical aircraft leave from the same point along the equator, at the same time, flying the same speed, one heading east, one west. Which plane will arrive at its origin first? Will the rotation of the Earth affect it? What would happen if the jet stream part of the equation is eliminated?
Time:  What do we use to set time?
Time:  Is International Standard Time the same as Coordinated Universal Time (UTC)?
Winter solstice: Why is the Sun is lowest in the sky on the winter solstice and why is the Full Moon highest then?
Winter sunsets: In the Northern Hemisphere, why does the Sun set to the south in the winter? 

Astronomy--- moon

Balance point:  At what point between the Earth and the Moon will their gravitational fields cancel each other
Blue-looking Moons: What causes a moon that looks blue?
Captured-rotation:  What is the relationship between the day and the year of a body that has captured rotation? Also, what other bodies of the solar system have captured rotation?
Cheshire moon:  The moon, now, (on March 25) is a crescent that looks like the Cheshire Cat smiling down at us — I almost never see it looking this way. Why does the crescent moon look like a grin?
Closer:  I just read the Q&A for "Goodbye Moon" and was wondering... If the moon is receding from earth, how close has the Moon been to earth since its creation?
Dark side:  Is the dark side of the Moon always dark?
Daytime: Why do we see the Moon in the daytime?
Day & night:  Does the Moon have day and night?
Distance:  How far away is the Moon from the Earth?
East sky: How often is the Moon in the eastern morning sky?
Eclipse:  Why isn’t there a solar eclipse every month?
Full Moon:  If we see a full moon tonight, will there be a full moon on the other side of the world tomorrow?
Goodbye Moon:  How far away is the Moon from the Earth?
Horizon Moon:  Recently in the early West Texas morning the moon was setting through a dusty horizon. Why did the moon seem so incredibly large? I am guessing it is the same reason the sun can look so large.
Lunar rover: Can the Hubble Space Telescope discern any manmade equipment left behind on the Moon?
Moonlight and sunlight don't dawdle: How long does the Moon and Sun light take to reach the earth?
Near-far moons:  Is the Harvest Moon when the moon comes closest to Earth? When is the moon farthest away?
New Moon / Phases of the Moon: How come a New Moon is always close to the Sun?  What causes the phases of the Moon?
New moon, south pole: Can one see the New Moon at the poles during their winters?
Opposite ends of Earth: Does the Crescent Moon look the same in the Northern and Southern Hemispheres?
Origin of the Moon: How did the Moon form?
Phases: Are the phases of the Moon the same all over the world or are they different?
Polar: Can I see the Moon at Barrow, Alaska this June when it's daytime all month there?
Space junk: Can space junk make a moonlet?
Spin: does the Moon rotate? Why do we always see the same side of the Moon?
Wandering: Why does the Moon appear to have a 19-year cycle of wandering?
Wind:  Is there wind on the moon? If not, why does the photograph of the astronauts on the moon show the flag extended?

Astronomy--- planets, comets & asteroids

Alignment: In the movie, "Tomb Raider," is it possible for all the planets to line up as perfectly as they showed?
Asteroids:  Where do asteroids get water?
Comets:  I've heard that a comet of naked-eye brightness will appear in May — if it still exists! What does that mean — "still exists"?
Day-night:  Why does Earth have day and night? Do all planets have the same?
Extra-solar:  Astronomers claim to have a photograph of a planet circling a brown dwarf 225 light years away. Must of been a heck of a flash bulb! How did they take the picture?
Ingredients:  How do scientists know what planets are made of?
Jupiter Rings: how many and how were they created?
Jupiter's moon Europa: are we hunting for life on Europa?
Jupiter's moon, Io:  How a moon of Jupiter measures light speed.
Jupiter's surface:  What is the surface like on Jupiter?
Meteors: When is the once-in-a-lifetime meteor shower occurring?
Mars:  Are the Mars’ Rovers still active or did they finally say goodbye?
Mars:  How long does it take sunlight to reach Mars? How do I mathematically find this out?
Mars:  Your article on the Mars rovers talks about evidence of shallow lakes and water once flowing on Mars. What happened to it? How could Mars be so wet in the past and so dry today?
Mars:  What does zero elevation mean on the Mars map that Google recently published?  Is it sea level?
Neptune and Pluto: Pluto will never ram Neptune.
Neptune:  If I'm 11 years old on Earth, how old am I on Neptune?
Planets:  What's the new definition of a planet?
Planets:  Will astronomers find more planets in our solar system?
Planet X: IS there a 10^th planet?
Planet X:  Update.  Last week (Jul. 26, 2005), astronomers announced they had discovered a new planet larger than Pluto in orbit around the Sun. The discovery renews debate over what exactly is a planet. In light of the finding, this column tackles the 10th planet question.
Planets, finding: How do you find planets in the night sky?
Pluto:  Was Pluto declassified as a planet and lumped with the Kuiper Belt Objects?
Pluto:  How long does it take for sunlight to reach Pluto?
Pluto:  I have been tracking the speed of the New Horizons spacecraft in the early stages of its journey to Pluto, and have noticed an increase in speed.  What is causing this steady increase, and will it continue?
Saturn:  How many rings does Saturn have?
Venus:  Is there ever a "full Venus" and how bright would it be? When we look through our telescope, we always see a crescent Venus. My son, Teddy, says the sun casts a shadow that causes Venus’ phases. Is he right?
Venus:  How long does it take Venus to orbit the sun?
Venus:  What is the transit of Venus?
Venus:  Who was the first person to see Venus cross the Sun?
Venus:  I’d like to watch the transit. How can I without hurting my eyes?
Weather:  Do other planets have weather? If so, what kind, what planets?

Astronomy--- stars & sun

Black holes, making in the lab:  Can scientists create a black hole in a laboratory?  What would it take to create a black hole in a lab?
Brightest star:  What is the name of the brightness star?
Eclipse, solar:  How often does a solar eclipse occur?
Fastest spinner:  The fastest spinning star.
Leap year:  When was the first leap year?
Leap year:  I heard on the radio it will be 400 years before we have another leap year like this one in 2000. Is that true?
Leap year:  What is the next leap year?
Light speed:  The nearest star from Earth is Proxima Centauri, which is 4 light years from Earth. So, is it true the stars that we see in the sky at any instant are not the stars exactly at that instant but more than 4 years old, which we see now due to the sluggishness of light? (P.S. Can we see asteroids with the naked eye?)
Milky Way:  We are in the Milky Way galaxy itself. Then how can we photograph our galaxy so that it seems taken from the opposite side of the Milky Way? Photo is in this link [and shown in Figure 1].
Milky Way:  How do astronomers know how many stars are in the Milky Way?
Neutron stars:  You are on a neutron star. How do the sky, horizon, and surface look? What color is the neutron star? White? Black? Like a mirror? What color is a neutron?
Neutron stars:  What is the star’s atmosphere made of? How can it have a magnetic field since the neutron star has no charge (by definition of a neutron)?
Nights:  How long is the average length of nights in my area? I need the information to compute the cost of security lights per year.
Pictures:  I have heard that all of NASA’s deep-space images are colorized. Is this true? Do the experts think that space phenomena, such as nebulas, are truly as colorful and beautiful as they are portrayed in science fiction movies?
Solar eclipse:  Why isn’t there a solar eclipse every month?
Solar sailing: The idea of using sunlight to blow spacecraft across the Solar System will not work, suggests a new analysis by Thomas Gold. How do solar sails work and is Gold right?
Star book:  What is a good book to help us teach star gazing to our grandchildren?
Star distances, up to 500 light years: How do scientist figure out distances to stars and galaxies?
Star distances, from 500 light years to 500 million light years: How do scientist figure out distances to stars and galaxies?
Star distances, beyond 500 million light years: How do scientist figure out distances to stars and galaxies?
Star distances: How good are the estimates?
Star dust:  Where does oxygen come from?
Star movement:  What causes stars to move?
Stars, naked eye: Is it possible to see stars from another galaxy with the naked eye?
Stars, photo, up: When NASA and astronomers photograph celestial bodies, how do they decide which way to orient the camera and images? In space there is no up or down nor any anchor orientation point (i.e., north/south).
Stars: how can I find stars over Thailand or anywhere in the world?
Space Station: how can I spot the Space Station at night?
Star shooting: Can you shoot stars in the daytime?
Sun:  My wife just asked how the guys that watch the skies know what is at the center of the sun.
Sun:  How many years does it take for heat generated in the sun’s core to reach its outer layer, the photosphere?
Sun:  What is the volume of the sun?
Sun, as a white dwarf: When our Sun turns into a white dwarf, what will it look like from Earth?
Sun: solar wind: Does space have wind? If so, is it constant or random?
Sun's magnetic poles: Does the Sun have poles?
Sunlight and moonlight don't dawdle: How long does the moon and sun light take to reach the earth?
Supernova:  In your answer about where oxygen comes from you show a picture of a "ring" of matter formed by a supernova. Shouldn't matter ejected by an explosion form a spherical "ball" or "shell" rather than a "ring"?
Time:  Is International Standard Time the same as Coordinated Universal Time (UTC)?
White dwarf:  How much does a little piece of a white dwarf weigh?
 

Astronomy--- universe & cosmology

Alternate (and parallel) universes:  What is meant by the term 'alternative universe' and is it real, or fictional?
Atoms and the universe: which is bigger?
Big Bang: explain the Big Bang theory
Big Bang: Will the Universe keep expanding forever or will there be a Big Crunch/Big Bang?
Big Bang: what's outside space?
Big Bang:  how do we know the Big Bang theory is true?
Big bang:  If dense, large concentrations of matter form black holes, how could the big bang ever have happened? Wouldn't it have stayed a black hole?
Big Bang:  Sometime in the future, will it be possible to get a picture from space before the big bang occurred? If it is not, please explain why. How old is the oldest space picture we have today? Theoretically, how old a picture can we get?
Big bang:  How could the big bang ever have happened? Wouldn't it have stayed a black hole?
Big bang:  Are the photons or electrons (not sure which) that we see in TV snow/static left over from the big bang?
Black holes: Do black holes die?
Black holes: What will happen if two black holes are close to each other? Do they collide?
Black holes, how many: How many black holes do we REALLY know about?
Black holes, proof: What is the proof of the existence of black holes?
Black holes: I was taught in school that gravity is a force between two masses. And that the speed of light is the fastest something can travel, because light has no mass. So why can light not escape from a black hole? If it has no mass, how can it be under the influence of gravity?
Black holes, making in the lab:  Can scientists create a black hole in a laboratory?  What would it take to create a black hole in a lab?
Can scientists create a black hole in a laboratory? Part 2.
Can scientists create a black hole in a laboratory? Part 3.
Egg universes: I assume that the universe shape is more or less like an egg. Is my assumption correct?
Galaxies colliding:  How can galaxies collide if space is expanding?
Gallaxies:  Are there anti-matter galaxies?
Space, Expanding: Does expanding space exceed the speed-of-light limit?
Space, Expanding: It is known that the Universe is accelerating while its  expanding due to Dark Energy. At what speed is the universe expanding now?
Space, Expanding, revisted:  I believe you are mistaken when saying a quasar is 27 billion light years away from us, as there is nothing in the universe that is currently farther away than about 13.7 billion light years away as this is currently the approximate age of the universe.
Space, expanding:  Does cosmic expansion move everything apart, even our the various parts of our bodies?
Universe:  Do you have insights about where space ends?
Universe:  Is the size of the Universe defined by how far light has traveled since the big bang?
Universe:  Is the Universe constantly expanding like a balloon?
Universe:  Is there an actual center of the Universe?