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Dear Mr. Lemonick: 
My daughter is in Kindergarten and has recently asked me "Is it always dark in outerspace?" All the pictures she sees appear to be dark. Please help me to give her the right answer and explanation that she can understand.  
Thanks, 
Cindy

Dear Cindy,
Is it always dark at night? Pretty much, yes--unless you're looking right at something bright, like a star or the Moon or a streetlight. It's the same in space: the only things that aren't dark are objects that shine, or objects that are shined ON. In between, there's just darkness. If you look at pictures of the Space Shuttle, taken in space, it's bright because the sun is shining on it. 

So why, you might ask, is everything bright on Earth in the daytime? After all, when there are no clouds, you can look away at from the sun into the empty sky and it's still bright. That's because even though the air looks clear, sunlight actually bounces off air molecules, in all directions. The bright blue sky is just sunlight bouncing into your eyes from all those air molecules in the atmosphere.

-Rachel, grade 8

You know that nobody could possibly travel faster than the speed of light, right? If they could, though, they couldn't  see the light from the flashlight.

Thank you  :) 
Rachel - Grade 8

What would happen is that the person would see light coming out of the flashlight at the speed of light. But even thought they were going that fast, and the beam from the light was going that fast from their point of view, the beam would also seem to going at the speed of light for a stationary observer looking on. Weird, huh?

What we call "weight" is the pull of gravity against our bodies. Gravity is stronger on the Earth than on the Moon, we weigh more. Gravity is weaker in space. 

So the answer is simple: as you move closer to the Moon, your weight increases BECAUSE gravity increases. You can't have one without the other.

Dear Katie,
Well, if they're inside the space shuttle or inside the space station, they don't use radios. They just talk. If you've seen them with radio headsets on, that's to talk to people on the ground. When they're outside in their space suits, there are two reasons for radios. First, space suits are airtight so the astronauts can breathe. That makes it hard for sound to get out (imagine someone sitting inside a parked car with all the windows rolled up and trying to talk to them). 

Second, sound needs air to travel, and there's no air in space. So even right next to each other, the sound couldn't travel from one astronaut's mouth to anothers' ear.

Dear Kirsten,
Wow. I'm not sure. It wasn't an asteroid, because they wouldn't have sparks shooting off. And if an asteroid were close enough to appear to move across the sky, the entire world would be on red alert, because it would be in danger of hitting us. Couldn't be a comet, for the same reason. If it was a very high-altitude meteorite, it would appear to move slowly. Maybe that was it--or maybe it was a piece of space junk, like a piece of an old satellite, plunging into Earth. I wish I'd seen it!

Dear Tom:
There doesn't have to be air, because a combustion engine carries its own oxygen to mix with hydrogen for burning. Spacecraft also carry thrusters with pressurized gas they can spurt out, with no burning, to push them in the opposite direction.

Dear Karen,
Actually, there are 22 isotopes of technetium, with as few as 47 and as many as 64 neutrons. It's certainly possible, since it's true. There's no rule saying you have to have the same number of neutrons as protons. It just tends to be more common.

I only have one question for you. How far away from earth is Pluto? 
Stephany

Dear Stephany:
Thank goodness you have only one question, because I only have one answer. Luckily, they match: Pluto is a about 3 1/2 billion miles away from Earth, on average.

Dear Rachel:
They're not telling us as a warning. They're telling us to let us know about a fascinating thing about the universe: things change, often in dramatic ways, over long periods of time--like galaxies colliding. Even if it was going to happen tomorrow, they wouldn't be warning us. The stars in each galaxy have so much space in between them that the odds are there won't even be a single collision; the galaxies will merge, rather than collide. So the folks a million years in the future can relax.

The aurora borealis is what happens when tiny particles emitted by the Sun come close to Earth and fall toward the magnetic north pole, making the air molecules glow. You can see them in Alaska, or anywhere that reaches above the Arctic circle. There are southern lights, too, in Antarctica. Sometimes, when they're very strong, you can see Northern Lights in Wisconsin, too, but it's much more rare.

Thanks, Steven, for some excellent questions. Someone DID find other planets outside the solar system. The first one was found in 1995, and since then more than 100 more have been found. All of them are huge--as big as Saturn, at least, and some bigger than Jupiter. We think life couldn't exist on them, but there are probably much smaller planets near some of them, something like Earth. We can't see anything that small that far away yet, but we're working on it.

Also, do you think that NASA or someone is trying to find life in space?

I know they are. Some astronomers outside of NASA are listening to hear if alien civilizations are sending out radio signals, and looking to see if they're flashing lasers. And within NASA, there's a lot of interest in exobiology, the study of (or, until we find it, the search for) life beyond Earth. We don't have the telescopes or space probes yet that can actually find life, but again, NASA is working hard to develop them. If we're lucky, we could find life of SOME sort, probably bacterial, on Mars or even outside our solar system, as early as ten years from now.

One more question,  later on in our lives will  NASA start transporting people into space and build a whole new comuntity?  Thanks!

That's a much harder question. It takes a lot more money to build spacecraft to transport people into space than it does to build telescopes or robotic space probes, because you need life-support and lots of safety equipment. And a lot more money beyond that to build a space station of some kind that could house any reasonable number of people. If our country decided this was really really important, and decided to put a lot of money into it, we could do it in a few years, just like we got to the Moon in the 1960s. Right now, NASA gets about $15 billion dollars every year from the government. The military gets 20 times that much. So until we spend the money, it won't happen.

Dear Calvin,
No, the Earth is not a star. The Sun is, though. A star is a huge ball of very very hot gas. 

Dear Mr. Lemonick,
A first grader wants to know if the sun's gravity keeps the planets from flying off into space, what keeps the planets from being pulled into the sun?

Dear First Grader,
That is an excellent question. It's the planet's motion that keeps them from being pulled in. At any given moment, the Earth's motion wants to continue in a straight line out into space. At that same moment, the Sun's gravity wants the Earth to fall straight into the Sun. When those two forces are combined, the result is a circular path around the sun.

Dear Bill,
Space starts about 100 miles up.

Once it gets to that speed, the rockets go off, so there's nothing to make it continue to accelerate. But in space, there's nothing to make it slow down, either. You have to realize that it isn't ging 17,500 m.p.h. straight up; it goes at an angle, which puts it into orbit.

A worm hole is a hole that goes from one part of the universe to another, by a shortcut. If they exist (no one knows), it's possible because space curves. If space were two-dimensional, it might be like the surface of an apple. To get from one side to another, a worm COULD crawl around the outside. But it would be faster to eat its way straight through. That's why it's called a wormhole.

In real space, you have to somehow imagine, not a curving surface like the skin of an apple, but all of space curving. I myself find it impossible to imagine, but physicists say it's true anyway. So a wormhole in space is like the wormhole in the apple--a shortcut, out of our universe entirely, and back again.

Dear Mr. Lemonick,
What would happen if we lost the moon? I have looked in about 10 moon books and still haven't found the answer to this question.
Lee H. (6th Grade)

Dear Lee,
Good question. Until recently, the answer would have been that we'd lose most of our ocean tides and a pretty sight in the night sky. But astronomers have now calculated that the Moon helps keep Earth stable, with the equator more or less facing the Sun. Without the Moon, Earth could flip unpredictably, and the seasons would suddenly be reversed--and then it could happen again and again. If that's true, then the loss of the moon could meant the end of life on Earth. 

We have several questions for you.

Classical Charter School 6th Grade

Do stars have atmospheres?

Well,  sort of. They definitely have a layer of gas beyond the visible surface, which is what an atmosphere is. But it's made of super-hot gas, so you wouldn't want to breathe it.

Is Pluto ever closer to the Sun than Uranus? 

Nope

Does Orion have a "head?" 

I don't think there's any bright star that counts as his head, no. You just have to imagine it.

Do constellations overlap, in other words, can stars be a part of more than one constellation? 

Not in any single scheme. That is to say, the constellations identified by the Greeks didn't overlap, but a Greek constellation might overlap a Chinese one. The boundaries, after all, aren't in the sky, but in our imaginations.

They're taken through a telescope. Before the 1970s, astronomers attached a large camera to the telescope, and made their pictures on photographic film. Now they use electronic cameras, just like the digital cameras lots of people use for their family pictures--except a LOT more powerful. The most detailed and spectacular pictures come from the Hubble Space Telescope. It isn't the biggest or  most powerful telescope, but it's in orbit where there's no air to slightly blur the pictures.

It's the only actual "piece," if you're talking about solid matter. The rest of the star is blown out into space in the form of super-hot gas--so it's still around, but in the form of individual atoms, not pieces.

Dear Liz,
Well....people began "spotting" other galaxies at least 300 years ago. About 80 years ago, they realized that these were indeed other galaxies, not strange objects within our own galaxy. We know know there are at least 100 billion galaxies in the universe. So If someone spotted another one....it's not a very exciting discovery.

Dear Jetta,
There's no air in outer space because gravity keeps it close to earth 

They use light-years because the distances are so huge that miles would involve gigantic numbers. One light-year is bewteen 5 and 6 trillion miles--the distance light travels in years. And it's a lot easier to say the galaxy is 100,000 light-years across than saying it's 500,000,000,000,000,000 miles across.

Dear Curtis,
Nope. When scientists say the universe is expanding, they really mean that the space between galaxies is stretching. We're in the same place we've always been in; it's just that the space between us and distant galaxies is getting greater. So when we look "out there" we shouldn't expect to see ourselves, because we're right here and always have been (aside from some minimal local motion. 

So why don't we see multiple images of OTHER galaxies? Same reason we don't see multiple images of the sun, whose image we see 8 light-minutes in the past. the light reaching us from any one galaxy now, in 2002, is light that's just gotten here after traveling a billion or two billion or whatever years. Next year, new light will arrive from that same galaxy--but this year's light will by then have gone a light-year past us, into deep space. 

Dear Miranda,
My new book should be out in March of 2003.

Dear Jenna,
Rumors of a hole in the atmosphere are completely untrue. First, the only "hole" scientists talk about is a hole in the ozone layer, which is a very thin layer of naturally occurring gas high in the stratosphere. Second, it's not really a hole; it's a thinning. Third, it's only happening above the North and South pole. 

It's still important, because, thin as it is, the ozone protects us from ultraviolet light from the sun, which causes sunburns. If the holes were to get bigger, we'd have to be a lot more careful about sunscreen, but they seem to be staying the same, and may start shrinking soon.

But even if all the ozone disappeared completely, all over the world, the atmosphere would still be there. We could breathe, planes could fly, and meteors would still burn up before they hit the ground, just like now.

Dear Mr. Lemonick, 
Is it true that scientists are considering changing pluto so it's not called a planet? If so then what would pluto be considered in general?
Jenna, Grade 7, age 12

Dear Jenna,
Some scientists do say Pluto shouldn't be called a planet,  because it's very different from the inner planets like Earth and Mars, which are mostly rock, and also different from the outer planets, like Jupiter and Neptune, which are mostly gas. Pluto is mostly ice--which means it's MOST like a comet, only much bigger. Over the past few years, astronomers have found other very large comet-like objects that are bigger than comets but smaller than Pluto; they also know that several of the large moons orbiting Neptune and Saturn are more like comets--and like Pluto--than like anything else.

So they argue that Pluto should be considered the biggest of this comet-like group of objects, which range in size from a few miles across to a thousand or more. 

But officially, the International Astronomical Union won't change anything. That's because putting Pluto in one category or another doesn't change anthing about it scientifically, and it doesn't really do any harm to have Pluto be in TWO categories at once. That's where it's going to stay.

Dear Renee,
Hmm. I don't think more moons are revolving around Pluto. I think you may mean Jupiter, where they discovered a new bunch just recently. They certainly don't appear out of thin air. Jupiter does attract new moons (the new ones are pretty tiny; a few miles across at most) from the asteroid belt, but we're also getting better at finding them, using the Hubble telescope and the Galileo spacecraft. 

Dear Colton and Jeff,
The space shuttle flies above 100 miles, which is more or less where outer space begins. There's no sharp dividing line, since earth's atmosphere fades gradually.

Dear Rachel,
Sure, elephants could float if you had a space ship big enough to hold them. When they say "weightless," they MEAN weightless--that counts for everything. (Think about it this way: do elephants have trouble floating in water just because they weigh more on land? Nope. Same thing in space). The rocket boosters fall back to earth, almost always in the ocean. Some of them have parachutes so NASA can get them back and use them again. Others just sink. 

Dear Stephanie,
Lots and lots. Before people went into space, they sent monkeys and dogs to make sure it was safe (lots of people don't think that's very fair, but that's how it happened). Since then, they've taken tadpoles, mice, bees and I can't even remember what else, to see if being in space changes the way they act or affects their health. That's to find out what might happent to humans if they spent a long time in space.

We don't actually know what would happen if someone tried to go through a black hole, but as far as scientists know anyone who did would be crushed smaller than an atom. A LOT smaller. The reason is that a black hole is a place where gravity is so strong it might as well be infinite. It's so strong that an entire star is squeezed into a space too small to measure. If a star can't maintain its size and shape in a black hole, there's not much chance for a human.

Dear Rachel,
No, because the blood would have oxygen in it. If you cut your veins, it would be blue, because there would be no oxygen to mix with it. But I wouldn't plan on trying the experiment.

Dear Ariana,
Mars is about the same age as Earth: about 4.5 billion years, give or take 100 million or so. Among the good websites: www.nasa.gov and www.planetarysociety.org

Dear Hilary,
Betelgeuse is about 10 billion years old. It's made of hydrogen, helium, carbon, oxygen and lots of other elements, but none heavier than iron.

Dear Mr. Lemonick,
How come whenever a black hole suckes in a giant star it still stays the size of a pin point? Do you think there is a worm hole on the other side of the black hole and that's why it doesn't get any bigger? 
Celeste, grade 6

Dear Celeste, 
Well, there COULD be a wormhole leading out of the core of a black hole, but there doesn't have to be one to explain why it doesn't get bigger. It doesn't get bigger because gravity is so strong inside a black hole that no matter how much stuff you put in, it all gets squeezed down to zero size 

Dear Rachel, 
The distance varies, depending on whether Pluto and Earth are on the same side of the Sun or on opposite sides, so the answer is different at different times of the years.  Not much different though: it goes from about 3.8 billion miles to about 3.6 billion.  If you prefer round numbers (which I do), you can say Pluto is nearly 4 billion miles from Earth.  That means it's 40 times farther from the Sun than Earth is--which also means the Sun is 1,600 times dimmer than it is here. 

Dear Luciana, 
The answer is that outer space begins where Earth's atmosphere ends--but that's a little bit hard to pinpoint. As you go higher and higher, the air gets thinner and thinner. At about 100 miles above the earth's surface, it's so thin that you can barely measure it. But there's still some there. Even 150 miles up, you can find air molecules, but very very few. 

So there's no sharp dividing line where outer space REALLY begins. We human beings like dividing lines, though, so we've agreed that 100 miles up is a good cutoff. That's where outer space officially begins.

Dear Mr. Lemonick,
In 1969 did anyone really land on the moon since the flag was waving?
Amy, Grade 6

Dear Amy, 
Good question! In pictures taken on the moon in 1969, the astronauts are shown standing next to the American flag they had planted, which looked as though it was was waving proudly in the breeze. Trouble is, there's no air on the moon, therefore no breeze. So was the photo a fake?

Nope. The people at NASA realized the flag would droop on the airless moon, and a droopy flag looks bad. So they sewed wires into the cloth to make the flag stiff and nice to look at. They didn't count on smart sixth-graders noticing something was wrong.

Dear Mr. Lemonick,
How fast does the space shuttle have to go to break through earth's atmosphere?
Thanks,
Alex, Grade 4

Dear Alex,
The space shuttle has to go at least 17,500 m.p.h.--but not to break through Earth's atmosphere. It has to go that fast to break free enough of Earth's GRAVITY to go into orbit. The atmosphere doesn't really hold it back much at all.

Dear Alicia,
Nobody knows how many more there are until we actually discover them, but astronomers think there are MILLIONS of planets orbiting stars in our galaxy. The scientists didn't know about them before because planets are really really hard to find. Just think of how tiny a star looks in the sky, and then realize that a planet is probably a million times dimmer than the star. It's so hard to do that the very first planet ever discovered beyond our own solar system was found just five years ago.

Dear Luke,
It's kind of a broad question. We know thanks to Einstein that space is distorted by the gravity of a black hole, and distances do change. A mile's worth of empty space becomes much less as you get closer to a black hole. But how much less depends on how close you are and how massive the black hole is. At the very center, distances become zero. Get far enough away, and distances are normal. In between, distances can be everything in between normal and zero.

Dear Kelly,
Many people believe God made the universe, and that includes lots of scientists. Most scientists also believe the universe was created with the laws of physics. Religious scientists therefore usually think that God made the universe indirectly , by creating the laws of physics.

Dear Mark, 
That's a very tough question, since nobody knows what IS the biggest star. Since I can't answer that one, I'll answer another that's in the ballpark: What's the  biggest star we can see from Earth? Unless I'm forgetting one, Betelgeuse is the winner. It's the reddish star you can see in the shoulder of Orion the Hunter. It's about 20 times as massive as our Sun, and it's about 800 times as large. If you put Betelgeuse where the Sun is, we'd be INSIDE the star. Luckily, Betelgeuse is about 650 light-years away, which is about 16 times as far a way as the nearest star. (One light-year is about 6 trillion miles.)