Astronomy for Students -- a short course by request

Questions from Students -- a long series of questions submitted to Barry by local junior high students

OTHER QUESTIONS

Could Adam and Eve see the stars?
Do stars come from the sun?
Is Pluto still a planet?
Is there life on Mars?
Can you stand under the moon?
How many galaxies are there?
What happens during a solar eclipse?
Will it fly?
Do planets put out their own light?

September, 2007

Ryan (aged 11) would like to ask if Adam and Eve could see the stars as the light from the closest star is meant to take 1000 years to get to the earth.

Answer: Thank you for your question.  First, just to correct something you said. Light from the nearest star reaches us in four years at the speed light is going now. Light from our sun (which is actually our nearest star) only takes eight minutes to get to us.

Now to respond to your question: Yes, Adam and Eve could see the stars.  Light traveled much faster when they were alive.  Let me see if I can explain it to you so you can understand.

When we look out into outer space, it seems like there is a lot of nothing with stars scattered around, right?  But we have found out that all that blank stuff is not 'nothing.'  There is a type of energy all over the place that is just tremendous.  It is called the Zero Point Energy, because we can find it even when there are no molecules and no heat.  It travels in short waves and medium waves and long waves in every direction.

Now, have you and a friend ever dropped rocks in a pond?  If you and your friend are standing apart from each other and each of you drops a rock, ripples will spread out from yours and ripples will spread out from your friend's.  And sometimes those ripples will meet each other and there will be a little bit higher wave or even a bit of foam for just a moment, and then it will be gone. 

The Zero Point Energy waves do the same thing.  They are constantly hitting each other and making little tiny bits of high energy for a moment.  We call these bits 'virtual particles.'  They are not real particles because they do not last.  But they do pop into existence for the tiniest bit of a second and then they are gone again.  

In the Bible, God says He stretched out the heavens.  Have you stretched a rubber band?  When you stretch it, you put your own energy into it and then when you let it go, some of your energy becomes that rubber band flying across the room.  When God stretched out the heavens, He put a whole lot of energy into space.  More than anyone can imagine.  At first that energy was just like the energy in the rubber band before you let it go.  That is called potential energy.  It's not moving yet, but it's ready to move as soon as you let it go.  When you let it go, all that potential energy becomes active energy.  We call active energy 'kinetic' energy. 

When God stretched space, at the very first moments there was not much kinetic energy.  It was mostly potential energy.  So there was not much Zero Point Energy, and that means there were not many virtual particles.

But very quickly, just like when you send a rubber band flying, that potential energy started to become kinetic energy -- the Zero Point Energy.  It did not happen all at once, but it did happen pretty fast. 

Now, when those waves of the Zero Point Energy make virtual particles, a little bit of light, called a photon, might be speeding along its way and hit that virtual particle.  That virtual particle absorbs the light, just like your shirt absorbs the sunlight so that the sunlight does not shine on your skin.  But the virtual particle is gone very quickly so the photon of light can go back on its way again.

If there are not many virtual particles, then the light can zip very quickly through space -- much faster than now.  Much MUCH faster than now!  So when Adam and Eve were alive, they were able to see many far distant stars shining in the new sky because the light was able to reach earth so fast. 

But through time, the light has taken longer.  That is not because the light gets tired or slows down because it has to go a long way.  No, it is because more and more virtual particles are popping into and out of existence because the Zero Point Energy has become greater and greater, so with more and more waves, they hit each other more often and there are more virtual particles everywhere, at any time.

For a long time most people thought that light was instant.  It seems that way, doesn't it?  You turn on a switch on the wall and the light shines in the ceiling right away.  Then people decided that light did take time to travel, but it was very, very fast.  A year before I was born, some scientists decided that light must always travel at the same speed as now.  This was a strange thing to decide, because for about 300 years, other scientists had been measuring how fast light travels and found out that it seemed to be getting slower with time.  There were a lot of articles about it and a lot of people discussing how strange it was that light seemed to be slowing down.

Today most teachers and professors will teach that light has always been the same speed.  But that is not true.  We know from what people measured before and we know because of some other things, too, that light was much faster in the past.

That is a long explanation.  I could have said, Yes, Adam and Eve saw the stars, but that would not have helped you understand why.  I hope this helps a little bit.  Please email me back if you have more questions or if you do not understand something I said.

March, 2007

From Max, fourth grade May 10, 2007

1.  Do the stars come from the sun? 
Answer:  No, they do not.  Our sun is a star.  It is not even a very big star!  It just looks big because it is closer to us than the other stars.  Our sun is the star God gave us to light up the earth. 

2.  Is Pluto still a planet?  I heard it wasn't!
Answer:  Although we all learned, when we were younger, that there were nine planets and Pluto was the furthest planet out from the sun, Pluto was so strange it probably never was a true planet the way the others are.  Why does it seem strange?  All the other planets go around the sun in their own sort of lop-sided circles and they never cross each other's paths.  But Pluto not only crossed paths with Neptune, the planet closest to it, but Pluto also goes around the sun at an angle.  All the other planets are like peas on a plate, going round and round the center sun.  They make a sort of flat shape if you look at the solar system sideways.  But Pluto isn't on the 'plate.'  It travels around the sun going way above the plate on one side and way under it on the other.  So astronomers today have decided that Pluto is really more like a large asteroid going around the sun its own way, the way a lot of other asteroids do.  Some of the large asteroids even have little moons of their own going around them, the same way Pluto does. 

Scientists are just like people everywhere.  The more they learn, the more they have to change some of the things they were thinking at first.  They have changed their minds about what Pluto is because of the things they have learned about it. 

3.  Is there life on Mars?  Because I heard the astronauts found water on Mars.
Answer:  There is certainly water on Mars.  What we have found is mostly ice on the north and south poles though.  Probably at one time, long ago, Mars had a giant flood the same way Earth did at the time of Noah.  Both Mars and Earth are planets which have a lot of radioactive materials deep inside and these radioactive materials, as they change, give off a lot of heat.  This heat made the rocks inside so hot that the water that was in the rocks at first (and yes, a lot of rocks have little bits of water all through them) steamed out and became big hot pools of water under the surface of the planet.  Finally, these waters got hot enough to explode out.  If you read Genesis 7:11, you will find that God tells us that these waters burst out from under the surface of the earth even before the rain started to fall.  We can see that the northern part of Mars was covered with water once upon a time, but that water is gone now.  Because Mars does not have air like earth does, the water which did not freeze at the north and south poles finally evaporated into space. 

Does this mean there is life on Mars?  No, not at all.  We know that water is necessary for life on earth, but that does not mean that there is going to be life everywhere there is water.  We are pretty sure that here in our own solar system -- the planets that go around our sun -- that there is no life on any planet but our earth unless perhaps there is something like little bacteria or something very small someplace else.  But out there in far distant space?  We have no idea what is out there.

4.  Is it possible to be directly underneath the moon when you are on earth?
Answer:  Yes, it is.  If the moon goes directly overhead, as it does over some parts of the earth, the people who live in those parts of the earth will be directly underneath the moon.

5.  How many galaxies are there?
Answer:  We live in one galaxy called the Milky Way Galaxy.  We are not even near the center of it, but we are way out on one the 'pinwheel' arms.  Our own galaxy has about 150,000,000,000 stars!  That's more than all the blades of grass in a big park.  Our Milky Way Galaxy is big, but not as big as some of the giant galaxies.  Astronomers have looked way out into space and found out that there are billions of galaxies.  Each of them has billions of stars.  One billion looks like this:  1,000,000,000.  We cannot really even imagine anything as big as outer space.  We cannot really even imagine all the stars and galaxies there are.  But the Bible tells us that God named every single star!  Can you imagine over billions and billions of names and God doesn't even forget one of them!

6.  What happens during a solar eclipse?  Is it light or dark out?
Answer:  I want you to do an experiment.  It will take three people, so get your Mom and Dad or a couple of friends to help you.  You stand in the middle of a room.  Another person turns on a flashlight and shines it at you.  The third person starts walking around you in a circle.  He will come between you and the flashlight so you cannot see the light from the flashlight.  You have just shown what happens during a solar eclipse.  You were the earth and the flashlight was the sun.  The person walking around you was the moon. 

Our moon goes around us just like we go around the sun.  Sometimes the moon comes between the earth and the sun during the daytime.  Then it blocks the sun's light on part of the earth.  That part of the earth will be as dark as night for about three minutes, until the moon moves out of the way on its path around the earth.  

From someone who did not sign his or her name:  May 10, 2007

A plane is standing on runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?

Answer:  The plane won’t take off as the conveyer is, effectively, holding the plane still in relation to the air, and it is the airspeed past the wings which will give a plane (or jet) its lift.

[there have been several disagreements to our response sent to us in emails. Here is a good explanation from Doug Harold which disagrees with us:

I believe that there is an error in the response. The plane will fly, because the wheels on an airplane are free-wheeling. Just release the brakes, & the prop or jet engine will cause the airplane to move forward & develop lift regardless of the conveyor. The conveyor could be running backwards at 1000 times the required take-off speed of the plane, & the plane will still accelerate in the opposite direction of the conveyor, develop lift, and take off normally. (Of course, this neglects the very small amount of friction in the wheel bearings.)

If you were to lock the brakes on the plane (& assuming that neither they nor the tires slip), then the plane will move backwards along with the conveyor (not developing lift) regardless of whether or not the engine is running. It could be running wide open, & the plane will still move backwards at the speed of the conveyor (as long as the brakes are locked).

On the other hand, if one were to fasten wings on a car & place it on the conveyor in a similar fashion, then the car would remain in place (& the wings would not develop lift). However, an aircraft does not develop forward thrust using its tires as a car does.

I realize this isn't an important issue. I just thought that I would mention it in passing.

in a second email, giving us permission to put his explanation up here, he continued:

As far as visualizing this problem, forget about the engine & prop for a moment. Instead, put the plane on the conveyor & hook up a horse standing on the ground beside the conveyor. With the brakes unlocked & the wheels spinning freely, will the horse be able to pull the plane forward (even with the conveyor running in the opposite direction)? Of course, it will; the thing to remember is that the wheels are able to spin freely & forward thrust does not depend on the motion of the conveyor. So the conveyor doesn't accomplish a thing in this case (so long as the brakes are not applied).

On the other hand, a car is altogether different, because it develops forward thrust using its wheels which are in contact with the conveyor. So if the conveyor is running backwards at the same speed that the cars speedometer reads, then the car is setting still.]

From Nicole May, 2007:

I don't understand something.  You said that the giant planets put on their own light but I had never heard of that.  Can you tell me more about that?  Thank you!

Answer: The question you asked related to the radiation reflected from the Sun by the giant planets. We can measure the amount of energy that the planets reflect from the Sun in all wavelengths. We can also measure the amount of energy the planets radiate into space. As it turns out, Jupiter, Saturn and Neptune radiate more energy into space than they receive from the Sun. The indication is that the interiors of these planets are hot. One estimate for Jupiter gives its core temperature as 20,000 degrees Kelvin. The heat may come from radioactive decay processes or gravitational compression, or both. Note that the giant planets do not produce energy by nuclear fusion as they are too small and too cool. However, the heat from their interiors is largely responsible for the turbulence we see in their cloud-tops, with some resulting from the high rotation rate. Surprisingly, Uranus does not radiate more energy into space than it receives from the sun and so its cloud-tops are not as active as the other giant planets. The reason for this has not yet been fully discerned.