Does the Universe have an edge?

I don't think anyone really knows. There are lots of ideas, though. If there has only been one Big Bang (which in itself seems unlikely to me), then the Universe has an average radius, approximately the age of the universe times the speed of light, ignoring the possibility of stuff that travels faster than the speed of light. Intergalactic space is thought to have an average density of something like 1 hydrogen atom per cubic meter [citation needed] although recent news from the big telescopes suggests that there are stars and planets also outside of galaxies. 1 atom/m^3 is pretty empty.  If the universe is alone, I suspect there is no way we will ever see its edge, as it is receding from us at or faster than the speed of light.

There are cosmologists who believe in all seriousness that our universe is expanding like a bubble in a foam of universes, in which case it is possible, I suspect, that we will some day detect the boundary, where it impinges on another universe. Does the edge slow down? Is there a shock wave? Please forgive me for being so Newtonian about this, but I can't imagine a foam of universes where all of them can expand indefinitely at or above the speed of light. Not, at least if they all share the same dimensions*. Then the question begs to be asked, does the foam have a boundary? What would be beyond that?

"It's turtles all the way down."

*What if our three familiar dimensions are actually dimensions #38576027184365756392,  #38576027184365756393, and #38576027184365756394, and other universes are also three dimensional but occupy other dimensions than our particular three of length, width, and height? (I am ignoring the 9, 11, 17 or whatever dimensions are required by string theory.)

How many moons are there in space?

Space is a really big place. There are billions of galaxies and each one has billions of stars. Recent discoveries suggest that planetary systems are the rule and not the exception around stars. So the number of moons in space is uncountable.

I suspect you meant to ask how many moons there are in our solar system. When I was young, a long time ago, books about the solar system gave precise numbers for the moons of each planet. Then came the Pioneer and Voyager spacecraft and vastly better telescopes. The answer is no one knows. It seems every time we a get closer look at the distant planets, like Saturn, Uranus, or Neptune, we discover they have more moons than we previously thought. Even Pluto is now known to have at least two moons.

This Friday (March 6, 2015) the dwarf planet Ceres, the largest body in the Asteroid Belt, will get a new moon, or at least a satellite. NASA’s Dawn spacecraft will slip into orbit around this body for a visit.

Ultimate Source Of Nuclear Energy

We have been asked during our energy program how nuclear energy fits into the mix when all of our other forms of energy derive ultimately from the sun.

The tie-in is actually pretty interesting. Most of the energy we use comes directly or indirectly from the sun, which is “burning” hydrogen created during the Big bang. Stars fuse hydrogen atoms into heavier elements only up to iron. The planets, and all the elements heavier than iron (further down the periodic table) are composed of stuff created in supernovae, dying exploding stars, that preceded the sun. Only a supernova is energetic enough to create the exotic and unstable elements up to uranium. So nuclear reactors, which run primarily on uranium, ultimately derive their energy also from stars, although not our sun.

Geology questions from a class after our Rocks! program.

How old is our meteorite?

The meteorite fell to earth from interplanetary space. That is, it probably originated inside our solar system. Because it is an iron-nickel meteorite it probably was part once of a larger body, a planet or other large object that was broken up in a collision with another large object.  Most of these collisions would have taken place in the first one or two billion years of our solar system which is about four and a half billion years old. That would make our meteorite probably about three billion years old, give or take a billion. That is really, really, really old, give or take a really.

How heavy are the rocks?

We have a big piece of petrified wood that doesn't travel on the van because it weighs about sixty pounds. Most of our rocks are a pound or two, the geodes and crystals weigh only fractions of a pound. We have tried to collect rocks that are big enough to be interesting to look at or are interesting enough that it doesn't matter if they are small.

How old is the pumice rock?

How old is the obsidian?

Both of these rocks were produced by explosions of the Valles Caldera volcano in the mountains behind Los Alamos and White Rock. I don't know if they were produced at the same time or during the same cycle of eruptions, but the last eruption was between one and two million years ago so that is as young as they can possibly be.

What is our newest rock?

Our newest rock is the concrete core sample which was cut out of a sidewalk sometime in the last twenty years. Concrete is a man-made rock, and I think this core was from a sidewalk somewhere up "on the hill" so it can't be more than fifty years old. There weren't sidewalks here more than about fifty years ago. Sometimes cores are cut to see what condition the concrete is in below the visible surface, other times they are cut to make a place to put up a new sign in the sidewalk.

The other young rocks are also man-made. Slag from the San Pedro Mine near Golden, NM is left over from a gold mining operation in the early part of the twentieth century, and we have one small piece of Trinitite in a plastic globe. The trinitite actually has a birthday, as it was formed when the sand below the first atomic explosion melted on July 6th, 1945.

How old is our oldest rock?

After the meteorite, which I discussed above, our oldest rock is a piece of quartzite from the Brazos Cliffs area near Tierra Amarilla, NM. The rock that forms these cliffs is the oldest surface rock in the state, and is about 1.7 billion years old. That is way before dinosaurs, in fact, it is possible a dinosaur may have tripped on our rock or turned it over looking for goodies to eat!

How many rocks do we have at the museum?

Please don't make me count them! In our rock museum, I think we probably use about forty rocks. We probably have three times that many either stored or in the sample bags. When we think of a rock that we would like to have for the program, we often go outdoors and look for it. It helps to know where to look.

How many pieces of pumice do we have?

We only travel with one piece of pumice, but you have to admit it is a good one! We have some small pieces, but pumice is so soft that when we take them around, they crunch against other rocks that are harder and they get ground into powder. So we usually leave them home.

What are our favorite and least favorite rocks?

I can only speak for myself, but all of the rocks in our program are favorites. My own personal least favorite rock is a boulder in a canyon near Taos that rolled one day when I stepped on it and I broke my leg.

My very best favorites are probably the meteorite and the dinosaur stomach rocks, but I am proud of collecting a very heavy piece of fossil pond scum that rarely visits classrooms because it is so heavy. Each of the rocks in the program has an interesting story, and most rocks you see around have good stories too. Sometimes it is hard to choose one rock story over another.

These are great questions, and as a teacher I can tell you that good questions are one of the nicest things you can give a teacher. Thanks for asking, and keep being good scientists!

Two hard astronomy questions from students.

1.) What makes gravity?

The easy answer is that we don't really know what gravity is. Sir Isaac Newton described it very well, but describing is different from explaining. Newton figured out that gravity pulls between any two objects with mass. Remember that mass is the amount of stuff, or matter, in something. The greater the masses the stronger the pull. He also figured out that gravity depends on the distance between the objects, that it gets weaker as the square of the distance. That means if the moon were twice as far away, Earth would pull on it 1/4 as strongly. Three times as far and the pull would be 1/9th. This was very clever for Newton, but he didn't know what gravity is.

Albert Einstein also took a crack at it, describing it as the bending of a space-time continuum (Whoa!) by objects with mass. What he meant was that space, in more than three dimensions, is bent or warped by mass in such a way as to bring massive objects together. Again, this is a description and not an explanation. Gravity has many mysteries wrapped up in it, all of our other forces have opposites, magnets can pull or push, electricity can pull or push, do you think some day somebody, maybe you, will discover the push that comes with the pull of gravity? Or maybe you will be the one to explain gravity! I bet there is a Nobel Prize waiting for the person who does.

2.) Why does the Earth spin?

I like this question! I am tempted to say that the earth is spinning because it was spinning yesterday and it has a lot of inertia. I don't think that answers your question, though.

The earth formed at the same time as the rest of our solar system out of debris (junk) left over after a star or several stars before our sun exploded. All this stuff flying through space was massive enough that gravity started pulling it together toward one big pile in the middle. This was the birth of our sun, but it was not that simple. The solar system is big, it is huge, it is GIGANTIC! The stuff was moving around in all directions, and it would make sense that on the average, there would be no overall rotational bias, or preference to be going one way any more than any other. But just like your kitchen sink or bathtub, there is always a slight preference for one direction or another. In the solar system's case, this might have been pushed along a little by the spin of the Milky Way galaxy. As the Solar System formed, it behaved like the whirlpool in a bathtub. Distant parts that were moving very slowly went faster as they fell closer to the sun. Not only that, but the orbits of the planets as they formed were all in the same direction, just like that whirlpool. The planets are left-overs from stuff that fell but missed hitting the sun and by collisions with other stuff settled into stable orbits.

The planets themselves were formed by stuff falling in on them, and the same thing happened again. A tiny amount of spin very far away was turned into more spin as the object fell closer and hit the earth. This in turn was probably being pushed by the spin of the solar system, as nearly all the planets spin in the same direction. We think the exceptions are planets that started out in the right direction and then were smashed by asteroids or small early planets that turned them to spinning backwards. So Earth was also like a whirlpool in a drain, most of the matter that fell on the planet as it formed had a preference to be spinning in from west to east, pushing our planet to spin in that direction.

Really, the earth is spinning because it was spinning yesterday, and it has a lot of inertia. :)

Here is a question for you: When you fill a sink with water, there are currents flowing in every direction in the water. If you let it sit, eventually those currents will slow down and stop because water has friction. How long do you think you have to wait for the water to be SO still that it won't make a whirlpool when you open the drain? Try it with a sink or tub where you can open the drain without reaching into the water, which will start currents again. Keep track of your results, and record which way the whirlpool spins if you still get one.

How do the stars make constellations?

Almost all of the stars we can see in the night sky are members of the Milky Way Galaxy. The brightest star for us is the sun, and it is a long way away, 93,000,000 miles. The next nearest stars are thousands of times further away. All of the stars are moving, but they are so far away that they appear to be standing still relative to each other. (This is also the reason why it looks like the moon follows you around when you are riding in a car.) The patterns they form in the sky are a complete accident that depends on their locations compared to each other, and on our position on Earth from which we see them. Some constellations are made of stars that are not even very close to each other! So the trick answer to your question is that stars don't make constellations, people make constellations up from the random arrangement of stars in deep space.

One of the special things about constellations is that we see stars as being placed on a surface like the inside of a bowl. But stars are really widely spread out through space. There is no bowl.

Try this: Place four or five small items all over a table at random. Erasers would work well. Now stand back several table lengths, stoop so your eyes are level with the table top, and close one eye. Can you see that the objects look like they are all in a line?

How was the world made?

This is an interesting and deep question. The scientists who study this question are called cosmologists. Most cosmologists agree that our universe was born about twelve billion years ago in an event they call the big bang. While the science of the big bang is pretty well understood, it is difficult to explain, and very weird stuff. Some things that are important to know are that it resulted in a lot of energy and a lot of hydrogen gas that was spread out in lumps in the early expanding universe. It also apparently produced even more ‘dark matter’ and ‘dark energy,’ but no one knows what they are yet. Maybe you will be able to help us with that some day!

            After a few billion years, some of the lumps of hydrogen gas settled down and gravity pulled the hydrogen in the lumps closer and tighter together. This made the temperature rise; heating the gas so hot that nuclear fusion began. In nuclear fusion, atoms combine to make larger atoms. Fusion releases a lot of energy, raising the temperature of the gas balls, and creating new and heavier elements. These balls are what we call stars.

            The big bang made mostly hydrogen and I think a little bit of helium. These are the two lightest elements. Stars can cook all the elements up to elements as heavy as iron out of hydrogen and helium, but as the amount of iron increases, it slows down the action of the star. Eventually the star runs out of energy and collapses. The collapse of the star can set off another huge reaction that blows it to smithereens and creates even more elements, up to the weight of uranium. These are scattered throughout the space where the star had been.

            Our sun was born after this had already happened. It started as a lump of hydrogen, and condensed to become a star. The star had enough gravity to attract some of the remains of the earlier star, which condensed first into a ring or rings like those around Saturn, and then those condensed into the planets. Earth and all of its materials including you and me are the product of hydrogen from the big bang and everything else is from stardust. Earth condensed about four and a half billion years ago, and our sun will keep on being like a sun for Earth for at least another four and a half billion years.