Category Archives: Explore

Center of Mass Fork Experiment

Center of mass (COM) it’s easy balancing act or a trick to try at home! All you need is 2 forks, a quarter, a cup, and some patience.

putting fork trick together (1)

Why does this look so weird? It all has to do with center of mass. COM is hard to define, but almost everyone has a great intuition for it! You find the COM of objects when you’re balancing things. Once an object is balanced, wherever you are holding up that object is where it’s COM is. You could probably guess where the center of mass is for a lot of symmetric objects. For example, a ruler’s COM is in the middle. But if you add some extra weight to the end, it’s COM will shift! 

rulers center changing (1)

A fork is pretty asymmetic, and that shows in it’s COM. 

Center of Mass Experiment

If you try to balance 2 forks on your fingers, you probably won’t win. This is where things get weird– the center of mass does not necessarily need to be within the object! For 2 forks, it ends up being just right outside of it. 

2 forks cm full (1)

Which makes the “trick” work. If you stick something, like a quarter, between the 2, now the center of mass of this collection of objects is now on the quarter. You will intuitively find the exact place on the quarter where the center of mass lies, when you achieve balance on something like the edge of a cup (pro tip: the more rigid the edge of the glass is, the better. We used the bottom of the cup here because that was less rounded, and hence stuck better, than the top of the cup). There you have it! Rather than thinking of it as a trick, think of it as you showing a weird property of physics in a simple way!

Can You Make Dry Ice Ice Cream!

You’ve probably heard of liquid nitrogen ice cream before. It’s made by mixing together ice cream ingredients with liquid nitrogen, which turns into a gas at -321º F. Learn more about that at https://www.thoughtco.com/cryogenics-definition-4142815. The intense coldness is what turns the ice cream ingredients from a liquid to a tasty solid.

Dry Ice Ice Cream

So by this logic, you should be able to make ice cream by just adding something really cold to your ice cream ingredients. Solid carbon dioxide, AKA dry ice, is a good candidate to experiment with. To be a solid, carbon dioxide has to be at least -109º F! When you mix dry ice into ice cream ingredients, something interesting happens. It does cool it down, but you additionally get a lot of bubbles. As the carbon dioxide sublimates from solid to gas, little pockets of gas gets trapped underneath the ice cream, and they escape to the surface in little bubbles of CO2.

dry ice ice cream (1)

Why don’t these bubbles form with liquid nitrogen? Both dry ice and liquid nitrogen are turning into gases. But, it’s a lot easier for a solid to sink to the bottom of the ice cream mix than a liquid. When making liquid nitrogen ice cream, if you leave the nitrogen alone, you won’t see it sink down to the bottom of the ice cream. So when the liquid nitrogen evaporates, the gas simply rises from the top of the mixture into the room. 

liquid nitrogen on top (1)

The little carbon dioxide bubbles that escape are the same as bubbles in a soda. That’s why it’s called carbonation! So in a way, you can create a sort of carbonated soft serve by mixing ice cream ingredients with dry ice– but be ready for it to be a bubbly mess.

LN CO2 comparison (1)

Note: You should never ingest liquid nitrogen or dry ice. It will burn you and harm you. When people eat liquid nitrogen ice cream, they’re just eating the ice cream ingredients, with all the liquid nitrogen changing phase into a gas before consuming it. The liquid nitrogen merely acts as a mechanism to cool down the ingredients. 

Written By: Amanda Williams

Gravity Falling Experiment: Feather in a Vacuum!

Galileo once proposed that all objects under gravity, whether they’re really heavy or really light, will fall and accelerate downwards at the same rate. In a famous experiment, he supposedly dropped both from the Leaning Tower of Pisa and proved it. 

gravity

Why is this true? For something with more mass, it does feel a stronger downward force from gravity.

BUT because of the mass, it’s harder for that thing to accelerate. (When you hear “accelerate,” think rate of falling).  So for something relatively heavy, the stronger pull of gravity and the toughness to accelerate it should perfectly balance each other out, causing things accelerate at the same rate. This fact is sometimes referred to as Newton’s 2nd Law. 

The problem with this explanation is that it seems to defy what we see every day, right? 

We dropped a penny and feather at the same time. You probably don’t need to do this experiment to guess what happens. The penny will hit the deck long before the feather. 

Feather Accelerating Different Rates

It’s not that Galileo and Newton are wrong, it’s just that their model is simple; it doesn’t take the full picture into account. The secret here is that Newton’s 2nd Law only holds true if gravity is the ONLY force acting on the two objects. If objects fall through the air, then air resistance plays a part. And of course, some objects are more affected by air resistance, like feathers. To design a better experiment, we could try the same objects, but get rid of the air! We’ll use a vacuum chamber.

get rid of the air vacuum

A vacuum chamber will suck out some air, creating less air resistance. The less air there is, the closer their rate of falling is! 

Vacuum Falling Rate Comparison

If you had no air at all, if you could truly get gravity to be the sole factor, then you could call the object being in free-fall, and you would prove Newton’s 2nd law true. For this reason, the feather experiment was re-created on the Moon by astronaut David Scott using a feather and a hammer. It works because yes, our Moon has gravity (because it has mass) but it doesn’t really have air resistance, because there’s basically no atmosphere. 

David Scott Feather Experiment

How about that? 

Written By: Amanda Williams

Crush Your Cans With Science and Recycle!

September 27th is Crush A Can Day and it’s a day to serve as a reminder that we CAN recycle our aluminum CANS! We love recycling and we’ve got a hot way to do it, with the help of science. 

how to crush a can and recycle

This is an experiment we recommend doing at home! All you need is a can, water, something hot like a stove, and tongs to keep you safe. First, scoop a little water into the can. By heating up the can, water expands into steam. This steam starts taking up all the room in the can, pushing out air.

recycle steam pushes out air

Seal the can with water. This causes two things: 

  1. The water cools down the steam, condensing it back into water. 
  2. Air can’t get back in the can.

seal the can

If air can’t get back in the can, and the steam is now taking up a lot less room because it’s cooler and condensed, you’ve created a can with nothing much in it- a vacuum! Our atmosphere exerts pressure on us all day every day. Up in Idyllwild, around 5000 feet in elevation, our atmosphere pushes about 12 pounds on every square inch of us (AKA 12 PSI). We typically don’t notice this pressure because it’s everywhere and usually evened out. But, not the case with our vacuum-can! And so, the can gets crushed by the pressure of our atmosphere that’s always there. 

crushed with pressure

We hope we’ve inspired you to recycle, and maybe experiment along the way!

Written By: Amanda Williams 

 

3D Printing an Asteroid

NASA has always been about accomplishing crazy. In the 1960s, the idea of people walking around on the moon was ludicrous, but NASA got them there anyways. Now, NASA is performing another crazy feat: sending a probe to an asteroid, collecting rock samples, and returning that probe to Earth. Additionally, the probe has created a digital map of the asteroid which we can recreate, simply by using a 3D printer.

OSIRISREx - 3D Printing Asteroid

In September 2016, the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer space probe (OSIRIS-REx for short) was launched aboard an Atlas V rocket. It quickly made its way into space and began its journey towards the asteroid designated 101955 Bennu. This journey lasted over two years as the robe used low-power thrusters and gravity assists from Earth to reach its destination.

Side by Side - 3D Printing Asteroid

Side by Side – 3D Printing Asteroid

OSIRIS-REx reached Bennu in December of 2018, and as it approached, it used its long-range PolyCam sensors to map out the surface of the asteroid. After arriving, OSIRIS-REx used its short-range cameras to take even higher resolution images of Bennu’s surface. NASA scientists used that data to create 3D models and released them to the public!

Rotation - 3D Printing Asteroid

Since we’re lucky enough to have a number of 3D printers here at camp, we decided to print our very own Bennu asteroid! You can see the results below, but if you want to have your own version of the asteroid, you can find the files at https://www.asteroidmission.org/updated-bennu-shape-model-3d-files/

Written By: Scott Yarbrough

Busting the Misconception Between Gravity and Atmospheric Pressure

A common misconception we see at AstroCamp is how gravity and atmospheric pressure work. It makes sense! The two seem interchangeable at a glance, however they both get weaker as altitude increases, and there can’t even be an atmosphere without gravity. Despite their similarities, the two are very different.

Gravity is a property of anything with mass. It’s one of the four fundamental forces in the universe, and it’s caused by an object bending spacetime around itself. The larger the object, the greater a force it will exert.

Pressure isn’t even a force (technically). It’s a measurement of how much force is being applied per unit area. A lot of force can be spread out over a large surface area so that the pressure is overall small, and a small force can be focused onto a small enough point to cause a high pressure.

When talking about atmospheric pressure, we’re talking about the average force per unit area the gas molecules are exerting on objects in the air. The air molecules are zooming everywhere and bouncing into everything. Every time they impact, they push with a tiny force.

Atmospheric pressure changes with 1) the rate of collisions and 2) the force of impact. More molecules mean more collisions, which leads to a higher air pressure. Similarly, heavier gases or gases moving at higher speeds will cause a higher impact force, also increasing the atmospheric pressure.

Air at sea level is being compressed by all of the air above it, weighing it down and increasing its density. When you increase altitude, the less air you have above you, so pressure goes down. This is why atmospheric pressure gets weaker the higher in altitude you go.

After learning how they both work, it’s easy to see why the effects of gravity and atmospheric pressure can get confused. But their differences are also prevalent enough that you should be able distinguish between the two!

Written By: Scott Yarbrough

Homopolar Motorcar

A homopolar motor is a device that relies on flowing electricity, magnetic fields, and the interaction between the two. It consists of a voltage source, neodymium magnets, and a conductor that allows electricity to flow. And it’s super easy to make yourself!

What you’ll need:

  • 1 AA battery
  • 2 neodymium magnets
  • Thick copper wire

 

————

Step 1

Place one of your magnets onto the positive terminal of the battery.

Holompolar Motorcar Step 1

Step 2

Use the already attached magnet to test the poles of the second magnet. Figure out which sides are repelling each other, and place the second magnet so that the repelling side faces away from the battery. This way, either both South poles or both North poles are facing outwards! (Note: it doesn’t matter which, as long as they’re consistent with each other!)

Holompolar Motorcar Step 2

Step 3

Shape your copper wire so that it can hook easily on the inside of the magnets. Try to maximize the amount of contact it has with the magnets on BOTH sides, so as much electricity as possible can flow. When it’s been properly shaped, hook the wire onto the motor!

Holompolar Motorcar Step 3

Instead of using a wire, you could use a sheet of aluminum foil! Lay it as flat as you can on a level surface, away from any metals that might attract your magnets. Make sure there are no tears or holes in the aluminum. Then place your battery-magnet motor on top! The aluminum will allow electricity to flow!

————

When a magnetic field is applied to an object carrying electricity, it applies a force to that object. This is called the Lorentz Force. Due to the electricity flowing through the magnets, this force becomes a torque, causing the motor to rotate and drive forward!

Homopolar Motorcar Rollin

Written By: Scott Yarbrough

For Mimi by Twin Musicom is licensed under a Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/)

Artist: http://www.twinmusicom.org/

What is Escape Velocity?

Escape Velocity is probably something you’ve heard on a TV show, or maybe you learned about it from NASA talking about their newest spacecraft. It is a commonly discussed term, but it isn’t the easiest thing to understand. Imagine you’re in a strange universe where only the Earth exists. The only gravity comes from its center, and it extends infinitely far away, getting weaker and weaker the further away you get. In order to get to that infinite point before you get pulled back by the Earth’s gravity, you need to be going at least 11.2 km/s (25,000 mph). This speed is the escape velocity!

escape velocity 1
This value depends on both the distance from the gravitational center of the object you’re escaping from and the mass of the object. The closer you are to a heavier object, the faster you need to go to reach escape velocity. For example, escape velocity from the Earth at a distance of the moon’s orbit is only 1.3 km/s (3,000 mph), but to escape from the sun’s gravity at the distance of the Earth is a whopping 44.7 km/s (100,000 mph)!

escape velocity moon

But since there’s no such thing as a universe where only the Earth exists, we have to worry about the gravity of other celestial objects! Once you escape from the Earth’s gravity, you’ll then be captured by the sun. If you escape that, then you’ll be captured by the Milky Way’s gravity! So the hypothetical infinite point is just that: hypothetical! No matter what, there’s always going to be something pulling on you with gravity.

Written By: Scott Yarbrough

What is Jacob’s Ladder?

If you’ve taken our Electricity and Magnetism class, you’ve seen this device before! You press a button and an electric arc rises to the top of two tall wires. This is the Jacob’s Ladder! But what’s happening here? 

Jacob's Ladder

The base of the Ladder is a transformer — a device that changes an incoming voltage. In the Ladder’s case, it increases it by a huge amount. That voltage is put into one of the vertical wires, increasing its electric potential. The electricity needs to flow somewhere, so it ionizes the air to jump to the other vertical wire. As the electricity arcs, it heats up the ionized air, which causes it to rise. As the wire get further apart, it becomes more and more difficult for the electricity to reach, and the arc eventually stops. Then the transformer builds up the electric potential again, repeating the process all over again. Though as electricity flows through the wires, they heat up. The hotter they are, the slower the electricity flows. Eventually, you’ll notice the arc having trouble getting to the top as it travels slower and slower.

Jacob's Ladder 2

This is just one of the many cool electricity demos we have at AstroCamp! Be sure to check out this and all the others on your trip.

Written By: Scott Yarbrough

 

Measuring the Brightness of Stars

There are countless stars that we can see in our night sky, and all of them are unique. Some are dim, barely visible without a telescope. Others are bright and can be seen even in the most light-polluted areas. We measure the brightness of these stars using the magnitude scale.

brightness of stars

The magnitude scale seems a little backwards. The lower the number, the brighter the object is; and the higher the number, the dimmer it is. This scale is logarithmic and set so that every 5 steps up equals a 100 times decrease in brightness. So magnitude 10 is 100 times dimmer than magnitude 5, which is 100 times dimmer than magnitude 0.

brightness of stars scale

Our sun — the brightest thing in our sky — is magnitude -26.7. Other objects like the moon or nearby planets have negative magnitudes, and other stars vary greatly. The dimmest objects humans can see with the naked eye is around 6; any dimmer and we need to use a telescope.

What we’ve been talking about is apparent magnitude. It measures the brightness of stars and other celestial objects as they are as viewed from Earth, without taking into account distance or actual luminosity. It’s fine for describing what things look like from here, but it isn’t very good at describing how much light those objects are actually emitting. Our moon is incredibly bright to us, but if it were farther away from us, its brightness would decrease a lot.

To better compare the brightness of objects to each other, we use the absolute magnitude scale. The logarithmic scale is the same, but we calculate what an object’s apparent magnitude would be if it were exactly 10 parsecs away from Earth (about 33 light-years away). This way, we eliminate distance as a factor for comparing the brightness of space objects.

brightness of stars gif

As you can see, the brightness measurement of stars is a little more complicated than it first appears. It may also be difficult to really visualize the difference in brightness. But it’s an easy task to find a catalog of stars, go outside, and experience it yourself!

Written By: Scott Yarbrough

WELCOME TO OUR ASTROCAMP BLOG

We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!

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