Tag Archives: Earth

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

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

Asteroid to Meteorite to Crater

Every day, about 40 tons of space rocks reach the top of Earth’s atmosphere. These asteroids come in many different sizes and have been floating around in space for billions of years. Once they reach the Earth, however, they become meteors — more colloquially known as shooting stars.

Meteorite 1

Friction with the air causes the rock to ignite and luminesce. Most of these are pretty dim and can only be seen at night. And most of these are also too small for any chunk to reach the surface of the Earth; the heat and friction vaporize the meteors completely. However, sometimes the meteor is large enough to withstand the friction until it hits the surface. These are classified as meteorites. Very few of these are large enough to leave a significant impact, but every once in a while, a large meteorite touches down. When this happens, it compresses the surface, which will decompress moments later as a shockwave, traveling through the rock and carving out a crater.

Meteorite 2

Very rarely, an extinction-level event meteor collides with our planet. Such an event happened 66 million years ago, and is a possible cause of the major extinction event that killed all the dinosaurs. The impact is hypothesized to be a billion time stronger than the first atomic bombs, sending ash and dust into the air that blocked sunlight for more than a full year.

Meteorite

Thankfully, such events are incredibly rare, so the most you’ll have to be worried about is a small dent in your car — and even that is unlikely to happen!

Written By: Scott Yarbrough

Why Do We Have Seasons?

Happy Thanksgiving! It’s been almost two months since autumn started — the leaves have begun to fall, and the air is getting a lot cooler. Without fail, this season comes at the same time every year and there’s a simple reason for it!

thanksgiving

It’s a common mistake to think that the seasons change due to the varying distance between the Earth and the sun. This is a thing that happens, but the real reason for the cycle is the Earth’s axial tilt. The axis upon which the Earth spins (once every 24-ish hours, resulting in our day-night cycle) does not line up perpendicularly with our orbital path (the oval-ish path the Earth takes around the sun).

thanksgiving

Instead, the Earth makes a 23.5° angle with the perpendicular, changing by only a few degrees on a 40,000 year cycle. Scientists believe this tilt occurred in the early days of our solar system, when our planet was not quite done forming. A large piece of space debris — called a “planetesimal” — collided with the early Earth, pushing it slightly on its side.

 

So what does this have to do with the seasons? Well, as the Earth orbits the sun, its axial tilt doesn’t change. So the northern and southern hemispheres receive different amounts of sunlight at different times of year. When the northern hemisphere is tilted towards the sun, it receives more direct sunlight for longer, causing that half of the planet to heat up more. Six months later, when the same hemisphere is tilted away from the sun, it receives less direct sunlight for less time, allowing that half of the planet to cool off.

thanksgiving seasons

As mentioned before, the Earth-Sun distance does change throughout the year — by about 4 million miles. The period when it’s at the shortest distance is during the southern hemisphere’s summer. All things equal, we would expect that summers in that hemisphere would be hotter and that winters would be colder, but that’s actually not the case. Since the southern hemisphere has a higher percentage of ocean, and since water requires a lot of energy to heat up and cools down very slowly, southern hemisphere seasons are actually milder than the seasons in the north.

So, as the cycle of seasons continues, we can eat our turkey and mashed potatoes and apple pie, and be thankful that this will all happen again in just another year’s time.

Written By: Scott Yarbrough

America Recycles Day

Jack Johnson sang it best in his song “The 3 R’s”. Reduce, reuse, recycle. This is how to live a more sustainable life, and leave a smaller carbon footprint. First, try to reduce the amount of waste you produce. Second, reuse items as much as possible. Third, recycle appropriate waste products as to have them not end up in our oceans or atmosphere.

November 15 is America Recycles Day. Each year millions of people across the U.S. take part in bringing awareness to the importances of recycling and creating less waste on our beautiful planet. Help teach others the benefits of recycling and continue to do so each day.

How you can participate:

  • Reduce
    • Lose the single use items and invest in reusable ones. Whether it’s changing from plastic shopping bags to cloth bags, disposable water bottles to those from companies like Camelbak and Nalgene, or to-go paper coffee cups to ceramic mugs or aluminum travel mugs, there are hundreds of options to reduce your impact on the world.

recycles

  • Reuse
    • When reducing what items you use is not a viable option, you should reuse them! Try reusable containers for lunch, rather than brown paper bags. Repair items rather than buying new ones, or shop at thrift shops. There is almost always some alternative option to buying new.

reuse

  • Recycle
    • If single use items must be a part of your day, then recycle. Papers, plastics, or aluminum can be recycled and made into new products, so try to do your part. You can also try to buy products that are made from those recycled goods.

recycles

Small changes in your day and your habits can have huge impacts on the world around you. Here’s how:

  • Reduces greenhouse gas emissions that contribute to global warming
  • Reduces the amount of waste sent to landfills and combustion facilities.
  • Conserves natural resources such as timber, water, and minerals.
  • Prevents pollution by reducing the need to collect new raw materials.
  • Saves energy

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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