Energy Drives Everything

Overview

Energy is the ability to move "stuff", so it is the essence to any planet's processes - actually, all of the processes in the universe.  No biggie.  Without it, nothing would move or change, and life would not exist since all  forms of life require energy.
 

But luckily we do have energy in the universe, and for Earth, the nearby Sun provides relatively consistent radiation that travels through space and illuminates our planet, transforming to a variety of forms that support nearly all surface  processes.  

 

Energy flows are the transformation of energy from one form to other(s). For example, we eat food that has chemical energy our body transforms to kinetic energy (from walking to pumping blood through the body), electrical energy (which allows us to think and coordinate and process sensory information and muscle movement), and thermal energy (we maintain a near-constant body temperature despite constantly losing energy - heat, radiation, and sound - to our surroundings).

Sunrise at the Cape Cod National Seashore.

Sunrise at the Cape Cod National Seashore.

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Main Types of Energy

Potential Energy: the energy possessed by an object because of its position relative to others, stresses within itself, its electric charge, or other factors, so, ultimately, it is stored energy.

  • Common types: gravitational energy, electric energy, magnetic energy, elastic energy, chemical energy, and nuclear energy, 

Kinetic Energy: the energy of motion, either as the movement of an object, particle, or set of particles.

  • Common types: thermal energy, sound energy, and electromagnetic radiation.  

Energy budgets are the rates of energy coming into and going out of an object that ranges in size from an electron to that of galaxies.  When more energy is being gained than lost, the object's total energy is increasing.  When more energy is being lost than gained, the object is losing total energy.  But there are times when the rates of incoming and outgoing energy are balanced, and the object's total energy remains constant.
 

A large portion of Earth Systems will deal with the transfer of thermal energy to and from objects of different temperature.  This transfer of thermal energy is called heat, and the primary mechanisms are conduction, radiation, advection, convection, and latent heat.

  • Conduction is the transfer of thermal energy through molecular collisions.  The molecules transfer the heat but don't move along with the heat.
  • Radiation is the emission and absorption of photons, which are massless packets of energy. Radiation that we see with our eyes is called "light".
  • Advection is the horizontal movement of fluids of different temperatures than the surroundings. Examples are a cold wind from the poles or the warm Gulf Stream in the Atlantic Ocean.
  • Convection is the vertical movement of fluids of different temperatures than the surroundings.
  • Latent heat is the heat required to create a phase change (solid, liquid, or gas) without change of temperature. Humans cool by secreting sweat onto our skin which evaporates and cools the skin. 


Collectively, these will be referred to as CRACL (Conduction, Radiation, Advection, Convection, Latent heat).

Phases of Matter

Solid

A substance in which its particles are arranged so  the shape and volume of the material are relatively stable or definite. The particles tend to be packed together much closer than those in a liquid or gas.

Liquid

A substance that flows freely but is of constant volume.  In other words, the material has a definite volume but not shape.

Gas

A substance that flows freely and does not have a defined volume - the gas will fill the volume of the container it is in.  In other words, the material has no definite volume or shape.

Plasma

A substance whose atoms have lost some or all of their electrons and it does not have a definite volume or shape. So it is a gas composed of ions and electrons.  Plasma is the dominant phase of matter in our Sun.

Conduction

Temperature and Molecular Collisions

Temperature is a measure of the average energy of motion of the atoms and/or molecules of a material, be it a solid, liquid, gas, or plasma.  Because it is an average, the value does not depend on the number of particles within the object, so the temperature of a drop of boiling water is the same as a bucket of boiling water.


Because the molecules are moving, they collide with each other and transfer kinetic energy (0.5*mass*velocity*velocity) from the those with more to those with less.   So if one part of the material has a greater temperature, molecular collisions transfer the energy away from the hotter area to the colder regions.  Because the particles in solids are closer together than in other phases, conduction is an important mechanism for heat transfer in solids.  


Conduction is also important at phase boundaries: solid/liquid, solid/gas, and liquid/gas.  Heat is transferred across the boundary, and the phases that can flow change density and may flow away from the boundary.  More will be explored in the advection and convection sections below.


The difference in temperature over distance is called a temperature gradient, which is a vector.  A vector has a magnitude and a direction.  Think of baseball: the pitcher throws a ball toward the catcher, and the ball's velocity is a vector.  There is the magnitude of how fast the ball is traveling, but the direction of the ball is just as important to identify if the catcher is going to catch the ball.


Temperature gradients always point in the direction from the hot toward the cold.  Heat conduction moves in the direction of the temperature gradient.  If you completed the data contouring activities, temperature gradient is always perpendicular to the isotherms which are contours of constant temperature.


Suggested Time for reading sections above, watching the animation and taking notes: 20 min.

Click on the image to go to a useful animation about heat conduction.

Click on the image to go to a useful animation about heat conduction.

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Radiation

Emission of Radiation

There are 5 ways electromagnetic radiation is generated or emitted from matter.  This short movie from NASA is one of the best overviews I have seen, and the website has useful information on the electromagnetic spectrum.

  • Electron shell change emits predominantly in the ultraviolet and visible light.
  • Molecular vibration generates mostly near infrared.
  • Molecular spin produces mostly far infrared to radio waves.
  • Nuclear reactions produce gamma to x-rays.
  • Thermal radiation: due to its broad spectrum emitted from objects with a temperature above absolute zero, we will focus on this for much of Earth Systems.  See blackbody radiation for the theoretical maximum radiation that can be emitted by an object based on its temperature.

Once electromagnetic radiation is emitted, it interacts with matter in three ways: absorption, reflection, and transmission.


Absorption is when the photon is captured by the matter, so the amount of energy within the matter increases.


Reflection is when the photon bounces off the matter.  No energy is gained or lost by the matter.


Transmission is when the photon passes through the material's matter.  As with reflection, no energy is gained or lost by the matter.


Articles What is Energy? and Solar Radiation and the Earth's Energy Balance


Suggested Time for Movie and Reading: 60 min.

Learn More

Build Near Infrared Goggles for $10: Yes, our eyes can see just into the NIR spectrum, but we need to block out most of the visible light.  Here is an inexpensive way to see things we normally can't!


Above is an image of a landscape using the NIR goggles.  Why is it red?  Infrared doesn't have a color in human vision!  But our eyes have three color detectors: red, green, and blue.  And only the red detectors can see a bit of the NIR, so our brain is told that everything is in shades of red.


Use the goggles to look at the black fabrics you used in the experiment above.  You will then be able to use them to pick the clothes you wear outside to keep warm or cool depending on the season.


Suggested Time: 30-45 min to explore outside once built (takes about 30-45 min to make) and purchased parts.

Download Blackbody Radiation Simulation Software

Blackbody Radiation software: explore the spectrum of radiation emitted from objects with a temperature above absolute zero and relate to Earth Systems processes, including how the Sun has changed, and will change, over billions of years.


Suggested Time: 2 60-minute blocks to explore ideas, complete the built-in challenges, and read the big ideas summarized in the software.


Acknowledgements

A special thank you to the beta testers of version 1-0.  Their insightful comments, meticulous attention to detail, and creative ideas improved the software greatly! 


Denise Alfonso, Lincoln Berkley, Elliot Blume-Pickle, Xiomara Contreras, Allison Culbert, Wilder Daniel, Carolina Diez, Mason Glidden, Alan Gould, Hyowon (Raphi) Kang, Becca Kranz, Audrey Lin, Mike Pappas, Kiley Remiszewski, and Corey Rost.  

Movie Demonstrating Software

Click to see the features of the software before deciding to download the program.

Watch the Movie

Mac users: Download the zipped dmg file. Uncompress and double click on the dmg file.  Drag the folder that pops up to the application folder on your computer.


Windows users: Select the location you want to put the files before uncompressing everything in the zip file.

Sections of Blackbody Radiation Simulation Software

Explore thermal radiation in linear scales...

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Add / hide information to focus on patterns and trends in emitted thermal radiation.

and in logarithmic scales.

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Compare thermal radiation emitted from common objects.

Explore the effects of the Sun changing temperature over time

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How would Earth responded as our energy source changed?

Radiation budgets of common Earth surfaces,

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As the Sun changes angle above the horizon throughout the day, the energy absorbed by the Earth's surface changes.  The amount of radiation emitted and absorbed from objects results in changing temperature.  

and the radiation budget of black fabrics under an intense light bulb.

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Radiation budgets may be a bit easier to think about when the intensity of the incoming light is constant when on and change instantly to completely off.

Examples of Cloth Used in Black Fabric Experiment

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Example fabrics for the Heating/Cooling of Black Fabrics. The top image is in visible light, and the bottom is in near infrared.  Data are included in the software.


Suggested Time: 30-45 min.

Convection Cells: Advection + Convection

All materials when heated or cooled change density.  When the material is a fluid (one that flows, so a liquid, gas, or plasma), densities differences create movement.  


Less dense materials rise, denser materials sink.


Most materials become less dense when heated. Water is an important exception since it becomes denser as it warms from 0ºC (32ºF) to 4ºC (39ºF).  Above 4ºC, water becomes less dense as it warms.


A fluid that is less dense than its surroundings will keep rising, and one that is denser than its neighbors, it sinks. It stops moving vertically when the the fluids become the same density or it hits a solid boundary.


When the rising fluid is warmer than the surroundings, it is called warm convection. Sinking fluid that is colder than the surroundings is cold convection.


When boundaries stop the vertical motion, the moving air moves horizontally, so convection turns into advection.


Suggested Time for Movie, Reading, and Challenges: 60 min.

Hot air balloons rise into the air.  One way to descend is to let it become a "cold" air balloon.

Hot air balloons rise into the air. One way to descend is to let it become a "cold" air balloon.

Video of Dense Liquid Next to Less Dense Liquid

Uneven heating of the Earth's surface creates fluids of different densities to be side by side.  The result: moving fluids.  Most of our surface wind is created this way - and the surface winds create our surface ocean currents.

Convection Cell Challenges

Heating from Below

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Example: It is noon time at a parking lot on a sunny summer day.  What happens to the air above the dark asphalt?

Heating from Above

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Example: It is noon time at a pond on a sunny summer day.  What happens to the pond water?

Cooling from Below

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Example: It is 4 AM over a parking lot on a clear, cool winter night.  What happens to the air above asphalt?

Cooling from Above

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Example: It is 4 AM at a pond on a chilly night in early autumn.  What happens to the pond water?

Latent Heat

Deposition

Frost crystals on a cold morning.

Deposition is when a gas  goes directly to the solid state.  This happens when frost forms on cold nights when the air has high relative humidity and when snow forms in the atmosphere.

Freezing

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Freezing is when a liquid becomes a solid.  Pond surface water freezes during cold winter months and is how hail is formed in severe weather events.


Condensation

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Condensation is when a gas becomes a liquid.  This happens when dew forms on cool mornings when the air has high relative humidity and when clouds form in rising moist air.

Sublimation

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Sublimation occurs when the solid becomes a gas.  On cold dry days, considerable amounts of snow may sublimate.

Melting

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Melting is when a solid becomes a liquid.  Melting pond ice keeps the water cold longer into the spring.

Evaporation

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Evaporation is is when a liquid becomes a gas.  Water evaporates quite quickly on warm, sunny days.

Phase Change of Water and Heat Transfer

Water is quite common on the Earth's surface, and its unique chemical and physical properties help it play a critical role in heat transfer in the oceans, on land, and in the atmosphere.


Phase Changes that Cool the Surrounding Environment

  • Sublimation -> Takes 620 cal for every gram of ice that sublimates 
  • Melting -> Takes 80 cal for every gram of ice that melts 
  • Evaporation -> Takes 540 cal every gram of water that evaporates

Phase Changes that Warm the Surrounding Environment

  • Deposition -> Releases  620 cal for every gram of ice forming from vapor
  • Freezing -> Releases  80 cal for every gram of ice forming from water
  • Condensation -> Releases  540 cal for every gram of water forming from vapor

For reference: a U.S. dime weighs 2.268 grams.

Condensation that forms clouds warms the air so it rises.

Condensation that forms clouds warms the air so it rises.

Fitting the Pieces Together: CRACL

Watch this video of a lava lamp and determine how conduction, radiation, advection, convection, and latent heat are involved in how it works.


Suggested Time for Movie and Analysis: 30 min.

CRACL Experiment

Hot Tea and Cold Milk

As the class completed our exploration of CRACL, Luke Dewees, then a sophomore, asked "Which would be cooler? Hot tea and cold milk sitting separately on a table added together after 10 minutes or hot tea with cold milk added immediately and left to cool for 10 minutes?"  So we ran this experiment to find out.

 

The volumes and starting temperature for both samples of hot tea and cold milk were identical, and the liquids were poured into identical paper cups. 


Work out all of the components of conduction, radiation, advection, convection and latent heat to support your answer.


See how your answer compares with the results of the actual experiment below.


Suggested Time for  Analysis and Reading: 30 min.

Thermal IR image of both drinks at the start of the experiment. Temperature scale is on right.

Thermal IR image of both drinks at the start of the experiment. Temperature scale is on right.

CRACL Challenges

A Mug of Hot Tea Sitting Outside on a Bench in the Shade on a Cold Winter Night

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Identify and label the effects of conduction, radiation, advection, convection and latent heat acting on the temperature and behavior of the tea and its surroundings.

A Glass of Iced Tea Sitting on a Bench in the Sun on a Hot Summer Afternoon

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Identify and label the effects of conduction, radiation, advection, convection and latent heat acting on the temperature and behavior of the tea and its surroundings.

Answers for CRACL Challenges

Suggested Time for Analysis: 60 min.

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Concept map of Earth's radiation budget.  What would Earth be like if it didn't have greenhouse gases?  How does it change when there is more than we currently have?  Discuss with team or peer.


Suggested Time: 30 min.