Transcript Document
Homework Assignment – Good job! I was very happy to see a great response. As of mid evening yesterday I had over 110 e-mails - but there are only 61 people in the class! Today Quick review Introduction to the electromagnetic spectrum First in-class activity – Ecological Footprint Last Class Understanding global change is understanding how the earth system functions. This requires information from many disciplines and Consideration of different time scales, ecosystem types And human interactions Over the last 150 years humans have - experienced a tremendous increase in population - altered much of the land surface - altered atmospheric greenhouse gas concentrations Over the last 150 years - temperatures have increased - rainfall patterns have changed Brazilian Rainforest Loss in Two Years 1995 1997 We are orbiting one of Many stars in many Galaxies We locate everything in Space based on the types of radiation or light it gives off. The various wavelengths are called the electromagnetic spectrum. This is our sun, a nice mid-sized, middle aged Star. It’s about 5 billion years Old, and has another 5 Billion or so years left. The energy that this star Gives off, modified and tempered by our atmosphere Allows life to exist here, So we can worry about global Change. All wavelengths travel at the speed of light, so if the wavelength is shorter, it must have a higher frequency. Listen to the radio or watch tv, Talk on a cb or… Learn what objects in space are Made of Heat your popcorn study galaxies Keep your food warm in your fast Food restaurant or See this lecture! Get a tan or maybe go extinct! Find out if your bone is broken Released from some radioactive elements Everything emits Electromagnetic Radiation Some general rules about EM radiation The type and amount of radiation emitted depends on the temperature of the object. The hotter the object the more radiation is emitted. (Our hot Sun emits lots of radiation/ light). Also, the hotter the object, the more energetic the radiation. Planck’s Law Looks a bit scary, but it isn’t Really that bad. The amount of energy released By an object at any temperature Is higher an shorter wavelengths Wein’s Law Not nearly as scary, but just as important The most common wavelengths an object emits are inversely related to Temperature. Sefan-Boltzmann Law Is the simplest formula yet The amount of energy emitted by an object is increases with temperature. What does all this mean to us? Our sun is really hot and emits most of it’s energy at shorter wavelengths. Good thing for us if we want to see, but not so good if we didn’t have an atmosphere. So just why is the atmosphere so important? The Doppler effect If an object is approaching us, The wavelengths appear to be getting shorter If an object is moving away from Us, the wavelengths appear to be Getting longer. Think of the sound of a train whistle as the train approaches and then Moves away. Calculating one persons impact on the earth Worldwide, the biologically productive space available per person is 2.2 hectares or 5.4 acres. - part of the land surface and part of the ocean - most deserts, polar regions, and cities excluded Class Assignment: Ecological Footprint http://www.mec.ca/Apps/ecoCalc/ecoCalc.jsp?FOLDER%3C%3Efolder_id=65723 Electromagnetic Spectrum – Web site for Review http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html Doppler effect http://webphysics.davidson.edu/Applets/Doppler/Doppler.html