NATS From the Cosmos to Earth Tides The gravitational attraction of the Moon varies as the square of the distance (Newton’s Law of Gravitation) - gravity stronger on side facing the Moon than on opposite side. The Moon pulls the ocean water towards it on facing side - creates tide - and pulls the Earth away from the ocean water on the other side - reason for tides twice a day. Time of tides varies by 50 min per day - Moon at its highest point every 24 hrs 50 min because Moon orbits Earth while Earth rotates.

NATS From the Cosmos to Earth The Sun also causes tides - why are they weaker than the Moons’? Neap tides - when Moon’s and Sun’s gravitational forces oppose each other Spring tides - when Moon’s and Sun’s gravitational forces add up

NATS From the Cosmos to Earth Tides

NATS From the Cosmos to Earth Tidal Bulge Because the Earth rotates, friction drags the tidal bulges off of the Earth- Moon line. This tidal friction causes the Earth’s rotation to slow and the Moon to move farther out.

NATS From the Cosmos to Earth The Moon pulls on tidal bulge - slows Earth’s rotation The excess mass in Earth’s tidal bulge exerts a gravitational attraction on the Moon that pulls the Moon ahead in its orbit - Moon moves farther away - Conservation of Angular Momentum

NATS From the Cosmos to Earth Matter and Energy

NATS From the Cosmos to Earth DEFINITION: Anything that occupies space and has mass PROPERTIES OF MATTER: Mass - a measure of a body’s resistance to a change in its state of motion - its inertia Density - mass per unit volume Dimensions - height, length, width Electric charge - positive/negative/neutral Heat content - everything above absolute 0 ( º F) has heat - no such quantity as cold - only absence of heat Resistance to flow of electric current - flow of charged particles - electrons Pressure - exerted by moving molecules in all directions - resists compression Matter

NATS From the Cosmos to Earth Energy Definition of Energy: Anything that can change the condition of matter Ability to do work – the mover of substance (matter) Work is a force acting over a distance Force: The agent of change – push or pull on a body Hence: Work is the change in the energy of a system resulting from the application of a force acting over a distance.

NATS From the Cosmos to Earth Four Types of Forces: Gravitational – holds the world together Electromagnetic – accounts for many observed forces - Push or pull on a body Strong Nuclear – hold nucleus together Weak Nuclear – involved in nuclear reactions Power: Rate of change of energy

NATS From the Cosmos to Earth Energy Units Energy: Joule = 1 kg m 2 /s 2 1 Joule = 1/4184 Calorie, so 2500 Cal = 1 x 10 7 J (average daily requirement for a human) Power: 1 watt = 1J/s Thus for every second a 100 W light bulb is on, the electric company charges for 100 J of energy. The average daily power requirement for a human is about the same as for a 100-W light bulb.

NATS From the Cosmos to Earth Solar energy striking Earth’s surface per second = 2.5 x J. Energy released by burning 1 liter of oil = solar energy striking square 100 m on a side in 1 second Energy Comparisons

NATS From the Cosmos to Earth Energy Three basic categories: Kinetic energy = energy of motion Potential energy = stored energy Radiative - energy carried by light

NATS From the Cosmos to Earth Types of Energy Energy cannot be created or destroyed, only changed –Mechanical – Potential- energy of position P.E.= mgh Kinetic- energy of motion K.E.=1/2mv 2 –Electrical –Chemical –Elastic –Gravitational –Thermal –Radiant –Nuclear

NATS From the Cosmos to Earth Potential Energy gravitational potential energy is the energy which an object stores due to its ability to fall It depends on: –the object’s mass (m) –the strength of gravity (g) –the distance which it falls (h) PE = mgh Before the sun was formed - matter contained in cloud diffuse gas cloud - most far from the center - large gravitational energy. As cloud contracted under its own gravity - gravitational energy converted to thermal energy until hot enough to ignite nuclear fusion m h g

NATS From the Cosmos to Earth Potential Energy energy is stored in matter itself this mass-energy is what would be released if an amount of mass, m, were converted into energy E = mc 2 [ c = 3 x 10 8 m/s is the speed of light; m is in kg, then E is in joules] The mass energy in a 1-kg rock is equal to as much energy as 7.5 billion liters of oil = enough to run all the cars in the U.S. for a week A 1-megaton hydrogen bomb converts only about 3 ounces of mass into energy.

NATS From the Cosmos to Earth Law of Conservation of Energy Energy can be neither created nor destroyed. It merely changes it form or is exchanged between objects. This principle (or law) is fundamental to science. The total energy content of the Universe was determined in the Big Bang and remains the same today.

NATS From the Cosmos to Earth Conversion of Energy Throwing a baseball Nuclear energy (nuclear fusion on sun) - Radiative energy (sunlight) - Chemical energy (photosynthesis) - Chemical energy in pitcher’s body (from eating plants) - Mechanical kinetic energy (motion of arm) - Mechanical kinetic energy (movement of the baseball). Thus, ultimate source of KE in baseball is mass energy stored in hydrogen of Sun - created in Big Bang. Hydroelectric dam Gravitational - mechanical - electrical Nuclear reactor Nuclear - thermal - mechanical - electrical Car Chemical - thermal - mechanical

NATS From the Cosmos to Earth Temperature and Thermal Energy Why does water burn your skin so much quicker than air? Why is falling into a 32º F lake more dangerous than standing outside naked on a 32º F? Temperature - measure of the average kinetic energy of the particles in a substance - particles in box on right have higher temperature - higher velocity = more KE = higher temperature Both boxes have same temperature - particles have same average velocity/KE - box on right has more thermal energy - energy contained in a substance - more particles

NATS From the Cosmos to Earth This diagram compares three common temperature scales. The Fahrenheit scale is used in the United States, but nearly all other countries use the Celsius scale. Scientists prefer the Kelvin scale because O K represents absolute zero, the coldest possible temperature.

NATS From the Cosmos to Earth Conversion Between Celsius and Fahrenheit ºF = ºC x 9/5 + 32º ºC = (ºF - 32) x 5/9

NATS From the Cosmos to Earth STATES OF MATTER: Gas — fixed quantity Liquid— fixed quantity and size, shape conforms to container Solid— fixed quantity, size and shape

NATS From the Cosmos to Earth The state of matter is determined by its temperature. Consider water: Below 32º F - ice - relatively low KE - each molecule tightly bound to it neighbors - solid At 32º F molecules have enough energy to break solid bonds of ice - remain together but move relatively freely - liquid At 212º F water boils and turns to gas - molecules break free of all bonds with neighbors - move independently of other molecules - gas

NATS From the Cosmos to Earth Size VirusSmallest Living Thing10 millionth of 1 cm cm Molecule1/100 of a Virus10 -7 cm Atom 1 1/10 of a Molecule10 -8 cm Nucleus1/100,000 of an Atom cm Proton Neutron 1/10 of a Nucleus cm QuarkMuch smaller than a Proton ??? 1 size of atom = 1 cm 1 cm 1000 km 1000 km = 600 miles, the distance from Dallas to El Paso Structure of Matter