Rainbows

A rainbow is a circular line of colors from the spectrum. Rainbows are formed when light sunshines onto suspended droplets of moisture in the air. The light is refracted, reflected internally and then refracted again. A rainbow spans a continous spectrum of colors which go from red on the outer part to violet on the inner arch. Rainbows can form anywhere water droplets in air are shone on by sunlight which has to be shining behind the person at a low altitude angle. Under certain circumstances people should be able to see two rainbows a primary rainbow and a secondary rainbow as shown in the picture to the right. It all depends on the angle of ray entry into the water drops. This is related to the unit we are taking on light which tells a little bit about rainbows. In this unit we also learn that the who sky is actually a rainbow but only parts of it can be seen by one observer. We also learned this is the reason to why you can never approach a rainbow. So for all those that believe you can go to the end of a rainbow and find a pot of gold it isn't so. It is just a made up story told to many people. Although no one can approach a rainbow the sight of a rainbow is still unique.

Sonic Boom

Sonic boom are shocks created by aircraft traveling at high speeds. Sonic booms generete large amounts of sound energy. A sonic boom is much like an explosion.

When aircraft travelling at high speeds occur pressure waves are built up at the tip of the aircraft and behind it. These pressure waves travel at the speed of sound. When the aircraft speeds up the waves are forced together. These waves are compressed together and eventually turn into single shock waves at the speed of sound. The shock wave begins at the tip of the aircraft til the end of the tail on the aircraft. The shock then forms a cone with the aircraft as the tip. From this point there is a rise in pressure at the tip of the aircraft followed by a sudden reture to normal pressure. The boom occurs when there is this change in pressure. This is how aircrafts make loud noises or "booms" as they call it when travelling at high speed. This is something I have always been interested in but didn't know it was related to physics until know.

Creation of Northern and Southern Lights

People that live towards the north and south poles have most likely experienced what is called the northern or southern lights. Here in turtleford I personally haven't experience them. Whose to say they do not occur here just because I haven't seen them. Back where I am from which is more north then here I saw the northern lights many times. I always wondered what created thse amazing displays of colors. Near the north pole the northern lights are referred to as aurora borealis. What causes these displays of "dancing colors" is this. High speed particles collide with atoms in Earth's atmosphere at a height of anywhere from 50 to a few hundred miles above the surface. These high speed particles or electrons are orginated from space specifically from solar wind generated from the sun. When the electrons from space strike atoms in the Earth's atmosphere they give of the electrons in the atom an energy boost. After a while these boosted electrons return to their normal energy level. It releases this energy as light causing the northern lights.

Electrons do not travel in straight lines. The magnetic force causes electrons to travel in spiral paths around magnetic field lines. Therefore electrons enter Earth's atmosphere at the north and south poles and this is why is most visible to see the northern and southern lights near the poles.

Lunar Eclipse

A lunar eclipse occurs when the Earth blocks out the light from the sun on the moon. The Earth eclipses the sun and therefore casts a shadow onto the moon. This can only occur when the Sun Earth and the Moon are in line with one another, the Earth being in the middle. As there are different types of Solar Eclipses there are also different types of Lunar Eclipses. Firstly a penumbral eclipse is when the Moon passes through the Earths penumbra which is the fuzzy region. This is related to the unit of light that an object casts a shadow which has an umbra the dark region and a penumbra the fuzzy region around the umbra. The penumbra causes a darkening of the moons surface. A partial lunar eclipse is when only a little portion of the Moon enters the umbra. A total lunar eclipse is when the moon travels completely in the Earth's umbra. This is when the entire moon is dark. A selenelion eclipse occurs when both the sun and the moon can be observed at the same time. This only occurs right before sunset or after sunrise. Both bodies will appear in the sky at different locations.
Once the moon enters the Earth's umbra it does not disappear. This is becasue of the refraction of sunlight by the Earth's atmosphere. Again this is related to the subject on light. Only if Earth had no atmosphere would the Moon disappear as it enters Earths umbra.
Every year there are usually two partial lunar eclipses. Unlike a solar eclipse where there is a certain area one must be to experience it a lunar eclipse can be seen from anywhere where it is night on Earth.
The next partial eclipse of the Moon is projected to occur on the 31st of this month. While the next total eclipse of the Moon is projected to occur on December 21,2010.

Solar Eclipse

An eclipse is when an opaque object, an object does not allow light to pass through it, is placed in the path of incoming light. For a solar eclipe the moon eclipes the sun. The moon is between the Earth and the Sun. It then casts a shadow upon Earth. The moon could either fully cover or partially cover the Sun. A solar eclipse can only happy during a new moon. Up to five solar eclipses can occur a year anywhere on Earth. Out of those five up to two are total eclipses.
There are four different types of solar eclipses. A total eclipse is when the sun is completely covered by the moon. An annular eclipse occurs when the sun and the moon are exactly in line but the size of the moon is smaller then that of the sun. The sun then appears as a very bright ring surrounding the outline of the moon. A hybrid eclipse is a crosse between a total and annular eclipse At some points on earth is the suface of the Earth visible as a total eclipse where as others it is annular. This type of eclipse is rare. Lastly a partial eclipse occurs when the sun and the moon are not exactly in line. The moon only covers the sun barely.
The last solar eclipse that occurred was during the summer on July 22. This eclipse was a total eclipse. It was recorded to be the longest of the 21 century which lasted six minutes thirty nine seconds. This eclipse occured off the coast of southeast Asia. The countries that got to experience this wonderful event were eastern China, Japa, India and Nepal. The prejected exlipse to surpass this one is estimated to about June 2132.

Hot Air Balloons

Why do Hot Air Balloons Fly
How the Ideal Gas Law and Archimedes's Principle Apply to Ballooning
Nov 10, 2008 Paul A. Heckert
Two fundamental principles of physics govern hot air balloon flight. They are not the same principles that govern airplane flight.
At a hot air balloon festival, hot air balloons slowly fill and then rise majestically in the predawn sky. These hot air balloons fly because of two fundamental principles of physics: the ideal gas law and Archimedes's principle.
Ideal Gas Law
The ideal gas law is a mathematical relationship between the volume pressure and temperature of a gas. For a given quantity of gas, the pressure, P, multiplied by the volume, V, divided by the temperature, T, remains a constant.
If a gas is heated, as in a hot air balloon, then its volume will increase. A heater in the balloon's basket heats the air inside the balloon and blows hot air into the balloon. As the volume of gas increases, it fills the balloon. Soon the balloon is full of hot air. If the air continues to heat up, it expands and flows out of the hole in the bottom of the balloon.
Hence a balloon filled with hot air contains fewer air molecules than the same balloon inflated to the same size with cool air. A hot air balloon will therefore be less dense than a balloon filled with cool air as a consequence of the ideal gas law.
Archimedes's Principle
Archimedes's principle states that when an object is suspended in a fluid, the buoyant force acting on an object is equal to the weight of the fluid displaced. As a consequence of Archimedes's principle, an object will float in a fluid if it is less dense than the fluid.

The article provided was found form the website (http://physics.suite101.com/article.cfm/why_do_hot_air_balloons_fly)

"In a hot air balloon it is filled with hot air that is less dense that when it is filled with cool air. For the hot air balloon to rise and carry the basket of passengers the balloon mush have a low density. This relates to the terminology we took on density. All together the balloon the basket and its passengers must weigh less than the total amount of air displaced by the balloon or it won't rise. When it does weigh less then the air in the balloon there is an upward buoyant force which exceeds the downward weight. This is the same princle that of helium balloons because the helim gas is much less dense than air."

Atmosphere On The Moon

"Ever wonder why people on the moon appear as they are flying or can jump for a far distance. The reality is that those people can't really fly or jump for miles. They aren't people like superman who have the capability to fly. It is because the moon has a very low gravitational pull. Unlike Earth's where objects stay on the ground due to the gravity. The moon's gravity is so much less then Earths that objects float or can jump high in the air. Thus because the Moon has low gravity it is to weak to hold an atmosphere. So for those who believe that once you are on the moon you have the capability to fly, it's not true. Its the realivily low gravity and the low escape velocity."


Atmosphere On The Moon
Why There Is no Atmosphere on the Moon
Weak Gravity Allows Gas Atoms to Escape so no Air on Small Planets
Buzz Aldrin saw such "magnificent desolation" when he stood on the Moon in July 1969 in part because it lacks an atmosphere. With no air or liquid water to erode the lunar geology, surface features retain their initial ruggedness. This lack of breathing air forced astronauts to wear special sealed spacesuits contributing to the desolation.
To understand why Earth's Moon and other small moons and planets have no atmosphere, it is first necessary to understand a little about gravity and escape velocity.
Gravity on the Moon
Some people think the Moon has no air because there is no gravity on the Moon. This is incorrect. Because the Moon is less massive than Earth the gravitational force on the Moon's surface is weaker than Earth's. There is still gravity on the Moon, but it is too weak to hold a significant atmosphere. Why?
Escape Velocity
When NASA launches a rocket into space, the rocket must reach a minimum speed to break the bonds of Earth's gravity. Rockets not reaching this minimum speed, called the escape velocity, fall back to Earth. Anything traveling at the escape velocity, or faster, can escape into space. Gravity pulls back anything traveling more slowly.
Earth's escape velocity is 11 kilometers/second. With less surface gravity, the Moon's escape velocity is 2.4 kilometers/second. Hence it is much easier to escape into space from the Moon than from Earth.
Heat and Molecular Motions
Gas atoms and molecules don't rest quietly. They move around fairly rapidly in random directions. As the gas temperature increases the average speed of the gas atoms increases. If the speed of a gas atom exceeds the escape velocity, that gas atom can escape into space.
Earth's average temperature is approximately 300 Kelvins. At this temperature the average (technically root mean square) speed of a nitrogen molecule is about 0.5 kilometers/second. Because this speed is much less than Earth's escape velocity Earth holds on to its nitrogen very tightly.
This speed is also less than the escape velocity from the Moon, but it is closer. So gas atoms and molecules can more easily escape from the Moon. To understand why, think about this analogy.
The average height for adult males is somewhere between five and six feet. However there are plenty of men that are either taller or shorter than this range. For example NBA basketball players are often over seven feet tall. However they don't have players over ten feet tall because that is too far above the average.
Escape Velocity and Atmosphere
As a rule of thumb, if the escape velocity is more than ten times the average speed of a particular type of molecule, that type of gas will remain in the atmosphere. Otherwise the molecules will escape over time. On Earth the escape velocity is high enough to hold its atmosphere. Molecules would have to be like the ten foot tall players to escape. On the Moon however the escape speed is low enough that the faster moving atoms can escape. Molecules would have to be like the almost seven foot tall NBA players to escape. So these gas atoms and molecules fly off into space. The Sun heats the remaining gas enough that those atoms and molecules eventually speed up and escape.
Hence less massive moons and planets including the Moon and Mercury have no significant atmospheres. Mars is a little more massive so it has a thin atmosphere. More massive Earth and Venus have significant atmospheres and the very massive gas giant outer planets retain very thick atmospheres.
This article was found from the website (http://physics.suite101.com/article.cfm/why_there_is_no_atmosphere_on_the_moon)