On earth, the regolith is typically called soil and is made from natural processes such as the weathering of rocks. The soil in this case is vital to the survival of the organisms residing in the planet because it is where plants grow and where human beings build. In the case of the moon however and other objects in outer space that have no known signs of life on them, the regolith serves no other known function except to reflect light from the surface. The regolith from these celestial bodies comes mostly from the debris left over from impacts with meteors or asteroids. Because most of these bodies do not have an atmosphere surrounding them, the impact is often very hard and even small meteorites can cause damage or leave debris.

The moon’s regolith in particular is called lunar regolith and was found to be around 20 meters only at its thickest portions. The composition is mainly rocks and minerals along with glass particles from impacts with asteroids. A famous photo of the lunar regolith was taken during the Apollo 11 mission and showcases the footprint of renowned astronaut Neil Armstrong.

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Based on the planet formation theory, these bodies meet each other?s orbits and then collide with each other, and with the great collision impacts, can eventually dominant planets as well. Studies show that in the situation in forming the solar system, it needed a few hundred planetisimals to form the solar system in which the planet earth is in now. Such collisions also resulted in the formation of dwarf or almost planetary state celestial bodies like Pluto or Ceres for example. In the course of 100 annum or years (not relating to the normal and common years), these nearly done planets collide and explode, causing big impacts and eventually making a new generation of planetary embryos, though much smaller.

These batches mature, collide, and induce more explosions, and eventually create a new batch of embryos, even smaller than the previous ones. This process is then repeated many times, until a handful of these are left and result to making planets. Though there is still little information regarding the movement and alignment factor of the planets that formed.

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Not all planetesimals merge on collision. Some are unlucky enough to break apart on impact. The one that are lucky enough to survive will eventually grow to approximately one kilometer in size when it can then attract each other to form even larger bodies. This process continues until the accumulation of matter forms into a moon or eventually a planet.

Components of planetesimals vary depending on their distance from the sun. The inner portion of the solar nebula is hot, thus the planetesimals that grow are mostly composed of metals and silicates. The outer portion of the solar nebula is much cooler, thus allowing the formation of planetesimals made mostly of water ice. This can account for the fact that the gas giants in the outer portion of our solar system are mostly composed of gas and liquid cores.

The term planetesimals is also used by some scientists when referring to asteroids, comets and other small astronomical objects that are believed to be debris produced by the planetary formation process.

Planetesimals provide scientists with valuable material from when they were first formed, which is key to further studies on the condition of the solar nebulae around the time our solar system was formed.

Planetisimal Theory

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The topic of global warming puts concern about the Earth’s polar ice caps. Has the Earth’s temperature warmed enough to cause the polar ice caps to melt, thus causing our oceans to rise? According to the EPA (Environmental Protection Agency), it took 100 years for the Earth’s sea level to rise to about 6 to 8 inches. But with the growing trend of global warming talks, people are becoming anxious about the polar ice caps melting. Are they really?

The largest polar ice cap on Earth is in Antarctica at the South Pole. It holds approximately 90 percent of the world’s ice content. If all of the ice in Antarctica melts, it will raise the sea levels all over world at about 61 meters or 200 feet. This is an unlikely occurrence, however, since the average Antarctic temperature is -37°C and never gets beyond freezing.

At the North Pole, the ice floats on the Arctic Ocean and are not likely to affect the sea level even if they melt.

Earths Polar Ice Cap

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The angle between a certain rotational axis of an object and the specific perpendicular line in regards to the object’s orbital plane is better known as its obliquity. In the solar system, the axial tilt of the earth is known formally as the obliquity of the ecliptic, since the name of the planet’s orbital plane is called the ecliptic plane. In formulas, it is represented by the Greek Character “Ε” or epsilon.

Apart from this, a planet’s axial tilt causes the seasons like spring or winter. This is due to the change of orientation of a planet’s obliquity, though the actual angular degree of tilt does not change, and the rotation moves until it reaches 360 degrees or one complete revolution. Thus, specifying which season it is now.

The planet earth has an approximate axial tile of 23.4 degrees. The axis stays tilted in the direction pointing to the stars for the entire year. This implies that a certain hemisphere — or half of the earth is in the direction towards the sun, half a year or half an orbit later, the other half will be now in the sun’s direction. Also, the current hemisphere that is facing the sun tends to have longer hours of sunlight.

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The study of subatomic particles like neutrinos normally lie within the realm of physics, but it is in astronomy that scientists are able to study neutrinos in action. For example, in 1968, an experiment was able to detect neutrinos produced by the burning gases on the sun’s surface. And in 1987, a burst of neutrinos was detected from the explosion of a supernova.

This 1987 event marked the “official” beginning of a branch of science called neutrino astronomy: a kind of a marriage between physics and astronomy whose main objective is to shed light on the nature and characteristics of neutrinos.

So far, three types of neutrinos have been discovered: the electron-neutrino, the tau-neutrino and the muon-neutrino. They, together with electrons, are classified as leptons. Leptons and quarks— collectively known as Fermions—are the fundamental building blocks of the universe.

Understanding Neutrinos

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The retrograde motion refers to the backward motion of a planet. This is caused by the combined motion of both the planets and that of the earth's. When both planets move eastward around the Sun and then the planet which has a smaller orbit will tend to move faster. Basically, when a faster planet dominates the Earth when it comes to their rotations, this planet's motion against the stars would be seen from the Earth in reverse.

Every once in a while, however, a particular planet would do something relatively odd and this would be slowing down its motion to the point that it seems to have completely stopped for that period of time. Afterwards, it would begin moving towards the opposite direction, towards the west. For a second time, it would stop again and resume its normal movements. Ptolemy had this idea that all the planets were carried on a smaller circle and whose center moves along another larger circle around the earth which he referred to as the deferent.

Retrograde Motion

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There are also several mid-sized lightweight planets, just a few times larger than our beloved planet Earth. Most extrasolar planets rotate around stars, but there are also planets that orbit around brown dwarfs and planets that do not orbit on any body at all, floating freely to space.

Because of the discovery of many extrasolar planets, the interest in the possibility of extraterrestrial life has intensified in the field of science and astronomy. Various missions and projects have been made to determine if there is extraterrestrial life on these planets.

Astronomers have found two possible candidates that may hold extraterrestrial life: red dwarf planets Gliese 581 and Gliese 581 D. These planets have many Earth like qualities so possibility of life here is high. Because of this, scientists have sent a message to Gliese 581. Being 20.3 light years away from earth, the message is estimated to arrive by year 2029 and response, if ever there will be, will not come until year 2049.

ExtraSolar Planets

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The interplanetary theory is a specific and established theory in astronomy that means planets are made up of certain elements formed together, and that the space between planets exists. These are mainly made up of atomic particles or substances ejected by the sun through solar winds or other means, and as well as dust particles from asteroids or comets.

Interplanetary space is defined as the space between different celestial bodies or planets. In these, spaces, gases, rocks, and dust particles compose this part of a planetary system.

An interplanetary medium on the other hand, is the raw material of space. It is what fills the solar system of the different components is has, and also fills our own solar system with which bodies of a larger solar system move such as the planets, comets, and the stars. This kind of matter is composed of different materials like space dust, cosmic rays and plasma due to the emission of solar winds coming from the sun.

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In Positional Astronomy, two celestial bodies are viewed from a particular place while on opposite sides of the sky. Distinctly, two planets are considered in opposition to each other if solar elongation (the measurement of the angle between a planet and the Sun) of 180o is present– which is considered maximum elongation. In simplest terms, Opposition is when a planet is opposite the Sun in the Earth's sky, or occurs when the Earth is situated between the planet and the Sun.

The point of reference is always the sun. The superior planets such as Mars, Jupiter, Saturn, Uranus, and Neptune, whose orbits lie external to the earth, can be in opposition to the sun. The excellent time to view a planet is during solar elongation, since it rises when the sun sets and is visible throughout the night, setting as the sun rises. On the other hand, Inferior planets, such as Mercury and Venus have different elongation periods than superior planets, which are further distant from the Sun than the Earth.

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