HOW DOES THE MOON AFFECT EARTH?


Despite being much smaller than the Earth, the Moon still has a great deal of influence on its parent planet. Its gravity is constantly pulling on Earth’s surface. This is not noticeable in relation to solid ground, but can clearly be seen in the movement of Earth’s tides. Twice a day, the oceans on Earth rise and fall. This is because the Moon’s gravitational pull is strongest on the side of Earth that is facing the Moon. Oceans on this side will be pulled into a bulge — high tide. Water on the opposite side is least affected by the Moon’s gravity, so it flows away from Earth in another bulge, resulting in another high tide. Areas of Earth at right angles to the Moon will have low tide.



A bigger instant effect would be on the ocean’s tides. But to understand the impact we need to know about how tides work. Tides are the result of the gravitational tug from the Moon and Sun that the Earth feels. If we disregard the Sun for now, the Earth’s oceans facing the Moon bulge up in response to the lunar gravitational force: a high tide. The difference in gravitational attraction on the near and far sides of the Earth means that, at the same time, there is also a high tide on the side furthest from the Moon. And because the ocean is liquid, between these two high tides there are two low tides. As the Earth is spinning, these high and low tides move across the globe over 24 hours, meaning each coastal location experiences two high tides and two low tides every day.



In reality, it is a little more complicated. The Moon’s 27-day orbit of the Earth means the times at which high and low tides occur change. You have to wait 12 hours plus 25 minutes between each high tide. And the Sun plays its part too. The Sun’s influence on tides is just under half as strong as the Moon’s.



When the Sun, Moon and Earth are all lined up, the Sun and Moon work together to produce ‘spring’ tides (though confusingly they don’t have to happen in spring). During spring tides, high tides are a little higher and low tides a little lower than normal. In contrast, when the Sun and Moon are at right angles to one another, the tides from the Sun partially cancel those from the Moon and we have the opposite: ‘neap’ tides. Here, high tides are a little lower and low tides a little higher than average.






WHAT HAPPENS DURING A LUNAR ECLIPSE?


          A lunar eclipse occurs when the Earth comes directly between the Sun and the Moon. As the Moon moves through Earth's shadow, the planet prevents direct sunlight from reaching the surface of the Moon. The Moon does not disappear but turns red because Earth's atmosphere bends the Sun’s rays. A lunar eclipse can occur only on the night of a full moon. The type and length of a lunar eclipse depend on the Moon's proximity to either node of its orbit.



          During a total lunar eclipse, Earth completely blocks direct sunlight from reaching the Moon. The only light reflected from the lunar surface has been refracted by Earth’s atmosphere. This light appears reddish for the same reason that a sunset or sunrise does: the Rayleigh scattering of bluer light. Due to this reddish color, a totally eclipsed Moon is sometimes called a blood moon.



          Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly 2 hours, while a total solar eclipse lasts only up to a few minutes at any given place, due to the smaller size of the Moon's shadow. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the full Moon.



          Earth’s shadow can be divided into two distinctive parts: the umbra and penumbra. Earth totally occludes direct solar radiation within the umbra, the central region of the shadow. However, since the Sun's diameter appears about one-quarter of Earth's in the lunar sky, the planet only partially blocks direct sunlight within the penumbra, the outer portion of the shadow.



          A penumbral lunar eclipse occurs when the Moon passes through Earth's penumbra. The penumbra causes a subtle dimming of the lunar surface. A special type of penumbral eclipse is a total penumbral lunar eclipse, during which the Moon lies exclusively within Earth's penumbra. Total penumbral eclipses are rare, and when these occur, the portion of the Moon closest to the umbra may appear slightly darker than the rest of the lunar disk.



          A partial lunar eclipse occurs when only a portion of the Moon enters Earth's umbra, while a total lunar eclipse occurs when the entire Moon enters the planet's umbra. The Moon's average orbital speed is about 1.03 km/s (2,300 mph), or a little more than its diameter per hour, so totality may last up to nearly 107 minutes. Nevertheless, the total time between the first and the last contacts of the Moon's limb with Earth's shadow is much longer and could last up to four hours.



          The relative distance of the Moon from Earth at the time of an eclipse can affect the eclipse's duration. In particular, when the Moon is near apogee, the farthest point from Earth in its orbit, its orbital speed is the slowest. The diameter of Earth's umbra does not decrease appreciably within the changes in the Moon's orbital distance. Thus, the concurrence of a totally eclipsed Moon near apogee will lengthen the duration of totality.



          A central lunar eclipse is a total lunar eclipse during which the Moon passes through the centre of Earth's shadow, contacting the anti-solar point. This type of lunar eclipse is relatively rare.










































HAS THE EARTH ALWAYS LOOKED THE WAY IT DOES TODAY?


Earth is the only planet in the Solar System that has a surface split into geological plates. These plates are constantly moving, carried on oceans of rocky mantle no faster than two centimetres each year. 250 million years ago all of the plates on Earth were compressed together in a giant super-continent called Pangaea. Over millions of years this land mass was pulled apart as forces caused the plates to move away from each other.



The earth has not always looked the way it looks today. In other words, the United States one billion years ago was in a totally different location than it is today!! How does this happen? And why does this happen? Let's take a look. In order for us to some understand of how the earth has changed over time, we first need to understand some of the things that took place, and are still taking place, in the earth.



What about the internal structure of the Earth? Our best clues about the interior come from waves that pass through the Earth's material. When earthquakes shake and shatter rock within the Earth, they create seismic waves which travel outward from the location of the quake through the body of the Earth. Seismic waves are disturbances inside the Earth that slightly compress rock or cause it to vibrate up and down. The velocity and characteristics of the waves depend on the type of rock or molten material they traverse.



Studies of seismic waves have revealed two important types of layering in the Earth: chemical and physical. Compositional layering refers to layers of different composition. Physical layering refers to layers of different mechanical properties, such as rigid layers verses "plastic" or fluid layers. 



Compositional layering was the first type of layering recognized. Seismic and other data indicate that the Earth contains a central core of nickel-iron metal. The core is surrounded by a layer of dense rock, called the mantle, that extends most of the way from the core to the surface. Near the surface, the densities of the rocks are typically lower. The crust is a thin outer layer of lower density rock about 3 miles thick under the oceans and about 18.5 miles thick under the continents.




















HOW LONG HAVE HUMANS LIVED ON EARTH?


Human beings are late arrivals on planet Earth. Humankind's earliest ancestor —Australopithecus afarensis — appeared over two million years ago. Neanderthals had evolved by 400,000 years ago, and Homo sapiens, modern humans, only existed around 100,000 years ago. Just how short a time this is can be seen when we look at the history of the Earth as a clock, with 12 o’clock midnight being the time that Earth was formed 4.6 billion years ago. Each hour on the clock represents 383 million years.



Millions of years ago, “humans” may have walked on two legs like us, but they were very different from us. They had to hunt and gather food and they had to brave the environment in order to survive. The structure and anatomy of early humans are much different than humans now. Currently, we humans are much lighter than our ancestors. We have large brains with a skull that has high and thin walls. We have thinner jaws and smaller teeth. Our ancestors millions did not have these features, but the features we see now slowly evolved as time passed.



When we think of humans in the past, we need to think of humans that have some of the same general characteristics as us, but they do not look or act like us.



We are still learning about our ancestors, but we guess that the first humans existed between five and seven million years ago: the median time is six million years ago. These humans walked upright on two legs, just like us. Around 90,000 years ago, these humans started making tools to catch fish. Then, around 12,000 years ago, humans began to grow food and change their surroundings in order to survive and eat. As food became more sustainable, and living became easier, humans began to produce more.



As humans developed and grew, their bodies changed. Their brains became bigger, which helped them to develop new tools, including language. They changed the world around them to better survive harsh and changeable weather. Over time, these humans created civilizations and became what we know as humans now.



It may seem like humans have been around for a while, because six million years seems like a long time; in the overall timeline of the Earth, however, six million years is not very long. The Earth itself is 4.5 billion years old. Nonetheless, the six million years humans have been on Earth has allowed them to evolve, build tools, create civilizations, adapt to their environment, and become the humans we are today.




















HOW DID LIFE BEGIN ON EARTH?


Nobody knows WHAT conditions are needed for life to begin. Some scientists have suggested that living cells may have been brought to Earth by a comet. When the Giotto probe investigated Halley’s Comet in 1986, it found molecules that were similar to living cells. If a comet like this collided with Earth at the right time, then life may have taken hold. Another theory is that powerful lightning bolts flashing through Earth’s early atmosphere may have caused chemical reactions, which created living cells.



One of the first ideas, popularised by biochemist Sidney Fox in the wake of the Miller-Urey experiment, was that amino acids assembled into simple proteins. In modern organisms, proteins perform a huge range of functions, including acting as enzymes that speed up essential chemical reactions. However, this proteins-first hypothesis has largely fallen out of favour.



A much more popular notion is that life began with RNA, a close cousin of DNA, in an “RNA World”. RNA can carry genes and copy itself just like DNA, but it can also fold up and act as an enzyme, just like a protein. The idea was that organisms based solely on RNA arose first, and only later developed DNA and protein.



The RNA World has amassed a lot of supporting evidence, but it is not clear that RNA alone was enough. In recent years, some researchers have suggested that RNA only really reaches its potential when it is paired with proteins – and that both must have existed for life to get started.



A third school of thought is that the first organisms were simple blobs or bubbles. These “protocells” would have resembled modern cells in one key attribute: they acted as containers for all the other components of life. More advanced protocells developed by the Nobel Prize winning biologist Jack Szostak also contain self-replicating RNA.



The final hypothesis is that life began with a series of chemical reactions that extracted energy from the environment and used that energy to build the molecules of life. This “metabolism-first” idea was championed in the late 1980s by Günter Wachtershauser, a German chemist turned patent lawyer. Wachtershauser envisioned a series of chemical reactions taking place on crystals of iron pyrite (“fool’s gold”), a scheme he dubbed the “Iron-Sulphur World”. However, nowadays this idea has been supplanted by Michael Russell’s suggestion that the first life was powered by currents of electrically-charged protons within alkaline vents on the sea bed.



While we cannot know for sure which of these scenarios played out on our planet, successfully creating life from chemicals in the lab would at least tell us which of the proposed mechanisms actually works. 


















WHAT IS THE ECOSPHERE?



The ecosphere is a narrow band around the Sun where the temperature is neither too hot nor too cold for life to exist. Earth is the only planet in this zone, and is therefore the only planet in the Solar System able to support life. Mercury and Venus are too close to the Sun for water to exist in liquid form. The remaining planets lie well beyond the ecosphere, where it is too cold for life. The temperature on Pluto can reach as low as —223 °C (-370°F)!



An ecosphere is a planetary closed ecological system. In this global ecosystem, the various forms of energy and matter that constitute a given planet interact on a continual basis. The forces of the four Fundamental interactions cause the various forms of matter to settle into identifiable layers. These layers are referred to as component spheres with the type and extent of each component sphere varying significantly from one particular ecosphere to another. Component spheres that represent a significant portion of an ecosphere are referred to as a primary component spheres. For instance, Earth’s ecosphere consists of five primary component spheres which are the Geosphere, Hydrosphere, Biosphere, Atmosphere, and Magnetosphere.


















WILL THERE ALWAYS BE LIFE ON EARTH?



Like all stars, our Sun will eventually die. In around five billion years its supply of hydrogen will run out, and it will become a red giant, expanding to well over thirty times its current size. As it grows, the Sun will engulf all the inner planets, making them far too hot for life to survive.



There’s nothing we can do to prevent this cataclysm. Yet according to scientists who study the far future, including Yale University astronomer Gregory Laughlin, the prospect for life is, oddly, rather bright. Given technological advances and the continuing evolution of our species, humans should be able to survive — in some form — long after Earth has ceased to exist.



But our distant descendants are going to have to do some planet-hopping. The first major cosmic crisis will strike in about 1.5 billion years. At that point, according to projections by environmental scientist Andrew J. Rushby at the University of East Anglia in England, the brightening sun will set off what might be termed “super-global” warming. Earth will be heated until the oceans boil.



By then, though, will we care? We already have the technology to establish bases on the moon and Mars. So a billion and a half years from now, we’ll likely have colonized the whole solar system — and perhaps other star systems in our Milky Way galaxy.



As the sun grows hotter, other planets will become more appealing. Just as Earth becomes too toasty to sustain life, Mars will reach a temperature that makes it habitable. Cornell University astronomer Lisa Kaltenegger has run models showing that the Red Planet could then stay pleasant for another 5 billion years.



About 7.5 billion years from now, the sun will exhaust its hydrogen fuel and switch to helium. That will cause it to balloon into an enormous red giant. Mars as well as Earth will be fried. On the other hand, the once icy moons of Jupiter and Saturn will have become tropical water worlds — prime real estate for human colonies. We could live there for a few hundred million years.



About 8 billion years from now, the flaring sun will make conditions intolerably hot all the way out past Pluto. “The exact dates depend on how much mass you estimate the sun will lose and how much planets will move,” Kaltenegger says. But the message is clear: Life will be impossible in our solar system.














HOW DID LIFE DEVELOP ON EARTH?

For much of its early history, Earth was a bubbling, volcanic ball — far too hot to sustain life. Over millions of years, the surface of the planet began to cool and harden, releasing enormous clouds of steam and gas. The moisture in these clouds eventually became rain, forming the seas. Scientists believe that the first life-forms originated in shallow pools of water, where different chemicals were concentrated to form single-celled organisms. These gradually evolved into more complex life-forms. All living creatures on Earth are still evolving.



Microbial life forms have been discovered on Earth that can survive and even thrive at extremes of high and low temperature and pressure, and in conditions of acidity, salinity, alkalinity, and concentrations of heavy metals that would have been regarded as lethal just a few years ago. These discoveries include the wide diversity of life near sea–floor hydrother­mal vent systems, where some organisms live essentially on chemical energy in the absence of sunlight. Similar environments may be present elsewhere in the solar system.



Under­standing the processes that lead to life, however, is complicated by the actions of biology itself. Earth’s atmosphere today bears little resemblance to the atmosphere of the early Earth, in which life developed; it has been nearly reconstituted by the bacteria, vegetation, and other life forms that have acted upon it over the eons. Fortunately, the solar system has preserved for us an array of natural laboratories in which we can study life’s raw ingredients — volatiles and organics — as well as their delivery mechanisms and the prebiotic chemical processes that lead to life. We can also find on Earth direct evidence of the interactions of life with its environments, and the dramatic changes that life has undergone as the planet evolved. This can tell us much about the adaptability of life and the prospects that it might survive upheavals on other planets.












WHY IS THERE LIFE ON EARTH?

Earth is the only place in the Solar System on which scientists have encountered life. Conditions on our planet are perfect for sustaining life — the surface temperature averages around 15°C (59°F) , allowing water to exist in liquid form. Water is a vital ingredient for life, and its presence on Earth has enabled an incredible variety of creatures to live on every part of the planet. Also, Earth is large enough to contain a protective atmosphere, but not big enough to become a suffocating gas planet like Jupiter or Saturn.



Although the exact process by which life formed on Earth is not well understood, the origin of life requires the presence of carbon-based molecules, liquid water and an energy source. Because some Near-Earth Objects contain carbon-based molecules and water ice, collisions of these objects with Earth have significant agents of biologic as well as geologic change.



For the first billion years of Earth’s existence, the formation of life was prevented by a fusillade of comet and asteroid impacts that rendered the Earth’s surface too hot to allow the existence of sufficient quantities of water and carbon-based molecules. Life on Earth began at the end of this period called the late heavy bombardment, some 3.8 billion years ago. The earliest known fossils on Earth date from 3.5 billion years ago and there is evidence that biological activity took place even earlier - just at the end of the period of late heavy bombardment. So the window when life began was very short. As soon as life could have formed on our planet, it did. But if life formed so quickly on Earth and there was little in the way of water and carbon-based molecules on the Earth’s surface, then how were these building blocks of life delivered to the Earth’s surface so quickly? The answer may involve the collision of comets and asteroids with the Earth, since these objects contain abundant supplies of both water and carbon-based molecules.



Once the early rain of comets and asteroids upon the Earth subsided somewhat, subsequent impacts may well have delivered the water and carbon-based molecules to the Earth’s surface - thus providing the building blocks of life itself. It seems possible that the origin of life on the Earth’s surface could have been first prevented by an enormous flux of impacting comets and asteroids, then a much less intense rain of comets may have deposited the very materials that allowed life to form some 3.5 - 3.8 billion years ago.



Comets have this peculiar duality whereby they first brought the building blocks of life to Earth some 3.8 billion years ago and subsequent commentary collisions may have wiped out many of the developing life forms, allowing only the most adaptable species to evolve further. It now seems likely that a comet or asteroid struck near the Yucatan peninsula in Mexico some 65 million years ago and caused a massive extinction of more than 75% of the Earth’s living organisms, including the dinosaurs. At the time, the mammals were small burrowing creatures that seemed to survive the catastrophic impact without too much difficulty. Because many of their larger competitors were destroyed, these mammals flourished. Since we humans evolved from these primitive mammals, we may owe our current preeminence atop Earth’s food chain to collisions of comets and asteroids with the Earth.