Earth orbits third from the Sun, at an average distance of 149,597,870.700 kilometers or 1 AU, placing it well inside the Solar System’s habitable zone, [1] while an equatorial diameter of 12,756 kilometers makes it the fifth largest body (excluding the Sun) in the solar family.

Humanity's home is known by many names (Earth, Terra, Gaia, Tellus, Avani or Honua just a few of the hundreds spanning time, culture and religion) but whatever it's called one salient fact is evident, conjecture aside it’s all we have and not just us humans but all life, because at this point in time, to the best of our knowledge, we’re all alone. Earth is the only planet in the entire universe that we can say with certainty harbors life.

The planetesimal theory of planetary formation hypothesizes that the Earth was created some 4.6 billion years ago with the contraction of a stellar nebula into larger and larger clumps of matter, the gas, dust and debris eventually coalescing into the Sun, planets and moons that comprise the Solar System.

Earth has an inner core, mostly iron, with a temperature of between 4,000 and 5,000 degrees Celsius, surrounded by an outer core, then a mantle, both in a semi-fluid state, surrounded by a crust comprised of solid plates constantly in motion floating on the mantle (there are eight major and numerous smaller plates, intense seismic activity most often occurring in areas where they interact).

Seventy-one percent of Earth’s surface is covered in water, the only planet in the solar system where surface water in large quantities exists in liquid form. The rest is land, everything from low lying islands barely above sea level, to towering mountain ranges, plateaus and vast plains.

Earth’s atmosphere is an envelope of gases, thicker at the bottom then gradually thinning before fading into outer space (the Karman line at 100 km [62 miles] generally considered the outer boundary). It consists of nitrogen seventy-seven percent and oxygen twenty-one percent, with carbon dioxide, argon and water comprising most of the remaining two percent. The amount of carbon dioxide is critical in the maintenance of Earth's surface temperature; its what’s called a greenhouse gas and along with water vapor is responsible for what is called the greenhouse effect (the same effect that heats up your car when you leave the widows closed on a sunny day). Too little and the temperature would plunge and we and the oceans would freeze. Too much and the temperature increases with catastrophic results: droughts, massive storms, hurricanes of immense destructive power, melting ice caps and loss of habitat as sea levels rise.
The Precambrian is the name given by geologists to a period that began over four billion years ago; it was a violent era of intense meteor bombardment and constant volcanism, a time when a hot lifeless atmosphere of nitrogen, carbon dioxide, hydrogen and water vapor enshrouded the planet. Then as the Earth cooled plate tectonics began defining the planets surface, water vapor condensed fell as rain and oceans formed.

Three and a half billion years ago life appeared, Archaea, one celled organisms that reproduced by dividing (asexual reproduction) and didn’t require oxygen to create energy. These were followed by cyanobacteria, which gradually introduced oxygen into the atmosphere through a process called photosynthesis. Later came eukaryotes an evolutionary jump, these were organisms with a nucleus in their cells that reproduced by combining their genetic makeup. Then near the end of the Precambrian another evolutionary jump, a group of organisms known as the Ediacaran fauna appeared a forerunner to the flood of life forms that was to follow.

Approximately five hundred and fifty million years ago in a time called the Cambrian period (the earliest period of the Paleozoic era) an event took place which came to be known as the Cambrian explosion. Life began to diversify and increase in complexity at an astonishing rate, almost all the main groups of animals known today first emerging. Later in the Paleozoic
fish appeared in the sea and multicellular plants, insects and amphibians appeared on land.
It was a time of trial and error for Mother Nature, new forms of life made an appearance and flourished, while others unable to compete disappeared, mute testimony to natural selection and the survival of the fittest. The Permian period closed out the Paleozoic, reptiles were dominant, the first mammal like reptiles came into existence and fern-like forests covered the land.

Then suddenly it was over, a catastrophe of global proportions triggered the greatest mass extinction in history and ninety percent of life on the planet was gone. What caused it is still unclear, a comet or asteroid impact, a major volcanic event or a nearby supernova are all possibilities.

The Mesozoic begins in the ashes of the Paleozoic and is divided into three geological periods called the Triassic, Jurassic and Cretaceous. It is often referred to as the Age of the Dinosaurs because these animals overwhelming dominated the land, sea, and air. Domination acquired as they filled vacant ecological niches left by the mass extinction of the late Paleozoic, niches that were also filled by birds and mammals, while flowering planets replaced conifers as the dominant vegetation. It was also the period in which the giant supercontinent of Pangaea began to break up into separate land masses.

During the Late Cretaceous the dinosaurs may have ruled and Tyrannosaurus Rex may have roared, but it was the small rodent like mammals that burrowed underground or scurried in the shadows whose unique physiology and way of life was about to guarantee them a place in the sun.

The Cenozoic era began about sixty five million years ago and is divided into the Tertiary and Quaternary periods, the latter being both a time of great ice ages and a time when plate tectonics and continental drift defined the Earth’s surface. The Mesozoic was the Age of Dinosaurs; the Cenozoic is the Age of Mammals. The boundary between Mesozoic and Cenozoic was abrupt and catastrophic, brought about by an event so devastating that it changed the world, caused mass extinction and ended the dinosaurs one hundred and eighty million year reign.

It probably began as a giant fireball streaking across the sky and then impact, a ten km wide asteroid slamming into the Yucatan with a force of one trillion megatons. Vaporized rock and debris are hurled high into the atmosphere, a massive firestorm sweeping outward from the detonation trees and animals in its path exploding into flame. The crust ruptures as intense volcanism spews forth magma, earthquakes follow triggering giant megatsunamis which race throughout the world’s oceans swamping coastlines with walls of water hundreds if not thousands of meters high. The sun vanishes as smoke, toxic soot and ash envelope the globe. Plants and animals die from the cold as temperatures plummet and a long nightmarish winter begins. Finally after several years the atmosphere begins to clear and the sun peaks through the haze. The temperature starts to rise, but it’s not over yet, increased carbon dioxide causes a runaway greenhouse effect that threatens to cook whatever has survived. The smaller animals that had huddled in their burrows for warmth dig deeper as they now seek to stay cool, until eventually, as temperatures begin to revert to past more tolerable levels, the survivors emerge but into a changed world. The dinosaurs are gone; the age of mammals has begun.

Man has been on this Earth a relatively short length of time. The fossil evidence seems to indicate that he began to evolve in Africa between five and six million years ago and began to migrate eastward about one and a half million years ago.

New studies by the Genographic Project, a joint venture between IBM and National Geographic, uses DNA samples gathered from indigenous groups around the world in order to trace the migration of early humans from when they first left Africa sixty thousand years ago to the present time. Though controversial the evidence as presented suggests that all present day humans (Homo sapiens) descended from a single common ancestor who lived in Africa some sixty thousand years ago.

Essentially it postulates that the migrations took place in waves: The first wave colonized Australia about fifty thousand years ago; the aborigines are their descendants. A second wave colonized the Middle East, India and China about forty-five thousand years ago and following the retreating glaciers moved into central Asia about forty thousand years ago. Small groups later migrated into Europe around thirty five thousand years ago, coming into contact with and eventually replacing and/or interbreeding with Neanderthals (a separate but related species, which recent studies indicate survived until about twenty four thousand years ago in the more remote parts of south western Europe [the last traces of Mousterian culture, stone tools of a type primarily associated with Neanderthals, were found in Gorham’s Cave a natural sea cave located on Gibraltar's east face]). Another migration took place approximately twenty thousand years ago, when Central Asians moved into Siberia before crossing the Bering Sea and populating the Americas. [2]   

For millennia early humans practiced what is called hunter-gathering, but around ten thousand years ago an important change began to take place, our ancestors started to domesticate plants and animals thus providing themselves with a readily available food source, something hitherto unknown, the new security this afforded allowing for a settled lifestyle and eventually the growth of small communities.

Mesopotamia around seven thousand years ago, contained many of these early communities which as they prospered and grew became cities with walls, granaries, temples, priests and a ruling elite. Interconnected by a network of roads and protected by a strong military this land located between the Euphrates and Tigris was the first to achieve that which we now call civilization.

Other civilizations were to follow, the Nile Valley, the Yellow River Valley, Crete, the Indus Valley and various Mesoamerican societies, all arising in areas conducive to growth and all with certain similar features in common, excess food, storage facilities, the protection afforded by walls and a strong military, a priesthood, a ruling elite, laws, roads and a viable trading network to encourage economic growth and stability.

The period between the birth of civilization and the present has been one of highs and lows, a time of religious, social and political upheaval, great plagues and the rise and fall of empires. Mankind has accomplished great things and committed great atrocities. Two world wars were fought with weapons capable of incredible carnage as democracies struggled for survival against totalitarian regimes capable of almost unimaginable evil. While today differing ideologies, religions and political systems along with a struggle to control the Earth's rapidly diminishing natural resources still embroil us in confrontations that have the doomsday clock set at a few minutes to midnight.

The Industrial Revolution that began in Britain in the late 18th and early 19th centuries changed the world and was instrumental in creating a middle class with a standard of living undreamed of just a few centuries earlier, unfortunately this revolution, by virtue of its very nature, also sowed the seeds of problems that might yet overwhelm us.

The innovative technologies that have produced the Internet, computers, cell phones and satellites along with new modes of transportation encompassing, land, sea, air and space have made the inconvenience created by geography a thing of the past; almost instant communication with anywhere on the planet is an accepted reality and travel is fast, safe and affordable.

On October 4, 1957, the Soviet Union
ushered in the space age with the launch into orbit of Sputnik 1, Earth's first artificial satellite. This was followed by Sputnik 2 and the first animal sent into orbit, a dog named Laika. The first man to orbit the Earth was Russian Yuri Gagarin on April 12, 1961, followed by American John Glenn on February 20, 1962.

Skylab an American space station was launched on May 14, 1973, and was occupied a total of 171 days by three missions before crashing back to Earth when plans to lift it to a higher orbit failed to materialize.

In 1986 Mir became the first permanent space station; staffed continuously it proved invaluable to the Russian space program, operational in low Earth orbit untill 2001.

The American Space Shuttle, a revolutionary leap ahead for America’s space program, was a manned partially reusable space vehicle designed to carry large payloads into low Earth orbit safely and cheaply, but there were problems and two were destroyed one on launch in 1986 and a second on re-entry in 2003. In spite of these tragedies the shuttle proved invaluable to the American space effort; it was the launch vehicle for the Hubble Space Telescope, placing it into a 380 mile (612 kilometer) orbit on April 24, 1990, and even with continuing
difficulties was instrumental (along with that infamously cramped but dependable workhorse the Russian Soyuz) [3] in the construction and resupply of the International Space Station. In 2011 the shuttles showing their age were finaly retired [4] to be replaced (possibly) by Orion a new generation spacecraft presently under development by Lockhead Martin (the Russians
having temporarily assumed the job of space station resupply).

The International Space Station (ISS) originally conceived of as a solely American endeavor (Space Station Freedom) has since become a joint venture of the international space community with an increasing number of space agencies becoming involved both directly and indirectly. It has been continuously occupied since first being boarded November 2, 2000. Its crew astronauts, cosmonauts, and a few extremely wealthy tourists. Following an end to over a decade of assembly/construction it can now, finaly, fully fulfill the purpose for which it was intented, namely to aid in the human exploration of space, to provide a laboratory for research of all types and to make available a base from which private enterprise can begin to participate in what till now (with the exception of the commercial satellite industry) has been largely a governmental undertaking.

The need for governments to initially lay the groundwork for man’s immergence into space is obvious, but governments are notoriously inefficient, costly and prone to bureaucratic boondoggles. It is now time for private enterprise to get involved in a major way.

On Tuesday, December 23, 2008, after careful consideration, NASA awarded two contracts to resupply the International Space Station following the retirement of the U.S. space shuttle fleet in 2011. The contracts worth up to 3.5 billion US were divided between relative newcomer SpaceX, a California company originally based in El Segundo and now located in Hawthorne, and Orbital Sciences Corporation (OSC) out of Dulles, Virginia, an established space contractor founded in 1982 and heavily involved in both the aerospace and defence industries

At 2:45 p.m. EDT (1845 GMT) Friday, June 4, 2010, Space Exploration Technologies (SpaceX) using a Falcon 9 rocket became the first private company to successfully launch and place into orbit a privately developed space vehicle (albeit a stripped down version of the real thing, called a Dragon Spacecraft Qualification Unit).

On Wednesday, December 8, 2010,
Space Exploration Technologies (SpaceX) became the first private company to not only place into orbit but also return to Earth a privately developed space vehicle (this time fully functional). The Dragon spacecraft lifted off at 10:43 a.m. EST (1543 GMT) from Cape Canaveral Air Force Station, Florida, atop a Falcon 9 rocket into low Earth orbit, performed an intricate set of maneuvers designed to mimic a rendezvous with the "ISS" then returned to Earth and a perfect splashdown some five hundred miles west of Baja, California.

CEO and founder Elon Musk stated that based on the results of their test flight (the first of three financed by NASA under the COTS program) he planned to ask NASA for permission to combine elements of the second and third missions and send the next Dragon directly to the International Space Station.

NASA agreed and at 3:44 a.m. EDT (0744 GMT) May 22, 2012, a cargoe filled Dragon spacecraft [6] lifted off atop a Falcon 9 rocket from Cape Canaveral Air Force Station, Florida, its destination the International Space Station.

On May 25, 2012, at 9:56 a.m. EDT (1356 GMT) a milestone in the human exploration of space. Flight engineer Donald Pettit, after a complex rendezvous, began the Dragon's capture process snagging the world's first commercial spacecraft with the International Space Station's Canadarm2. The process was completed at 12:02 p.m. EDT (1602 GMT) with the successful berthing of the cargo ship to the station's Harmony module.

At 5:53 a.m. EDT (0953 GMT) May 26, 2012, Petitt opened the hatch and entered the Dragon with the comment that everthing was secure (supplies) and that it (the Dragon) smelled like a new car. The craft was carrying 544 kg (approximately 1200 pounds) of food provisions and equipment.

On May 31, 2012, at 0807 GMT, the Dragon, filled to the brim with returning cargo, was separated from the ISS by crewmembers before being officially released to space from the station's robotic arm at 0949 GMT.

The Dragon's Draco thrusters fired at 1451 GMT to slow the craft and begin descent (unlike the unmanned cargo craft of Russia, Europe and Japan the Dragon is designed for safe reentry), splashdown occurring in the Pacific some 560 miles (900 kilometers) west of the Baja California coast at 11:42 a.m. EST (1542 GMT).

The mission lasted a total of 9 days, 7 hours and 58 minutes.

On Friday, August 3, 2012, after carefull consideration and a year-long review of commercial manned spaceflight technology, NASA awarded three grants (CCiCap/CCP) totaling 1.1 billion US to be divided between Boeing, SpaceX and Sierra Nevada Corp., to be paid over the next 21 months, with a view to bringing commercial manned spaceflight that much closer.

On October 7, 2012, at 8:35 p.m. EDT (0035 GMT October 8) SpaceX launched the first of a dozen cargo runs to the International Space Station, the mission considered successful despite the failure of a booster rocket (one of nine) which resulted in a secondary payload not reaching its designated orbit.

Following delivery of almost 900 pounds of supplies, and a three week layover, the spacecraft returned to Earth carrying approximately 1,700 pounds of medical samples, science experiments, old equipment and general waste. (The Dragon is the only [unmanned] supply vehicle with return capability.)

Unless something unique occurs further Dragon flights will not be listed individually but are ongoing.

Orbital Sciences, a second space contractor, successfully launched its Antares rocket on Sunday, April 21, 2013, at 5:00 p.m. EDT from its launch pad at NASA's Wallops Flight Facility, Wallops Island, Virginia, its practice (dummy) payload deposited into orbit 158 miles (254 km) above the planet a few minutes later. If all goes well a demonstration flight is planned for the near future when Orbital will launch its Cygnus cargo ship loaded with supplies and attempt a successful docking with the ISS.

On Wednesday, September 18, 2013, the future arrived at 10:58 a.m. EDT (1458 GMT) when an unmanned Cygnus spacecraft loaded with 1,500 pounds (700 kg) of supplies lifted into orbit atop its Antares launch vehicle. The spacecraft, after playing catchup with the ISS, arrived in its vicinity on Sunday, September 22 where having readied itself with a number of practice manoeuvres it was snagged (albeit a week late [September 29] due to a computer glitch) by a robotic arm operated by astronauts Luca Parmitano and Karen Nyberg, and berthed to a free port on the station's Harmony module, the capture confirmed at 8:44 a.m. EDT (1244 GMT).

On October 22, 2013, filled with refuse, the one time cargo ship was uncoupled and released to a fiery fate over the Pacific. (Unlike its rival, SpaceX's Dragon, Cygnus is designed to burn up on reentry.)

Following a successful end to its demonstration mission Orbital has now joined SpaceX with regularly scheduled resupply flights to the ISS; the first of which launched at 1:07 p.m. EST on Thursday, January 9, 2014, carrying 3,000 pounds of equipment, experiments, fruit and Christmas presents and docked with the International Space Station three days later. The delivery, originally intended for before Christmas, was delayed by a space station breakdown, frigid weather and a solar storm.

On 13 July 2014 a successful launch and delivery.

And then on October 28, 2014, an explosion seconds after takeoff: The Cygnus cargo ship and cargo were lost, the launch pad damaged. The cause of the explosion and its impact on Orbitals' ability to fulfill its contractual obligations is yet to be determined. Tuesday's planned flight was to be the third of eight.

Elon Musk of SpaceX has ridiculed the Antares AJ-26 engine as hoplessly outdated. Frank Culbertson of Orbital has defended the engine as "very robust and rugged." Replacement engines are apparently in the pipeline.

On September 16, 2014, NASA announced that Boeing and SpaceX had been awarded contracts (worth $4.2 billion and $2-6 billion respectively) to transport astronauts to and from the International Space Station. (NASA has set a goal (perhaps optimistically) of 2017/18 for the first crew launch.)

The spacecraft of both companies must undergo vigorous safety testing before flight certification. Once certifiication is complete each company will launch between two and six missions.

On January 10, 2015, SpaceX trying something radically new had an oops moment. Following a successful supply launch the cutting edge company attempted to vertically land the first-stage of its launch vehicle on a barge located 200 miles off Jacksonville, Florida. It was a close-run thing but no cigar, the rocket crashing upon landing.

And then another problem: On June 28, 2015, an unmanned SpaceX rocket carrying supplies and a first-of-its-kind docking port (designed to accommodate future manned
commercial spacecraft), experienced something a little more serious than the incident of January 10. The rocket exploded two and a half minutes in while travelling at 2,900 mph (4,670 kph) about 27 miles (43 kilometers) up. All seven earlier SpaceX supply runs had gone extremely well. Their were no casualties.

On December 21, 2015, an out of the box SpaceX managed to not only deliver 11 commercial satellites into orbit but also land its reusable rocket
the first time an orbital class booster had returned intact from space. Elon Musk, the company's CEO referred to it as "a fundamental step change compared to any other rocket that's ever flown." Truly a revolutionary moment.

They're back in the game: Orbital ATK
Orbital Sciences Corporation and the Aerospace and Defense groups of Alliant Techsystems which merged in 2015has been using another company's Atlas rockets in order to fulfill its obligations to NASA and keep supplies flowing to the ISS. The first flew in December 2015, the latest April 2017. It was followed by an Antares 230 in regular service in November 2017, with three further missions scheduled on an extended contract. Orbital ATK was purchased by Northrop Grumman for the princely sum of 7.8 billion plus an assumption of debt in 2018.

SpaceX, known for being cutting edge, has done it again with its launch of a Falcon 9 rocket on April 8, 2016, from Cape Canaveral, Florida. Following separation the Falcon's reusable first stage executed a perfect landing on an offshore robotic barge the Dragon cargo vessel continuing on to the ISS where it joined five spaceships,
four Russian and ATK's Cygnus, already docked. Following the unloading of its cargo which included a portable habitat (the Bigelow Expandable Activity Module) the vessel was reloaded with science experiments incuding biological samples for orbital return. (The Dragon is the only cargo vessel, at present, capable of returning intact to Earth.)

Following a morning launch from Cape Canaveral on July 18, 2016, a Dragon spacecraft streaked into space. It was the company's second attempt at delivery
to the ISS of a docking port, the first a disaster. The cargo vessel was captured and berthed early on the 20th with no problem. Test flights of manned vessels are planned for the near future.

On September 1, 2016, a setback that will impact the entire space industry. A Falcon 9 launch vehicle experienced a fiery explosion during a propellant fill for a static fire test. The payload, an Amos-6 satellite vital to a partnership between Facebook and Eutelsat (a French communications company) and their plans to expand broadband internet coverage to large
unserviced parts of Africa was toast (no pun intended). Planned upcoming launches were placed in doubt and deliveries to the ISS disrupted. "No doubt SpaceX will fix the problems, but if you're a customer time is money," said former NASA administrator Scott Pace. "It may give competitors an opening and slow down SpaceX."

The uncertainty following the explosion in September was largely mitigated with a return to operations on January 14, 2017. Liftoff took place at 09:54 (17:54 GMT) from Vandenberg Air Force Base. The launch, a high  pressure event for its customer (Iridium Satellite Communications) and SpaceX went off without a hitch.

It seems that in the face of adversity SpaceX always comes through. On February 19, 2017, they (back in the delivery business) launched a cargo ship to the ISS. It was SpaceX's first launch from Florida since the disaster of September 2016. Further to the comeback (and in keeping with NASA's goal) the company expects to add human spaceflight to its itinerary within two years. (On December 15, 2017, another step forward, the launch of a recycled rocket with a recycled capsule on a NASA delivery run.)

On February 6, 2018, SpaceX seemingly determined to be first, best and biggest did it again. The company blasted a 230 foot (70 m) behemoth into space. Dubbed the Falcon Heavy it can lift 140,700 lbs (63,800 kg) into low Earth orbit, more than twice the load of the now retired Space Shuttle. In fairness, however, there were some problems: one of three reusable boosters was lost as it relanded and Musk's cherry red roadster used as payload and intended for Martian orbit is apparently on its way to the asteroid belt or thereabouts. Glitches notwithstanding the Falcon Heavy is an incredible accomplishment and there's more. Named the BFR, "Big Falcon Rocket" and already under development is a new ship that Musk hopes will take humans to the Moon and Mars.  As per its latest design change (it's a work in progress), the BFR will consist of a reusable booster stage, named Super Heavy, and a reusable second stage with an integrated payload section,
named Starship, that eight stories tall will for long voyages include cabins, large common areas, central storage, a galley, and for Mars' missions a solar shelter.

On March 2, 2019, SpaceX's Demo-1 (DM-1) Crew Dragon lifted off from NASA's Kennedy Space Center, Florida, bound for the International Space Station.

On March 3, 2019, as the Dragon
(unmanned except for a test dummy named Ripley and a plush, stuffed "Little Earth" toy jokingly referred to as a "zero-g indicator") closed in on the ISS the crew made ready: Cosmonaut Oleg Kononenko took high resolution photos of the spacecraft's approach while sequestered in the Russian segment by Roscosmosthere were concerns about safety, or perhaps as some have speculated it was politics/melodrama. The two astronauts, for their part, watched their displays, followed procedures and waited. Then came the docking sequences, soft capture, hard capture followed by station (Dragon) attached, followed by cheers, a follow up (power hookups, pressurization and so forth) and an easing of tensions—two hours later the hatch to the capsule was swung open and the trio, wearing protective gear, entered to begin removing supplies and taking air samples.

"Congratulations to all nations, private space firms and individuals who wake up every day driven by the magic of exploration," said Anne McClain at a welcoming ceremony broadcast over NASA TV. "This day belongs to all of us."
The sentiment was expanded upon when David Saint-Jacques tweeted This morning, I monitored the first time ever approach and automatic docking of Crew #Dragon to the ISS. The dawn of a new era in human spaceflight! #daretoexplore

Even for a company renowned for its firsts, March 2nd and 3rd were doozies
—the first crew vehicle to launch from USA soil since the retirement of the Space Shuttle in 2011; the first commercial-crew vehicle to dock with the Space Station; the first to dock autonomously (no helping hand [or arm] from the station's personnel) and the first to dock utilizing the new, untried (in space) international docking adapter.

Five days later, with a full load, an autonomous separation then splashdown in the Atlantic (again a first and near perfect),

Coming up, a little more testing, then this summer the flight crew of Bob Behnken and Doug Hurley gets added to the mix. Go Dragon!!!

Following the mission's completion Nasa administrator Jim Bridenstine summed it up
with feeling—all this is leading to a day when we are launching American astronauts in American rockets from American soil.

Boeing's CST-100 Starliner is scheduled for a crewless run shortly, then a little more testing, and then this summer the flight crew of Edward Michael Finke (replacing Eric Boe), Nicole Aunapu Mann and Chris Ferguson gets added to the mix.
Go Starliner!!! (Or perhaps not—citing "limited launch opportunities" NASA has announced a last minute venue change: Starliner's first test flight is now postponed till August while the second test flight, with astronauts, won't take place until later in the year. Go Starliner eventually!!!)

Setbacks come in twos: On April 20, 2019, the Dragon crew capsule that flew without incident to the ISS became engulfed in smoke and flame during static testing of its abort thrusters on an engine test stand. The thrusters are crucial in an emergency; located on the side of the capsule, they are designed to fire and move the spacecraft away from the rocket before or during launch.

"This is why we test." NASA Administrator Jim Bridenstine said following the incident. "We will learn, make the necessary adjustments and safely move forward with our commercial crew program."

The Dragon was supposed to undergo unmanned in-flight abort testing in June, with another capsule making the first flight with crew as early as July. SpaceX itself has so far released few details on the accident and how it might impact future flights. Go Dragon hopefully!!!

As humanity moves outward into the Solar System and beyond both private enterprise and governments have a role to play:

China, coming from behind, is rapidly becoming a major participant. It plans to have its own space station (CSS) in orbit by 2020-2022 and a man on the Moon by 2024-2030. At present it's one of only two countries (the other being Russia) capable of independently launching an astronaut into orbit.

For their part western space agencies (most notably NASA), with the routine of orbital resupply being assumed by private enterprise, are concentrating more on things in keeping with an expanding mandate: deep space exploration, the search for and mapping of NEOs and the development of suitable shielding necessary to protect deep space astronauts from the genetic damage inflicted by cosmic rays and solar radiation.

Outer space is the new frontier: excursions to the edge of space (Virgin Galactic), inflatable hotels in orbit (Bigelow Aerospace), zero-g laboratories, domed colonies on Mars and solar powered factories located at Lagrangian points processing materials mined on the Moon and beyond. The possibilities, almost endless, are limited only by the vision, imagination and courage of those that dare to dream.

Stephen Hawking, passed professor at Cambridge University, theoretical physicist and best selling author with his book "A Brief History of Time" issued provocative statements many times throughout his career: "I don’t think the human race will survive the next thousand years unless we spread into space. There are too many accidents that can befall life on a single planet. But I'm an optimist. We will reach out to the stars." Or "We won’t find anywhere as nice as Earth unless we go to another star system." And "It is important for the human race to spread out into space for the survival of the species; life on Earth is at the ever-increasing risk of being wiped out by a disaster, such as sudden global warming, nuclear war, a genetically engineered virus or other dangers we have not yet thought of."

Heady words to be sure, but just how valid are they? As another great author H.G.Wells speculates in his 1933 book of future history, what is "the shape of things to come?"

The Solar System is located in the Orion Arm of the Milky Way galaxy at a distance far removed from the supermassive black hole at the Galactic Center; a region that scientists call the galactic habitable zone, a spherical shell of lessened radiation defined as relatively calm, safe and favorable to the formation of life, where supernova are less frequent and heavier elements more prevalent. The Earth is situated within the Solar System in what is called the circumstellar habitable zone, a spherical shell surrounding the Sun where liquid water can exist on a planets surface and where objects such as comets and asteroids are found less frequently than in more distant regions such as the asteroid and Kuiper belts.

So if the question is does that make us safe? The answer is no, safer perhaps but not safe:

If a supernova were to occur within 200 light years of Earth the cosmic radiation produced could seriously damage the Earth's ozone layer, allowing increased ultraviolet radiation to reach the surface
(a possible cause of some previous extinctions) and affect susceptible species, while within 50 light years it would almost certainly mean the end of all life. Two stars which appear problematic are Sirius B, a massive white dwarf, orbiting the main sequence star Sirius A (colloquially known as the "Dog Star") and at at a distance of only 8.6 light years one of Earth's nearest neighbors, and the second IK Pegasi B (150 light years) a white dwarf just shy of the Chandrasekhar limit in orbit about the main sequence star IK Pegasi A, which is in the end stages of its evolution and poised to become a red giant. When this occurs accretion will push IK Pegasi B past the limit of 1.44 solar masses possibly initiating a Type Ia supernova.

A more likely harbinger of catastrophic change would be an asteroid of significant size impacting the Earth. An asteroid striking the Yucatan peninsula caused the Cretaceous-Tertiary extinction event sixty five million years ago and ended the age of the dinosaurs. The Arizona Meteor Crater also known as the Barringer Meteorite Crater was created fifty thousand years ago by an asteroid only fifty meters across, all life out to four kilometers from the blast would have been killed instantly while the shock wave would have flattened everything up to twenty kilometers away. The Tunguska event of 1908 was probably an asteroid or comet exploding at a height of between five and ten km. If it had happened over a large metropolis such as London, instead of Siberia, it would have destroyed much of the city with substantial loss of life, thousands perhaps hundreds of thousands dead and many more injured.

Future asteroid impacts are inevitable because believe it or not near-Earth misses are a common occurrence. Below are some of the larger and or most dangerous:

On December 9, 1994, an asteroid 1994 XM1, approximately 10 meters across, passed by Earth at a distance of only 105,000 km (65,000 miles). Asteroid 2002 EM7, approximately seventy meters long, just missed us on March 8, 2002. On August 18, 2002, asteroid 2002 NY40, a five hundred meter (0.3 mile) behemoth, approached to within 1.3 times that of the Moon. On July 3, 2006, asteroid 2004 XP14, a whopping four fifths of a kilometer wide, passed by at a distance only 1.1 that of the Moon, while asteroid 2007 TU24, 250 meters in diameter, passed by on January 29, 2008, at a distance of only 1.4 times that of the Moon, and asteroid YU55, a four hundred meter biggie, zoomed between the Earth and Moon at a speed of 30,000 miles per hour on November 8, 2011. On February 15, 2013 in what is perhaps a harbinger of things long overdue, a double event with two asteroids having the Earth in their crosshairs on the same day. The larger of the space rocks, 150 foot (45.72 meter) 2012 DA14 missed, passing within 17,000 miles (27,000 km) of our planet, while the second, smaller, about 50 ft (15.24 meters) but with better aim didn't, penetrating the atmosphere at over 40,000 mph (64,000 km/h before exploding with the force of a nuclear bomb high over the Russian city of Chelyabinsk. Though their were no reported deaths hundreds were injured with property damage in the millions of dollars. On May 31, 2013, 1998 QE2, a giant space rock 2.7 kilometers (1.67 miles) wide, approached to 5.8 million kilometers (3.6 million miles) of Earth or about 15 times the Earth Moon distance. The asteroid proved to be somewhat unique when astronomers discovered a moon approximately 600 meters (0.37 miles) in diameter, in orbit around the larger body. According to NASA about 16 percent of near-Earth asteroids 200 meters or larger are binary
an asteroid 2004 BL86, 1,800 ft [549 meters] in diameter, also a binary, passed by Earth at a distance three times that between the Earth and Moon on Monday, January 26, 2015. On October 31, 2015  a dead comet, 2015 TB145 (nicknamed Spooky) with a diameter of 2000 ft (600 meters) followed it. Had it been on a collision course the devastation from impact would have been catastrophic: Spooky, like many others, was a continent killer. According to NASA middle sized chunks of rock and ice like TB145 hit the Earth approximately once every 160,000 years. We had three weeks notice of the near miss. On February 06, 2017, Asteroid 2015 BN509, a peanut shaped rock larger than the Empire State Building (200 by 400 meters) flew past us at 44,000 mph (75,500 km). NASA labeled it a future hazard. Asteroid 2112 TCA, the size of a house, safely passed by on the 12th of October 2017 (27,300 miles), the close approach giving asteroid trackers a chance to test/hone their ability to operate in a coordinated fashion. Estimates are TCA will return in 2050 and 2079, with a one-in-750 chance of hitting Earth in 2079. The lost then found again Asteroid 210 WC9 passed by Earth at a speed of 28.655 miles per hour (46.116 km/h) on May 15, 2018, at 22:05 UTC. The close brush, about half the distance between the Earth and Moon. Asteroid 2002 NT7 with a diameter of 1.2 miles (2 kilometers) and an initial Palermo hazard rating of 0.06 passed within 0.4078 AU of Earth on January 13, 2019. And finally—for now—the more worrisome 99942 Apophis with an estimated diameter of 885 feet (270 meters) will pass Earth within the orbits of geosynchronous communication satellites on Friday, April 13, 2029, to return April 13, 2036. (At present odds of an 2036 impact by Apophis are considered negligible.) [7] While newly found Asteroid 2013 TV135 at about 1300 plus feet (396 meters) has, despite media hype to the contrary, little or no chance of impacting our planet in 2032.

In the event that the unimaginable were to become reality how prepared are we?

Well at the moment not very, but there is a glimmer of light on the horizon, initiatives are currently being advanced by the "Association of Space Explorers" an international organization composed of astronauts and cosmonauts who believe it is imperative to develop a plan which will facilitate a global response in the event an asteroid of significant size is discovered on a collision course with Earth.

By reply, a group of scientists, engineers and other professionals have been tasked to come up with possible recommendations by both individual governments and the United Nations. [8]

In conjunction, recognizing that the further away a threat is detected, the more time there is to affect a solution has prompted the United States Congress to ask NASA to be more aggressive in its tracking of Near-Earth Objects (NEOs). The new mandate may include the building of innovative detection systems or investment in systems already under development such as Pan-Starrs or the Large Synoptic Survey Telescope.

If annihilation from space isn’t enough home grown events also threaten our existence:

Present day global warming possibly caused by a runaway greenhouse effect [9] [10] is becoming a matter of grave concern as storms increase in intensity and some species face extinction.

In the Southern Hemisphere the Antarctic ice sheets are becoming increasingly stressed by temperatures that have risen (in some regions) 2.5 degrees Celsius in the last 50 years: Larsen B, one of numerous coastal ice shelves (floating extensions of the ice sheets) broke free in 2002. The 12,000 year old ice mass had a surface area of  3,250 kilometers, bigger than the state of Rhode Island. Larsen A, considerably smaller broke off in 1995 and Larson C, much larger could quite possibly follow suit in the near future. Other shelves have also broken free and glaciers such as Pine Island and Thwaites are shrinking. If the melting trend continues many scientists believe that the southern continent could become a significant contributor to rising sea levels. [11]

In the Northern Hemisphere things appear to be even worse; Arctic ice is melting at an ever increasing rate and as with elsewhere appears caught in a feedback loop. The more the ice melts the less reflectivity and less reflectivity means increased melting. The latest data (though controversial) indicates that summer sea ice will have almost vanished within forty years. The North Pole will be open water, the Northwest Passage a reality, the frigid world of explorers such as Frobisher, Hudson and Perry a distant memory.

If you’re worried that the runaway greenhouse effect will turn Earth into another Venus don’t be; Mother Nature has a solution, one that she has applied numerous times in the past. Recent ice cores taken from Greenland’s ice sheet reveal that Earth's climate has undergone many abrupt transformations, changes that are directly linked to massive amounts of fresh melt water pouring into the North Atlantic Ocean and a consequent shutting down of the heat pump known as the Gulf Stream. The loss of this moderating influence, would in a period of only two or three years cause atmospheric temperatures to plunge drastically. The worst-case scenario, a full blown ice age, secondary scenario, a mini ice age and subsequent disruption of worldwide weather patterns, extremely long bitter winters, crop failures and either flooding or drought depending on location.

The ozone layer is located in a region of the Earth’s atmosphere called the stratosphere. The gas is extremely tenuous with concentrations of only a few parts per million and is created when ultraviolet light strikes oxygen molecules and begins a process called the ozone-oxygen cycle. Although the amount of ozone as a percentage of the atmosphere is very small it plays a role of vital importance, absorbing dangerous ultraviolet radiation, which if allowed to reach the surface unfiltered can
lead to increases in skin cancer
, serious genetic damage to living organisms both plant and animal and possibly the extinction of vulnerable life forms.

Ozone depletion due to the introduction of man made organohalogen compounds such as chlorofluorocarbons (CFCs) has been ongoing for a long time, ozone levels dropping as much as four percent a decade. Even greater seasonal declines over the North and South Poles have resulted in the appearance of what are called ozone holes.

The hole over the North Pole is relatively small, it is the hole over the South Pole that is the most disconcerting; discovered in 1985 by Farman, Gardiner and Shanklin then confirmed by satellite the huge hole stunned the scientific community. World wide measurements by surface based Dobson spectrophotometers confirmed the worst, that the ozone layer was in a state of depletion everywhere except the tropics. Recognizing the seriousness of the findings an international treaty called the Montreal Protocol was signed by the major offending nations. CFCs, halons and other related substances were phased out and eventually banned in 1996.

The ozone layer is expected to recover significantly over the coming century due to the ban on ozone-depleting substances, and the Antarctic hole despite reaching a size of 29 million square km on September 24, 2006, (large enough to cover parts of Australia and New Zealand) will hopefully revert to pre-1980 levels by the year 2075.

Terrorism and the proliferation of nuclear weapons are twins linked by insanity their promise Armageddon and the end of humanity:

The short period during which atomic weapons were confined to the arsenals of a few relatively stable countries, the so-called nuclear club, Great Britain, France, the United States, India et al. appears to be over, for like a malignant tumor the club is growing and its newest member North Korea is neither stable nor rational, while Iran, a country regarded by many to be a major sponsor of world terrorism, is knocking at the door ready to join.

Worrisome developments? Yes:

As more and more countries acquire nuclear weapons, the possibility of nuclear war either accidentally or by design increases exponentially the consequences frightening. Add to this the prospect of these weapons falling into the hands of terrorists whose avowed goal is the destruction of the West and the future seems grim indeed. A nuclear strike by one country or group on another would invite immediate retaliation and result in the death of millions, escalation could then plunge us into all out war, the conflagration followed by nuclear winter, the collapse of civilization and the possible end of all life an insane scenario no sane minded individual could possibly want or even truly imagine.

Clearly there are problems, but the great adventure has begun and the stars beckon; it's time to leave our petty squabbles behind and go forward in a spirit of both optimism and co-operation. Our survival as a race may well depend on us spreading throughout the cosmos so that an event no matter how cataclysmic can’t destroy us all, but lets proceed with the right motivation and not like the aliens of science fiction who having devastated their own world are desperately scouring the galaxy in search of another. The future is what we make it, lets hope we make it right.

Earth has one moon: Luna

[1] The designation (habitable) does not mean that all planets within the zone harbor life nor that life can’t exist outside the zone. Mini-habitable zones within a star system may exist in which the sun is not the primary factor determining a planetary bodies ability to sustain life e.g., Europa, one of the moons of Jupiter, constantly stressed (heated) by gravitational interaction with its giant primary.
[2] In what can only be considered a surprising addition to the saga of human expansion, recent mitochondrial DNA gathered from amongst the indigenous peoples of North America (the Ichigua tribe have an extremely high incidence of pre-Columbian European DNA) and hard evidence such as a Solutrean biface (two-sided) flint point 
found at Cactus Hill, Virginia, which is similar to but predates the 12,000 year old Clovis points of New Mexico by thousands of years, offers the possibility that small migrations of ice age Europeans (perhaps, as Dennis Stanford [head of archaeology at the Smithsonian] has suggested, utilizing a combination of animal hide boats and an ice bridge which connected North America with Europe) established themselves in the Americas millennia before a land bridge from Asia to Alaska opened up allowing a much larger migration from Siberia. It also appears that upon contact those of European descent (the skeleton of what is known as Kennewick Man, complete with a Cascade point lodged in its pelvis, was found in Washington state, is approximately 9,300 yrs old and has a skull with features [albeit controversial] characteristic of modern day Caucasoid peoples) were either eliminated or as the genetic markers indicate, assimilated.

[3] A Soyuz capsule is docked with the International Space Station at all times to be used as an escape craft in the event of emergency.

[4] After 30 years of service NASA's space shuttle fleet is no more, Atlantis, last of its kind, landed in the pre-dawn hours Thursday, July 21, 2011, at Kennedy Space Center, Cape Canaveral, Florida, following a final resupply mission to the International Space Station.

[5] The twenty-five thousand dollar Orteig Prize offered by hotel owner Raymond Orteig was won by Charles Lindbergh in 1927, when he became the first aviator to fly solo non-stop from New York to Paris in his single engine plane the Spirit of St. Louis.

[6] Attached to the Falcon 9's second stage, a second payload, the cremated remains of more than 300 hard core space fans (some of them second timers from a failed earlier launch, some well known such as Mercury astronaut Gordon Cooper and actor James Doohan "Scotty" of  Star Trek fame). The second stage will circle the Earth for a year or so, a memorial for those for whom space meant so much, before eventually falling back into the Earth's atmosphere and incineration.

[7] If Apophis were to impact Earth estimates are that the energy released would be in the 510 megaton range which though horrendous would be unlikly to trigger any long lasting global effects (the largest hydrogen bomb explosion was 50 megatons, the Krakatoa erruption was the equivalent of 200 megatons while the dinosaur ending Chicxulub impact was approximately 100,000,000 megatons).

 United Nations officials and leaders of various space agencies were briefed on the threat of Near-Earth Objects (NEOs) and the need for a coordinated global response by members of the Association of Space Explorers and other experts on November 25, 2008. The UN having begun discussions on the issue early in 2009 will continue to meet formally on an ongoing basis.

[b] In early 2012 a new consortium of universities, research institutes and high tech companies drawn from the UK, Germany, France, Spain, Russia and the US was established to deal with the threat of asteroids, comets and other space debris found to be on a collision course with Earth. Named NEOShield the project led by the German Aerospace Center (DLR) and supported by European Commision money will explore the means by which an impact threat can be successfully mitigated. Methods being explored include a kinetic impactor (slamming something heavy into the object), a gravity tractor (the miniscule mass of a spacecraft positioned near the object could theoretically, over time, affect its course) and blast deflection (detonating a nuclear device near, on or under the surface of the object).

[c] On February 25, 2013, the Canadian Space Agency launched into orbit the Near-Earth Object Surveillance Satellite (NEOSSat) the first satellite designed to search for and track asteroids and space debris. If it performs as hoped the mission which lifted off from the Satish Dhawan Space Centre in Sriharikota, India, atop an Indian Polar Satellite Launch Vehicle (PSLV) will discover at least half of the asteroids 1 kilometer or larger within Earth's orbit as well as moniter orbiting space junk to try and minimize collisions.

[9] The verdict is still out on whether global warming is a cyclical event heavily influenced by solar activity or man-made the result of carbon emissions.

[10] There is a distinct difference between the term greenhouse effect which is a warming of the atmosphere due to naturally occurring greenhouse gases and without which the Earth’s surface would be as much as 30 
C colder and the afore-mentioned runaway greenhouse effect which is a result of gases introduced by humans, stemming in part from the industrial revolution and the subsequent large scale burning of fossil fuels.

[11] Antarctica is more than just coast, however, and the overall picture somewhat more complicated; temperatures in the interior of the vast continent have apparently fallen over the same period the harsh desert valleys noticeably cooler.

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