Christopher Furlong/Getty Images
NASA scientist and climatologist James Hansen participates during Climate Change Campaign Action Day on March 19, 2009 in Coventry, England.
April 19, 2012 --
Forty years ago this week, the crew of Apollo 16 captured this image of Earth rising above the lunar landscape. The Apollo missions enabled humanity to see for the first time our planet as it appears from space. As Apollo 13 commander Jim Lovell once said: “When I was orbiting the moon and could put my thumb up to the window and completely cover the Earth, I felt a real sense of my own insignificance. Everything I'd ever known could be hidden behind my thumb.” As we approach Earth Day on April 22, we look at the efforts of people throughout the ages to explore, understand and portray our world and its place in the Universe.
Trustees of the British Museum (image rotated
Babylonia Believed to be the earliest known representation of Earth, this stone tablet from Babylon shows the world as a disc, surrounded by a ring of water called the "Bitter River." The world is dominated by the area surrounding Babylon itself, and the Euphrates River bisects most of the inner circle. Unearthed in southern Iraq in the late 1800s, the tablet is housed in the British Museum.
Sixteenth-century interpretation of Ptolemy's
Celestial Spheres In his 2nd century treatise, the "Almagest," Claudius Ptolemy proposed an explanation for the apparent movement of stars and planets, in which Earth was central and immovable, and surrounded by, at progressively greater distances, the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn and a sphere of ‘fixed stars.’ This geocentric view of the cosmos did not meet its first real challenge until Copernicus proposed that the planets revolved around the Sun, and Galileo used his telescope to observe the phases of Venus.
Library of Congress, via the History Blog
Flat Earth The Greek philosopher Aristotle determined that Earth was spherical and not flat almost 2,500 years ago. The notion of a flat earth retained at least a few die-hard devotees for a surprisingly long time. For example, this 1893 map by Orlando Ferguson, recently acquired by the Library of Congress, cites “Scripture that condemns the globe theory” and promotes a book that “knocks the globe theory clean out.”
ANALYSIS: What if Earth Were a Cube?
De Costa, B.F. (September 1879). "The Lenox G
Lenox Globe It is popularly believed that ancient cartographers filled in unknown and unexplored areas of the world with the phrase ‘Here be dragons’. In fact, only one known ancient map – the so-called Lenox Globe, which is believed to date to around 1510 - displays the phrase ‘HC SVNT DRACONES’, from the Latin “hic sunt dracones.” (The phrase is written near the equator on the eastern cost of Asia.) Some nineteenth-century writers, however, believed that it referred, not to dragons, but to the ‘Dagroians’, a people who “feasted upon the dead and picked their bones.”
PHOTOS: Sea Monsters Real & Imagined
Image Database of the Kano Collection, Tohoku
Terra Australis Incognita In this copy of a 1602 map that was created on behalf of China’s Wanli emperor by Italian Matteo Ricci and collaborators, the familiar outlines of most of the world’s continents are coming into shape, although obviously many details remain unfinished. To the map’s makers, however, the likes of Australia, New Zealand and Antarctica are not even figments of the imagination, replaced instead by an enormous southern landmass. The notion of an unknown southern land – a terra australis incognita - was first mooted by Aristotle in 322 BCE; not until 1820 did Fabian von Bellingshausen become the first man to see the Antarctic continent.
South Pole For centuries, gaps in maps were filled by explorers who set out across land and sea, often at immense personal risk. The true nature of “Terra Australis” had long been established by the time Robert Falcon Scott and comrades stood at the South Pole on Jan. 17, 1912; but existing knowledge could not diminish the terrible toll the conditions exacted on the men. “Great God!” wrote Scott in his journal, “this is an awful place.” All five members of Scott’s polar team died before they could reach their base camp.
PHOTOS: Forgotten Discoveries of Scott's Antarctica
Moscow at night Time and technology have enabled us to explore, not just across the surface of the globe or even beneath its waves, but from on high. Here, Moscow is seen at night from the International Space Station, flying at an altitude of approximately 240 miles on March 28, 2012. A solar array panel for the space station is on the left side of the frame. The Aurora Borealis, airglow and daybreak frame the horizon.
Pale Blue Dot In contrast to earlier suppositions about our place in the firmaments, we know now that our globe is not at the center of the cosmos, and that other celestial bodies are not attached to interlaced spheres that rotate around us. We are but one world among many, in one solar system among many, in one galaxy among many. In this image, taken by the Voyager I spacecraft from a distance of 4 billion miles, Earth is but a speck – a pale blue dot – in the cosmic night.
NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring
Blue Marble If satellite images of Earth now seem almost routine, they never lose their ability to enthrall. This picture of the western hemisphere was captured on January 25 by NASA’s latest Earth observation satellite, Suomi NPP. By February 1, it had registered over 3 million views on Flickr – testament to the beauty and fascination of our Blue Marble.
PHOTOS: Earth's Blue Marble Beauty
Climate scientist James Hansen is retiring from NASA this week to devote himself to the fight against global warming.
Hansen's retirement concludes a 46-year career at NASA's Goddard Institute for Space Studies in New York, but he plans to use his time to take up legal challenges to the federal and state governments over limiting greenhouse gas emissions.
In recent years, Hansen, 72, has become an activist for climate change, which didn't sit well with NASA headquarters in Washington. "As a government employee, you can't testify against the government," Hansen told The New York Times.
Supporting his "moral obligation" to step up to the fight now, Hansen adds in the Times article that burning a substantial fraction of Earth's fossil fuels guarantees "unstoppable changes" in the planet's climate, leaving an unfixable problem for future generations.
The distinguished NASA scientist has spent his career at the Goddard Institute on the campus of Columbia University. He has testified in Congress dozens of times, and has issued warnings and published papers that drew criticism from climate-change skeptics. (The Reality of Climate Change: 10 Myths Busted)
Hansen was arrested in February while protesting the proposed construction of the Keystone XL Pipeline that would carry heavy crude oil from Canada to the U.S. Gulf Coast. "We have reached a fork in the road," he told the Washington Post at the time, adding that politicians must understand they can "go down this road of exploiting every fossil fuel we have — tar sands, tar shale, off-shore drilling in the Arctic — but the science tells us we can't do that without creating a situation where our children and grandchildren will have no control over, which is the climate system."
With his departure from NASA, Hansen told the Times he plans to lobby European leaders to institute a tax on oil derived from tar sands, whose extraction leads to more greenhouse gas emissions than conventional oil. He could not have done these things as a government employee, he said.
Hansen will probably work in a converted barn on his farm in Pennsylvania, but may possibly set up a small institute or take an academic appointment, according to the Times. He will continue to publish papers in academic journals, but will not run the powerful computers and other resources NASA provided for tracking and forecasting global warming and its effects.
Raised in a small town in Iowa, Hansen initially studied the planet Venus, but switched to studying the effect of human greenhouse gas emissions on Earth during the 1970s.
He was one of the first scientists to raise alarm about global warming and its effects on climate and the environment. After testifying at a Congressional committee in 1988 that man-made global warming has begun, Hansen was quoted widely as saying, "It is time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here."
Hansed joined NASA's Goddard Institute as a post-doctoral scholar in 1967 and became a federal employee in 1972. He became director in 1981, and was the longest-serving director in the institute's history. "He has pushed forward the frontier of our knowledge of Earth's climate system and of the impacts that humanity is having on Earth’s climate," Nicholas E. White, director of the Sciences and Exploration Directorate at Goddard, said in a statement.
Climate scientists applaud Hansen for leading the predictions of climate change's effects. But some say these predictions were exaggerated. For example, he has said in recent years that vast carbon dioxide emissions might ultimately cause a runaway greenhouse effect like on Venus that would boil the oceans and make Earth uninhabitable, the Times reported. Other scientists say this hasn't happened in the past and that Hansen overstated the risk.
Hansen was embroiled in a political fight in 2005, when a young political appointee in George W. Bush's administration tried to muzzle Hansen in the press. But Hansen revealed this to the public in an interview reported by the Times, and the administration lifted its restrictions.
Despite his environmentalist stance, Hansen has also criticized the environmentalist movement. He strongly opposed a failed climate bill in 2009, because he said it would have given the federal government billions of dollars without truly limiting emissions.
Hansen, who is registered as an independent, believes carbon dioxide emissions should be taxed, but that the money should be returned to the public as a rebate, instead of going to the government.
Hansen told the Times he senses a mass movement on climate change is beginning, led by young people, which he plans to support.
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