‘Looking from Space at the Human Impact on Earth’, at the Gresham Lectures

‘Looking from Space at the Human Impact on Earth’, at the Gresham Lectures


The Gresham Lectures are free, open to the public and available online as recordings. They range from history to science, economics and philosophy. KCW Today went along to “Scratching the Surface? Looking from Space at Human Impact on Earth” by Carolyn Roberts, last October 13.

“Who in here hasn’t seen their house on Google maps?”, Professor Roberts asked. Point made. Satellites scan huge swathes of land in our planet daily, producing 50 centimeter resolution pictures at more than 30,000 Km from the ground. Yet nothing scratches our curiosity like knowing what our neighborhood looks like from above; more than Machu Picchu, the Pyramids or the Great Barrier Reef for example.

This self-centric view of the universe is quite typical, so the speaker made the audience take a step back from the bubble of daily life. A flurry of high quality space pictures arrested the attention of the 80 or so people at the packed Barnard’s Inn hall, (which also includes an overflow room seating 60).


Chapman Glacier Aster

Chapman Glacier – Aster


Tulip fields in the Netherlands, untouched glaciers in Antarctica, India’s Diwali nightlights and a refugee city in Jordan. Roberts showed how the unique abilities of imaging satellites, originally set up for the Cold War, are also useful for agriculture, disaster management, bio-conservation and weather and climate study.

A hydrologist (study of water, flow and water deposits) by trade, Roberts showed how satellites go beyond simple photography to reveal water deposits below ground, volcanic sediments and even sea algae. Invisible to the naked eye, these objects have distinct thermal, microwave and radio features that one can program into the scan.

To be sure, these are all the same, but with different energy levels. All the colors in the rainbow making visible light have the same properties of infrared signals used to switch the TV channel. They travel at the same speed and in the same way, but visible light has more energy than infrared. The size of our eye cones is what determines what frequency, or energy of light we can see.

One can then splice these frequency channels (visible light, infrared, radio) to turn the river Nile red for example, revealing “colors” never seen before. As Roberts explained, it was like switching your cyan cartridge in the printer with thermal vision. Similarly to synesthesia where the human brain can confound flavour with colour, so too can satellite imagery be made to blend light we can’t see with that which we can and realise new patterns in water, dust and weather activity around the Earth.



Egypt Nile Delta from Space in infrared (ESA)


It is surprisingly cheap to order your own satellite photos. Prices range from $25 to $0.01 per square kilometer depending on quality of service.

And how much should privacy be respected? This difficult subject was left in the air. Military bases don’t play by the rules, of course. Whether we should worry or rejoice at satellite pictures of our neighborhood, with ever increasing image quality, was left to the (rather unconcerned) audience. As they say, it’s easier to ask for forgiveness than permission…

The next talk on this series will be: ‘Hotting up: Meeting the Challenges of Climate Change in the Twenty-First Century, next Thursday, 10th of November.

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