11.1
Light pollution affects humans, many other animals, and plants
For millions of years, life on Earth has developed in the absence of artificial light, with the majority of species adapting to diurnal or nocturnal activities. Since the invention of electricity, humans have increasingly reduced nocturnal darkness with artificial lights, causing serious light pollution issues, which has implications for Earth’s environment, animal behaviour and human health. The majority of animal populations are reliant on diurnal and nocturnal patterns. From physiology and reproduction to orientation and predation, artificial light can disrupt wildlife populations across the globe. We are also losing the dark skies that our ancestors have enjoyed. In many urban and suburban environments, the Milky Way is now all but impossible to see at night.
11.2
There is a lot of human-made debris orbiting Earth
With the development of space technology, humanity has been able to send numerous objects into space using rockets. Since the start of the era of space exploration, the amount of human-made debris in space, such as pieces of rockets or old satellites, has increased dramatically. Currently there are an estimated 500,000 pieces of debris, also known as space junk, orbiting Earth. As space junk travels at high speeds, any collision with a spacecraft or satellite can cause serious damage. This is particularly risky for the International Space Station and other crewed spacecraft. Space debris monitoring and the development of technologies for collecting satellites and debris, is an active area of research and development.
11.3
We monitor potentially hazardous space objects
During the early stages of the Solar System’s formation, the newly formed planets were frequently struck by smaller bodies like asteroids. Some craters on Earth’s surface and all those seen on the Moon’s are direct evidence that those impacts can be very hazardous. Although it is still a topic of research and debate, it is believed that the extinction of the flightless dinosaurs and a huge number of other species may have been due to a big asteroid impact with Earth, roughly 65 million years ago. Although the probability of an impact of this magnitude is very low nowadays, it is important to monitor all the celestial objects that may become a potential threat to life on Earth. Within the next few years, monitoring programs by space agencies, observatories and other institutions should be able to identify all potentially hazardous asteroids one kilometre or larger in size. None of the known asteroids are presently on a collision course with Earth.
11.4
Humans have a significant impact on Earth’s environment
Industrialization has brought society numerous advantages, but has also caused several environmental problems on Earth. Through deforestation and the pollution of rivers, oceans and the atmosphere, we are damaging the vital sources of clean air, food and water that are necessary for life on Earth. Humanity has caused the extinction of numerous species, and continues to dig for minerals and energy resources in endangered environments. Human induced climate change (global warming) is affecting our environment on large scales, placing us and many species at risk.
11.5
The climate and the atmosphere are heavily affected by human activity
Without its atmosphere, our planet would be an icy world with an average temperature of – 18°C. However, the greenhouse gases of the atmosphere partially absorb the heat radiation emanating from the ground and radiate it back towards Earth’s surface, which makes Earth habitable. Human activity has drastically increased the levels of the major greenhouse gases in Earth’s atmosphere, creating an imbalance in Earth’s energy budget. The increase of these gases causes more energy to be trapped on Earth, creating higher average temperatures. Earth is unable to radiate the excess energy away via its natural systems, thereby altering global climate patterns, which are sensitive to energy imbalances.
11.6
A global perspective is necessary to preserve our planet
Every single person is an inhabitant of this planet. The concepts of global stewardship and responsibility can help us understand that everyone can act, as part of a group or individually, to help solve global problems. It is necessary to conserve Earth for our descendants. At present, Earth is the only planet in the Universe, which we know for certain can sustain life.
11.7
Astronomy provides us with a unique cosmological perspective that reinforces our unity as citizens of Earth
All human beings on Earth live under one sky, and share the view into the depths of the Cosmos. Images from space showing the “Blue Marble” of planet Earth have provided us with a deeper understanding of our common spaceship. Seen from the outside, the borders between individual countries disappear altogether. Images from spacecraft like Voyager 2 and Cassini help us realise that the “Pale blue dot” is a mere speck in the vastness of the Universe.
