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Oxygen, O 2, meanwhile, was present in the atmosphere at just 0.001% of its present atmospheric level. [12] [13] The Sun shone at about 70% of its current brightness 4 billion years ago, but there is strong evidence that liquid water existed on Earth at the time. A warm Earth, in spite of a faint Sun, is known as the faint young Sun paradox. [14]
The ablation and vaporization caused by Earth's fall on a decaying trajectory towards the Sun may remove Earth's mantle, leaving just the core, which will finally be destroyed after at most 200 years. [102] [103] Earth's sole legacy will be a very slight increase (0.01%) of the solar metallicity following this event. [104]: IIC
The estimated time until a gamma-ray burst, or massive, hyperenergetic supernova, occurs within 6,500 light-years of Earth; close enough for its rays to affect Earth's ozone layer and potentially trigger a mass extinction, assuming the hypothesis is correct that a previous such explosion triggered the Ordovician–Silurian extinction event ...
Sunlight is also captured by plants as a chemical potential energy via photosynthesis, when carbon dioxide and water are converted into a combustible combination of carbohydrates, lipids, and oxygen. The release of this energy as heat and light may be triggered suddenly by a spark, in a forest fire; or it may be available more slowly for animal ...
Energy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light. Energy is a conserved quantity—the law of conservation of energy states that energy can be converted in form, but ...
Earth's energy budget (or Earth's energy balance) is the balance between the energy that Earth receives from the Sun and the energy the Earth loses back into outer space. Smaller energy sources, such as Earth's internal heat, are taken into consideration, but make a tiny contribution compared to solar energy.
Many hypothetical doomsday devices are based on salted hydrogen bombs creating large amounts of nuclear fallout.. A doomsday device is a hypothetical construction – usually a weapon or weapons system – which could destroy all life on a planet, particularly Earth, or destroy the planet itself, bringing "doomsday", a term used for the end of planet Earth.
Sagan and Mullen suggested during their descriptions of the paradox that it might be solved by high concentrations of ammonia gas, NH 3. [4] However, it has since been shown that while ammonia is an effective greenhouse gas, it is easily destroyed photochemically in the atmosphere and converted to nitrogen (N 2) and hydrogen (H 2) gases. [9]