Sep 29, 2016 · Each piece by itself was not enough to constitute a critical mass (the minimum amount of nuclear material needed to maintain fission)—but by colliding the pieces, critical mass was reached and a fission chain reaction occurred.. Modern nuclear weapons work slightly differently. Critical mass depends on the density of the material: as the density increases, the critical mass decreases.

The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet's most pressing problems. Joining with people across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future.

Jul 14, 2008 · Solar power. Like wind power, the sun provides a tremendous resource for generating clean and sustainable electricity. The environmental impacts associated with solar power can include land use and habitat loss, water use, and the use of hazardous materials in manufacturing, though the types of impacts vary greatly depending on the scale of the system and the technology used—photovoltaic (PV ...

Apr 10, 2017 · Sustainable agriculture 101. OK, so sustainable agriculture is the wave of the future. But what is it, exactly? Sustainability has many facets. Environmental sustainability, for example, means good stewardship of the natural systems …

Oct 4, 2024 · The way radiation enters the environment or human body can affect what health outcomes researchers expect to see. Nuclear toxicologists investigate the absorption, distribution, metabolism, and excretion (ADME) of radioactive materials in the environment to understand the exposure risks more fully and better predict resultant health outcomes.

Oct 29, 2020 · Scientists agree that we need to swiftly and dramatically cut emissions of heat-trapping gases. Also necessary: safely and sustainably removing carbon dioxide from the atmosphere, and accelerating investments to prepare for the impacts of climate change.

Oct 4, 2024 · Acute exposure to radiation (as in direct contact with radioactive material or being near a nuclear detonation) can result in cutaneous radiation injury (CRI), a skin burn that can occur at radiation doses as low as 2 grays (Gy) or 200 rads 2, increasing in severity as the dose increases.At the site of a nuclear detonation, humans are incinerated; people farther away can receive skin burns.

Jul 14, 2008 · In contrast, most renewable energy sources produce little to no global warming emissions. Even when including “life cycle” emissions of clean energy (ie, the emissions from each stage of a technology’s life—manufacturing, installation, operation, decommissioning), the global warming emissions associated with renewable energy are minimal [].

Jul 16, 2009 · The Sun-climate connection. The Sun is the source of most of the energy that drives the biological and physical processes in the world around us—in oceans and on land it fuels plant growth that forms the base of the food chain, and in the atmosphere it warms air which drives our weather.

Nov 9, 2021 · Which countries are most responsible for climate change? Cumulative carbon dioxide emissions are the dominant driver of climate change. These began rising during the Industrial Revolution (especially after 1850)—which means richer countries like the United States, which made an early transition to a heavily fossil fuel-based economic system, have an outsized role in contributing to the ...