In physics, a ripple tank is a shallow glass tank of water used to demonstrate the basic properties of waves. It is a specialized form of a wave tank. The ripple tank is usually illuminated from above, so that the light shines through the water. Some small ripple tanks fit onto the top of an overhead projector, i.e. they are illuminated from below. The ripples on the water show up as shadows on the screen underneath the tank. All the basic properties of waves, including reflection, refraction, interference and diffraction, can be demonstrated. Ripples may be generated by a piece of wood that is suspended above the tank on elastic bands so that it is just touching the surface. Screwed to wood is a motor that has an off centre weight attached to the axle. As the axle rotates the motor wobbles, shaking the wood and generating ripples. Demonstrating wave properties A number of wave properties can be demonstrated with a ripple tank. These include plane waves, reflection, refraction, interference and diffraction. Plane waves When the rippler is lowered so that...

University of Wisconsin engineers have done it, devising a new and better way for military vehicles to communicate.

The chain is known for serving day-glo shakes that look like they grew in Willy Wonka’s secret garden: whipped-cream mountains adorned with doughnuts, creamsicles or entire frosted cupcakes.

Stocks had their worst day since June after a five-month rally fueled by virtually free money from the Fed, a handful of tech monopolies, and a truckload of wishful thinking about a V-shaped recovery and a vaccine delivered in record time.

Joseph Eugene Stiglitz (; born February 9, 1943) is an American New Keynesian economist, a public policy analyst, political activist, and a professor at Columbia University. He is a recipient of the Nobel Memorial Prize in Economic Sciences (2001) and the John Bates Clark Medal (1979). He is a former senior vice president and chief economist of the World Bank. He is also a former member and chairman of the US Council of Economic Advisers. He is known for his support for the Georgist public finance theory and for his critical view of the management of globalization, of laissez-faire economists (whom he calls "free-market fundamentalists"), and of international institutions such as the International Monetary Fund and the World Bank. In 2000, Stiglitz founded the Initiative for Policy Dialogue (IPD), a think tank on international development based at Columbia University. He has been a member of the Columbia faculty since 2001 and received the university's highest academic rank (university professor) in 2003. He was the founding chair of the university's Committee on Global Thought. He also chairs the University of Manchester's Brooks World Poverty Institute...

Lead poisoning is a condition where there is too much lead in the body. Lead interferes with many processes. It is toxic to many organs and tissues, including the bones and brain. The half-life of lead in these tissues is measured in weeks for blood, months for soft tissues, and years for bone. Lead in the bones, teeth, hair, and nails is bound tightly and not available to other tissues, and is generally thought not to be harmful. In adults, 94% of absorbed lead ends up in the bones and teeth, but children only store 70% in this way, a fact which may partially account for the more serious health effects on children. In 2013, lead is believed to have resulted in 853,000 deaths worldwide Causes The risk of lead poisoning is very small in developed countries. However, lead might be used in paints, petrol or food containers in some countries where it might be legal, such as in developing countries. Other ways a person can be exposed is from: lead pipes a lead water tank pipework with lead fittings Causing the water supply to be contaminated. Symptoms...

Titanic tank battles were once fought on what is now Belarus. Now, a dedicated team of salvagers scour marsh and forest to find these forgotten reminders of World War Two.

Economist Impact combines the rigour of a think-tank with the creativity of a media brand to engage an influential global audience.