spaceplasma:

Tokamaks: the future of fusion energy

Fusion is the energy that powers our Sun and other stars.  It has been a goal of scientists around the world to harness this process by which the stars “burn” hydrogen into helium (i.e. nuclear fusion) for energy production on Earth since it was discovered in the 1940′s.

Nuclear fusion is the process by which light nuclei fuse together to create a single, heavier nucleus and release energy.  Given the correct conditions (such as those found in plasma), nuclei of light elements can smash into each other with enough energy to undergo fusion. The “easiest” (most energetically favorable) fusion reaction occurs between the hydrogen isotopes deuterium and tritium.  When the nucleus of a deuterium atom crashes into the nucleus of a tritium atom with sufficient energy, a fusion reaction occurs and a huge amount of energy is released, 17.6 million electron volts to be exact. 

Why fusion? To put this in terms of energy that we all experience; fusion generates more energy per reaction than any other energy source.  A single gram of deuterium/tritium fusion fuel can generate 350 million kJ of energy, nearly 10 million times more energy than from the same amount of fossil fuel!

Fusion power has the potential to provide sufficient energy to satisfy mounting demand, and to do so sustainably, with a relatively small impact on the environment. Nuclear fusion has many potential attractions. Firstly, its hydrogen isotope fuels are relatively abundant – one of the necessary isotopes, deuterium, can be extracted from seawater, while the other fuel, tritium, would be bred from a lithium blanket using neutrons produced in the fusion reaction itself. Furthermore, a fusion reactor would produce virtually no CO2 or atmospheric pollutants, and its other radioactive waste products would be very short-lived compared to those produced by conventional nuclear reactors.

Fusion reactions require so much energy that they must occur with the hydrogen isotopes in this plasma state. Plasma makes up all of the stars, and is the most common form of matter in the visible universe. Since plasmas are made of charged particles every particle can interact with every other particle, even over very long distances. The fact that 99% of the universe is made of plasmas makes studying them very important if we are to understand how the universe works.

How do we create fusion in a laboratory? This is where tokamaks come in. In order for nuclear fusion to occur, the nuclei inside of the plasma must first be extremely hot, like in a star. Unfortunately, no material on Earth can withstand these temperatures so in order to contain a plasma with such high temperatures, we have to be creative. One clever solution is to create a magnetic “bottle” using large magnet coils to capture the plasma and suspend it away from the container’s surfaces. The plasma follows along the magnetic field, suspended away from the walls. This complex combination of magnets used to confine the plasma and the chamber where the plasma is held is known as a tokamak. Tokamaks have a toroidal shape (i.e. they are shaped like a donut) so they have no open ends for plasma to escape. Tokamaks, like the ASDEX Upgrade (pictured above), create and contain the hottest materials in the solar system. The aim of ASDEX Upgrade, the “Axially Symmetric Divertor Experiment”, is to prepare the physics base for ITER.

ITER (International Thermonuclear Experimental Reactor and Latin for “the way” or “the road”) is an international nuclear fusion research and engineering project, which is currently building the world’s largest experimental tokamak nuclear fusion reactor. The ITER project aims to make the long-awaited transition from experimental studies of plasma physics to full-scale electricity-producing fusion power plants.

Further readings:

For teaching: nuclear physics

mucholderthen:

5 Scary Charts from the US Government’s National Climate Assessment
SOURCE: The Huffington Post 

In May [2014] the U.S. government released its third National Climate Assessment, writing that climate change is already “triggering wide-ranging impacts in every region of our country and throughout our economy.”

Wile the full report is over 800 pages, there’s a 137 page highlights document. The Huffington Post chose these five charts as most indicative of “how much things have changed in recent decades and what we might expect later this century.”

  1. We’re Seeing More Heavy Precipitation than We Used To
  2. It’s Gotten Warmer Almost Everywhere
  3. We’re Seeing a Lot of 100-Degree Days
  4. Drought Is Becoming a Major Problem for Much of the Country
  5. Business as Usual = More Temperature Rise

For teaching: climate change

eduardo-:

mucholderthen:

Destination Moon: The 350-Year History of Lunar Exploration
Infographic by Karl Tate
July 16, 2014  ||  Space.com

Why is Robert Goddard not mentioned here whatsoever? Without him (and his inventions, ie. the liquid-fuelled rocket and the multiple-stage rocket, both of which Wernher von Braun co-opted for the V2 decades later), we would have continued to struggle to even leave the ground.

For teaching: aerospace engineering, astrophysics

paleoillustration:

John Meszaros:

Anomalocaris group. going clockwise from the lower left, the animals are: Anomalocaris canadensis, Amplectobelua symbrachiata, Hurdia victoria, Opabinia regalis, Kerygmachela kierkegaardi, Schinderhannes bartelsi, Pambdelurion whittingtoni and Laggania cambria.

Lobopods. Clockwise from top: Microdictyon sinicum, Hallucigenia sparsa, Onychodictyon ferox and Aysheaia pedunculata. Note, by the way, that what appear to be “eyes” on Microdictyon, Hallucigenia and Onychodictyon are actually sclerotized armor plates.

For teaching: evolution

teded:

A Guide to the Energy of the Earth

Energy moves in and out of Earth’s physical systems, and during any energy transfer between them, some energy is lost to the surroundings as heat, light, sound, vibration, or movement.

Our planet’s energy comes from internal and external sources. Geothermal energy from radioactive isotopes and rotational energy from the spinning of the Earth are internal sources of energy, while the Sun is the major external source, driving certain systems, like our weather and our climate.

Sunlight warms the surface and atmosphere in varying amounts, and this causes convection, producing winds and influencing ocean currents. Infrared radiation, radiating out from the warmed surface of the Earth, gets trapped by greenhouse gases and further affects the energy flow.

From the TED-Ed Lesson A guide to the energy of the Earth - Joshua M. Sneideman

Animation by Marc Christoforidis

For teaching: environmental science, climate change, ecosystem ecology