From Physics Research Features

Greenhouse Effect

Wed, 01 May 2013 00:00:00 EST

This is the famous “Keeling curve” of carbon dioxide concentration in the atmosphere versus time, from about 1958 to about 2007, measured in Hawaii. Notice that the rate of warming (indicated by the slope of the blue line) increases slowly but steadily over time. Carbon dioxide is an important greenhouse gas. Greenhouse gases absorb the infrared radiation given off by Earth. This absorbed radiation is promptly re-emitted in all directions; much of it returns to Earth, raising the temperature of its surface by a substantial 33°C. Carbon dioxide is produced by burning fossil fuels. As more countries industrialize, the use of fossil fuels increases, as does the amount of carbon dioxide in the atmosphere The inset in the graph shows the annual cycle: For six months, plant photosynthesis absorbs carbon dioxide from the atmosphere, and the curve goes down; then, for the next six months, the decay of dead plants returns carbon dioxide to the atmosphere, and the curve goes up. To learn more, visit Greenhouse Effect and also this UCAR page.

Solar Flares--Solar Prominences

Mon, 01 Apr 2013 00:00:00 EST

This image of a solar prominence was captured in extreme ultraviolet light on December 31, 2012. The prominence is ionized gas--charged particles, with electrons stripped from atoms, which move due to forces from magnetic fields. To learn more about solar prominences, visit Solar Flares--Solar Prominences. To see a different solar prominence, with an image of Earth added to show the scale, click here.

APS Division of Fluid Dynamics 2012 Gallery of Fluid Motion

Fri, 01 Feb 2013 00:00:00 EST

This image is a high-resolution computer simulation of the head-on collision of two tiny drops, one moving up and one moving down. The drops approach each other with a high velocity, so there is considerable energy in the collision. For more information, see this description. The diameter of each drop is only about twice the thickness of human hair. Imagine how hard it would be to do this experiment and see what actually happens. Also, compare the image at left, and also this additional Corrie White image, with the simulation above: Note how the edge of the disk and film break up into drops in a similar way.

NASA's IMAGE Satellite View of Aurora Australis from Space

Tue, 01 Jan 2013 00:00:00 EST

You are looking at a composite: The image of the southern lights (Aurora Australis) is superimposed on a "Blue Marble" image of Earth; both images were captured by satellite. Click on NASA's IMAGE Satellite View of Aurora Australis from Space to see a video of this aurora. Notice that the Aurora occurs at about the same latitude. That's because the Aurora's green light is produced by charged particles from the sun, which collide with oxygen atoms in the atmosphere. These charged particles follow the Earth's magnetic field lines. Where these lines come close together, near the two poles (like the field lines of a bar magnet), the Aurora can occur. For more on this process the Astronomy Notes.

Mission to the Edge of Space

Sat, 01 Dec 2012 00:00:00 EST

The figure at the bottom of the photo is Felix Baumgartner, shortly after he jumped from an altitude of 39 kilometers (24 miles). There, the thin atmosphere produces very little air resistance, so he was almost in free fall (in free fall, the only force acting on an object is gravity). He accelerated rapidly, broke the sound barrier, and went on to about Mach 1.2 (20% above the speed of sound). For more detail on the jump, visit mission timeline. To learn more about the Stratos project, see Mission to the Edge of Space.

Physics Images: Bent-Core Liquid Crystals

Thu, 01 Nov 2012 00:00:00 EST

Here is an image of a “bent-core liquid crystal”— to learn more about these substances, visit Physics Images: Bent-Core Liquid Crystals.

Fold Everything

Mon, 01 Oct 2012 00:00:00 EST

This photo shows a stent, a small metal cylinder inserted into a diseased artery to open it up. To be inserted, the device must be collapsed, and origami folding provides a way to do that. The stent is shown in the photo above, both folded and unfolded. Airbags are folded carefully to fit into small volumes inside an automobile. To find out how the mathematics of origami produces the folding design, visit Airbag Folding. For a short National Geographic article on origami applications, see Fold Everything.

Mars Science Laboratory Mission

Sat, 01 Sep 2012 00:00:00 EST

The image above shows a view from Curiosity's landing site inside Gale Crater; the elevated area in the distance is the crater wall. For more information on this image, visit Wall of Gale Crater. To learn more about this crater, visit The Strange Attraction of Gale Crater. A different Curiosity image shows distinct layering in Mount Sharp, located in the middle of Gale Crater. Curiosity will travel to Mount Sharp to investigate the geology there. To learn more about Curiosity's mission on Mars, visit Mars Science Laboratory Mission.

The Apollo Program: Apollo 15

Wed, 01 Aug 2012 00:00:00 EST

You're looking at the vicinity of NASA’s Apollo 15 landing site, located almost in the center of the image, on the lava surface at the eastern edge of Mare Imbrium (click for a lunar map to find it). Naturally a smooth impact basin would be the best place for the lunar lander to put down. You can also see part of the Apennine mountain range in the image above. The Apollo Program's mission was to explore and map the moon. To learn more about Apollo 15, see The Apollo Program: Apollo 15. Do you see the squiggly line running up and down in the middle of the image? It's actually a trench called the Hadley Rille. Here is a video of Apollo 15 landing, with the Hadley Rille in the background. On a lava-filled basin, and with a mountain range and a rille so close, the astronauts could explore plenty of lunar geology.

Radioisotope Power Systems

Sun, 01 Jul 2012 00:00:00 EST

The glowing pellet is an oxide of plutonium, the fuel for a radioisotope thermoelectric generator (RTG). It is photographed in the light it emits, because its radioactive decay produces considerable heat. The RTG converts this heat into electricity. RTGs power the spacecraft that visited Mars, Jupiter, and Saturn--and the RTG keeps working over decades. To find out more, visit Radioisotope Power Systems.

The Invention of the Electric Guitar

Fri, 01 Jun 2012 00:00:00 EST

The photo shows a modern electric guitar prototype developed in 1940 by a physicist at North Carolina State University. Check out this NCSU webpage to learn more. Read about the development of the electric guitar in The Invention of the Electric Guitar.

Newton's 3rd Law

Tue, 01 May 2012 00:00:00 EST

What is the purpose of the small rotor on the back of this helicopter? In fact, it's needed because of Newton's third law--for every action force there is an equal and opposite reaction. The helicopter puts a force on the main rotor shaft to make it turn, and the rotor shaft puts an equal and opposite force back on the helicopter. This reaction force creates a torque that, by itself, would make the helicopter spin in the opposite direction as the rotor. To counter this torque, the small rotor on the tail creates an opposing torque, so the two are balanced. To learn more, see Newton's 3rd Law. For an example of reaction forces, see this video.

X-rays from free electrons

Sun, 01 Apr 2012 00:00:00 EST

The spiral track above was made by an electron moving in a magnetic field. Since motion along a curved path requires a force perpendicular to the direction of motion, the electron is accelerated. Accelerated charges radiate electromagnetic waves, so the electron loses energy and spirals inward. To learn more about this process, see X-rays from free electrons.

Electronic Handedness in Copper-Silver Combo

Thu, 01 Mar 2012 00:00:00 EST

Notice how the two images above have opposite handedness? These images show electronic properties of a small layer of copper on top of silver, but neither silver nor copper have any handedness themselves. To learn more, visit this American Physical Society webpage.

APOD: Companion of a Young, Sun-like Star Confirmed

Wed, 01 Feb 2012 00:00:00 EST

You are looking at the first telescopic image of a confirmed planet in orbit around a Sun-like star. The young planet is still quite warm, and therefore radiating considerable energy, which makes it relatively easy to detect. To learn more, see APOD: Companion of a Young, Sun-like Star Confirmed.

Wing Vortices

Sun, 01 Jan 2012 00:00:00 EST

This image from ONERA, the French aerospace lab, shows a simulation of the wake of an aircraft, looking along the direction the aircraft is moving. To learn more, visit Wing Vortices, and be sure to check out the diagrams there. Also, compare the image above with this photo (from PTG Issue 33, in the Archives) showing the pattern of smoke released behind the wingtip of a crop-duster. How well did the simulation model the crop-duster wake?

Fluid morphs into startling designs, surprising MIT researchers

Thu, 01 Dec 2011 00:00:00 EST

This ferrofluid was subjected to a magnetic field perpendicular to its surface. The surface broke up into hexagonal regions, each with its own spike. For a MIT News article showing other ferrofluid patterns created by the same physicist, see Fluid morphs into startling designs, surprising MIT researchers.

Time Flies

Tue, 01 Nov 2011 00:00:00 EST

Einstein's theory of special relativity says that a moving clock, when compared to a stationary clock, runs slow. And general relativity, his theory of gravity, says that the weaker the gravitational field, the faster a clock in that field runs. These predictions were tested in 1971 by flying atomic clocks around the world. Einstein's relativity theories correctly explained what happened. To learn about a more accurate update to this experiment 25 years later, see Time Flies. Click on the image to see a photo of the atomic clocks in the updated experiment.

The Contrail Effect

Sat, 01 Oct 2011 00:00:00 EST

The false-color image above shows jet contrails in the skies above the mid-Atlantic coast on 1/26/2001. Check out this NASA photo of the sky taken on the ground at about the same time. Visit The Contrail Effect to find out how contrails can affect Earth's climate, and how this was investigated after 9/11.

How does GPS work?

Thu, 01 Sep 2011 00:00:00 EST

The photo shows a Global Positioning System satellite. To find out how the system works, visit How does GPS work?, and be sure to see the video to understand how three or four different GPS satellites specify your position on Earth. For more, check out this Beyond Discovery page from the National Academy of Sciences.

Benoît Mandelbrot, Novel Mathematician, Dies at 85

Tue, 02 Aug 2011 00:00:00 EST

This famous fractal is the Mandelbrot set. Click to make the image larger, and look at the boundary between the black and blue—it is made up of the larger image, at smaller and smaller scales. Check out this Fractal Geometry page from IBM, especially the video (scroll down) that zooms in on the Mandelbrot set. The image is named for Benoît B. Mandelbrot, who made it by graphing a set of complex numbers described by an equation. He coined the term “fractal” and popularized fractal research by showing its importance to other fields besides mathematics. Read more about his life and accomplishments at Benoît Mandelbrot, Novel Mathematician, Dies at 85.

Footloose

Fri, 01 Jul 2011 00:00:00 EST

In 1984, astronaut Bruce McCandless made this untethered spacewalk—the first ever, and one of only a few. He maneuvered with a "jet pack" strapped to his body as he orbited Earth at about 18,000 miles an hour. Click on the image to see McCandless at his maximum distance from the shuttle. Whenever the jet pack's engines were off, McCandless was in free fall—the only force on him was Earth's gravity (neglecting air resistance and the gravitational attraction of the shuttle). To learn more, visit Footloose and this APOD page.

Chaos Theory: A Brief Introduction

Wed, 08 Jun 2011 00:00:00 EST

This image shows the "Lorentz attractor," a graph that represents the behavior of a simple model of Earth's weather. Weather is just one example of a chaotic system, in which seemingly irregular behavior does follow certain patterns. For an overview of chaos theory that concisely explains the characteristics of chaotic systems, see Chaos Theory: A Brief Introduction.

Mechanics of a Meltdown Explained

Thu, 12 May 2011 00:00:00 EST

The long red tubes are zirconium-alloy-clad fuel rods being fastened together into large bundles that will form the core of a nuclear reactor. Inside the zirconium cylinders are stacked pellets of uranium oxide, the reactor fuel. To find out what happens to the zirconium cladding and the fuel rods in a "nuclear meltdown", visit Mechanics of a Meltdown Explained. The article explains the problems faced by the Fukushima power plant after the March 2011 earthquake in Japan.

Not Just Another Old Flame

Tue, 12 Apr 2011 00:00:00 EST

The photo shows two flames, one on Earth and one in space, with both flames on identical candles. For a NASA website on flames in space, see Not Just Another Old Flame.