Photo Researchers ftp March 2011

This model car uses a reversible PEM (proton exchange membrane) fuel cell. Hydrogen and oxygen gasses are stored in the tanks located in the back of t...

This model car uses a reversible PEM (proton exchange membrane) fuel cell. Hydrogen and oxygen gasses are stored in the tanks located in the back of t...

Hydrogen fuel cell. Reversible PEM (proton exchange membrane) fuel cell. This fuel cell is used to produce electricity for a model car.

Photo of blue laser beam hitting a screen

Secure Digital (SD) memory card by Patriot Memory with a 2 GB capacity. SD cards are used in portable electronic devices.

Subscriber identity module (SIM) cards are used for storing the service-subscriber key and data information on a mobile phone. Shown is a 3G mini-SIM...

Coiled uninsulated copper wire 1 mm in diameter.

Indium (In) is a rare, soft, malleable post-transition metal. Shown here are two strips of Indium foil.

Propane fuel tank. Pressurized liquefied propane fuel cartridge. Note a label that warns about multiple hazards: flammable, exposure; pressure, carbon...

Close-up of a label on a pressurized liquefied propane fuel cartridge. It warns about multiple hazards: flammable, exposure; pressure, carbon monoxide...

Distilled water in a plastic container.

Digital composite image of a falling apple.

Stroboscopic composite image of a falling apple.

A spring scale is used to measure weight of an apple (170 gram). The scale uses Hooke's law that states that the extension of a spring is proportional...

Water running from a faucet. Note that the diameter of the stream decreases as water speed increases due to gravity.

Water running from a faucet into a glass

A slow-exposure photograph of a cylinder rolling along a flat surface. A red LED is placed on the axis (center) of the cylinder. Another red LED is pl...

A slow-exposure photograph of a cylinder rolling along a flat surface. A red LED is placed on the axis (center) of the cylinder. Another red LED is pl...

A claw hammer is used as a lever to pull a nail from a wood board.

A crowbar is used to pull a nail from a wood board. It is a lever, one of the simple machines.

Green and Black Poison Frog, Dendrobates auratus, in tropical rainforest, Chilamate, Costa Rica

Green and Black Poison Frog, Dendrobates auratus, in tropical rainforest, Chilamate, Costa Rica

Red-eyed Tree Frog, Agalychnis callidryas, on a heliconia flower, Chilamate, Costa Rica. This species is also known as Red-eyed Leaf Frog and Gaudy Le...

Red-eyed Tree Frog, Agalychnis callidryas, on a heliconia flower, Chilamate, Costa Rica. This species is also known as Red-eyed Leaf Frog and Gaudy Le...

Hog-nosed viper, Porthidium nasutum, in lowland primary tropical rainforest, near Chilamate, Costa Rica. The Hog-nosed viper is a venomous pit viper.

Eyelash viper, Bothriechis schlegelii, Arenal National Park, Costa Rica

Arenal Volcano releasing gas and ash cloud, La Fortuna, Costa Rica

Arenal Volcano releasing gas and ash cloud, La Fortuna, Costa Rica

Arenal Volcano, La Fortuna, Costa Rica

Pyroclastic bombs of ash, dust and gas roll down the cone of Arenal Volcano, La Fortuna, Costa Rica

Pug-nosed anole, Norops capito, on a moss covered branch, rainforest, Chilamate, Costa Rica

Pug-nosed anole, Norops capito, on a moss covered branch, rainforest, Chilamate, Costa Rica

Ecology, environment presentation at INBio Parque, Costa Rica. INBio is the National Institute of Biodiversity - an organization devoted to studying a...

Tropical spider in orb web, rainforest, Chilamate, Costa Rica

This millipede, Class Diplopoda, is walking on the forest floor in rainforest, Chilamate, Costa Rica.

Entrance sign to the La Selva Biological Station. The station, run by the Organization for Tropical Studies (OTS), is one of the most important rainfo...

Snake (Bushmaster, Lachesis stenophrys) eggs, in the rainforest, Chilamate, Costa Rica

Common bean (red kidney bean variety), Phaseolus vulgaris, seedling sprouting, showing the 2 cotedylons. These are green, epigeal cotyledons which con...

Common bean (red kidney bean variety), Phaseolus vulgaris, seedling sprouting, showing the 2 cotedylons. These are green, epigeal cotyledons which con...

Corn, Zea mays, seedling recently germinated and illustrating gravitropism (geotropism). The three seeds were germinated at different orientations and...

Corn, Zea mays, seedling recently germinated and illustrating gravitropism (geotropism). The seed was germinated upside down and in the dark. Neverthe...

Corn, Zea mays, seedling recently germinated and illustrating gravitropism (geotropism). The seed was germinated in a sideways orientation and in the...

Corn, Zea mays, seedling recently germinated. The upward growing shoot at this point consists of the coleoptile being fed by the endosperm stored with...

An acorn from chestnut oak, Quercus prinus (syn. Quercus montana)

Pile acorns from chestnut oak, Quercus prinus (syn. Quercus montana)

Acorns from chestnut oak, Quercus prinus (syn. Quercus montana). One of the acorns has been cut in half to reveal the inside of the seed.

Acorns from chestnut oak, Quercus prinus (syn. Quercus montana). One of the acorns has been cut open to reveal the seed from within.

Three acorns from northern red oak, Quercus rubra.

Three acorns and a leaf from northern red oak, Quercus rubra.

Female teenage high school students using a digital sensor to measure dissolved oxygen levels in a stream.