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Images Dated 26th August 2004

Choose from 106 pictures in our Images Dated 26th August 2004 collection for your Wall Art or Photo Gift. All professionally made for Quick Shipping.

Common crab Featured 26 Aug 2004 Print

Common crab

Common crab. Top view of the Common or Rock crab, (Cancer pagurus) also known as the Edible crab for its tasty meat. Coloured red-brown on top with a yellow-white underside, the claw tips on its powerful pincers are black. The Common crab is a relative of the swimming crabs but lacks flattened paddles on its hind limbs and consequently it is only a moderate swimmer. It prefers to eat mussels but also feeds on worms, other molluscs, algae and carrion. It lives mostly around the shore on stone and gravel bottoms, ranging from the coasts of Norway, Britain, France and Portugal, through to the Mediterranean

© Kevin Curtis/Science Photo Library

Hering illusion Featured 26 Aug 2004 Print

Hering illusion

Hering illusion. This illusion was created by the physiologist Edward Hering in the 19th century. It exploits the brain's understanding of perspective to fool it into thinking that the two horizontal red lines bow outwards. In fact they are straight and parallel. This is achieved due to the presence of the grey lines radiating from a point. They give the illusion of depth. In this 2D representation of 3D space a straight line would be drawn curving slightly inwards, since the part in the middle seems lower than that at the side. So, similarly, a straight line in 2D space represents a slight outwards curve in 3D space


Hermann-Hering illusion Featured 26 Aug 2004 Print

Hermann-Hering illusion

Hermann grid illusion. The intersections of the white horizontal and vertical lines in this image appear to be grey. But when looked at directly they are clearly white. This is because of the role played by the edge of the retina. Our peripheral vision is designed to prioritise identifying shapes and edges. To this end the brightness of an image on the edge of the retina is diminished when it is not important to shape identification. At the intersections, a lot more of the area is white light compared to elsewhere on the lines, and there is an effect called lateral inhibition. The brightness is dimmed for this area, and we observe it as grey