Each galaxy has billions of stars. Such galaxies are not uniformly spaced in the universe but exist in groups and clusters; a group containing up to 40-50 galaxies and clusters containing about thousands of galaxies. These along with isolated galaxies may form larger clusters known as galactic superclusters. These are the largest structures of matter found in the universe. Our …
Read More »What are fossils?
Fossils are the petrified remains of living things. There are three types of fossil, and each type is useful in telling us how creatures lived millions of years ago. The first type of fossil is part of the body of the creature, usually the hard part of the body like the shell or the skeleton, which is preserved as it …
Read More »What are Fizeau’s fringes?
Fizeau’s fringes occur in interferometry. One of the most common methods used to test the flatness of a polished surface is by analysing the interference patterns formed when the surface is placed against another polished flat transparent surface. When two surfaces are fully in contact, a pattern of concentric dark and light circles is seen and these patterns (or fringes) …
Read More »What are fissure eruptions?
In volcanoes, lava emerges through a pipe in the top of the mountain. Sometimes, lava also reaches the surface through long cracks in the ground, called fissures. In 1783, lava spilled out of a 32-km (20-mile) long fissure in Iceland and buried 565 square km (218 square miles) of land.
Read More »What are ferns?
A fern is any one of a group of about 12,000 species of plants. Unlike mosses, they have xylem and phloem (making them vascular plants). They have stems, leaves, and roots like other vascular plants. Ferns do not have either seeds or flowers (they reproduce via spores). By far the largest group of ferns are the leptosporangiate ferns, but ferns …
Read More »What are eddy currents?
Eddy currents may be defined as currents induced in a thick conductor when it is placed in a changing electric field. Consider a metallic block placed in a continuously changing magnetic field by keeping the block fixed and changing the magnetic field with the help of an alternating current. Due to the continuous change of magnetic flux linked with the …
Read More »What are dendrimers?
Dendrimers are repeatedly branched, roughly spherical large molecules. The name comes from the Greek word “δένδρον” (pronounced dendron), which translates to “tree”. Synonymous terms for dendrimer include arborols and cascade molecules. However, dendrimer is currently the internationally accepted term. A dendrimer is typically symmetric around the core, and often adopts a spherical three-dimensional morphology. The word dendron is also encountered …
Read More »What are cladograms?
Cladistics is the hierarchical classification of species based on evolutionary ancestry. It’s distinct from other taxonomic classification systems because it focuses on evolution rather than similarities between species. This is because it places heavy emphasis on objective and quantitative analysis. Cladistics generates diagrams called cladograms that represent the evolutionary tree of life. The starting point of cladistic analysis is a …
Read More »What are chilblains?
These affect the fingers and toes when they get very cold in winter. An inflammation sets in and produces red swellings that can hurt and/or itch once the coldness wears off.
Read More »What are block mountains?
When the huge plates that cover the Earth move, they create enormous tension that cracks rocks, forming long faults. Blocks of land pushed up between roughly parallel sets of faults form block mountains. Examples include the Ruwenzori Mountain range in Central Africa and the Sierra Nevada in the south-western USA.
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