Ask The Science Experts

Some magnets are natural (lodestone and magnetite are naturally occurring), and some magnets are man-made. The magnets made in the laboratory are usually made of a mixture of iron, cobalt, nickel and other elements. The substances are magnetized by a couple of different methods. You could move a permanent magnet in one direction across the material to magnetize it. You could produce an electric current through coils around the substance to magnetize it. And some magnets can be made from a chemical reaction (ie., certain elements will become magnetic when reacting with oxygen).

Wikipedia gives a great description of exactly what a magnet is and how it works. Some of which I’ll summarize here. [source: Wikipedia] A magnet is a material or object that produces a magnetic field. This magnetic field is invisible and causes the most notable property of a magnet: a force that pulls on nearby magnetic materials, or attracts or repels other magnets. The structure of the invisible magnetic field of a magnet is made visible by the pattern formed when iron filings are scattered around the magnet, as in the graphic above.

A permanent magnet (also called a hard magnet) is one that stays magnetized. An example is the common magnets you put on a refrigerator door. Permanent magnets occur naturally in some rocks, particularly lodestone, but are now more commonly manufactured. A soft magnet (also called an impermanent magnet) is one that will gradually lose its magnetization. Soft magnetic materials are often used in electromagnets to enhance (often hundreds or thousands of times) the magnetic field of a wire that carries an electric current and is wrapped around the magnet; the field of the soft magnet increases with the current.

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The short answer is because of the nature of the ionosphere of the Earth. The ionosphere consists of several different layers of gases that have become conductive from the bombardment of the atoms by: solar radiation, by electrons and protons emitted by the sun, and by cosmic rays.

These layers, sometimes called the Kennelly-Heaviside layer, reflect AM radio signals, thus enabling AM broadcasts to be received by radios that are a long way from the transmitting station. At night, the ionosphere layers partially dissipate and become an excellent reflector of the short waveband AM radio waves.

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Source: The Handy Science Answer Book.

What does Doppler radar mean and how is it different from other radar?

RADAR, an acronym for Radio Detection and Ranging, operates by transmitting a wave and recording the time it takes that wave to bounce off of an object and return to the source. Since we know the speed the transmitted wave is traveling, we can calculate the distance of the object.

Doppler radar operates on the same principle, but it also detects an objects motion by measuring the frequency shift between the outgoing wave and the returning wave. An object moving toward the radar would increase the returning wave’s frequency while an object moving away from the radar decreases the wave’s frequency. For weather purposes, this provides important information about the speed and direction of winds within thunderstorms.

Source: USA Today, Ask the Weather Experts. Posted by admin for the best selling toys of 2008 at Atomic Elephant Science & Toy Co.

Mathematical theory suggests that most comets may come to the solar system from very far away, as far away as 100,000 Astronomical Units. In this picture, the solar system is buried deep within the cloud.

An Astronomical Unit (or AU) is the distance from the earth to the sun and is equivalent to about 93,000,000 miles. Mars is 1.5 AU from the sun, Jupiter is 5 AU from the sun, and Pluto is 39 AU from the sun. So comets come from very far away indeed.

Comets are observed to come to the solar system from all directions, therefore the place where the comets come from is thought to be a giant sphere surrounding the solar system. This sphere is called the Oort cloud after Jan Oort who suggested its existence in 1950.

But some comets may come to the solar system from closer in. The place where these comets come from is called the Kuiper Belt, which is located past the orbit of Pluto. Source: the University Corporation for Atmospheric Research.

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Echolocation is the ability to locate objects by bouncing sound waves off of them, and then measuring the time taken for an echo to return, and calculating the direction the echo came from.

These sound waves are very high-pitched, and most humans are unable to hear them. A device called a bat detector is able to pick up these sounds and convert them into sounds which we can hear as a series of clicks, pops and whistles.

Source: http://www.uksafari.com/bats4.htm.

The principle factor affecting a moving (and spinning) baseball is air drag. Imagine a standard fastball thrown with a straight overhead motion. The ball will be spinning naturally on a horizontal axis (with the top of the ball rotating back toward the pitcher). This spin causes the magnitude of the drag vectors to be different near the top half of the ball than they are on the bottom half. Without the spin, the drag force would be equal on both hemispheres of the ball… Read the rest of this entry »

First, the simplest definition of density: it is how heavy something is relative to its size. A pound of rocks weighs the same as a pound of ping pong balls. But the ping pong balls take up a lot more space. Hence, the rocks are much more dense. Another way to look at density is to think of it as a measure of the “compactness” of matter.

More background… at the center of an atom is a very dense core called the nucleus. It’s composed of protons and neutrons (held very tightly together). Surrounding this nucleus in somewhat of a cloud are the electrons. Atomically speaking, the electrons are very far apart and far from the nucleus. Consider this: the entire atom composed of an electron cloud surrounding the nucleus is about 99.9% empty space.

The electrons are negatively charged and repel anything else negatively charged with a very strong electromagnetic force, or EMF. Now imagine a force strong enough to overcome this EMF and compress atoms to a much greater density. This is what happens in old and dying stars– the compressing force of gravity starts to overcome this electromagnetic force. The atoms start squeezing together resulting in what’s called degenerate matter. Stars involved in this process are called white dwarfs and the matter in them can reach a density of one million times that of water.

While this is very dense, it is not the densest state that matter can reach. If the dying star is massive enough, its gravitational force can be powerful enough to overcome the repelling force in the degenerate matter. The center of this body is now called neutronic fluid and these stars are now called neutron stars or pulsars. Now we’re getting pretty dense. A 1cm cube of neutron star material would weigh 100 million tons and if dropped would fall straight through to the center of the earth.

Now for even bigger stars (more than three times the mass of our sun), it can have a gravitational force strong enough to break down even this neutronic matter. After this, there will be no barrier left. The matter can not compress any further and it is basically a single point called a singularity. A star that has collapsed into itself to this point is called a black hole.

Since there is no way to measure anything of this magnitude, estimates are made by estimating the matter outside and near this singularity. If we use matter on Earth as a first order of magnitude, degenerate matter (inside white dwarfs) is about one million times as dense. Neutronium (inside neutron stars) is about one trillion times as dense. And finally, black holes, which are about ten trillion times as dense.

Source: Why Nothing Can Travel Faster than Light. Contemporary Books, 1993. Posted by admin for the best selling toys of 2008 at Atomic Elephant Toy.