The speed of light, typically noted as c in math and physics formulas is 299,792,458 meters per second (186,282 miles per second). Note, this figure is for the speed in a vacuum as light will propagate at different speeds through different mediums.

Here’s the speed of light compared to other fast things (in miles per hour):

Unmanned spacecraft, Helios 1 and 2. 157,082 mph. Light is 4,269 times faster than the fastest vehicle ever built by man.

Manned spacecraft, Apollo 10. 39,665 mph. Light is almost 17,000 times faster.

Jet, SR-71 Blackbird, the world’s fastest jet has traveled at 2,193 mph. Light is 305,799 times faster.

Sound: 768 mph. Very much slower than light. 873,000 times slower.

World’s fastest car, Bugatti Veyron. 267 mph. Pretty fast, but compared to light, it’s 2,511,673 times slower.

World’s fastest bird, Spine-tailed Swift, 171 mph. This is crazy fast for a bird. But almost 4 million times slower than light.

World’s fastest mammal, the cheetah has been clocked at 71 mph. 9.4 million times slower than light.

World’s fastest insect, the dragonfly. One species has been measured at 36 mph.

World’s fastest man, Usain Bolt. While faster than anyone else on the planet at 23 mph, he’s still 29 million times slower than light.

Yuri Gagarin was the first person in space when he orbited the Earth on April 12, 1961. He was only 25 years old at the time. Gagarin was a Russian cosmonaut. A cosmonaut is what the Russians call their astronauts. And for you really young readers, a Russian is what we used to call someone who was from what we used to call Russia, or the former Soviet Union.

Yuri’s orbit was made in the Vostok I and took just one hour and 48 minutes to complete. He became an international hero after his flight. For anyone interested, I encourage you to check out Wikipedia’s page on Yuri Gagarin. He was a very accomplished pilot and sadly, was killed in a jet crash when he was only 34 years old.

Yuri Gagarin in his cosmonaut suit

Image sources:

http://un-dx.ucoz.com/yuri-gagarin-news11.jpg

http://www.eliteoftheworld.com/images/gallery/1306195171yuri-gagarin-2.jpg

By most standards, John Dalton is credited with having been the first to propose (and somewhat prove) that all matter was made of atoms. He did this in the early 1800s in his experiments calculating the atomic weights of gaseous elements. Isaac Newton also proposed such a theory in the 1600s although the technology in his time didn’t allow him to experimentally prove his theory. Even before Newton was the ancient Greek philosopher Democritus who had a similar proposal.

The first scientist to significantly “prove” the existence of atoms was Rutherford who “invented the cloud chamber and used it to show that when thin gold foil is bombarded by helium nuclei (alpha particles), the particles are occasionally deflected by a very large angle, but usually pass straight through. This gave rise to the realization that the gold was composed of atoms, with a tiny nucleus at the middle which could occasionally collide with an alpha particle and send it flying.” [source: newton.dep.anl.gov]

The following physics equations and formula sheets are some of the more useful ones I’ve come across in my recent years as a physicist. Some of these are intended to be used as-is, but you can always pull various equations and formulas from the specific topics you need and create your own.

AP Physics Exam Table of Information and Equations. 8 pages, 285k PDF. This is the sheet provided by The College Board to students when taking the AP Physics Exam. This is one of the more detailed formula sheets available. Current version copyright 2007.

MCAT Physics Equation Sheet

Physics Formula Sheet 2009-2010

Reference Guide & Formula Sheet for Physics. 8 pages, 209k PDF. An excellent formula sheet with a few hundred equations and constants. Many of these equations could be used in high school-level classes, but the majority seem more relevant to the physics undergraduate student. Prepared by Dr. Hoselton and Mr. Price of the Trinity Valley Preparatory School of Fort Worth, TX. Latest update: May 2005.

Source: The New York Times Book of Science Questions and Answers.

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.

Source: The Handy Science Answer Book.

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.

For example, if you have 10 grams of Isotope X, with a half-life of one minute, after one minute that 10 grams will become 5 grams. Then 2.5 grams after another minute. Another minute and it’s 1.25 grams. The half life of the isotope is always one minute.

Source: the University of Colorado Physics Department with their great applet showing the decay of beryllium-11 to boron-11.

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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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.