Physical Science

Iran has announced its activation of a second set of uranium centrifuges. These machines are at the core of the uranium-enrichment process. Find out where the centrifuge fits into the equation.

By Marshall Brain

Nuclear materials get used in many forms of nuclear medicine -- everything from PET scans to chemotherapy uses them. Learn how nuclear medicine works.

By Craig Freudenrich, Ph.D.

On the one hand, nuclear power offers a clean energy alternative that decreases fossil fuel dependence. On the other, it summons images of quake-ruptured Japanese power plants leaking radioactive water. What happens in reactors in good times and bad?

By Marshall Brain, Robert Lamb & Patrick J. Kiger

The air we breathe contains 21 percent oxygen. Would we be better off breathing 100 percent oxygen?

By Marshall Brain

Alfred Nobel revolutionized several industries with his invention of dynamite. Learn more about how dynamite works and its controversial history.

By Yara Simón

Just about everyone has seen a television show or movie in which a criminal suspect is questioned while detectives watch from behind a one-way mirror. How does a piece of glass manage to reflect light from one side while remaining clear on the other?

Rust is the common name for iron oxide, which is created when iron bonds with oxygen. In fact, pure iron is only rarely found in nature because it interacts with oxygen so easily.

You may know a bit about polygraphs, but do you know which physical reactions it actually monitors?

The decibel scale measures sound based on human hearing, which makes it one of the most unusual scientific measurements. How are decibel calculated and what do they tell us about sound?

By Sascha Bos

I recently used chlorine bleach to clean the siding on my house, and I was amazed at how well it worked! What is bleach? How does it remove stains? Is the chlorine in bleach the same as the chlorine in drinking water or in swimming pools? Is chlorine safe to use?

By Yara Simón

Just how far can the human eye see? There's no exact formula to figuring it out, but we do have an idea.

By Patrick J. Kiger

I once saw this device shaped like a light bulb. It had a vertical support inside it, and on that support there were four vanes with four diamonds on the end. One side of the diamond was black and the other was white. I did a little research and found out that it was called a Crookes' radiometer -- how does it work?

I have a thin piece of plastic mounted on the back window of my RV. It magnifies things so I can see better when I'm backing up. How can such a thin piece of plastic magnify things? A regular glass magnifying lens would have to be curved on both sides and much thicker.

By Austin Henderson

Bullet size is measured in calibers, but how are wires and nails measured? Learn about bullet size and caliber in this article.

Many ads for new clocks advertise their ability to automatically synchronize themselves with the atomic clock in Boulder, Colorado. This atomic clock is more precise because it uses the frequencies of atoms as its resonator.

Chemical formulas provide a concise explanation for reactions. In this article, we explain the formula for the reaction in a smoke detector.

When an airplane flies faster than the speed of sound, you hear a large booming sound. But how can something that seems so simple cause such a boom?

By Austin Henderson

Radar is used to track storms, planes, and weapons and also to create topographic maps. Learn about radar, radar technology and Doppler shift.

By Marshall Brain

Here's something to consider: The place you call home likely has walls and glass windows. Both are adept at keeping rain, snow and wind from bothering you in your abode. Only one, though, allows light to enter. Why is that?

By William Harris

It begins with an unassuming "H" and ends in crazy elements that you've likely never heard of. But the periodic table, encapsulated on a mere sheet of paper, can be a scientist's best friend and a testament to our human drive to organize the world.

By Craig Freudenrich, Ph.D.

When it comes to stimulating the human central nervous system, meth can hold its shaky, toothless head high. Why is this drug so additive?

By Tom Scheve & Nathan Chandler

If the sight of a mushroom cloud burning above the horizon suggests that the nuclear weapon-equipped world might end with a bang, then nuclear winter presents the notion that post-World War III humanity might very well die with a whimper.

By Robert Lamb

Who made it possible to light up your home at night? Thomas Edison, right? Yes, but without the work of Nikola Tesla, we would be living in a different world.

By William Harris

Criminals always leave traces behind after a crime is committed. In fact, footprints, tire tracks and tool marks are often more prevalent than fingerprints at a crime scene. What can impression evidence tell an investigator?

By John Fuller

One of the most influential ideas in forensic science history is known as Locard's exchange principle. This simple, yet groundbreaking idea forever changed the way we fight crime. But who was Edmond Locard, anyway?

By John Fuller