Monthly Archives: June 2018

What is Ferrofluid?

Back in the early 1960s, a fledgling NASA was presented with lots of new problems. Going to space was unlike anything humans had ever done, and engineers and scientists were constantly searching for answers to issues they had never even considered before.

ferrofluid 2 2One of these problems was dealing with the properties of a liquid in low-gravity environments. On Earth, a liquid will stay at the bottom of its containers as gravity pulls it down. But without gravity, the liquid will float all around its container, forming spheres of liquid.

Since the rockets used by NASA relied on liquid fuel, there was a problem getting the fuel pumped to the engines once the spacecraft was in orbit. Several ideas were tried, and though NASA eventually settled on small solid rockets to settle the liquid fuel near the intake, one of the ideas proposed by a scientist named Steve Papell was a ferrofluid fuel.

A ferrofluid is any liquid with metallic metal suspended in it. The metal has a special material coating to prevent the small pieces from attracting or repelling each other, but when the solution is exposed to an exterior magnetic field, the ferrofluid is attracted to the magnet. It also increases in density and becomes somewhat rigid.

ferrofluid 2 1

When Steve Papell suggested using a magnetic fuel, his idea would be to control the flow of the fuel by using magnets. Instead of letting the

liquid blob in the center of the tank, it could now be held towards the fuel intake and make the system more efficient. Though it was a good idea, NASA found other, better solutions for the rocket issue.

That didn’t mean the end of ferrofluids, however. Another scientist named R.E.Rosensweig improved upon the design and developed a new branch of fluid dynamics known as ferrohydrodynamics.

Since then, ferrofluids have been used in many devices — the most common of which is in electronic devices such as hard disks, using it to form liquid seal that will be held in place by magnets. This seal prevents dust and other materials from entering the hard drive.

Despite its practical uses, ferrofluid is just cool to look at. If you ever have the chance, grab a magnet and play around with it!

Written By: Scott Yarbrough

Pendulums and Gravity

In the video above, I talk about how pendulums actually work. If you haven’t watched it, the principle is simple: an object is suspended from a fixed point and allowed to swing back and forth – the mass of the object and the time it takes to swing back and forth are independent of each other, relying only on the length of the string and the strength of gravity.

Normally, you’d think of gravity on Earth’s surface as being constant, but the Earth isn’t a perfect sphere, meaning that the force of gravity near the equator is slightly weaker than at higher or lower latitudes. And how did we discover this fact? Pendulums!

Pendulum and Gravity 1

In the year 1671, a French scientist named Jean Richer travelled to French Guiana. Among several experiments and astronomical observations during his two-year trip was to take measurements with a clock pendulum.

He set up the pendulum in the same way I did in my video, but he adjusted the length of the pendulum so that one half-swing took exactly one second, a common technique at the time. What he found was that the pendulum length needed to be slightly shorter than it did back in Paris, by about 3 millimeters. Though a small difference, it was significant enough to begin a discussion about the varying gravitational field of Earth.

Pendulum and Gravity 2

This was later proved by Isaac Newton by determining that due to the Earth’s rotation, it was thicker at the equator, meaning the surface was further away from Earth’s center of mass. This was further supported by Newton’s idea that gravitational force decreases as the distance between two objects increases.

Scientists started to use pendulums to take measurements of the gravitational field in other locations and began to create a model of the Earth’s true oblong shape. Since then, we’ve developed more accurate methods to measure the same thing, but they were pioneered by those first efforts.

Written By: Scott Yarbrough

Video Music: Funky Chunk Kevin MacLeod (incompetech.com)

Licensed under Creative Commons: By Attribution 3.0 License

http://creativecommons.org/licenses/by/3.0/

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