Tag Archives: science explained

Friday Fun: Hammer and Feather Drop on Moon

Gravity acts in the same way on a feather and hammer. The reason the hammer falls faster on earth is due to air resistance (well and if you try outside – wind could blow the feather too).

At the end of the last Apollo 15 moon walk, Commander David Scott performed a live demonstration for the television cameras. He held out a geologic hammer and a feather and dropped them at the same time. Because they were essentially in a vacuum, there was no air resistance and the feather fell at the same rate as the hammer, as Galileo had concluded hundreds of years before – all objects released together fall at the same rate regardless of mass. Mission Controller Joe Allen described the demonstration in the “Apollo 15 Preliminary Science Report”:

During the final minutes of the third extravehicular activity, a short demonstration experiment was conducted. A heavy object (a 1.32-kg aluminum geological hammer) and a light object (a 0.03-kg falcon feather) were released simultaneously from approximately the same height (approximately 1.6 m) and were allowed to fall to the surface. Within the accuracy of the simultaneous release, the objects were observed to undergo the same acceleration and strike the lunar surface simultaneously, which was a result predicted by well-established theory, but a result nonetheless reassuring considering both the number of viewers that witnessed the experiment and the fact that the homeward journey was based critically on the validity of the particular theory being tested.

Experimenting Social Network

Social media is definitely a fad filled with lots of ways to waste time. It also does have real value, ways to connect to things people care about and wish to focus on. Reddit is a good site for finding interesting resources online. Sub-reddits are topical areas within Reddit (I have set up management and investing sub-reddits). A new experiment subreddit looks very interesting:

Each experiment will go through a few threads. The first step will be a query for experimental methods. Someone will present a problem or piece of information they want to find out, and then others will suggest methods. Once this is agreed upon, it will be carried out, and a second thread will be posted detailing the method and providing a place to post results via the comments. Then, a third thread can be made to discuss the results. Having more than one thread for every experiment will make things more accessible and easier to sort.

Don’t research ways other people have experimentally determined these things. Submit original ideas to the experimental design thread. Try to come up with a novel way to discover things, but don’t be completely limited by this suggestion. This is chiefly about rediscovery, not repeating someone else’s experiment, but sometimes there’s fun and merit in that as well.

I have joined. You can go to Reddit and join this subreddit to see experiences with experimenting to learn about the world around us.

What is a Molecule?

One of the things I keep meaning to do more of with this blog is provide some post on basic science concepts that may help raise scientific literacy. Some of these will be pretty obvious but even reminders on some facts you know can sometimes help.

What is a molecule?

A molecule is the smallest particle of a compound that has all the chemical properties of that compound. Molecules are made up of two or more atoms, either of the same element or of two or more different elements. The example of molecules are water (H₂O) and carbon dioxide (CO₂) and molecular nitrogen (N₂).

Organic molecules contain Carbon, for example, Methane CH₄). The original definition of “organic” chemistry came from the misconception that organic compounds were always related to life processes.

A few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The division between “organic” and “inorganic” carbon compounds while “useful in organizing the vast subject of chemistry…is somewhat arbitrary”

Ionic compounds, such as common salt, are made up not of molecules, but of ions arranged in a crystalline structure. Unlike ions, molecules carry no net electrical charge.

Home Experiment: Tape Makes Frosted Glass Clear

Interesting result. A comment on Reddit seems plausible to me:

The surface of frosted glass is etched so that it scatters light when it hits this rough surface. The glue on the tape fills in any irregularities, letting the light pass through with much less scatterring (notice, the image is still not perfect).

Additional experimenting could include, what the view is like from the other side of the glass. What the view is like if you also put tape on the other side of the glass.

Paper Towels vs Electric Dryer

Sustainability Showdown: Paper Towels vs Electric Dryer

First off, let’s address one common misconception: for the most part, nobody’s cutting down trees just for paper towels. Most paper towels you find in public bathrooms are made from recycled paper, and even those that aren’t are made from industrial waste created in the manufacturing of regular paper.
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The reason hand dryers came out ahead ended up having surprisingly little to do with the actual act of drying your hands. Most of the emissions and contributions to greenhouse gases come from decomposition of the towels in a landfill.
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Like all life-cycle analyses, this one’s a bit messy, but no studies appear to support the use of paper towels over a hand dryer. Even in the best paper cases, hand dryers come out ahead. To top it off, if a business uses 100% clean energy, the impact and emissions from a hand dryer become a orders of magnitude better than those for paper towels.

So the next time you’re standing with drippy hands and a dilemma on the wall, you can choose the hand dryer, and let the green part of your brain breathe freely.

General Relativity Einstein/Essen Anniversary Test

photo of the batteries for the cesium clocks in the family van by Tom Van Baak

Project GREAT: General Relativity Einstein/Essen Anniversary Test is not your average home experiment but it is another great example of experiments people run at home.

In September 2005 (for the 50th anniversary of the atomic clock and 100th anniversary of the theory of relativity) we took several cesium clocks on a road trip to Mt Rainier; a family science experiment unlike anything you’ve seen before.

By keeping the clocks at altitude for a weekend we were able to detect and measure the effects of relativistic time dilation compared to atomic clocks we left at home. The amazing thing is that the experiment worked! The predicted and measured effect was just over 20 nanoseconds.
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But the time dilation was somewhere in the 20 to 30 ns range. The number we expected was 23 ns so I’m very pleased with the result.

Albert Einstein, Marilyn Monroe Hybrid Image

This image looks like Albert Einstein up close. If you back up maybe 3-5 meters it will look like Marilyn Monroe. Image by Dr. Aude Oliva.

Hybrid images paper by Aude Oliva, MIT; Antonio Torralba, MIT; and Philippe G. Schyns University of Glasgow.

We present hybrid images, a technique that produces static images with two interpretations, which change as a function of viewing distance. Hybrid images are based on the multiscale processing of images by the human visual system and are motivated by masking studies in visual perception. These images can be used to create
compelling displays in which the image appears to change as the viewing distance changes. We show that by taking into account perceptual grouping mechanisms it is possible to build compelling hybrid images with stable percepts at each distance.
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Hybrid images, however, contain two coherent global image interpretations, one of which is of the low spatial frequencies, the other of high spatial frequencies.
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For a given distance of viewing, or a given temporal frequency a particular band of spatial frequency dominates visual processing. Visual analysis of the hybrid image still unfolds from global to local perception, but within the selected frequency band, for a given viewing distance, the observer will perceive the global structure of the hybrid first, and take an additional hundred milliseconds to organize the local information into a coherent percept (organization of blobs if the image is viewed at a far distance, or organization of edges for close viewing).

Very cool stuff.

This is just a smaller image of the above (all I did was shrink the size). For me, this already looks like Marilyn Monroe, but also needs a shorter distance to see the image seem to change.

Friday Fun: Dolphins Play with Air Bubble Rings

Bubbles in water

The bubble is the most stable situation for an amount of gas phase in water (liquid phase). A surface tension is associated with the surface between the gas phase and the liquid phase, the surface tension tends to minimize the surface area. This is also described in the section on bubbles in bubble models. Given a volume of gas, the sphere (bubble) shape is the shape that has the smallest surface area with respect to the containing volume.

The situation of a bubble in water is comparable to a balloon. The balloon surface is elastic. The tension of it tries to minimize the surface: if you don’t tie a knot in the balloon after blowing it up, air escapes and the surface of the balloon is minimized to the initial unstretched situation.
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Bubbles do not turn into rings naturally. Something has to be done for that. However, they have long lives and often make it up to the surface. Hence they are stable structures.
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Dolphins create bubble rings by blowing air in a water vortex ring: by flipping a fin they create a vortex ring of water. The then blow air in the ring, which goes to the center of the vortex ring. In the water vortex ring the natural location of the air is in the center of the vortex. When air and water move in a circular path like they do in the vortex ring, air and water are separated due to the centripetal force. Since density of water is larger than air, water moves at the outside, while the air ends up in the middle.

Follow the link for much more on the physics of bubble rings.

Sun Missing It’s Spots

Image courtesy of SOHO, shows an image of the sun on July 19th 2000 and March 18th 2009.

Sun Oddly Quiet

The sun is the least active it’s been in decades and the dimmest in a hundred years. The lull is causing some scientists to recall the Little Ice Age, an unusual cold spell in Europe and North America, which lasted from about 1300 to 1850. The coldest period of the Little Ice Age, between 1645 and 1715, has been linked to a deep dip in solar storms known as the Maunder Minimum.
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Sunspots, which can be visible without a telescope, are dark regions that indicate intense magnetic activity on the sun’s surface. Such solar storms send bursts of charged particles hurtling toward Earth that can spark auroras, disrupt satellites, and even knock out electrical grids.

European Eels in Crisis After 95% Decline in Last 25 years

Eels in crisis after 95% decline in last 25 years

But the action the Environment Agency is about to take is upsetting those who rely on the eel for their livelihoods. A ban on exporting eels out of Europe – they are a popular dish in the far east – is proposed, along with a plan to severely limit the fishing season and the number of people who will be allowed licences.

It seems pretty obvious we have over-fished the oceans. Without effective regulation we will destroy the future of both the wildlife and our food source.

The eel remains one of the world’s most mysterious creatures. It is generally accepted that European eels – Anguilla anguilla – are born in the Sargasso Sea near Bermuda.

As leaf-like larvae, they are swept by the Gulf Stream towards Europe, a journey that may take a year. When the larvae reach the continental shelf they change into “glass eels” and in the spring begin to move through estuaries and into freshwater.

The animals develop pigmentation, at which point they are known as elvers and are similar in shape to the adult eel. Elvers continue to move upstream and again change colour to become brown or yellow eels.

When the fish reach full maturity – some can live to 40 and grow to 1m long – they migrate back to the ocean. Females are reported to carry as many as 10m eggs. They return to the Sargasso Sea, spawn and die.