Leonardo da Vinci

Self portrait at about age 60.

Even though Leonardo da Vinci is primarily thought of as a painter, he made many contributions to science. His greatest talent was in accurately observing and recording the world around him and most of his surviving work is mechanical, anatomical and architectural drawings and manuscripts. His main concern was always how things worked and he used his eyes to see how things were made and then record them in such a way as to make it clear as to how they functioned. For da Vinci, art was a tool for discovery and invention, whether it was to detail how the human hand works or to create a prototype of an airplane or helicopter.

  Leonardo spent much time in Florence where he dissected bodies in the St. Maria Nuova hospital, recording the position and shape of organs as well as trying to figure out what they did by analyzing their structure. During his lifetime he worked on 30 bodies.

Leonardo da Vinci's design for an aerial screw.

  He was also fascinated with the flight of birds and how humans could fly, drawing several human-powered flying machines. He saw air as a medium with properties similar to water, such as current. His drawings of pumps and screws show that he understood how these machines could interact with a fluid. Leonardo’s design of a helicopter was based on a screw that would propel itself upward through the air. 

  Leonardo was also the first to explain why there is a ghostly image of the full Moon whenever there’s a crescent Moon on the horizon at sunset. Astronomers call it Earthshine and Leonardo correctly attributed it to our own planet reflecting light back to us from the Moon. Yet Da Vinci’s legacy goes beyond his drawings and discoveries. He showed that inquisitiveness together with observation can reveal how things work, and how that information could be used in the creation of buildings, machines or inventions.

1) True or false: Da Vinci had a good understanding of fluid dynamics.

2) Most of Leonardo da Vinci’s surviving work is of ___________________________.

a) paintings  b) sculptures  c) drawings and manuscripts  d) inventions

3) True or false: Leonardo dissected a few bodies to further his understanding of anatomy.

4) Many of Leonardo’s inventions were ______________________.

a) motor-driven flying machines  b) based on observations in nature  c) easily constructed at the time  d) all of the above

5) Reflected light from Earth that is visible on the Moon’s night side is called __________.



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Lunar Blues

As I write this tonight, mother nature is taunting me. Overhead there is a total lunar eclipse in progress and I’m missing it because it’s completely overcast and raining. Such is life. Lunar eclipses are fairly common, happening a couple times a year on average. But this one is different. It just so happens that this morning, December 21, is the beginning of winter solstice. A pure coincidence, but it means that the Moon will be at its maximum height in the sky to provide superb viewing of the eclipse. The last time that happened was in 1638.

The stages of a total lunar eclipse.

  A lunar eclipse occurs when the Earth passes directly between the Sun and Moon, blocking the Sun’s light and casting a shadow on the Moon. Because the Moon is opposite the Sun, the Moon will always be full the night of a lunar eclipse. As the Moon progresses into the Earth’s shadow, it changes color from gray to orange or even red. This is because even though the Moon is in shadow, sunlight can still reach it indirectly by refracting through Earth’s atmosphere. Since our atmosphere filters out blue-colored light (that’s why the sky is blue), only light from the red/orange portion of the spectrum passes through and actually makes it to the Moon and this light is what we see during a total lunar eclipse. If the atmosphere has more particles in it, say from recent volcanic activity, for example, the Moon will take on a deeper shade of red.

  Eclipses are said to be either umbral or penumbral. The word “umbra” is from the Latin word for “shadow” and this is what we call a total eclipse. Penumbra is Latin for “almost shadow” and this refers to a partial eclipse. The next opportunity we will have to see a total lunar eclipse here in the U.S. will coincide with a somewhat more dubious date—Tax Day—April 15, 2014.

1) True or false: A lunar eclipse occurs when the Moon passes between the Earth and the Sun.

2) During a total lunar eclipse the moon will ________________.

a) disappear  b) turn orange  c) turn blue  d) cast its shadow on the Earth.

3) True or false: The moon will appear redder if there has been recent volcanic activity.

4) Regarding winter solstice, which of the following is not true?

a) It occurs when the Earth’s axis is tilted farthest away from the sun.  b) It signifies the first day of winter in the U.S.  c) It occurs on the shortest day  and longest night  d) It occurs when the Earth is farthest from the Sun.

5) Umbra is Latin for ________.



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From Osmium to Aerogel

A 2.5 kg brick sits on top of a piece of aerogel weighing 

only 2 grams. Photo courtesy of NASA/JPL.

Density is the amount of mass per unit volume of a substance. The Greek mathematician and scientist Archimedes is credited with using the concept of density to determine whether or not a crown made for King Hiero was made of pure gold. Legend has it that the king thought his goldsmith was cheating him by substituting silver for some of the gold he was given to make the crown, so he asked Archimedes to test the crown without destroying it. Archimedes was stumped until one day when getting into his bath he caused the water to overflow. He realized that he could put a weight of pure gold equal to the weight of the crown into a bowl and add water until it was filled to the brim. Then when he removed the gold and put the crown in it would make the water overflow if it contained silver because silver is not as dense and therefore it would take up more volume. It’s said that upon this discovery, Archimedes ran through the street naked shouting “Eureka!” which means “I found it!” in Greek. No word on what happened to the goldsmith.

  Osmium is the densest naturally-occurring element, being twice as dense as lead. In nature, osmium is found alloyed with platinum. Alloys of osmium and platinum are used where hardness and durability is needed such as electrical contacts or in the tips of fountain pens. The least-dense metal, lithium, is so light that it floats in water. But the record for the lightest solid is held by Aerogel which weighs only three mg per cubic centimeter, or about one tenth the density of the lightest Styrofoam! 

  Manufactured by JPL in Pasadena, California, it’s nearly transparent with a blue cast and is surprisingly sturdy. It’s made of pure silica but is 99.8% porous. It makes an excellent insulator—almost 40 times better than fiberglass. Aerogel was used on NASA’s Stardust Mission that returned to Earth in 2006 after a flyby with a comet. Its purpose was to collect dust particles for analysis back on Earth. These dust particles travel so fast that they would penetrate most solids and be vaporized—yet when the collide with Aerogel they  are buried in the material and come to a relatively gradual stop so that they can be collected.

1) True of false: An alloy of gold and silver is less dense than pure gold.

2) The least-dense metal is __________________.

a) aluminum  b) lithium  c) silver  d) Aerogel

3) True or false: Osmium is twice as dense as gold.

4) Which of the following is not true about Aerogel?

a) Aerogel is man-made  b) Aerogel is very delicate c) Aerogel is lighter than Styrofoam by an order of magnitude  d) Aerogel was made for NASA.

5) Archimedes shouted ___________ upon solving the puzzle of the king’s crown.


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Exoplanets

Three exoplanets orbiting HR8799, a star 120 light-years

away, photographed using the Palomar Observatory’s

Hale Telescope. The light from HR8799 has been
masked with the aid of a coronagraph.

We’re all familiar with the eight planets in our solar system, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, but did you know that since 1992 there have been hundreds of planets discovered outside our solar system? And that number is rapidly increasing with thousands of new planets waiting to be confirmed. Planets outside our solar system are called exoplanets. 

   Recent advances in telescope technology allow exoplanets to be seen directly, but it helps if the planet is very large, even larger than Jupiter, for example, and far from the star that it orbits so that it’s not lost in the glare. A relatively hot exoplanet that gives off infrared radiation is also easier to detect.
   In 2010, three exoplanets orbiting HR8799, a star 120 light-years away, were photographed using a portion of the Palomar Observatory’s Hale Telescope. This was the first time exoplanets were photographed using a relatively small telescope by attaching a coronagraph to it. A coronagraph blocks out the direct light from a star so that nearby objects—which would otherwise be hidden by the star’s glare—can be seen. The three planets are thought to be gas giants like Jupiter, but more massive.
   Most exoplanets, however, are indirectly detected. One method is measuring minute variations in a star’s velocity due to the gravitational tug a planet has on it. Exoplanets that orbit pulsars can be indirectly detected by measuring tiny changes in the pulses of radio waves that are emitted. This is how the first exoplanet was discovered.

Liftoff of NASA’s Kepler Spacecraft 

aboard a Delta II Rocket.

   Astronomers can also detect planets by observing a drop in a star’s brightness as a planet crosses directly in front of it. In 2009 NASA launched the Kepler Mission in an attempt to discover Earth-like planets using this method. Kepler’s space telescope will continuously monitor 145,000 stars looking for periodic changes in brightness that would indicate an exoplanet moving across the face of the star. Kepler’s goal is to find an Earth twin—similar in size and distance from its star so that water could exist in liquid form on its surface—thought to be essential for the formation of life. James Fanson, Kepler Project Manager at JPL in Pasadena, had this to say of the Kepler Mission: “Our team is thrilled to be a part of something so meaningful to the human race—Kepler will help us understand if our Earth is unique or if others like it are out there.”