DART

 

The Double Asteroid Redirect Test (DART) was NASA's successful test on September 26, 2022 of its plan to defend Earth from an asteroid's on collision course with our planet.

DART spacecraft zeroed in on Dimorphos, Didymos little moon which is 160 m in diameter and at a distance of 6.8 million miles or 11 million kilometers from Earth.  It stroke the little asteroid at a speed of 14,000 miles per hour hoping to divert from its orbit.

A picture of the little asteroid Dimorphos taken 2 min before the impact shows in great detail rocks on its surface.

Images from James Webb telescope showed a vast cloud of dust indicating a much larger force of the impact that it was expected.  The images were similar to those obtained by the Italian Space agency LICIAcube the little craft that separated from DART moments before its impact on Dimorphos.  NASA announced on Oct 11, 2022 DART's mission proved successful in adjusting the trajectory of Dimorphos, suggesting that a deadly space rock could be deflected in the future.  Before DART's impact it took the little asteroid 11 hours and 55 min to orbit its Didymos.  The spacecraft's impact changed the smaller asteroid's orbit by 32 min. 

Oumuamua

On October 19, 2017, astronomers at Hawaii’s PanSTARRS telescope detected an object in the sky that was moving unusually fast and likely had originated from another solar system. As it was the first interstellar object to be detected within our solar system, they named it Oumuamua, the Hawaiian word for a scout or messenger. (Artist depiction in Wikipedia)

An article at Scientific American describes six unusual facts about Oumuamua. The first one being that astronomers didn’t expect such an object to exist but the most unusual fact about it is that it deviates from an orbit that is shaped by the gravitational force of our sun. As the object is moving, in a hyperbolic trajectory, the question arises what gives it the extra acceleration.  As Oumuamua’s acceleration has not been seen with asteroids astronomers wandered whether the object may be an Unidentified Foreign Object sent to our solar system by an alien civilization.

It is known that there are conditions similar to those on Earth in a quarter of all planetary systems around other stars and there are 100 billion stellar systems in our galaxy the Milky Way.  Also 100 billion galaxies exist in the known universe making the existence of other intelligent beings elsewhere likely.  Could other intelligent beings send a scout to observe our solar system?  Future discoveries about the Cosmos will unravel mysteries such as Oumuamua, fast radio bursts, or what happens to space-time inside a black hole.

The pale blue dot

The Earth is a very small dot in a vast cosmos.  Think of the rivers of blood spilled by generals and emperors so that, in triumph, they could become the temporary masters of a fraction of the dot.  There is no better demonstration of our folly than the distant image of our world.  It underscores our responsibility to deal kindly with one another and to preserve out the pale blue dot, the only home we will ever know.  The Earth is where we will make our last stand.  (Picture by NASA, narrative modified from Carl Sagan, 1986)

The Storm

When we completed the passage of the Strait of Bonifacio and entered the Tyrrhenian Sea we were confronted by electric storms that had us surrounded in all four of the horizon’s cardinal points.  Lightning illuminated the night sky between the clouds and the sea in a phantasmagoria of “fireworks”, a stunning and awesome example of nature’s titanic power.  The spectacle was so astonishing that it made us reflect about something “out there,” higher than humans and difficult to comprehend.

The earth is the only known planet with an abundance of liquid water, which covers 70 percent of its surface and gives the planet its blue appearance from space. Earth has been aptly nicknamed the “blue marble”.  Incidentally, NASA recently found and reported evidence of high salinity water on Mars—a discovery that may have major implications regarding the existence of life outside earth.

Sea waves are oscillations caused by the friction of air when it moves across the surface of the water. This friction transfers energy and forms surface waves that are perpendicular to the direction of the wind.  When the wind is from the north, the direction that the waves move is southerly.  In a big body of water like the Tyrrhenian Sea, as depicted in a study from the University of Athens, the waves can be very large, and the longer a northerly wind blows, the larger the waves can become in the southern boundaries at the latitudes of Aeolian Islands and northern coast of Sicily.    

The top of a wave is known as its crest and the foot as its trough. The distance between two crests is the wavelength. The size of ocean waves depends upon the wind speed and the distance over which the wind blows upon the water. The smallest waves are called ripples.  As strong and prolonged winds push against raised crests, though, larger and more irregular waves form, which are known as seas.  When the waves reach shallow waters near the coast they slow down, but their height increases. 

The waves reach their maximum height when the rate at which they are traveling nearly matches the speed of the wind. Over time, they naturally separate into long, powerful waves with a common direction and wavelength. Constructive interference can cause rogue waves with documented heights above 25 meters.  An encounter with rogue waves can have serious or even catastrophic consequences, even on large vessels over 100 meters in length. 

When the wind dies down, seas and swells are slowly reduced by gravity and destructive interference from other waves.

Most waves are less than 3 meters high although it is not unusual for strong storms to double or triple that height especially in open seas.

When I was watching the electric storms, which had us surrounded, I was wondering which one could reach and strike us.  The northern one caught up with us just as the clouds were covering up the stars. The seas were roaring and building up, but since it was pitch-black we could not see the waves’ height. We could feel that we were being propelled by big waves and strong winds, though, and we could hear the “whistling” of the wind’s song produced by the strumming of the shrouds.  The anemometer at the top of the mast was recording wind velocities of 30-35 knots and gusts of 40-50 knots, so our captain Nikos decided it was time to reduce canvas.  With Kostas, our youngest sailor, doing the heavy lifting in front, and me in the middle handling the lines, we quickly double reefed the main and hoisted a storm jib in front—actions that kept the boat well balanced.  The experience during the night was frightening and made us feel vulnerable, especially when we realized the waves’ size at sunrise.  Riding the waves and occasionally achieving speeds up to 12 knots, due to planning, the fright turned into exhilaration and eventually changed into a peaceful state that was beyond our understanding.  It was at this moment that our desire to continue became paramount not because of an innate desire to experience more thrills but because of our longing to reach “Ithaca,” where loved ones were eagerly waiting for our return.