Mario Livio

Mario Livio is an astrophysicist and an author of popular science books. His research interests range from extrasolar planets to supernova explosions and cosmology.

Mar 312015
 

On April 24th, the Hubble Space Telescope will celebrate 25 years since its launch. This provides an excellent opportunity to very briefly summarize what I regard as Hubble’s greatest scientific achievements.  I should emphasize two things: (1) I have used my personal judgment (and biases) in creating this list; other scientists may have different opinions. (2) I do not claim that these are all exclusive Hubble discoveries.  By its very nature as an all-purpose telescope, in most cases Hubble helped cement existing suggestions, rather than making singular discoveries. Nevertheless, in all the topics listed below, Hubble’s contribution has been crucial.

Figure 1.  Distant supernova explosions.

Figure 1. Distant supernova explosions.

What do I personally regard as Hubble’s “Top 6” scientific achievements?  Here is my list:

(1) The discovery that not only is the expansion of our universe not slowing down, it is accelerating!  These findings, made through monitoring distant stellar explosions (called Type Ia supernovae: Figure 1), have led (in combination with other measurements) to the realization that a mysterious form of “dark energy” constitutes about 70% of the cosmic energy budget.

(2) The mapping of the large-scale, three-dimensional distribution of “dark matter”—matter that neither emits nor absorbs light, but which forms the scaffolding on which the cosmic structure is constructed.

Figure 2. The Hubble Ultra-Deep Field 2014. Credit: NASA, ESA, H.Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (ASU), Z. Levay (STScI).

Figure 2. The Hubble Ultra-Deep Field 2014. Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (ASU), Z. Levay (STScI).

(3) The determination of the history of the cosmic star-formation rate.  This achievement came through a series of deep observations of the universe (Figure 2 shows the “Hubble Ultra-Deep Field 2014”).

(4) The determination of the Hubble constant—the current rate of cosmic expansion.  The uncertainty in the value of this important cosmological parameter has been reduced from a factor of two, to about 3%.

Figure 3. The optical jet from the center of the galaxy M87. Credit: NASA and the Hubble Heritage Team (STScI/AURA).

Figure 3. The optical jet from the center of the galaxy M87. Credit: NASA and the Hubble Heritage Team (STScI/AURA).

(5) The discovery that supermassive black holes reside at the centers of most galaxies, and that the masses of the black holes are tightly correlated with the masses of the stellar bulges that surround them (thus demonstrating that galaxies and their central black holes evolve in tandem). Figure 3 shows the jet emanating from the accretion disk surrounding the central black hole in the galaxy M87.

(6) The determination of the make-up of the atmospheres of a few extrasolar giant planets. Through exquisite observations of transiting exoplanets when they eclipse their host star, Hubble discovered that the atmospheres of a few such objects contain sodium, hydrogen, carbon, and even water.

Given these spectacular achievements, I cannot wait to see what else Hubble has in store for us in the next five (or possibly more) years.  Moreover, we are looking forward to a potentially even more exciting list, to come after Hubble’s successor—the James Webb Space Telescope—is launched (planned for 2018).

Mar 102015
 

The Golden Ratio, that curious never-ending, never-repeating number 1.61803398875… has an uncanny tendency to pop up where it is least expected (see my previous piece “The Golden Ratio and Astronomy”).  Consequently, I cannot say that I was extremely surprised when a recent study of four pulsating stars observed by the Kepler telescope found them to have frequencies with a ratio very close to the Golden Ratio.  Still, while there are many known pulsating stars of the same type (known as RR Lyrae variables; Figure 1, shows a spectacular Hubble image of the Cepheid variable RS Puppis), none until now were found to pulsate in what physicists call a “strange non-chaotic” manner.  Basically, as the variable star expands and contracts, its brightness increases and decreases at a certain frequency.  What researchers John Linder, Vivek Kohar, Behnan Kia, Michael Kippke, John Learned and William Ditto found, was that four stars observed by Kepler exhibited a fractal pattern—a behavior that repeated on smaller and smaller scales.  The structure was still “non-chaotic,” meaning that unlike the weather, it exhibited a certain order.  These were precisely the same four stars (and in particular the star KIC 5520878) in which the ratio of the primary frequency to the secondary one was near the Golden Ratio.  This was, by the way, the first time that such a fractal, non-chaotic pattern was observed outside the laboratory (Figure 2 shows a reconstructive representation of the data time series).

Figure 1.  The Cepheid variable RS Puppis.   Credit:  NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration.

Figure 1. The Cepheid variable RS Puppis. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration.

Figure 2.  A reconstructive representation of the time series data (left, from Kepler Space Telescope data) and corresponding phenomenological model (right), showing fractal behavior. Reproduced with permission from William Ditto.

Figure 2. A reconstructive representation of the time series data (left, from Kepler Space Telescope data) and corresponding phenomenological model (right), showing fractal behavior. Reproduced with permission from William Ditto.

 

 

 

 

 

 

 

 

 

At the moment, the precise implications of these findings are not yet clear.  The hope is that through studying more “Golden” variable stars, the team will gain further insights into the physical processes involved in stellar pulsations.

The Golden Ratio has also recently shown up in a completely unrelated investigation—one that resulted in the discovery of a beautiful curve.  Edmund Harriss, a University of Arkansas mathematician, started with a similar process to one that produces a “Golden spiral.”  If you take a Golden rectangle—one in which the ratio of the length to the width is equal to the Golden Ratio—and draw a square in it, the remaining rectangle is also a Golden rectangle (Figure 3). If you continue this way and then connect the dividing points, you get a Golden spiral (Figure 3).

Figure 4.  A rectangle with length to width ratio of about 1.325 creates two similar rectangles and a square. Reproduced with permission from Edmund Harriss.

Figure 4. A rectangle with length to width ratio of about 1.325 creates two similar rectangles and a square. Reproduced with permission from Edmund Harriss.

Figure 3. The construction of a Golden spiral from a Golden rectangle. Credit: Jeffrey L. Ward.

Figure 3. The construction of a Golden spiral from a Golden rectangle. Credit: Jeffrey L. Ward.

Inspired by this process, Harriss started with a rectangle from which, rather than cutting a square, he cut a rectangle.  He found that the original rectangle has a length-to-width ratio of 1.32472… which he could cut in such a way that the blue and orange rectangles are in the same proportion as the large rectangle (Figure 4).  Continuing in this way (the entire process is described here), Harriss eventually discovered the “Harriss spiral” (Figure 5)—a delightful new curve.  Besides the aesthetic properties of the new spiral, Harriss hopes that this type of geometrical investigation will lead to new insights in the field of “algebraic numbers”—solutions to simple algebraic equations.

Figure 5.  The Harriss spiral. Reproduced with permission from Edmund Harriss.

Figure 5. The Harriss spiral. Reproduced with permission from Edmund Harriss.

I cannot wait to see where the Golden Ratio will appear next.

 

Feb 172015
 
Figure 1.  Darwin at old age. Reproduced by kind permission of the Syndics of Cambridge University Library.

Figure 1. Darwin at old age. Reproduced by kind permission of the Syndics of Cambridge University Library.

On February 12th, we celebrated Charles Darwin’s 206th birthday (Figure 1 shows Darwin late in life). This calls for at least a brief essay, to remind ourselves of Darwin’s remarkable achievement.

Evolutionary biologist Ernst Mayr wrote once that Darwin’s theory of evolution “caused a greater upheaval in man’s thinking than any other scientific advance since the rebirth of science in the Renaissance.”

Indeed, together with the Copernican revolution, the Darwinian revolution basically demolished the human anthropocentric view of the universe. The impact of the Darwinian revolution was and still is felt far beyond the boundaries of science.

But Darwin’s theory did much more than that. By boldly stating that species are not eternal and immutable, Darwin introduced the concept of an evolving, rather than a static world. This fundamental idea was later expanded, and its adoption encompasses everything from the Earth, to the stars, to galaxies, and to the universe as a whole. Even though the laws of nature (as far as we can tell) stay unchanged, everything within the cosmos is evolving.

Another major consequence of the new Darwinian perspective has been the complete denial of any cosmic teleology. Evolution by natural selection has no long-term “strategic plan” or ultimate goal. Rather than striving toward some perfection, natural selection simply tinkers by elimination of the individuals with characteristics that are less adapted to the particular conditions of their environment.

If not for the fact that Darwin’s theory had meaningful implications for the nature and status of humans, I doubt that his theory would have caused quite the same outcry.

In fact, Darwin himself chose to dodge the issue of humans in the first edition of On the Origin of Species, by only cryptically hinting that “In the distant future… Light will be thrown on the origin of man and his history.”  Only in his later book, The Descent of Man, did Darwin explicitly explain that humans are nothing special, but just another product of a continuous evolution. The seeds of this idea, however, had already been planted in On the Origin of Species: “Probably all the organic beings which have ever lived on the earth have descended from some one primordial form.”

The history of science since Darwin has shown us time and again that from a purely physical perspective, humans are but tiny specks of dust in the grand universal scheme.  Even the stuff we’re made of—ordinary (baryonic) matter—constitutes less than five percent of the cosmic energy budget.

Darwin beautifully reminded us to be humble at the end of The Origin: 

We must, however, acknowledge, as it seems to me, that man with all of his noble qualities, which sympathy which feels for the most debased, with benevolence which extends not only to other man but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system—with all these exalted powers—Man still bears in his bodily frame the indelible stamp of his lowly origin.”

Feb 032015
 

Stephen Hawking famously warned in 2010 that based on the history of humankind, an alien, more advanced, civilization would probably destroy us.  “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet,” he said.  Hawking expressed a similar fear of advanced artificial intelligence (AI) machines.  In 2014 he pronounced: “The development of full artificial intelligence could spell the end of the human race.”  Taken seriously, these two statements could even imply that we should neither search for extrasolar advanced civilizations, nor strive for superior AI machines.

I was contemplating these issues when I received the annual EDGE question from the “intellectual impresario” John Brockman.  Every year, Brockman sends to about two hundred thinkers a single question, and he posts all the answers on his website, edge.org.  The question for 2015 was: “What Do You Think about Machines that Think?” (see: http://edge.org/annual-question/what-do-you-think-about-machines-that-think).  Below is the answer I gave. I strongly recommend reading all the answers, since they are quite fascinating.

Nature has already created machines that think here on Earth—humans.  Similarly, Nature could also create machines that think on extrasolar planets that are in the so-called Habitable Zone around their parent stars (the region that allows for the existence of liquid water on a rocky planet’s surface).

The most recent observations of extrasolar planets have shown that a few tenths of all the stars in our Milky Way galaxy host roughly Earth-size planets in their habitable zones.  Consequently, if life on exoplanets is not extremely uncommon, we could discover some form of extrasolar life within about 30 years. In fact, if life is ubiquitous, we could get lucky and discover life even within the next ten years, through a combination of observations by the Transiting Exoplanet Survey Satellite (TESS; to be launched in 2017) and the James Webb Space Telescope (JWST; to be launched in 2018).

However, one may argue, primitive life forms are not machines that think. On Earth, it took about 3.5 billion years from the emergence of life to the appearance of Homo sapiens.  Are the extrasolar planets old enough to have developed intelligent life?  In principle, they definitely are.  In the Milky Way, about half of the Sun-like stars are older than the Sun.  Therefore, if the evolution of life on Earth is not entirely atypical, the Galaxy may already be teeming with places in which there are “machines” that are even more advanced than us, perhaps by as much as a few billion years!

Figure 1.  The regions in the human brain that “light up” when we are curious.  Credit: Victor Aguilar.

Figure 1. The regions in the human brain that “light up” when we are curious. Credit: Victor Aguilar.

Can we, and should we, try to find them?

I personally believe that we almost have no freedom to make those decisions.  Human curiosity (Figure 1) has proven time and again to be an unstoppable drive, and those two endeavors will undoubtedly continue at full speed. Which one will get to its target first? To even attempt to address this question, we have to note that there is one important difference between the search for extraterrestrial intelligent civilizations and the development of AI machines.

Progress towards the “singularity” (AI matching or surpassing humans) will almost certainly take place, since the development of advanced AI has the promise of producing (at least at some point) enormous profits.  On the other hand, the search for life requires funding at a level that usually can only be provided by large national space agencies, with no immediate prospects for profits in sight. This may give an advantage to the construction of thinking machines over the search for advanced civilizations. At the same time, however, there is a strong sense within the astronomical community that finding life of some form (or at least meaningfully constraining the probability of its existence) is definitely within reach.

Which of the two potential achievements (the discovery of extraterrestrial intelligent life or the development of human-matching thinking machines) will constitute a bigger “revolution”?

There is no doubt that thinking machines will have an immediate impact on our lives. Such may not be the case with the discovery of extrasolar life. However, the existence of an intelligent civilization on Earth remains humanity’s last bastion for being special. We live, after all, in a Galaxy with billions of similar planets and an observable universe with hundreds of billions of similar galaxies. From a philosophical perspective, therefore, I believe that finding extrasolar intelligent life (or the demonstration that it is exceedingly rare) will rival the Copernican and Darwinian revolutions combined.

Jan 202015
 
Figure 1.  “Perseus and Andromeda” by Lord Frederic Leighton. Walker Art Gallery, Liverpool. At Google Cultural Institute.

Figure 1. “Perseus and Andromeda” by Lord Frederic Leighton. Walker Art Gallery, Liverpool. At Google Cultural Institute.

Figure 2.  Illustration of the expected collision between the Milky Way and the Andromeda galaxy.  (http://hubblesite.org/newscenter/archive/releases/2012/20/image/a/format/web_print/).

Figure 2. Illustration of the expected collision between the Milky Way and the Andromeda galaxy. (http://hubblesite.org/newscenter/archive/releases/2012/20/image/a/format/web_print/).

In Greek mythology, Andromeda, the daughter of Cepheus and Cassiopeia, was stripped and chained to a rock, only to be saved from certain death in the claws of a sea monster by Perseus (Figure 1 shows a wonderful depiction of the myth by Lord Frederic Leighton).

In the northern sky, a constellation is named Andromeda, and it contains the galaxy M31 (so cataloged by astronomer Charles Messier on August 3rd, 1764), commonly known as the Andromeda galaxy.  At a distance of 2.5 million light years, the Andromeda galaxy is next door in astronomical terms. Its mass is only about twice that of the Milky Way, making the two galaxies if not quite twins, then close sisters.

By measuring very precisely the motion of Andromeda relative to the Milky Way, astronomers using the Hubble Space Telescope were able to determine in 2012 that the Milky Way and Andromeda are destined for a head-on collision in about 4 billion years. About two billion years later, the two sister spiral galaxies will completely merge, most probably producing an elliptical galaxy. While solar system will not be destroyed during the collision, it is very likely that it will be flung into a new region of the merged galaxy.

Figure 2 is a photo illustration of what the night sky may look like as the two galaxies will be on their way to that fateful encounter. This view was inspired by detailed computer modeling of the future collision.

Recently, astronomers combined data from two large surveys to discover that, like its mythological namesake, Andromeda has experienced a rather violent history. One of the surveys (SPLASH) used the Keck telescope to measure the radial (in our direction) velocities of more than 10,000 stars. The other survey (the Panchromatic Hubble Andromeda Treasury; PHAT) used the sharp vision of the Hubble Space Telescope to produce an unprecedented, high-definition image of a part of Andromeda (see Figure 3 and the
Zoom into M31 video on the web page of STScI News Release Number: STScI-2015-02).

Figure 3.  A high-definition panoramic view of a part of the Andromeda galaxy. A product of the Panchromatic Hubble Andromeda Treasury (PHAT) program.  (Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson [University of Washington], the PHAT team, and R. Gendler; http://hubblesite.org/newscenter/archive/releases/2015/02/image/a/format/ xlarge_web/.)

Figure 3. A high-definition panoramic view of a part of the Andromeda galaxy. A product of the Panchromatic Hubble Andromeda Treasury (PHAT) program. (Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson [University of Washington], the PHAT team, and R. Gendler; http://hubblesite.org/newscenter/archive/releases/2015/02/image/a/format/ xlarge_web/.)

The two sets of observations revealed an intriguing distinction between young and old stars in Andromeda. While we normally associate youth with rebellion, and old age with discipline, the youngest stars were found to rotate in an orderly fashion around Andromeda’s center, while the older stars displayed a less ordered, more chaotic motion.

Possible explanations for these observations include a series of past bombardments of Andromeda by a number of smaller satellite galaxies, and an evolution of Andromeda’s disk from a more puffed-up configuration to a thinner one. Either way, it appears that our sister galaxy may have had a rougher past than the Milky Way. This fascinating object is just about the most distant thing we can see in the night’s sky with the naked eye.

Jan 082015
 

It is very rare that a scientific experiment not only continues to be generally productive, but to yield cutting-edge results for 25 years. Yet, this is precisely what is happening with the Hubble Space Telescope. This, by now legendary telescope, is entering its 25th year of operation in 2015. Through the creative work of many scientists and engineers, and five imaginative servicing missions by daring shuttle astronauts, Hubble has been repeatedly rejuvenated, and its results never cease to amaze.

As part of the 25th anniversary celebrations, astronomers used Hubble with its current complement of instruments, to re-observe with a higher resolution a target that had produced one of Hubble’s most iconic images—the Eagle Nebula, dubbed the “Pillars of Creation.”

The original image was created in 1995 from observations by astronomers Jeff Hester and Paul Scowen, then at Arizona State University. That image was taken by Hubble’s Wide Field Planetary Camera 2 (WFPC2).

The new images were taken in visible light (Figure 1) and near-infrared light (Figure 2) by the more advanced Wide Field Camera 3 (WFC3). They give a fresh, sharper, more detail-rich view of these magnificent pillars of gas and dust.

Figure 1.  Hubble image of the Eagle Nebula in visible light.  Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

Figure 1. Hubble image of the Eagle Nebula in visible light. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

Figure 2. Hubble image of the Eagle Nebula in near-infrared light. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

Figure 2. Hubble image of the Eagle Nebula in near-infrared light. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

 

 

 

 

 

 

 

 

 

 

In this case, however, the images represent much more than their purely scientific value.

They showcase the longevity and impact of a telescope that has become a household name. A telescope that has brought the excitement of scientific discovery into the homes of billions of people around the globe. A telescope that has transformed many of our theories and speculations about the universe into hard scientific fact.

The new images of the Eagle Nebula demonstrate that Hubble is far from being done. We hope that its discoveries will continue to fascinate us for many years to come, and that its operation will overlap (for at least a few years) with its great upcoming successor—the James Webb Space Telescope (to be launched in 2018).

Dec 092014
 

Dark matter continues to live up to its name. The most recent results from the European Space Agency’s Planck spacecraft appear to cast serious doubt on previous claims of potential detections of the elusive dark matter particles.

For decades, astronomers have found what appears to be compelling evidence for the existence of matter that does not emit any light, but whose gravitational pull is responsible for holding cosmic structures together.  In fact, dark matter far outweighs ordinary matter—the stuff of which galaxies, stars, planets, and humans are made of—in its contribution to the universe’s energy budget.  Yet, all attempts to actually detect the particles that constitute dark matter have so far failed (see a concise recent review at: http://www.nature.com/news/physics-broaden-the-search-for-dark-matter-1.14795).

There have been, however, a few promising signs in the form of an unexpected positron anomaly—an excess in the number of the positively charged anti-particles of the electrons.  The excess was detected by the Alpha Magnetic Spectrometer (AMS)—an experiment on board the International Space Station.  Last year, this experiment reported that in analyzing cosmic rays, contrary to expectations, the ratio of positrons to electrons increased with increasing energy of the particles.  This finding was consistent with previous results from the European Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) and NASA’s Fermi Gamma-ray Space Telescope.  The suggestion was that the excess positrons could be created when dark matter particles and anti-particles annihilate each other.  Not surprisingly, given the long history of non-detections, the AMS and Fermi results generated headlines such as “Dark Matter Possibly Found” and “Fermi data tantalize with new clues to dark matter.”

Unfortunately, while confirming that about 26% of the cosmic energy budget appears to be in the form of dark matter, the new Planck results appear to negate the possibility that the AMS/Fermi/ PAMELA excess positrons have been produced by dark matter annihilations.

Basically, if annihilations of dark matter particles were to occur in the early universe, they would have produced energy that in turn would have increased the fraction of ionized atoms.  By measuring the temperature fluctuations and the polarization (the difference in the amplitude of vibrations in different directions) of the cosmic microwave background, the Planck team was looking for imprints of this increased ionization fraction.  What they found instead was that if the probability for annihilation did not change with time, then the mass of the dark matter particles and the probability of annihilation that would have been required to explain the positron excess were excluded by Planck.

Figure 1 shows the probability of annihilation (“cross section” in the professional jargon) as a function of the mass of the (putative) dark matter particles.  The blue region is excluded by Planck.  The AMS/Fermi/PAMELA results fall in this region.  In other words, we are still left in the dark with respect to the identity of dark matter particles.

Figure 1. The probability for dark matter annihilation as a function of the mass of dark matter particles. The blue region shows the region excluded by Planck. The AMS/Fermi/PAMELA results fall in the excluded region.  Credit: ESA – The Planck collaboration.

Figure 1. The probability for dark matter annihilation as a function of the mass of dark matter particles. The blue region shows the region excluded by Planck. The AMS/Fermi/ PAMELA results fall in the excluded region. Credit: ESA – The Planck collaboration.

Nov 202014
 
Figure 1.  The five-pointed star, a pentagram.

Figure 1. The five-pointed star, a pentagram.

Humans have been fascinated by stars—those luminous points of light embedded in the night’s darkness—for millennia.  Long before any understanding of their scientific significance emerged, the stars’ association with the heavens has turned them into symbols of the warfare between light, or spirit, and darkness, or material forces.  The five-pointed star (the pentagram) in particular (Figure 1), with its symbolic representation of the twinkling of stars, has become an icon of the human microcosm.

When did the five-pointed star first appear?  And what has transformed it into such a popular symbol?  While we cannot be certain about the answers to these questions, some of the examples of historical facts are truly fascinating.  In particular, the relation between the pentagram and the celebrated “Golden Ratio,” has motivated a number of historians of mathematics to investigate the topic quite thoroughly.

A pentagram appears on a jar dated to 3100 BCE, found north of Thebes in Egypt.  The incision appears to have been done in one continuous motion, and the fact that such a feat can be easily achieved for the five-pointed star may have been one of the initial sources of attraction of this figure.  As an Egyptian hieroglyph, a pentagram enclosed in a circle meant the netherworld—the underworld of the dead.

Interestingly, pentagrams from the same period were found in Mesopotamia.  Those included a five-pointed star on a tablet from Uruk, dated to about 3200 BCE; a design on a vase dated to 3000 BCE from Jemdet Nasr; and another design in spindle whorl from the same time, also from Jemdet Nasr.

In Sumarian and Akkadian cuneiform texts, the meaning of the five-pointed star was the “regions of the inhabited world.”  Thus, we can find it in sentences such as: “which are not the regions warmed by the brightness of your light.”

Figure 2.  A sketch of the flint scraper from Tell Esdar in the Israeli Negev desert, depicting a pentagram.

Figure 2. A sketch of the flint scraper from Tell Esdar in the Israeli Negev desert, depicting a pentagram.

At Tell Esdar, in the Israeli Negev desert, archaeologists found a flint scraper with a pentagram (Figure 2), dated to the Chalcolithic period (4500–3100 BCE). This again appears to be a rapidly executed graffiti figure.

Figure 3.  A speculative association between the pentagram and Hygeia, the Greek goddess of health, was suggested in 1934 by historian A. de la Fuÿe.

Figure 3. A speculative association between the pentagram and Hygeia, the Greek goddess of health, was suggested in 1934 by historian A. de la Fuÿe.

The group of people that truly elevated the five-pointed star to the status of a more universal symbol was composed of the followers of the Greek mathematician Pythagoras.  Through Aristotle we learned that they “applied themselves to mathematics, and were the first to develop this science; and through studying it they came to believe that its principles are the principles of everything.”  Even though the Pythagoreans had a rather mystic understanding of reality, there is no doubt that we can see here the roots of mathematical modeling of the universe and its workings.  The second century rhetorician Lucian tells us that the pentagram “was a recognition-symbol amongst the Pythagoreans, and they used it in their letters.”  He also adds that: “Indeed the pentagram, the triple intersecting triangle which they used as a symbol of their sect, they called ‘Health.’”  Why did they choose the pentagram, and what is its relation to health?  Historian A. de la Fuÿe speculated that the pentagram could have originally been an anthropomorphic symbol of Hygeia, the Greek goddess of health (Figure 3).  While the connection appears tenuous, it shows the level of interest that the five-pointed star has generated over the years.

To conclude, the allure of the heavens has combined with mathematics and historical mythology to produce one of the most common symbols of modern times.  Five-pointed stars appear today on the flags of no fewer than sixty nations, and on innumerable commercial logos.  They represent authority (as in “five-star” generals) and excellence (as in “five-star” hotels).  Our understanding of the processes that make real stars shine has not taken anything away from the attraction of the five-pointed star.  Interestingly, telescope images of real stars usually show spikes. Those are not intrinsic to the stars, but rather are created by diffraction effects within the telescope’s optics. For Hubble, for instance, as for many other telescopes, there are four spikes, but in the case of the upcoming James Webb Space Telescope there will be six.

Nov 042014
 

This past week we had a sad and harsh reminder that when it comes to space exploration, no undertaking can be considered “ordinary,” and success is never guaranteed.

On Friday, Virgin Galactic’s SpaceShip Two exploded in California’s Mojave Desert, killing one pilot and badly injuring a second one (Figure 1).  This was apparently the result of a device intended to slow down the spaceship, operating too soon.

Figure 1.  The explosion of Virgin Galactic’s SpaceShip Two shortly after separation from its carrier spacecraft.  Credit: AP.

Figure 1. The explosion of Virgin Galactic’s SpaceShip Two shortly after separation from its carrier spacecraft. Credit: AP.

Figure 2.  The explosion of the Antares supply rocket.  Credit: Brad Scriber, National Geographic.

Figure 2. The explosion of the Antares supply rocket. Credit: Brad Scriber, National Geographic.

Earlier in the week, on Tuesday, the unmanned supply rocket Antares of Orbital Sciences Corporation, was exploded shortly after its launch from NASA’s Wallops Flight Facility in Virginia (Figure 2).  This rocket was carrying cargo to the International Space Station, but when a serious problem developed, it was intentionally detonated prior to impacting the ground.

We should also remember that of the total of 135 Space Shuttle flights, two ended in major tragedies—with the loss of lives of fourteen astronauts and of Space Shuttles Challenger and Columbia.  In addition, a number of shuttle missions, such as STS-2, STS-44, and STS-83, were cut short because of equipment failure.

There is essentially no stage in a space mission that does not involve considerable risks.  Both the U.S. and Russia have experienced great disasters, even in training and pre-launch activities.  Then there are the known dangers of liftoff, re-entry, and landing.  Yet, all of these hazards and uncertainties have neither extinguished nor even diminished human curiosity and the urge to explore.  In some cases, such as the Apollo 13 mission and the first servicing mission to the Hubble Space Telescope, malfunctions became the source of ingenuity for scientists and engineers, and the impetus for heroic acts by the astronauts.  Similarly, the successful landing of the “Curiosity” rover on Mars, following the famous “Seven Minutes of Terror,” has by now become an origin of inspiration for many space missions.

While the potential for various mechanical and electronic failures is always on the mind of everyone involved with large and ambitious space endeavors, such as the upcoming James Webb Space Telescope, these are always treated as challenges that need to be overcome, rather than as deterrents.  In this sense, I believe that all the scientists, engineers, and astronauts involved in space science and inquiry, fully subscribe to the famous words of President John F. Kennedy when he described the goals for the space effort on September 12, 1962:

The hazards are hostile to us all.  Its conquest deserves the best of all mankind, and its opportunity for peaceful cooperation may never come again… We choose to go to the Moon… and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win.”

Oct 222014
 
Figure 1.  “Newton” by William Blake. Original is in the collection of Tate Britain. The image is in the Public Domain (http://en.wikipedia.org/wiki/Newton_(Blake)#mediaviewer/File:Newton-WilliamBlake.jpg).

Figure 1. “Newton” by William Blake. Original is in the collection of Tate Britain. The image is in the Public Domain (http://en.wikipedia.org/ wiki/Newton_(Blake)#mediaviewer/File:Newton-WilliamBlake.jpg).

Figure 2.  “The Ancient of Days” by William Blake. Originally published in 1794, as a frontispiece to “Europe a Prophecy.”  Image is in the Public Domain(https://en.wikipedia.org/wiki/The_Ancient_of_Days#mediaviewer/File:Europe_a_Prophecy_copy_K_plate_01.jpg).

Figure 2. “The Ancient of Days” by William Blake. Originally published in 1794, as a frontispiece to “Europe a Prophecy.” Image is in the Public Domain (https://en.wikipedia.org/ wiki/The_Ancient_of_Days #mediaviewer/File:Europe_a_ Prophecy_copy_K_plate_01.jpg).

Between 1795 and 1805, the mystic poet, painter and printmaker William Blake produced a print that he entitled “Newton” (Figure 1). Just like the mythological figure Urizen, that to Blake portrayed law and reason in his piece “The Ancient of Days” (Figure 2), Blake’s Newton holds a compass.  To Blake, this compass represented an instrument that clips the wings of imagination.  Blake was a strong opponent to some of the aspects of the movement of the Enlightenment and its attempts to explain nature and all phenomena within it.  In his view, Newton and the empiricist philosophers Francis Bacon and John Locke all conspired “to unweave the rainbow.”  You’ll notice that in the print “Newton,” the scroll on which Newton draws his diagrams appears to emanate from Newton’s mouth.  Newton himself is so absorbed in his diagrams that he seems to be blind to the beautifully complex rock behind him, which probably symbolizes the creative, artistic world.  Blake went so far as to declare:

“Art is the tree of life.
Science is the tree of death.”

Somewhat similar sentiments were expressed by Blake’s contemporary, the young poet John Keats, who wrote:

“Philosophy will clip an Angel’s wings
Conquer all mysteries by rule and line,
Empty the haunted air, and gnomed mine—
Unweave a rainbow…”

Figure 3.  A Hubble image of the interacting galaxies Arp 273, dubbed “The Rose”  (http://hubblesite.org/newscenter/archive/releases/2011/11/image/a/format/web_print/).

Figure 3. A Hubble image of the interacting galaxies Arp 273, dubbed “The Rose” (http://hubblesite.org/ newscenter/archive/releases/2011/11/image/a/format/web_print/).

In my humble opinion, the views of both Blake and Keats were grossly misguided.  Scientists are not blind to the beauty of the world.  When I see an image such as the one taken by the Hubble Space Telescope that was dubbed “The Rose” (Figure 3), I believe that I am as capable to appreciate its exquisitely complex elegance as any artist.  The fact that I also happen to know that this image represents two interacting galaxies, where the gravitational pull of each one of them is affecting the other, does not subtract anything from my ability to perceive its beauty.  The additional knowledge that our own Milky Way galaxy is going to collide in a similar fashion with the Andromeda galaxy (in about 4 billion years; based on other Hubble observations), only adds to the emotional impact of this image.  Furthermore, the fact that we know that galaxies evolve through a series of such collisions and mergers puts this image into a broad cosmic perspective.

Similarly, Newton’s understanding of how the rainbow is formed did not take anything away from the rainbow’s aesthetic attractiveness; it only added a level of depth to its significance. The best example of the fusion of art and science is, of course, provided by the phenomenal work of Leonardo da Vinci (see e.g., https://blogs.stsci.edu/livio/2013/10/08/the-da-vinci-astronomy/).