Astronomy – stars, comets, and meteorites

Dovid HaMelech writes in Tehillim  (19:1), “The Heavens speak of Hashem’s  glory.” Every day as astronomers peer  further and deeper into the universe, the  heavenly proclamation of Hashem’s  might accelerates into an encyclopedia  of ever vaster intricacy. Let us view  a tiny sampling through the lens of  Chazal. 

INVISIBLE STARS 
Discussing the verse (Tehillim  148:3), “Halleluhu kol kochvei ohr,”  “Praise Him, all shining stars,” the  Gemara at the beginning of Pesachim  (2a) intervenes with an objection, “Do  only stars that shine have to praise  while stars that do not shine not have  to praise?”

The question has been raised – what  does the Gemara mean by “stars that  do not shine?” Does this imply that  there are stars out in space that do not  shine? There are a number of possible  answers to this question.

The first and simplest answer is that  the Gemara is referring to meteorites,  planets or even stars that are too  small or too distant to be sighted from  earth without the aid of binoculars  or telescopes. After all, doesn’t the  Gemara (Berachos 32b) itself state that  there are about a billion, billion stars  that exist even though the most hawkeyed  person would probably spot less  than 5,000 of them on the clearest  night?

A second, more sophisticated  explanation could be that the invisible  stars include black holes or neutron  stars. First postulated during the  eighteenth century, black holes were  also predicted by Einstein’s Theory of  General Relativity in 5676/1916. The  idea is that when massive stars collapse  under their own weight, their particles  become so tightly packed that one  teaspoonful of their matter can reach  several tons. This gigantic, dense mass  exerts such a crushing force of gravity  that nothing can escape its python like  grip, not even light. As a result,  stars are not only invisible to us here  on Earth but also invisible to someone  passing right next to them.

Of course, to pass that close would  be a dangerous experiment as anything  or anyone passing too near would risk  entering the black hole’s point of no  return. To make things worse, any object  entering the black hole’s powerful  gravitational field will theoretically  experience a brief, unpleasant process  known as “spaghettification.” What  is spaghettification? Exactly what it  sounds like. The powerful gravity pulls  things into spindly spaghetti shapes.

Astrophysicists theorize that a giant  black hole, containing millions or  billions the mass of our sun, presently  lurks like a spider in the middle of the  Milky Way galaxy we call home.  A third, even more exotic category  of invisible star could be a newly  discovered substance which fits neatly  into our worldview of kedusha and  light waging an unending battle against  tumah and darkness. This comparison  is even suggested in the title of a recent  book on the subject of this substance  – Dark Side of the Universe.

This mysterious matter was first  postulated by Franz Zwicky. Back in  5693/1933, he suggested the existence  of a substance which, while totally  invisible, manifests its existence by  “lensing.” “Lensing” is based on  another idea of Einstein – that gravity  distorts space. Because distorted space  warps the light traveling through it, we  can detect these invisible objects when  they bend the light of stars like a giant  lens and jolt the stars from their correct  place on the celestial plane.

Although dark matter and dark  energy may comprise up to 96% of  the universe, no one quite knows what  they are and whether they are large  or small. Scientists have debated for  years whether dark matter consists of  WIMPs (Weakly Interacting Massive  subatomic sized Particles) such as the  photino, the zino and the higgsino,  or MACHOs (Massive Compact  Halo Objects), which would include  objects as large as stars and planets.

The MACHO project, launched in  5751/1991, detected the presence of  so many MACHO objects that they are  suspected to comprise half the Milky  Way. Could these MACHOs be the nonshining  stars the Gemara mentions?

A fourth explanation of the Gemara  is, perhaps, the simplest of all. Examine  Rashi (d”h Ha kemashma lan) at the  end of the sugya and see what he says. 

R. YEHOSHUA’S  COMET 
The Gemara (Horayos 10a) relates:  “There was an incident that R.  Gamliel and R. Yehoshua were traveling  in a ship on the high seas. R. Gamliel  brought only bread while R. Yehoshua  brought bread and fl our. When the  bread of R. Gamliel was depleted, he  relied on the fl our of R. Yehoshua. [R.  Gamliel] asked him, ‘How did you  know we would be so delayed that  you took care to take extra flour?’ [R.  Yehoshua] replied to him, ‘There is a  certain star which rises every seventy  years and confuses the sailors and I  was concerned that it might rise now  and confuse us.’”

The star R. Yehoshua mentions may  have been Halley’s Comet that appeared  in 3826/66 CE, four years before  the Churban, because R. Yehoshua  and R. Gamliel passed away not so  long afterwards in 3877/117 CE and  3875/115 CE, respectively. Although  the Chinese sighted Halley’s Comet  centuries earlier in 3521/240 BCE,  and it was sighted many times since in  China, Japan, Persia and Babylon, no  one except R. Yehoshua realized that it  was the same comet returning each and  every time.

More recently, Edmund Halley  confidently predicted that this  comet would return in 5527/1757  after realizing that it had previously  appeared three times, at intervals of 76  years. This is the time it takes this nine  mile long comet to hurtle to the edge  of the solar system and back. Because  of this prediction, Halley’s Comet was  named after him when it was spotted  in 5528/1758, fourteen years after his  death.

Since then, a handful of Jews have  claimed that this is grave injustice  – after all, was it not R. Yehoshua who  first realized the periodic (regularly  returning) nature of “Halley’s” Comet  and, if so, should it not be called R.  Yehoshua’s Comet? Although R.  Yehoshua is indeed the first person to  describe the cyclical nature of comets,  it is by no means certain which comet  he was describing. First, R. Yehoshua  said that his star was due every seventy  years and not every seventy-six years!

Although one can claim that he was  only giving an approximate figure,  this argument weakens accrediting R.  Yehoshua with the discovery.

Furthermore, Halley’s Comet is  usually very large and distinctive. How  could experienced sea-dogs, familiar  with the stars after endless years of  navigation, confuse this giant-tailed  comet with the regular stars they knew  like the back of their hands? How  could the distinctive Halley’s Comet  lead them astray off familiar shipping  routes?

Because of these two problems,  perhaps another candidate comet can  be suggested in its place. This is the  12P Pons/Brooks Comet, discovered in  5643/1883, by the most famous comet  hunter of the last century, William  Roberts King. Its cyclic route of 70.9  years is closer to R. Yehoshua’s 70-  year figure. Also, as this comet is less  spectacular than Halley’s Comet, it is  more likely to be confused with other  stars. Perhaps clinching the matter  is the quick calculation that the 12P  Pons/Brooks Comet was due to pass  overhead in about 3871/111 CE, a few  years before R. Yehoshua’s passing. 

ICY METEORS 
The Gemara (Taanis 9b) discusses  the source of rain.

“It was taught in a Baraisa – R.  Eliezer says, ‘The whole world drinks  from the waters of the ocean, as it says  (Bereishis 2:6), ‘And a mist rose from  the land and watered all the face of  the earth,’ etc. R. Yehoshua says, ‘The  whole world drinks from the upper  waters since it says (Devorim 11:11),  “From the rain of the heavens, you will  drink water,” etc.’”

Some years ago, a University  of Iowa space physicist, Frank  Louis, asserted the claim that many  meteorites are made of ice and dissolve  into water as they plow into Earth’s  atmosphere. This seemed to offer a  new understanding of R. Yehoshua’s  statement regarding the source of rain.  Perhaps the upper waters he mentions  are molten meteorites.

However, there are serious  objections to this suggestion. The  Ramban on Chumash warns that the  “waters above the ‘rakia’” mentioned  in Bereishis is a reference to deep  Kabbalistic concepts and the same  might apply to this sugya. Also,  the Baraisa includes R. Yehoshua’s  description of how rain reaches Earth  and the process is a totally different  mechanism than melting meteorites.

Also, the numbers do not crunch.  Every year, our planet sweeps up  35,000 to 100,000 tons of space  debris as it circles the sun. This  consists of a wide variety of flotsam,  including dust, meteorites and icy  meteorites. Is this enough to make  a significant contribution to earth’s  rainfall? It is not! 6.6 billion tons of  rain fall every year in the United States  alone, and the total amount of rain,  snow and ice pelting down annually  worldwide equals 505,000 billion  tons! Accordingly, even if one argues  that 35,000 tons of icy meteorites blast  through the atmosphere on an annual  basis, this would contribute far less  than a billionth of the world’s annual  water supply – literally a drop in the  ocean.

Perhaps we can say the same for our  knowledge of what is really going on  above our heads – a drop in the ocean!

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