IDA Information Sheets

I recently received a membership renewal notice from the International Dark-Sky Association (IDA) quoting Christopher Kyba that if light pollution continues to grow at the rate it currently is, “Orion’s belt will disappear at some point.”

This made me remember that I had written an IDA Information Sheet back in March 1997 that also had addressed how light pollution could erase much of the Orion constellation. I wrote,

Orion, arguably the most prominent of the constellations, begins to look more like “Orion, the Hunted” under a magnitude +4.0 sky. Under a magnitude +3.0 sky, Orion is on his deathbed. When light pollution is so bad that we have a magnitude +2.0 sky, only blazing Betelgeuse, regal Rigel, and Bellatrix and Alnilam remain to regale us.

Speaking of the IDA Information Sheets, I was the IDA Information Sheet Editor from 1996-1999, during which time I revised and edited most of the existing information sheets, edited and added many new ones from a number of contributors, as well as contributed many new ones that I authored, though I never credited myself as the author. One of the ones that I wrote was IDA Information Sheet 120, referenced above (and shown below). I have a complete hard copy set of IDA Information Sheets 1 through 175, the last of which was published in June 2000. I also have WordPerfect Macintosh source files for IDA Information Sheets 1 through 158, the last of which was completed on October 27, 1999.

Here’s IDA Information Sheet 120:

It is a shame that these IDA Information Sheets are no longer available anywhere on the Internet. At the very least, they are of historical interest, and I would say that much of the content is still relevant. Presumably, the IDA still has all of these information sheets, but after the Dave Crawford era, they have decided to remove access to them.

Finally, I want to express my disappointment that the International Dark-Sky Association has recently decided to change their name to DarkSky International. They are still in the process of changing everything over, but once that transition is complete, the IDA will be no more. The break with the Dave Crawford era will be complete. I, for one, will never forget how much Dave Crawford was able to accomplish during those early years, and how proud I was to have been a part of it.

The IDA/DSI is still a great organization, and I strongly encourage you to generously support it, as I do. It remains the most effective organization in the world addressing light pollution and the loss of our night sky and the natural nighttime environment.

Classical Music Timeline: 1790s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

March 11 – Symphony No. 96 in D major, Hob. I/96 “Miracle” by Joseph Haydn (1732-1809) was first performed in London, England

June 23Ave verum corpus, motet in D major, K. 618, by Wolfgang Amadeus Mozart (1756-1791) was first performed in Baden bei Wien, Austria

December 5 – Wolfgang Amadeus Mozart (1756-1791) died in Vienna, Austria

February 29 – Gioachino Rossini (1792-1868) was born in Pesaro, Italy

March 23 – Symphony No. 94 in G major, Hob. I/94 “Surprise” by Joseph Haydn (1732-1809) was first performed in London, England

Joseph Haydn (1732-1809) completed Piano Sonata “Un piccolo divertimento” (Variations) in F minor, Hob XVII: 6

Ludwig van Beethoven (1770-1827) wrote Rondo a Capriccio in G major, now known as “Rage Over a Lost Penny”, op. 129

February 2 – Symphony No. 102 in B♭ major, Hob. I/102 by Joseph Haydn (1732-1809) was first performed in London, England

Joseph Haydn (1732-1809) completed String Quartet in G major, op. 76, no. 1, Hob. III:75

Joseph Haydn (1732-1809) completed String Quartet in C major, op. 76, no. 3, Hob. III:77 “Emperor”

Joseph Haydn (1732-1809) completed String Quartet in B♭ major, op. 76, no. 4, Hob. III:78 “Sunrise”

January 31 – Franz Schubert (1797-1828) was born in Vienna, Austria

Ludwig van Beethoven (1770-1827) completed Romance No. 2 in F major for violin and orchestra, op. 50

Ludwig van Beethoven (1770-1827) completed Piano Sonata No. 8 in C minor, op. 13 “Pathétique”



Hidden Wonders of the Southern Sky

Here in southern Arizona, we can theoretically see 92.4% of the celestial sphere. I say “theoretically” because atmospheric extinction, light pollution, local topography, and obstructions limit the amount of the celestial sphere that we can see well. Also, far southern objects (down to δ = -58° at φ = 32° N) spend very little time above our horizon each day.

Practically speaking, then, we see somewhat less than 92% of all that there is to see from spaceship Earth.

Percent of the Celestial Sphere Visible

\% = 50\left [ 1-sin\left ( \left|\varphi \right| -90^{\circ}\right ) \right ]

where |φ| is the absolute value of your latitude in degrees

What are the most prominent objects we are missing, and what objects that we can see are they closest to?

Alpha Centauri

Never visible north of latitude 27° N, the nearest star system beyond our solar system is Alpha Centauri. Alpha Centauri A & B are bright stars, having a visual magnitude of 0.0 and +1.3, respectively, and in 2023 they are separated by just 8 arcseconds, about 1/4 of the angular separation between Albireo A & B. While Alpha Centauri A & B—which orbit each other once every 79.8 years—lie just 4.36 ly away, a faint red dwarf companion, Proxima Centauri (shining at magnitude +11.1), is even closer at 4.24 light years. It is not yet known whether Proxima Centauri, discovered in 1915, is gravitationally bound to Alpha Centauri A & B, or just presently passing through the neighborhood. Proxima is a full 2.2° away (over four moon-widths) from Alpha Centauri A & B.

When Arcturus (α Boo) and Zubenelgenubi (α Lib) are crossing our celestial meridian, so are Alpha & Proxima Centauri below the southern horizon.

Large Magellanic Cloud

The Large Magellanic Cloud (LMC), the largest satellite galaxy of our Milky Way galaxy and easily visible to the unaided eye, lies directly below our southern horizon when Rigel has crossed the meridian and Bellatrix is preparing to do so.

Small Magellanic Cloud

The Small Magellanic Cloud (SMC), the second-largest satellite galaxy of the mighty Milky Way lies underneath our southern horizon when M31, the Great Andromeda Galaxy, crosses the meridian near the zenith.

47 Tucanae

The 2nd brightest globular cluster in the sky (after Omega Centauri) is impressive 47 Tucanae. It is just 2.3° west and a little north of the Small Magellanic Cloud, so crosses the meridian below our horizon just as M31 is nearing the meridian.

Eta Carinae Nebula

Four times larger and brighter than the Orion Nebula, NGC 3372, the Eta Carinae Nebula, is a spectacular star-forming region containing a supermassive (130 – 180 M) binary star (Eta Carinae) that may go supernova at any time. When Leo the Lion is straddling the meridian, the Eta Carinae Nebula sneaks across as well.

Any other spectacular objects I should be including that are south of declination -58°? If so, please post a comment here.

Classical Music Timeline: 1780s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

Wolfgang Amadeus Mozart (1756-1791) completed Violin Sonata No. 25 in F major, K. 377 (374e)

Joseph Haydn (1732-1809) completed Symphony No. 73 in D major, Hob. I:73 “La Chasse”

March 23 – Symphony No. 35 in D major, K. 385 “Haffner”, by Wolfgang Amadeus Mozart (1756-1791) was first performed in its final form in Vienna, Austria

November 4 – Symphony No. 36 in C major, K. 425 “Linz”, by Wolfgang Amadeus Mozart (1756-1791) was first performed in Linz, Austria

Joseph Haydn (1732-1809) completed Symphony No. 83 in G minor, Hob. I/83 “The Hen”

March 9 – Wolfgang Amadeus Mozart (1756-1791) completed Piano Concerto No. 21 in C major, K. 467

Joseph Haydn (1732-1809) completed Symphony No. 82 in C major, Hob. I/82 “The Bear”

March 2 – Wolfgang Amadeus Mozart (1756-1791) completed Piano Concerto No. 23 in A major, K. 488

May 1The Marriage of Figaro, K. 492, by Wolfgang Amadeus Mozart (1756-1791) was first performed in Vienna, Austria

Joseph Haydn (1732-1809) completed Symphony No. 88 in G major, Hob. I/88

Joseph Haydn (1732-1809) completed String Quartet No. 37 in C major, op. 50, no. 2, Hob. III/45

January 19 – Symphony No. 38 in D major, K. 504 “Prague”, by Wolfgang Amadeus Mozart (1756-1791) was first performed in Prague, Czech Republic

October 29Don Giovanni, K. 527, by Wolfgang Amadeus Mozart (1756-1791) was first performed in Prague, Czech Republic

Joseph Haydn (1732-1809) completed String Quartet No. 43 in G major, op. 54, no. 1, Hob. III:58

Luigi Boccherini (1743-1805) completed Sinfonia in C minor, G. 519

June 26 – Wolfgang Amadeus Mozart (1756-1791) completed Symphony No. 39 in E♭ major, K. 543

July 25 – Wolfgang Amadeus Mozart (1756-1791) completed Symphony No. 40 in G minor, K. 550

Joseph Haydn (1732-1809) completed Symphony No. 92 in G major, Hob. I/92 “Oxford”



Quotable Arthur C. Clarke

Sir Arthur Charles Clarke (1917-2008)

Clarke’s Three Laws

  1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
  2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
  3. Any sufficiently advanced technology is indistinguishable from magic.

The greatest tragedy in mankind’s entire history may be the hijacking of morality by religion.

I don’t believe in God but I’m very interested in her.

The rash assertion that “God made man in His own image” is ticking like a time bomb at the foundation of many faiths, and as the hierarchy of the universe is disclosed to us, we may have to recognize this chilling truth: if there are any gods whose chief concern is man, they cannot be very important gods.

Science can destroy religion by ignoring it as well as by disproving its tenets. No one ever demonstrated, so far as I am aware, the non-existence of Zeus or Thor—but they have few followers now.

I would defend the liberty of consenting adult creationists to practice whatever intellectual perversions they like in the privacy of their own homes; but it is also necessary to protect the young and innocent.

I would like to assure my many Buddhist, Christian, Hindu, Jewish, and Muslim friends that I am sincerely happy that the religion which Chance has given you has contributed to your peace of mind (and often, as Western medical science now reluctantly admits, to your physical well-being). Perhaps it is better to be un-sane and happy, than sane and un-happy. But it is the best of all to be sane and happy. Whether our descendants can achieve that goal will be the greatest challenge of the future. Indeed, it may well decide whether we have any future.

There is the possibility that humankind can outgrown its infantile tendencies, as I suggested in Childhood’s End. But it is amazing how childishly gullible humans are. There are, for example, so many different religions—each of them claiming to have the truth, each saying that their truths are clearly superior to the truths of others—how can someone possibly take any of them seriously? I mean, that’s insane. Though I sometimes call myself a crypto-Buddhist, Buddhism is not a religion. Of those around at the moment, Islam is the only one that has any appeal to me. But, of course, Islam has been tainted by other influences. The Muslims are behaving like Christians, I’m afraid.

Sometimes I think we’re alone in the universe, and sometimes I think we’re not. In either case the idea is quite staggering.

Perhaps, as some wit remarked, the best proof that there is Intelligent Life in Outer Space is the fact it hasn’t come here. Well, it can’t hide forever—one day we will overhear it.

The fact that we have not yet found the slightest evidence for life—much less intelligence—beyond this Earth does not surprise or disappoint me in the least. Our technology must still be laughably primitive, we may be like jungle savages listening for the throbbing of tom-toms while the ether around them carries more words per second than they could utter in a lifetime.

The moon is the first milestone on the road to the stars.

We are just tenants on this world. We have just been given a new lease, and a warning from the landlord.

Human judges can show mercy. But against the laws of nature, there is no appeal.

This is the first age that’s ever paid much attention to the future, which is a little ironic since we may not have one.

As our own species is in the process of proving, one cannot have superior science and inferior morals. The combination is unstable and self-destroying.

Our age is in many ways unique, full of events and phenomena that never occurred before and can never happen again. They distort our thinking, making us believe that what is true now will be true forever, though perhaps on a larger scale.

It is not easy to see how the more extreme forms of nationalism can long survive when men have seen the Earth in its true perspective as a single small globe against the stars.

New ideas pass through three periods:

  1. It can’t be done.
  2. It probably can be done, but it’s not worth doing.
  3. I knew it was a good idea all along!

Politicians should read science fiction, not westerns and detective stories.

There is hopeful symbolism in the fact that flags do not wave in a vacuum.

The Information Age offers much to mankind, and I would like to think that we will rise to the challenges it presents. But it is vital to remember that information—in the sense of raw data—is not knowledge, that knowledge is not wisdom, and that wisdom is not foresight. But information is the first essential step to all of these.

Communication technologies are necessary, but not sufficient, for us humans to get along with each other. This is why we still have many disputes and conflicts in the world. Technology tools help us to gather and disseminate information, but we also need qualities like tolerance and compassion to achieve greater understanding between peoples and nations. I have great faith in optimism as a guiding principle, if only because it offers us the opportunity of creating a self-fulfilling prophecy. So I hope we’ve learnt something from the most barbaric century in history—the 20th. I would like to see us overcome our tribal divisions and begin to think and act as if we were one family. That would be real globalisation. [December 2007]

Classical Music Timeline: 1770s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

December 16 – Ludwig van Beethoven (1770-1827) was born in Bonn, Germany

Wolfgang Amadeus Mozart (1756-1791) completed Divertimento in E flat, K. 113

Giovanni Battista Sammartini (1700?-1775) almost certainly completed Symphony in F Major (J-C 36) by this year, probably much earlier

Joseph Haydn (1732-1809) completed Symphony No. 45 in F♯ minor, Hob. I:45 “Farewell”

April 16 – Wolfgang Amadeus Mozart (1756-1791) completed Symphony No. 27 in G major, K. 199/161b

October 5 – Wolfgang Amadeus Mozart (1756-1791) completed Symphony No. 25 in G minor, K. 183/173dB

Wolfgang Amadeus Mozart (1756-1791) completed Violin Concerto No. 5 in A major, K. 219

January 15 – Giovanni Battista Sammartini (1700?-1775) died in Milan, Italy

September 12 – Wolfgang Amadeus Mozart (1756-1791) completed Violin Concerto No. 3 in G major, K. 216

Joseph Haydn (1732-1809) completed Piano Sonata in E minor, Hob. 16:34

Wolfgang Amadeus Mozart (1756-1791) completed Violin Sonata No. 21 in E minor, K. 304 (300c)

Before 1770



George F. R. Ellis weighs in on the concept of infinity in his excellent paper, Issues in the Philosophy of Cosmology, available on astro-ph at He writes:

9.3.2 Existence of Infinities

The nature of existence is significantly different if there is a finite amount of matter or objects in the universe, as opposed to there being an infinite quantity in existence. Some proposals claim there may be an infinite number of universes in a multiverse and many cosmological models have spatial sections that are infinite, implying an infinite number of particles, stars, and galaxies. However, infinity is quite different from a very large number! Following David Hilbert, one can suggest these unverifiable proposals cannot be true: the word “infinity” denotes a quantity or number that can never be attained, and so will never occur in physical reality.38 He states:

Our principal result is that the infinite is nowhere to be found in reality. It neither exists in nature nor provides a legitimate basis for rational thought . . . The role that remains for the infinite to play is solely that of an idea . . . which transcends all experience and which completes the concrete as a totality . . .

This suggests “infinity” cannot be arrived at, or realized, in a concrete physical setting; on the contrary, the concept itself implies its inability to be realized!

Thesis I2: The often claimed physical existence of infinities is questionable. The claimed existence of physically realized infinities in cosmology or multiverses raises problematic issues. One can suggest they are unphysical; in any case such claims are certainly unverifiable.

This applies in principle to both small and large scales in any single universe:

The existence of a physically existing spacetime continuum represented by a real (number) manifold at the micro-level contrasts with quantum gravity claims of a discrete spacetime structure at the Planck scale, which one might suppose was a generic aspect of fully non-linear quantum gravity theories. In terms of physical reality, this promises to get rid of the uncountable infinities the real line continuum engenders in all physical variables and fields40. There is no experiment that can prove there is a physical continuum in time or space; all we can do is test space-time structure on smaller and smaller scales, but we cannot approach the Planck scale.

Infinitely large space-sections at the macro-level raise problems as indicated by Hilbert, and leads to the infinite duplication of life and all events. We may assume space extends forever in Euclidean geometry and in many cosmological models, but we can never prove that any realised 3-space in the real universe continues in this way—it is an untestable concept, and the real spatial geometry of the universe is almost certainly not Euclidean. Thus Euclidean space is an abstraction that is probably not physically real. The infinities supposed in chaotic inflationary models derive from the presumption of pre-existing infinite Euclidean space sections, and there is no reason why those should necessarily exist. In the physical universe spatial infinities can be avoided by compact spatial sections, resulting either from positive spatial curvature, or from a choice of compact topologies in universes that have zero or negative spatial curvature. Machian considerations to do with the boundary conditions for physics suggest this is highly preferable; and if one invokes string theory as a fundamental basis for physics, the “dimensional democracy” suggests the three large spatial dimensions should also be compact, since the small (“compactified”) dimensions are all taken to be so. The best current data from CBR and other observations indeed suggest k = +1, implying closed space sections for the best-fit FL model.

The existence of an eternal universe implies that an infinite time actually exists, which has its own problems: if an event happens at any time t0, one needs an explanation as to why it did not occur before that time (as there was an infinite previous time available for it to occur); and Poincaré eternal return will be possible if the universe is truly cyclic. In any case it is not possible to prove that the universe as a whole, or even the part of the universe in which we live, is past infinite; observations cannot do so, and the physics required to guarantee this would happen (if initial conditions were right) is untestable. Even attempting to prove it is future infinite is problematic (we cannot for example guarantee the properties of the vacuum into the infinite future—it might decay into a state corresponding to a negative effective cosmological constant).

It applies to the possible nature of a multiverse. Specifying the geometry of a generic universe requires an infinite amount of information because the quantities necessary to do so are fields on spacetime, in general requiring specification at each point (or equivalently, an infinite number of Fourier coefficients): they will almost always not be algorithmically compressible. All possible values of all these components in all possible combinations will have to occur in a multiverse in which “all that can happen, does happen”. There are also an infinite number of topological possibilities. This greatly aggravates all the problems regarding infinity and the ensemble. Only in highly symmetric cases, like the FL solutions, does this data reduce to a finite number of parameters, each of which would have to occur in all possible values (which themselves are usually taken to span an infinite set, namely the entire real line). Many universes in the ensemble may themselves have infinite spatial extent and contain an infinite amount of matter, with all the problems that entails. To conceive of physical creation of an infinite set of universes (most requiring an infinite amount of information for their prescription, and many of which will themselves be spatially infinite) is at least an order of magnitude more difficult than specifying an existent infinitude of finitely specifiable objects.

One should note here particularly that problems arise in the multiverse context from the continuum of values assigned by classical theories to physical quantities. Suppose for example that we identify corresponding times in the models in an ensemble and then assume that all values of the density parameter and the cosmological constant occur at each spatial point at that time. Because these values lie in the real number continuum, this is a doubly uncountably infinite set of models. Assuming genuine physical existence of such an uncountable infinitude of universes is the antithesis of Occam’s razor. But on the other hand, if the set of realised models is either finite or countably infinite, then almost all possible models are not realised. And in any case this assumption is absurdly unprovable. We can’t observationally demonstrate a single other universe exists, let alone an infinitude. The concept of infinity is used with gay abandon in some multiverse discussions, without any concern either for the philosophical problems associated with this statement, or for its completely unverifiable character. It is an extravagant claim that should be treated with extreme caution.

38An intriguing further issue is the dual question: Does the quantity zero occur in physical reality? This is related to the idea of physical existence of nothingness, as contrasted with a vacuum. A vacuum is not nothing!

40To avoid infinities entirely would require that nothing whatever is a continuum in physical reality (since any continuum interval contains an infinite number of points). Doing without that, conceptually, would mean a complete rewrite of many things. Considering how to do so in a way compatible with observation is in my view a worthwhile project.

So, given this discussion of infinities, the answer to the doubly hypothetical question, “Can God make a rock so big he can’t pick it up?” is likely a “Yes”! – D.O.

Classical Music Timeline: Before 1770

This is the first of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

September 10? – Henry Purcell (1659-1695) was born in London, England

March 4 – Antonio Vivaldi (1678-1741) was born in Venice, Italy

March 31 – Johann Sebastian Bach (1685-1750) was born in Eisenach, Germany

Dido and Aeneas, Z. 626, by Henry Purcell (1659-1695) was first performed in London, England

November 21 – Henry Purcell (1659-1695) died in London, England

Giovanni Battista Sammartini (1700?-1775) was born in Milan, Italy

Antonio Vivaldi (1678-1741) completed Gloria, RV 589

Johann Sebastian Bach (1685-1750) completed Puer natus in Bethlehem, for children’s chorus, cello, and organ, by this date

Antonio Vivaldi (1678-1741) completed Credo, RV 591

June 18 – Johann Stamitz (1717-1757) was born in Havlíčkův Brod, Czech Republic

March 24 – Johann Sebastian Bach (1685-1750) completed Brandenburg Concerto No. 1 by this date

March 24 – Johann Sebastian Bach (1685-1750) completed Brandenburg Concerto No. 2 by this date

Antonio Vivaldi (1678-1741) completed Chamber Concerto for Lute and 2 Violins in D major, RV 93

Johann Sebastian Bach (1685-1750) completed Concerto for 2 Violins in D minor, BWV 1043, by this date

Giovanni Battista Sammartini (1700?-1775) completed Symphony in D minor (J-C 23), perhaps earlier

March 31 – Joseph Haydn (1732-1809) was born in Rohrau, Austria

July 28 – Antonio Vivaldi (1678-1741) died in Vienna, Austria

February 19 – Luigi Boccherini (1743-1805) was born in Lucca, Italy

Johann Stamitz (1717-1757) completed Symphony in A major, “Mannheim No. 2” and Symphony in B♭ major, “Mannheim No. 3”, perhaps earlier

July 28 – Johann Sebastian Bach (1685-1750) died in Leipzig, Germany

January 27 – Wolfgang Amadeus Mozart (1756-1791) was born in Salzburg, Austria

Johann Stamitz (1717-1757) completed Trio in E major, op. 5, no. 3, perhaps earlier

March 27 – Johann Stamitz (1717-1757) died in Mannheim, Germany

Joseph Haydn (1732-1809) completed Symphony No. 22 in E-flat Major, Hob. I:22 “The Philosopher”

Wolfgang Amadeus Mozart (1756-1791) completed Bastien and Bastienne, K. 50


Nearest Stars & Planets

Here’s a table of all known star systems within 15 light years (ly) of our Solar System. I will endeavor to keep this list up to date, so please post a comment here if anything needs to be corrected or added.

There are 41 star systems1 within a volume of

V = \frac{4}{3}\pi r^{3} = \frac{4}{3}\pi (15\;ly)^{3} = 14,137\;ly^{3}

Assuming that these 41 star systems are uniformly distributed within a sphere of radius 15 ly, the average distance from any star to its nearest neighbor is given by

\bar{d} = r\left [ \frac{\pi }{3n\;\sqrt[]{2}} \right ]^{\frac{1}{3}} = (15\; ly)\left [ \frac{\pi }{3(41)\;\sqrt[]{2}} \right ]^{\frac{1}{3}} = 3.94\;ly

So, even though it seems that 41 star systems within a distance of 15 ly from our Solar System is a lot, the volume of 14,137 cubic light years is not that small, and the average distance between any star and its nearest neighbor is about 3.94 ly. Our nearest neighbor is Proxima Centauri, which at a distance of 4.24 ly is quite close to the 3.94 ly average distance derived above.

Nearest Stars (within 15 light years)

Star Distance (ly) Spectral Type Constellation Planets?
Sun 0.00 G2V zodiacal Yes
Proxima Centauri 4.24 M5.0V Centaurus Yes
Alpha Centauri A & B 4.36 G2V & K0.0V Centaurus Unknown
Barnard's Star 5.97 M3.5V Ophiuchus Unknown
Luhman 16 A & B 6.59 L8 & T1 Vela Unknown
WISE 0855-0714 7.26 Y2 Hydra Unknown
Wolf 359 7.87 M5.5V Leo Yes
Lalande 21185 8.29 M2.0V Ursa Major Yes
Sirius A & B 8.65 A1V & DA2 Canis Major Unknown
Luyten 726-8 A & B 8.79 M5.5V & M6.0V Cetus Unknown
Ross 154 9.70 M3.5V Sagittarius Unknown
Ross 248 10.29 M5.5V Andromeda Unknown
Epsilon Eridani 10.48 K2.0V Eridanus Yes
Lacaille 9352 10.72 M1.0V Piscis Austrinus Yes
Ross 128 11.01 M4.0V Virgo Yes
EZ Aquarii A, B, & C 11.27 M5.0VJ Aquarius Unknown
61 Cygni A & B 11.40 K5.0V & K7.0V Cygnus Unknown
Procyon A & B 11.44 F5IV-V & DQZ Canis Minor Unknown
Struve 2398 A & B 11.49 M3.0V & M3.5V Draco Yes
Groombridge 34 A & B 11.62 M1.5V & M3.5V Andromeda Yes
DX Cancri 11.68 M6.0V Cancer Unknown
Epsilon Indi A, B, & C 11.81 K4.0V, T1, & T6 Indus Yes
Tau Ceti 11.89 G8.5V Cetus Yes
Gliese 1061 11.98 M5.0V Horologium Yes
YZ Ceti 12.11 M4.0V Cetus Yes
Luyten's Star 12.25 M3.5V Canis Minor Yes
Teegarden's Star 12.50 M6.5V Aries Yes
Kapteyn's Star 12.83 M2.0VI Pictor Unknown
Lacaille 8760 12.95 K9.0V Microscopium Unknown
SCR 1845-6357 A & B 13.05 M8.5 & T6 Pavo Unknown
Kruger 60 A & B 13.08 M3.0V & M4.0V Cepheus Unknown
DENIS J1048-3956 13.19 M8.5V Antlia Unknown
UGPS 0722-05 13.43 T9 Monoceros Unknown
Ross 614 A & B 13.49 M4.0V & M5.5V Monoceros Unknown
Wolf 424 A & B 13.98 M5.0VJ Virgo Unknown
Wolf 1061 14.05 M3.5V Ophiuchus Yes
van Maanen 2 14.07 DZ7 Pisces Unknown
Gliese 1 14.17 M1.5V Sculptor Unknown
TZ Arietis 14.59 M4.0V Aries Yes
Gliese 674 14.84 M2.5V Ara Yes
Gliese 687 14.84 M3.0V Draco Yes
LHS 292 14.90 M6.5V Sextans Unknown

1 Here we are considering Proxima Centauri and Alpha Centauri A & B to be one star system.

Henry, T.J. 2020, The Nearest Stars in The Observer’s Handbook 2023, ed. J. Edgar, The Royal Astronomical Society of Canada, p. 284-288.

Blinding Headlights

I’ve lived in Tucson, Arizona for ten months now, and I have to tell you, it is no fun driving here at night. While it is a joy living in a city that for a change isn’t horribly overlit and that takes light pollution seriously (though that is starting to erode), it is often hard to see at night because of the many vehicles on the road with blinding headlights. In recent years, this has become a huge problem throughout the U.S., and the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) needs to act quickly and decisively to deal with this dangerous nuisance.

Not only have headlights gotten brighter and bluer (which makes glare much worse), many vehicles have multiple sets of headlights, including “fog lights” that are anything but. High-profile vehicles such as pickup trucks and SUVs are especially bad when it comes to causing blinding glare for smaller, less extravagant vehicles. Jacked-up pickup trucks are the worst, and there are a lot of them here.

When one of these headlight-offensive vehicles is heading towards you, it makes it difficult to see the road ahead. It is especially hard to see pedestrians and bicyclists. Pavement markings are also harder to see because of the glare from the oncoming vehicle, especially when those lines are badly faded and in need of re-painting (as they often are here).

Tucson has far too many busy intersections without a protected left turn, and if you find yourself in a left-turn lane being stared down by a headlight-offensive vehicle in the opposite left-turn lane, the glare blinds you so much that it is difficult to see oncoming vehicles in the through-traffic lanes.

When a headlight-offensive vehicle comes up behind you and, as they often do, practically rides your bumper because driving at or near the speed limit isn’t fast enough for them, you’re hit with their intense glare in all three rear-view mirrors. This makes it harder to see the road ahead, and you have to slow down—which tends to aggravate them more than they already are. If you’re lucky, they can pass you—though sometimes they will illegally cross a double yellow line to do it.

Because of all these intense and unregulated vehicle headlights, I now avoid driving at night whenever possible.

Sure, headlights like these helps the perpetrator see better so they can drive down the road at night exceeding the speed limit (which is seldom enforced here, by the way), but everyone else—drivers, bicyclists, and pedestrians—is blinded.

What are the specific problems with modern vehicle headlights that need to be addressed, and what are the solutions?

  • Problem: The average vehicle’s total headlight lumen output (and individual headlight luminance) has dramatically increased in recent years, causing a corresponding increase in discomfort and disability glare for everyone else.
  • Solution: Headlights would not have to be so bright if speed limits were lower at night on many city streets and thoroughfares, and if the posted speed limits were actually enforced.
  • Solution: Implement adaptive driving beam (ADB) technology that uses sensors to detect oncoming traffic and adjusts the projected beam pattern to allow plenty of light for the driver without blinding other motorists. (ADB is widely used in Europe, but is not yet legal in the United States.)
  • Problem: Light-emitting diode (LED) and High Intensity Discharge (HID) headlights emit more light at the blue end of the visible spectrum than traditional warm-white or yellowish halogen headlights do, and these bluer lights result in significantly greater visual discomfort and impairment for other drivers.
  • Solution: Limit the amount of blue light that headlights can produce.
  • Problem: Poor headlight aim leads to dangerous glare for others.
  • Solution: Require regular headlight aim inspections and adjustments. Anytime a vehicle’s suspension is lifted, require headlight aim to be adjusted downward accordingly.

Here’s a petition you might want to sign:

I’d like to close this article by quoting one of the many insightful comments in the Comments section of the New York Times article listed under References below.

Like everything else, it is no longer about the collective good and the laws that protect it. Individualism now rules—individual freedom. Headlights have become a First Amendment issue—an element of free speech.

And they have become part of the conservative anti-government backlash. Laws regulating headlights are seen as government intrusion into personal freedoms. It is seen by many to be like the COVID mask issue. Too many people think personal freedom trumps everything else–even collective health and safety.

And there is a free-market aspect to this. Manufacturers are looking for ways to add features to cars that will make them more attractive to buyers. They know the lights are unsafe, yet they put them on their vehicles.

America has lost all common sense.

Evanston, IL | June 9, 2021

Mark my words, if we keep heading down this path of excessive individual freedom (read: selfishness) without significant responsibility for the common good (that means everybody, not just your tribe), it will be our undoing. The United States will become a miserable place to live for the majority of us for at least a generation. I’m not hopeful that we can turn this around in time. Too many of us are “asleep at the wheel” and too easily swayed by misinformation and propaganda.


Mele, Christopher. “Blinded by Brighter Headlights? It’s Not Your Imagination.” New York Times, June 5, 2021,