Today we celebrate the 190th anniversary of the birth of Scottish mathematician and physicist James Clerk Maxwell (13 Jun 1831 – 5 Nov 1879). Between 1864 and 1873, Maxwell developed four important mathematical equations that describe the behavior of electric and magnetic fields and their interrelated nature. He showed that any oscillating electric charge produces an electromagnetic field, and that this electromagnetic field propagates outward from the oscillating charge at the speed of light. He then correctly deduced that light itself is an electromagnetic phenomenon, and proposed that since electric charges can oscillate at any frequency, there should be a whole spectrum of electromagnetic waves of which visible light is only a small part. We now know that the electromagnetic spectrum does include many other types of “light”, namely gamma rays, x-rays, ultraviolet, infrared, microwave, and radio waves. They are all exactly the same phenomenon, differing only in their properties of frequency, wavelength, and energy.
Like many of you, I have more than one email address. One of those email addresses I use as a catch-all for nonprofits, political organizations, and commercial entities.
Over time, the volume of email I’ve received at that address has increased exponentially. Many senders subscribe me without my having ever opted in, and many senders send multiple emails a day (or per week)—and they don’t always give you the option to opt down. I unsubscribe from many every month, but the emails I receive daily keeps on growing.
I’m tempted (often), to unsubscribe from everything, but every once in a while I get an email that is important enough or useful enough that I’m glad I got it.
What to do? I am making a conscious effort to cut all of the insidious time wasters out of my life (this becomes much more important as we get older), freeing up precious time for what is most important. Email is one of the worst offenders.
Many online discussion groups have a “daily digest” option with all of the posts for the day being assembled into a single email, with a topical index at the top. I would like the ability through my email service provider to batch together emails from a variety of senders into a single daily email. It would work something like this:
- Create a list of email domains that you want batched (facebookmail.com, ewg.org, onefairwage.org, etc.)
- Activate the digesting service so that all emails coming from these domains gets batched into a single daily email with the subject line and sender of all the emails listed in the top section, followed by the full contents of the emails in sequence below that.
You’d have the option to receive the email sorted by time received in either ascending or descending order. You’d also be able to add or remove email domains from your list at any time.
Sure, it is going to be one long email for many of us, but it would go a long way towards reducing the clutter in our inboxes.
Another option would be to have an email service provider (unfortunately, digest.com is already taken) that will provide you with a pass-through email address that does this digesting for you, then forwards the daily email to the email address of your choice. You would update your senders with the pass-through email address. Let the digesting begin!
A giant cloud of mostly hydrogen gas with enough material to make over a million suns is heading towards our Milky Way at a speed of 45 miles per second. Called the Smith Cloud (after Gail Bieger-Smith who discovered it in 1963), this 9,800 × 3,300 ly high velocity cloud (HVC) is about 40,000 ly distant and is expected to slam into our Milky Way galaxy in about 27 million years, causing the birth of many new stars a quarter-way round the galaxy from us.
The Smith Cloud is located in the constellation Aquila, and has an apparent diameter around 11° across its long axis. It is only visible using radio telescopes (spin-flip transition of neutral atomic hydrogen), or by detecting hydrogen absorption lines Doppler shifted and superimposed upon the spectra of more distant stars that are shining through the cloud.
The origin of the Smith Cloud is unknown. It may have originated within the Milky Way galaxy itself, or it may be extragalactic. The upcoming collision may not be the first time the Smith Cloud has encountered the disc of the Milky Way. It may be embedded in a large halo of dark matter which would have kept the cloud from being completely disrupted during any past encounters.
The Smith Cloud is a great example of an object that would never have been discovered were it not for radio astronomy. Felix J. Lockman, who has published extensively on the Smith Cloud, has created Radio Astronomy: Observing the Invisible Universe for The Great Courses. Dr. Lockman’s engaging lecture style, his clear explanations, and thorough knowledge of the subject matter makes this the perfect introduction to the subject. Highly recommended!
Incidentally, Jay Lockman discovered a region in Ursa Major that is relatively free of neutral hydrogen gas and dust, thus affording a clearer view into the distant universe. It is named, appropriately, the Lockman Hole.
Alig, C. et al. “Simulating the Impact of the Smith Cloud.” The Astrophysical Journal 869 (2018): 1-6.
Hu, Y. et al. “Magnetic field morphology in interstellar clouds with the velocity gradient technique.” Nature Astronomy (2019): 1-7.
Lockman, F.. “Accretion Onto the Milky Way: The Smith Cloud.” Proceedings of the International Astronomical Union 11 (2015): 9 – 12.
I subscribe to The Week which does a good job summarizing news events of the past week from a number of sources. In the May 21, 2021 issue, they quote an article from Noah Smith on Bloomberg.com that tells us, once again, how bad it is that the U.S. birth rate is declining.
Birth rates need to decline everywhere in the world because population growth is the cause of climate change, loss of biodiversity, and increasing poverty, conflict, suffering, and inequality. It is obvious by now that if we want to avoid a dystopian future for the human race, we’d better start encouraging people to have fewer children (one or zero is enough). That is the only humane way to reduce human population. Why would any sane person want to reduce our population through any other means?
Quoting from the article, “America’s declining birth rate”,
A “baby bust” points to “a grim economic future” for America, said Noah Smith.
Not as grim as the economic future that awaits us as the world’s resources are rapidly depleted and the natural world collapses due to too many people on our planet.
U.S. births fell 4 percent in 2020 to their lowest rate since World War II, the federal government reported last week.
Is it any wonder? The pandemic has upended all of our lives. That would have been reason enough, but add to that the toxic politics of this country which is like a horribly abusive marriage from which there is no escape. Then, add the host of existential crises facing the world, plus powerful manipulators constantly lying to us and distracting us to keep us from doing anything about these problems, and you have a country that clearly is on the verge of open warfare, if not collapse. Why would anyone want to bring a beautiful child into such a hopeless future?
“This puts an increasing financial and physical burden on the young,” who must pay the soaring costs of Social Security, Medicare, and caring for their own aging family members.
We have no one to blame but ourselves for the world’s most expensive medical care that for many is no longer of the highest quality. We need a non-profit, single-payer system such as Medicare for All.
“In 2010, the number of working-age adults per older adult was 4.8; by 2060, it’s projected to be only half that”—meaning that the tax burden on workers will need to double.
We are not paying enough taxes as it is. This is especially true for the wealthiest among us, including large corporations. And spending less on the military would help a lot, as it already consumes an obscene percentage of our federal budget.
The graying of the population will also lead to lower productivity and economic stagnation.
It depends on how you measure productivity and economic growth. Many seniors are highly productive members of society, even when they are not paid for their work. These encore careers allow many seniors to contribute directly to the betterment of society in more substantial ways then when they were traditionally employed.
If humans are to survive on this planet, we must transition away from an ever-increasing-consumption approach to economic growth and towards one of sustainability and improving everyone’s quality of life (not only materially).
Per-capita productivity will increase if we build robots and other machines to do the most unrewarding and dangerous work that humans now do. People can be retrained for more interesting work and more service-oriented careers.
And it will put the U.S. at a marked disadvantage in our competition with China, which has four times our population.
So what? Why must we continue to take this “us vs. them” approach? We need to think, and act, globally.
Increased immigration would help, but it’s not enough to keep our population growing.
Why must our population grow? Growth is killing us and this planet. We need a new economic system where progress isn’t equivalent to unbridled growth.
“Americans need to have more children,” and surveys show they want to—but are held back by the high costs of housing, education, and child care.
Well, then don’t vote Republican. And one child is enough.
America has a choice to make: to be a graying nation in decline or a great nation, “confident enough in ourselves to believe that there should be more of us.”
This is nonsense. Since when is a graying nation in decline? Let’s value every individual for who they are and what they can contribute, regardless of their age. And who cares about a “great nation”? I’m more interested in a “great world”. And making a “great contribution” of my time and energy to others.
We need a new economy. Where everything is recyclable. Where everything is built to last. Where everything is repairable. How are we ever going to get to that without strong government regulation to encourage needed behaviors and discourage harmful ones? And binding international laws?
For more information…
The elements that make up the stars also exist here on Earth. In fact, our Earth, and indeed all the planets, were created from the dust and gas produced by previous generations of stars that existed before our Sun and solar system formed. We truly are made of stardust!
Stars are made up almost entirely of hydrogen and helium. Here is a table of the most abundant elements in our Sun.
|Element||% by atoms|
It is not a trivial matter to determine the abundance of elements in the Sun. For most elements, astronomers have to look at the strength of spectral absorption lines in the photosphere. Some elements, like fluorine, chlorine, and thallium, require looking for their spectral lines inside of sunspots, which are cooler-than-average regions of the photosphere. Other elements require that we look at spectral lines in the solar corona, or capture and analyze the solar wind. And some elements we are simply unable to detect.
The region of the photosphere that is amenable to spectral study represents only about 2% of the mass of the Sun. Since the Sun’s formation 4.6 Gyr ago, some gravitational settling of heavier elements and diffusion of hydrogen towards the surface means the Sun is not uniform in composition. Fortunately, the relative abundances of the elements heavier than helium are probably similar throughout the Sun.
Lithium, the third element in the periodic table after hydrogen and helium, is the odd element out. It has a relative abundance in the solar photosphere that is only 1/170th that found in meteorites. The Sun’s original supply of lithium has largely been destroyed by the high temperatures inside the pre-main-sequence Sun, and today at the hot bottom of the Sun’s convection zone.
Light pollution is a problem here on Earth, but on the Sun we have a problem with “line pollution”. There are so many spectral lines that the weak signatures from some elements become difficult or impossible to isolate and measure. There is much blending of overlapping lines, and some elements—most notably iron which is the ninth most abundant element in the Sun—are “superpolluters” with hundreds to thousands of spectral lines from both excited and ionized states.
Sometimes, the spectral lines of interest are in a region of the electromagnetic spectrum (ultraviolet, for example) that can only be observed from space, and that creates additional challenges.
Notably, the noble gases helium, neon, argon, krypton, and xenon have no photospheric absorption lines that can be observed, and we must look to coronal sources such as the solar wind, solar flares, or solar energetic particles for information about their abundances.
Helium—the second most abundant element in the Sun—requires an indirect approach combining a theoretical solar model and observational helioseismology data to tease out its abundance.
The following elements are undetectable in the Sun: arsenic, selenium, bromine, technetium, tellurium, iodine, cesium, promethium, tantalum, rhenium, mercury, bismuth, polonium, astatine, radon, francium, radium, actinium, protactinium, and all the synthetic elements above uranium on the period table.
Interestingly, helium was discovered in the Sun before it was discovered on Earth! That’s why this element is name after Helios, the Greek god of the Sun.
The energy source that allows stars to shine steadily, often for billions of years, is fusion. Fusion in a star can only occur where both the temperature and pressure are very high. Usually (but not always!), this occurs in the core of the star. When the element hydrogen fuses into helium, a huge amount of energy is released in the process. Lucky for us, fusing hydrogen into helium is difficult to do in a one-solar-mass star. On average, any particular hydrogen atom in our Sun has to “wait” about five billion years before having the “opportunity” to participate in a fusion reaction!
In order for sustained fusion to occur in the core of a star, the star must have sufficient mass so that the core temperature and pressure is high enough. Present thinking is that the lowest mass stars where sustained fusion can occur have about 75 times the mass of Jupiter, or about 7% the mass of the Sun.
Little did I know at the time, but a decade (or was it two?) ago, I purchased a jacket at the Kitt Peak National Observatory Visitor Center store that is the best, most comfortable, most durable jacket I have ever owned. And, as often is the case with the most extraordinary products, it is no longer available.
Port Authority made the jacket in Sri Lanka, but a search of the Registered Identification Number RN 90836 indicates that San Mar Corporation is the owner. The product ID is Port Authority J-755.
My jacket has faded quite a lot over the years, as demonstrated by the upturned collar below.
Though the Kitt Peak Port Authority J-755 jacket is, sadly, no longer available (wish they would bring it back!), as of this writing I was finally able to find something fairly close: the Port Authority J754 Challenger. I ordered one from A2Z Clothing (True Navy/Grey Heather) and will report back here after I’ve had a chance to evaluate it.
Update May 14, 2021
Received the Port Authority J754 Challenger in the mail yesterday from A2Z Clothing. I’m very happy with their service. This jacket is similar enough to the Kitt Peak jacket that I’ve ordered two more. (I’ve learned in recent years that it is a good idea if you find an article of clothing you like to order two more right away for later use, because there’s a high probability that when you need to replenish, it won’t be available any more.)
There are some differences. The collar of the new jacket is 22″ wide and 4″ deep. The Kitt Peak jacket collar is 19″ wide and 3″ deep. I prefer the less substantial collar of the Kitt Peak jacket.
The new jacket is made in Vietnam, and the old jacket was made in Sri Lanka.
shell: 100% nylon
body lining: 75% polyester, 25% rayon
sleeve lining: 100% nylon
inter lining: 100% polyester resin coated
J-753, RN 90836
shell: 100% nylon
lining: 100% polyester
sleeve lining: 100% nylon
insulation: 100% polyester resin coated
J-754, RN 90836
The Quinn Martin television series The Invaders premiered on January 10, 1967 and ran for two seasons, the forty-third and final 51-minute episode airing March 26, 1968. If I ever saw an episode of this series at the time it was aired, I sure don’t remember it. What I do remember watching at the time was Lost in Space (which ran for three seasons from September 5, 1965 through March 6, 1968) and Star Trek (which also ran for three seasons from September 8, 1966 through June 3, 1969).
Obviously, the target audience for Lost in Space was kids, and being ages 9-11 during its run, I regularly watched it. Looking back on it now, I see the show could have been so much better than it was. The Robinsons, Major Don West, the Robot, the Jupiter 2 spacecraft were all really cool (I still think so!). But as fine an actor as Jonathan Harris was, the Dr. Zachary Smith character just ruined the show. And I could have done without the (often) unbelievably cheesy aliens and bad science.
When Star Trek launched on September 8, 1966 (when I was 10), I am embarrassed to admit I didn’t like it as much as Lost in Space and missed most of the episodes. Boy, did that ever change! Once Star Trek went into syndication in the early 1970s, I saw all the episodes and became a lifelong fan, and it remains today my favorite science fiction television series.
Somehow, I totally missed The Invaders at the time, but having just finished watching the series on DVD (without ads!) from beginning to end, I am amazed at how good of a show it was. First of all, Roy Thinnes as architect David Vincent is truly outstanding. He makes the show a success, no question about it. Next, the scripts are phenomenal. Exceptional stories that keep you on the edge of your seat more often than not. And a fabulous array of guest stars further strengthen the show. Let’s not forget to mention the remarkable photography by Andrew J. McIntyre.
If you are unfamiliar with The Invaders, the basic premise is that alien beings from a dying world come to Earth with the goal of eradicating humanity and making it their new world. On Earth, they can assume human form, and infiltrate society in their quest for domination. David Vincent learns of their plans and embarks on a lonely and dangerous quest to convince those in power that their threat is real and must be stopped.
All of the episodes are worth watching, but here are my favorites:
- Doomsday Minus One [Season 1, Episode 8]
- Moonshot [Season 1, Episode 15]
- Wall of Crystal [Season 1, Episode 16]
- The Ransom [Season 2, Episode 15]
- The Vise [Season 2, Episode 22]
Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites. In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my 17 × 11 arcminute field of view.
I’ve put together a video montage of satellites I serendipitously recorded during the second half of 2020. Many of the satellites move across the field as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation. North is up and east is to the left.
Interestingly, two of the satellites above (7 & 22) are in retrograde orbits, that is their orbital inclination is > 90˚ and their east-west component of motion is towards the west instead of the east. However, one of the prograde-orbiting satellites (11) appears to be orbiting retrograde. It has an orbital inclination close to 90˚ (87.5˚), and must appear retrograde because of the vector sum of the line-of-sight motion of the satellite plus the Earth’s rotation, but I have not yet found an expert who can confirm this.
Satellite #12 has an interesting story. It is piece of debris from the Iridium 33 satellite after the 10 Feb 2009 collision between Iridium 33 and Cosmos 2251. A cautionary tale as now thousands of internet satellites are being launched into orbit.
Because of the long integration time, satellite #14 was only captured on a single frame, but the satellite trail clearly shows this piece of Fregat debris is tumbling and leading to rapid and no doubt periodic changes in brightness.
The satellite trail of #17 looks funky because wind was shaking the telescope as the satellite crossed the field.
There were four satellites I was unable to identify, shown in the video below. They are either classified satellites or, more likely, small pieces of space debris that only government agencies are keeping track of. Interestingly, three of the four unidentifiable satellites were moving in retrograde (westward) orbits.
On 29 Nov 2020, I recorded a rapidly tumbling Briz-M rocket body. Below the video you’ll find the light curve showing the large amplitude of its reflected light variation.
The NOAA-13 environmental satellite failed shortly after launch, and as you can see from the light curve below the video, it got dimmer as it crossed the field—probably indicating that this retrograde, non-operational satellite is slowly tumbling.
Occasionally, I record other phenomena of interest. Meteors during this period are described here, and you will find a couple of jet contrails in the video below.
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21
I’ve been seriously listening to classical music—both through live performance and recordings—for nearly 50 years, and am always surprised to find that I still discover or am introduced to works that are new to me and extraordinarily moving. “How can I have gone so many years without discovering this?” I often ask myself when I hear such a piece. Often, these “new” works are by well-known composers, but sometimes they are by composers I have never heard of. And, of course, some of them are new works by living composers.
For example, in 2017, I created a continuously-updated blog entry for “Symphonies by Women” because I was embarrassed to admit I couldn’t name a single one off the top of my head. Well, as you can see there are hundreds, and some of the few I have had the privilege to hear are really good.
There is an enormous amount of unknown music out there, and if only 1% of this unknown music is first-rate, then there must be hundreds of composers and thousands of works that deserve more attention. In France, Thanh-Tâm Le, who has recently helped me so much with this list of symphonies by women, has compiled a larger list of almost 18,000 symphonies by both men and women, and that is only symphonies!
Do you have some favorite classical works (both new and old) that you only know through a live performance or a non-commercial recording? Do you have some favorite works on vinyl or CD that are not currently available on CD? I know I do.
I’ve created a discussion group on groups.io called Classical Music Little-Known Favorites where I hope you and others will post audio files, YouTube videos, etc., of little-known works that you are enamored of. My hope for this group is that music lovers all around the world will join and present new and neglected works for us to enjoy and champion. Please join and spread the word!
As the expanding universe cooled, the first neutral1 hydrogen atoms formed about 380,000 years after the Big Bang (ABB), and most of the hydrogen in the universe remained neutral until the first stars began forming at least 65 million years ABB.
The period of time from 380,000 to 65 million years or so ABB is referred to as the “dark ages” since at the beginning of this period the cosmic background radiation from the Big Bang had redshifted from visible light to infrared so the universe was truly dark (in visible light) until the first stars began to form at the end of this period.
All the while, neutral hydrogen atoms occasionally undergo a “spin-flip” transition where the electron transitions from the higher-energy hyperfine level of the ground state to the lower-energy hyperfine level, and a microwave photon of wavelength 21.1061140542 cm and frequency 1420.4057517667 MHz is emitted.
Throughout the dark ages, the 21 cm emission line was being emitted by the abundant neutral hydrogen throughout the universe, but as the universe continued to expand the amount of cosmological redshift between the time of emission and the present day has been constantly changing. The longer ago the 21 cm emission occurred, the greater the redshift to longer wavelengths. We thus have a great way to map the universe during this entire epoch by looking at the “spectrum” of redshifts of this particular spectral line.
380,000 and 65 million years ABB correspond to a cosmological redshift (z) of 1,081 and 40, respectively. We can calculate what the observed wavelength and frequency of the 21 cm line would be for the beginning and end of the dark ages.
The observed wavelength (λobs) for the 21 cm line (λemit) at redshift (z) of 1,081 using the above equation gives us 22,836.8 cm or 228.4 meters.
That gives us a frequency (ν) of 1.3 MHz (using the equation above), where the speed of light c = 299,792,458 meters per second.
So a 21 cm line emitted 380,000 years ABB will be observed to have a wavelength of 228.4 m and a frequency of 1.3 MHz.
Using the same equations, we find that a 21 cm line emitted 65 Myr ABB will be observed to have a wavelength of 8.7 m and a frequency of 34.7 MHz.
We thus will be quite interested in taking a detailed look at radio waves in the entire frequency range 1.3 – 34.7 MHz, with corresponding wavelengths from 228.4 m down to 8.7 m.2
The interference from the Earth’s ionosphere and the ever-increasing cacophony of humanity’s radio transmissions makes observing these faint radio signals all but impossible from anywhere on or near the Earth. Radio astronomers and observational cosmologists are planning to locate radio telescopes on the far side of the Moon—both on the surface and in orbit above it—where the entire mass of the Moon will effectively block all terrestrial radio interference. There we will finally hear the radio whispers of matter before the first stars formed.
1 By “neutral” we mean hydrogen atoms where the electron has not been ionized and resides in the ground state—not an excited state.
2 Incidentally, the 2.7 K cosmic microwave background radiation which is the “afterglow” of the Big Bang itself at the beginning of the dark ages (380,000 years ABB), peaks at a frequency between 160 and 280 GHz and a wavelength around 1 – 2 mm. So this is a much higher frequency and shorter wavelength than the redshifted 21 cm emissions we are proposing to observe here.
Ananthaswamy, Anil, “The View from the Far Side of the Moon”, Scientific American, April 2021, pp. 60-63
Burns, Jack O., et al., “Global 21-cm Cosmology from the Farside of the Moon”, https://arxiv.org/ftp/arxiv/papers/2103/2103.05085.pdf
Koopmans, Léon, et al., “Peering into the Dark (Ages) with Low-Frequency Space Interferometers”, https://arxiv.org/ftp/arxiv/papers/1908/1908.04296.pdf