The Dodgeville area is badly in need of an off-road paved (asphalt) bike path. Every time I go to Madison, I am envious of all the bike trails they have. Why can’t small towns like Dodgeville and rural areas have some paved bike paths, too? Brigham County Park in rural Dane County has a beautiful new trail. Why not Iowa County?
I’d really like to see the Military Ridge Trail between Dodgeville and Ridgeway paved. Anyone interested in serving on an ad hoc committee with me to make that happen?
There is a 5.1-mile paved trail called the Shake Rag Trail which runs along US Highway 151 between Dodgeville and Mineral Point, but it is far from ideal. First of all, there is no safe way to bike to it from Dodgeville! You can ride through the hospital parking lot to Heritage Lane, head south until you get to Brennan Rd., turn right, but when you get to WI Highway 23, you have to ride along the east shoulder of that busy road with fast-moving vehicles for 0.4 miles to get to the bike path, as shown in the map below.
What a relief! You’ve now reached the paved bike path, and it is off-road!
But, after traveling only 0.5 mile, the bike path suddenly ends at Chris-Na-Mar Road.
You now ride 0.7 miles on Chris-Na-Mar Road, and then the off-road bike path starts up again.
Now, you get to ride 1.3 miles on an off-road paved bike path. Yay! But the bike path again abruptly ends at County Road YD. It is not clear what you should do next except maybe turn around?
Persistence pays off, and if you soldier on you’ll find that you can ride 2.1 miles on County Road YD until you reach the off-road bike path again. You’re almost to Mineral Point!
The bike path goes another 0.5 mile until it ends at Shakerag St. in Mineral Point. You’ve traveled a total of 5.1 miles on the Shake Rag Trail, but less than half of it was on a bona fide bike path.
Don’t get me wrong, I’m really glad that the Shake Rag Trail got built. But for any of you who have ridden the crushed rock Military Ridge Trail between Dodgeville and Ridgeway (all off-road), you’ll understand how much nicer Military Ridge Trail would be than the Shake Rag Trail if only it were paved.
With the advent of relatively inexpensive CCD cameras, amateur astronomers with modest-sized telescopes are in an excellent position to contribute valuable scientific data to the astronomical community. One type of object that can be very interesting and useful to observe is the eclipsing binary. And there are a lot of them.
Due to a sometimes fortuitous alignment of the orbital plane of a binary star along or near our line of sight, one or both stars pass directly in front of the other periodically, and this type of object is known as an eclipsing binary.
The brightest eclipsing binary in our sky is Algol (Beta (β) Persei). Known to vary in brightness since antiquity, astute ancient Arab astronomers gave Beta Persei the name “al Ghul” which, loosely translated, means “the Demon Star”. Today, we know that Algol’s brightness variations are caused by a hot blue B8V star (Algol A) going behind and in front of its cooler and less massive but larger K0IV companion (Algol B). Since the two stars orbit each other once every 2.867328 days (they are very close, separated by just a little over 5½ million miles), every 2 days, 20 hours, 48 minutes, and 57 seconds Algol B passes in front of much-brighter Algol A for a few hours, and the single point of light we see from Earth dims by 1.3 magnitudes. This is the primary eclipse. A secondary eclipse also occurs half a period before or after each primary eclipse. When Algol A passes in front of Algol B, the brightness of the point of light we see drops by only 0.05 magnitude. This shallow secondary minimum occurs because Algol B is not nearly as bright as Algol A.
Eclipsing binaries like Algol (which are close enough to each other to form an interacting pair) are interesting subjects for amateur astronomers to monitor. Periods can change, phases can shift, and unexpected events can occur, such as when Dr. Jim Pierce (now Emeritus Professor of Astronomy at Minnesota State University in Mankato) and I were the first to observe ultraviolet flare events from the eclipsing binary V471 Tau at Iowa State University’s Erwin W. Fick Observatory in 1978.
A schedule, if you will, of eclipsing binary primary eclipses (like other astronomical events) is called an ephemeris. Eclipsing binary ephemerides look like this one for Algol:
HJD = 2452500.21 + E × 2.867315
Here, HJD is the heliocentric Julian date of minimum light. Julian date is a continuous count of days and fractions thereof elapsed since an arbitrary starting date of noon Universal Time (UT) on January 1, 4713 B.C. The heliocentric Julian date removes the orbital motion of the Earth from the ephemeris calculations, centering the times of events on the Sun rather than the Earth. An event could be observed to occur as much as 8.3 minutes earlier or later than calculated depending on where the Earth is in her orbit relative to the star. The first number in the equation above, in this case 2452500.21, refers to the heliocentric Julian date of some arbitrary starting minimum. The E stands for epoch, simply a consecutive integer count of successive minima, and the second number, in this case 2.867315, refers to the orbital period of the eclipsing binary in days. The Kreiner website takes the chore out of choosing the appropriate value of E for the time you want to observe by calculating the HJDs (and corresponding Earth-based UT dates and times) of the eclipsing binary you choose over the next several days.
You should monitor a star before, during, and after the eclipse, so having a rough of idea of what object you should observe and when does not require you convert heliocentric Julian date to the Julian date at the telescope. However, any event times from data you record at the telescope must be converted to HJD for it to be useful. There is an online tool to do this for you. Of course, you not only need to know the UT date and time of an event, but also the equatorial coordinates (right ascension and declination) of the object you were observing to calculate the heliocentric Julian date.
We’re not even going to get into barycentric Julian date (BJD), or the fact that the distance between the Sun (or the barycenter of the solar system) and the eclipsing binary of interest is growing (radial velocity > 0) or shrinking (radial velocity < 0), and that this means that the period we measure is not exactly the same as the true orbital period of the system. But it is very close.
The Intergovernmental Panel on Climate Change (IPCC) issued an important special report yesterday on climate change. In the accompanying press release, they state the following:
Limiting global warming to 1.5°C would require “rapid and far-reaching” transitions in land, energy, industry, buildings, transport, and cities. Global net human-caused emissions of carbon dioxide (CO2) would need to fall by about 45 percent from 2010 levels by 2030, reaching ‘net zero’ around 2050. This means that any remaining emissions would need to be balanced by removing CO2 from the air.
This report will be a key scientific input into the Katowice Climate Change Conference in Poland in December, when governments review the Paris Agreement to tackle climate change.
We are already seeing the consequences of 1°C of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice.
Warming of 1.5ºC or higher increases the risk associated with long-lasting or irreversible changes, such as the loss of some ecosystems.
In the Summary for Policymakers, the IPCC states that “warming from anthropogenic emissions from the pre-industrial period to the present will persist for centuries to millennia and will continue to cause further long-term changes in the climate system, such as sea level rise, with associated impacts.”
This last point is very important. Even if humanity disappeared from the face of the Earth tomorrow, it will take centuries to millennia for greenhouse gases in our atmosphere to return to pre-industrial levels.
Richard Wolfson, Professor of Physics at Middlebury College in Middlebury, Vermont, states in his excellent 2007 video course, “Earth’s Changing Climate” (The Great Courses, Course No. 1219),
The atmosphere, living things, soils, and surface ocean waters all represent short-term carbon reservoirs. Cycling among these reservoirs occurs mostly on relatively short time scales. In particular, a typical carbon dioxide molecule remains in the atmosphere only about five years. But the rapid cycling of carbon through the atmosphere-biosphere-surface ocean system means that any carbon added to that system remains there much longer—for hundreds to thousands of years. Because the added carbon cycles through the atmosphere, the level of atmospheric carbon dioxide goes up and stays up for a long time.
We’ve known about this aspect of climate change for a long time. It is based on solid science. Any action we take now, either positive or negative, will affect Earth’s environment many generations into the future.
I know of no better introduction to climate science than Richard Wolfson’s video course. Even though it was produced 11 years ago, it is still completely relevant.
Excellent astronomy magazines have come and gone throughout the past several hundred years, and the time has come to start digitizing microfilm, microfiche, or printed copies of all these magazines and journals, and make them available at an affordable price to individuals and institutions on DVD and via the Internet. First on my list? Popular Astronomy, which was published from 1893 until 1951 at Carleton College in Northfield, Minnesota, a worthy predecessor to Sky & Telescope.
I’ve been in the work force for 38 years, and I have always had a cubicle with full-height partitions or an office of my own. As a computer programmer, I’ve always needed to concentrate intensely for most of the work day. That requires a certain amount of freedom from visual and auditory distractions. I need to focus.
This week, the work environment I have had throughout my career is being taken away from me, forcibly, as it is for all of us where I work. We had no input. No explanation was given. The decision was made at the highest levels of our company’s management. We are moving to open office.
We still have cubicles—if you want to call them that—but no partition is higher than eye level when sitting in an office chair. No more upper shelves, no more book shelves. Only a work surface and a meager amount of drawer storage underneath. No more physical barriers between rows. Just one big, noisy, overilluminated room. Everything and everyone exposed for all to see from anywhere in the room.
Speaking of illumination, as part of the office “improvements” they have also replaced the warm white fluorescent lights we have used for decades—with a correlated color temperature (CCT) around 3000 to 4000 K—with significantly brighter and bluer LED lights having a CCT of 4000 to 5000K or higher. It provides a cold, harsh, clinical illumination, not at all like the natural daylight they are trying to emulate. LEDs are, of course, readily available in the warmer color temperatures of 2700K to 4000K.
I am not alone. Many of my coworkers—some much younger than me—do not like open office nor the bluer, brighter lights we now have to endure.
This just adds additional stress to an already stressful job. When is management going to learn that one size does not fit all?
Anyone need a top-flight SAS programmer with good communication, mentoring, and teaching skills?
9.1 Issue G: The anthropic question: Fine tuning for life
One of the most profound fundamental issues in cosmology is the Anthropic question: why does the Universe have the very special nature required in order that life can exist? The point is that a great deal of “fine tuning” is required in order that life be possible. There are many relationships embedded in physical laws that are not explained by physics, but are required for life to be possible; in particular various fundamental constants are highly constrained in their values if life as we know it is to exist:
Ellis goes on to quote Martin Rees.
A universe hospitable to life—what we might call a biophilic universe—has to be special in many ways … Many recipes would lead to stillborn universes with no atoms, no chemistry, and no planets; or to universes too short lived or too empty to evolve beyond sterile uniformity.
Also, why do we live in a universe with three spatial dimensions and one time dimension? Others are possible—even universes with two or more time dimensions.
But it appears that only three spatial dimensions and one time dimension is conducive to life (at least life as we know it), as shown in the diagram above (Whittle 2008).
In fact, altering almost any of the parameters would lead to a sterile universe and we could not exist. Is the universe fine-tuned for our existence?
Let’s assume for the moment it is. Where does that lead us?
As our understanding of physics advances, we will eventually understand why these parameters must have the values that they do. -or-
We will eventually learn that some of these parameters could have been different, and still support the existence of life. -or-
God created the universe in such a way that life could exist -or-
We’re overthinking the problem. We live in a life-supporting universe, so of course we find the parameters are specially tuned to allow life. -or-
There exist many universes with different parameters and we just happen to find ourselves in one that is conducive to life. (The multiverse idea.)
#4 is the anthropic explanation, but a deeper scientific understanding will occur if we find either #1, #2, or #5 to be true. #3 is problematic for a couple of reasons. First of all, how was God created? Also, deism has a long history of explaining phenomena we don’t understand (“God of the gaps”), but in time we are able to understand each phenomenon in turn as science progresses.
The anthropic explanation itself is not controversial. What is controversial is deciding to what degree fine tuning has occurred and how to explain it.
In recent years, the multiverse idea has become more popular because, for example, if there were a billion big bangs and therefore a billion different universes created, then it should not be at all surprising that we find ourselves in one with just the right set of parameters to allow our existence. However, there is one big problem with the multiverse idea. Not only do we have no physical evidence that a multiverse exists, but we may never be able to obtain evidence that a multiverse exists, due to the cosmological horizon problem1. If physical evidence of a multiverse is not forthcoming, then in that sense it is not any better than the deistic explanation.
To decide whether or not there is only one combination of parameters that can lead to life we need to rule out all the other combinations, and that is a tall order. Recent work in this field suggests that there is more than one combination of parameters that could create a universe that is hospitable to life (Hossenfelder 2018).
Thinking now about why our universe is here at all, it seems there are just two possibilities:
(1) Our universe has a supernatural origin.
(2) Our universe has a natural origin.
If our universe has a supernatural origin, then what is the origin of the supernatural entity (e.g. God)? If, on the other hand, our universe had a natural origin (e.g. something was created out of nothing), didn’t something have to exist (laws of physics or whatever) before the universe came into existence? If so, what created those pre-conditions?
In either case, we are facing an infinite regression. However, we could avoid the infinite regression by stating that something has to exist outside of time, that is to say, it has no beginning and no ending. But isn’t this just replacing one infinity with another?
Perhaps there’s another possibility. Just as a chimpanzee cannot possibly understand quantum mechanics, could it be that human intellect is also fundamentally limited? Are the questions in the previous two paragraphs meaningless or nonsensical in the context of some higher intelligence?
1We appear to live in a universe that is finite but very much larger than the region that is visible to us now, or ever.
G.F.R. Ellis, Issues in the Philosophy of Cosmology, Philosophy of Physics (Handbook of the Philosophy of Science), Ed. J. Butterfield and J. Earman (Elsevier, 2006), 1183-1285.
Sabine Hossenfelder, Lost in Math: How Beauty Leads Physics Astray (Basic Books, 2018).
M. J. Rees, Our Cosmic Habitat (Princeton and Oxford, 2003).
WWV continuously broadcasts time signals at 2.5, 5, 10, 15, and 20 MHz, and WWVH does the same at 5, 10, and 15 MHz.
There are many uses for these radio stations. For example, I have a shortwave radio in my observatory and use the WWV voice time broadcasts on 2.5, 5, and 10 MHz to make sure my GPS clock is properly synchronized, and also use it to set my computer clocks accurately and well as my wristwatch.
WWV and WWVH are an important and reliable “low tech” backup to the Global Positioning System (GPS) satellite constellation which can be used to derive accurate times.
Well over 50 million devices use the 60 kHz signal provided by WWVB to allow them to maintain accurate time, and eliminating this particular service would be devastating. Whether or not shutting down WWVB is part of the proposed budget cuts remains to be seen.
These U.S. Government radio stations have been announcing accurate time since World War II. We must do all we can to ensure their continued operation.
Last night I re-watched the excellent two-hour PBS NOVA special Black Hole Apocalypse, and this time I jotted a few questions down.
Has Gaia DR2 improved our knowledge of the distance to the O-star black hole binary system Cygnus X-1 (6000 ly) and the mass of the black hole (15M☉)?
Are there any known pulsar black hole binary systems?
Could LIGO (and now Virgo in Italy) detect a stellar-mass black hole infalling into a supermassive black hole at the center of the Milky Way galaxy or another galaxy?
Do supermassive black holes play a role in galaxy formation? If so, how does a supermassive black hole interact with dark matter?
Wouldn’t material infalling into a black hole undergo extreme time dilation and from our vantage point take millions or even billions of years to cross the event horizon? If so, don’t all black holes—even supermassive ones—form from rapid catastrophic events such as core-collapse supernovae and black hole collisions?
Gaia DR2 (Gaia Data Release 2) has indeed measured the distance to the Cygnus X-1 system. The “normal” star component of Cygnus X-1 (SIMBAD gives spectral type O9.7Iabpvar) is the 8.9-magnitude star HDE 226868. Gaia DR2 shows a parallax of 0.42176139325365936 ± 0.032117130282281664 mas (not sure why they show so many digits!).
The distance to an object in parsecs is just the reciprocal of the parallax angle in arcseconds, but since the parallax angle is given in milliarcseconds, we must divide parallax into 1000. This gives us a best-estimate distance of 2,371 parsecs or 7,733 light years. Adding and subtracting the uncertainty to the parallax value and then doing the arithmetic above gives us a distance range of 2,203 to 2,566 parsecs or 7,186 to 8,371 light years. (To get light years directly, just divide the parallax in millarcseconds into 3261.564.)
This is 20% to 40% further than the distance to Cygnus X-1 given in the NOVA program, and looking at the source for that distance (Reid et al. 2011) we find that the Gaia DR2 distance (7,186-8,371 ly) is outside the range given by Reid’s VLBA radio trigonometric parallax distance of 5,708-6,458 ly. It remains to be seen what effect the Gaia DR2 distance, if correct, will have on the estimate of the mass of the black hole.
The estimate of the mass of the black hole in Cygnus X-1 is calculated using modeling which requires as one of its input parameters the distance to the system. This distance is used to determine the size of the companion star which then constrains the scale of the binary system. Because the Cygnus X-1 system is not an eclipsing binary, nor does the companion star fill its Roche equipotential lobe, traditional methods of determining the size of the companion star cannot be used. However, once we use the distance to the system to determine the distance between the black hole and the companion star, as well as the orbital velocity of the companion star, we can determine the mass of the black hole.
Now, moving along to the next question, have any pulsar black-hole binary systems been discovered yet? The answer is no, not yet, but the hunt is on because such a discovery would provide us with an exquisite laboratory for black hole physics and gravity. Something to look forward to!
Could LIGO ( and Virgo) detect a stellar-mass black hole infalling into a supermassive black hole at the center of the Milky Way galaxy or another galaxy? No. That would require a space-based system gravitational wave detector such as the Laser Interferometer Space Antenna (LISA)—see “Extreme mass ratio inspirals” in the diagram below.
The above diagram illustrates that gravitational waves come in different frequencies depending on the astrophysical process that creates them. Ground-based detectors such as LIGO and Virgo detect “high” frequency gravitational waves (on the order of 100 Hz) resulting from the mergers of stellar-mass black holes and neutron stars. To detect the mergers of more massive objects will require space-based gravitational wave observatories (millihertz band) or pulsar timing arrays (nanohertz band) in the case of supermassive black holes binaries within merging galaxies. The future of gravitational wave astronomy looks very bright, indeed!
Do supermassive black holes play a role in galaxy formation? Probably. We are not yet able to explain how supermassive black holes form, especially so soon after the Big Bang. Does dark matter play a major role? Probably. The formation of supermassive black holes, their interaction with dark matter, and their role in galaxy formation are all active topics or current research. Stay tuned.
To succinctly restate my final and most perplexing question, “How can anything ever fall into a black hole as seen from an outside observer?” A lot of people have asked this question. Here’s the best answer I have been able to find, from Ben Crowell:
The conceptual key here is that time dilation is not something that happens to the infalling matter. Gravitational time dilation, like special-relativistic time dilation, is not a physical process but a difference between observers. When we say that there is infinite time dilation at the event horizon we don’t mean that something dramatic happens there. Instead we mean that something dramatic appears to happen according to an observer infinitely far away. An observer in a spacesuit who falls through the event horizon doesn’t experience anything special there, sees her own wristwatch continue to run normally, and does not take infinite time on her own clock to get to the horizon and pass on through. Once she passes through the horizon, she only takes a finite amount of clock time to reach the singularity and be annihilated. (In fact, this ending of observers’ world-lines after a finite amount of their own clock time, called geodesic incompleteness, is a common way of defining the concept of a singularity.)
When we say that a distant observer never sees matter hit the event horizon, the word “sees” implies receiving an optical signal. It’s then obvious as a matter of definition that the observer never “sees” this happen, because the definition of a horizon is that it’s the boundary of a region from which we can never see a signal.
People who are bothered by these issues often acknowledge the external unobservability of matter passing through the horizon, and then want to pass from this to questions like, “Does that mean the black hole never really forms?” This presupposes that a distant observer has a uniquely defined notion of simultaneity that applies to a region of space stretching from their own position to the interior of the black hole, so that they can say what’s going on inside the black hole “now.” But the notion of simultaneity in GR is even more limited than its counterpart in SR. Not only is simultaneity in GR observer-dependent, as in SR, but it is also local rather than global.
K. Liu, R. P. Eatough, N. Wex, M. Kramer; Pulsar–black hole binaries: prospects for new gravity tests with future radio telescopes, Monthly Notices of the Royal Astronomical Society, Volume 445, Issue 3, 11 December 2014, Pages 3115–3132, https://doi.org/10.1093/mnras/stu1913
Mingarelli, Chiara & Joseph W. Lazio, T & Sesana, Alberto & E. Greene, Jenny & A. Ellis, Justin & Ma, Chung-Pei & Croft, Steve & Burke-Spolaor, Sarah & Taylor, Stephen. (2017). The Local Nanohertz Gravitational-Wave Landscape From Supermassive Black Hole Binaries. Nature Astronomy. 1. 10.1038/s41550-017-0299-6. https://doi.org/10.1038/s41550-017-0299-6 https://arxiv.org/abs/1708.03491
J. Ziółkowski; Determination of the masses of the components of the HDE 226868/Cyg X-1 binary system, Monthly Notices of the Royal Astronomical Society: Letters, Volume 440, Issue 1, 1 May 2014, Pages L61–L65, https://doi.org/10.1093/mnrasl/slu002
Already early this week you will see an occasional Perseid meteor gracing the sky, but next weekend the real show begins. The absolute peak of this year’s Perseids is favorable to observers in North America, and with no moonlight interference we are in for a real treat—provided you escape cloudy weather. I highly recommend “going mobile” if the weather forecast 24-48 hours before the peak night indicates less than ideal conditions at your location.
The Perseids this year are expected to peak Sunday night August 12/13. Highest observed rates will likely be between 2 a.m. and 4 a.m. Monday, August 13. Here’s a synopsis of the 2018 Perseids.
Many years ago I wrote a short poem while listening to the final and most otherworldly section of The Planets by Gustav Holst: Neptune, the Mystic.
Here it is:
Neptune, the Mystic from The Planets by Gustav Holst
Royal Philharmonic Orchestra, Vernon Handley
Ambrosian Chorus, John McCarthy
Alto ALC 1013
The endless poetry of space Sends shivers across my spine,
And there upon the threshold sounds The now distant drone of time.
Music fills the spacecraft Starlight fills the night,
And there upon the threshold think I wonder, was I right?
The Planets was written by Holst between 1914 and 1916, and the premiere performance was at The Queen’s Hall, London, on September 29, 1918. Adrian Boult conducted the orchestra in a private performance for about 250 invited guests. The Queen’s Hall was destroyed by an incendiary bomb during the London Blitz in 1941, seven years after Holst’s death in 1934.
Pluto was discovered by Clyde Tombaugh in 1930, and was considered to be the ninth planet until its controversial demotion by the IAU in 2006. A number of composers have added a Pluto movement to ThePlanets (“Pluto, the Renewer” by Colin Matthews, for example), and even an improvised performance (“Pluto, the Unpredictable”) by Leonard Bernstein and the New York Philharmonic. I remember enjoying “Pluto, the Unknown” by American composer Peter Hamlin performed by the Des Moines Symphony in 1992, but unfortunately no recording of this work exists.