What your astrological sign tells about you

c20ff4414e099f9a1caf1de20f8df9baNothing, except your gullibility if you believe in astrology. I have taught introductory astronomy at the college level for decades, and I know that there is a pervasive misunderstanding that connects astrology with astronomy. But let’s get this straight. Astronomy is a legitimate  science dealing basically with the physical components of the Universe including planets, stars and galaxies. Astrology is an ancient fortunetelling practice based on the human desire to know the future. Astrology is, at best, a pseudoscience. To put it bluntly, comparing astronomy to astrology is like comparing a board certified surgeon to the activities of a medieval barber.

Humans have an amazing ability to see patterns and connections, and it is in part this ability that draws people to astrology just as surely as it draws others to astronomy and other forms of true science. The critical difference is in knowing which patterns and connections are real and meaningful, and which are simply wishful thinking, or as some prefer, “magical thinking.”

When you look with a wishful eye, you can see patterns and recognizable shapes in just about anything, from stars or clouds in the sky to tea leaves in the bottom of a cup to faces on a piece of toast to the arrangement of amorphous blobs on a shower curtain. Seeing basically random patterns and then associating them with real objects or ideas is called “pareidolia.”

When we assign meaning to such misperceived random patterns, it is called “apophenia.” The bottom line is that the human mind can see patterns where none really exist, and then assign meanings to those occurrences. There are often unrelated events that happen at the same time, so if that fits into a preconceived way of thinking it is assumed as evidence. For example, let’s say that two of your favorite singers happen to be born on the same day. Therefore they have the same Zodiacal “sign.” For someone who believes in astrology, that might “prove” that astrology is true, even though the vast majority of other singers have birthdays throughout the year, under other “signs.”

From any reasonable standpoint, that’s just a coincidence. We remember coincidences more than non-coincidences, and as such, we attribute more meaning to coincidences even though they are statistically meaningless. We don’t remember non-coincidences.

What do the following pairs have in common?

January 8
Elvis Presley & Kim Jong Un

March 10
Chuck Norris & Osama bin Laden

April 28
Jay Leno & Saddam Hussein

Well at first glance, neither member of the pair has much to do with the other. All are different nationalities; all strongly different personalities; all very different political leanings. They are all famous for one thing or another. They are all male, which is not a significant factor here. The only other factor I know of is that they each pair shares the same birthday. That’s January 8, March 10 and April 28, in order. So, from an astrologer’s standpoint, they all have the same “sign.”

Since they all share the same birthdays, one would think that astrologically they would be very similar people. But they are not. Each member of the pair is greatly different from the other member. But what is interesting is that astrologers, or just people interested in astrology, will fall all over themselves trying to find points of connection between each member of the pair. They will cherry pick often minor details to validate their beliefs. This is much the way politics works, too.

Just because we see patterns does not make them real. The untrained or mis-trained mind believes what it wants to believe, but science requires evidence. There is no valid evidence for astrology, only arbitrarily held beliefs and expectations.

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The Inverse Square Law

Or why nearby street lights are bright and distant streetlights are dim

The Inverse Square Law is the mathematical description for how the brightness or intensity of radiated energy (such as light) varies with distance. In other words, it describes, mathematically, why and how lights appear brighter when you are close and dimmer when you are far away. This is simple enough. We intuitively use the concept to gauge distances (at least with familiar light sources such as car headlights).

Because this precise mathematical description exists, comparing the known brightness of a light (such as a light bulb) to its measured brightness at a known distance allows you to calculate the distance.

Say you are sitting next to a roaring campfire. Most of the heat you feel is due to infrared radiation, a form of electromagnetic radiation like light. If you are uncomfortable, you move a few feet away and the temperature, which is a measure of the amount of infrared radiation you are receiving, drops considerably. The amount that the radiation drops can be precisely calculated with the inverse square law.

Now let’s say that you are sitting 2 feet from a lamp. With a light meter (photometer) you measure the light intensity at a level 8. (You don’t need to know what the units are here, just that it is at a level 8). Now you move twice as far away, to 4 feet, and re-measure the intensity. If this were a simple “inverse” relationship (without the “square” part), then you would expect the light meter to measure 4, because since you are twice as far away, “one over two” is 1/2 or one-half. However, light followed the “inverse square” law, so instead of “one over two” you have “one over two squared.” Two squared is two times two, or 4. So you have 1/4, or one fourth the original intensity. Thus, the new intensity is 2.

With this precise mathematical knowledge, we can work backwards to figure out distances. Suppose that we know that at 10 feet a bright lamp gives and intensity on the light meter of, say, 16. Then we move to some distance where the light meter reads 4. Since we know the inverse square law, we know that 4 is 1/4 of 16, so that means that we must be twice as far away. Thus we are 20 feet from the lamp.

We can use the same method to determine the distances to some stars. If we know the true brightness of a star (that is, how bright it is at a given distance), we can use the inverse square law derive distance by  comparing how bright it appears to its true brightness.

The inverse square law works with radiated electromagnetic energy whether it be visible light, infrared, radio waves or even high powered x-rays and gamma rays. It even applies to gravity.




(I should note that this applies to unfocused or omni-directional light. That is, light that is radiated equally in all directions, say from a star or a round light bulb. Light that is focused or “collimated,” such that light rays are sent out in parallel beams, do not follow the inverse square law. This would include projectors, flashlights and lasers. However, since there really is no such thing as a perfectly collimated light source, even lasers spread out a bit. This can be described mathematically, just not with the common inverse square relationship.)




(Graphic of the inverse square law from Wikimedia Commons. Image by “Borb”)

Unattributed material copyright 2018 by Final Copy, Inc. Permission granted to redistribute online with attribution for non commercial, educational purposes. All other rights reserved.

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Daylight Saving Farce

Daylight Saving Time ClocksDaylight Saving Time returns this Sunday morning at 2 am for most of the US and Canada. As I have written several times before, this is an ill considered and costly practice that does more harm than good. Usually sold to the public as somehow saving energy or helping farmers or keeping school children safe, it does now of those things. In fact, there is reason to believe that it actually makes matters worse.  I am not going to go into all that right now, but will refer you to an excellent article in Forbes: The 5 Reasons To Keep Daylight Saving Time Have No Science To Back Them Up

The author of the aforementioned article, astrophysicist Ethan Siegel, lists the following 5 Reasons commonly used to promote Daylight Saving Time:

1.) It saves fuel.
2.) It helps farmers.
3.) Daylight Saving Time improves safety.
4.) We enacted it for energy conservation.
5.) Daylight Saving Time is now standard.

But in fact, as Siegel points out and I agree, none of these reasons is true. In fact, the evidence shows that Daylight Saving Time actually hurts energy conservation and appears to lead to more deaths. And yet we continue endure this ridiculous practice, dutifully springing forward and falling back each year.

Why? It generally boils down to special interest groups or business concerns with vested interests buying off the votes of members of Congress, who in turn vote in favor of the special interests with no regard to the effect on the public. The link above gives a better argument, but that is the main reason in a nutshell.

Daylight Saving Time comes, originally, from a joke of Benjamin Franklin. I’m sure that Franklin never thought anyone would take the idea (which he actually proposed for France, Paris in particular, not the US). But here we are. Feeble-minded Congress members, swayed by financial contributions from special interests and businesses (the small minority that actually benefit from the policy), impose disruptive and egregious rules on the American public.

Of course this is not the only example, but it is clearly motivated not by reason, evidence and the best interests of the people. Daylight Saving Time saves nothing except the financial interests of Congress and businesses that profit from it.

Daylight Saving Time is a farce and should be abolished.


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A Blood Red Blue Super Moon Eclipse!

SupermoonThe image here may be what some folks are expecting on Wednesday morning. Sorry. I don’t want to dampen anyone’s enthusiasm, but as Carl Sagan said:

“For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring.”

If you don’t know what I am talking about, you’ve probably been living under a rock for the past few months. Otherwise, you probably know that there is a total lunar eclipse coming this Wednesday morning (January 31, 2018). You may also have heard a lot of talk about it being a super moon and a blue moon and a blood moon.

It turns out this that Full Moon is at or near its closest point to the Earth. In this case, it is not quite as “super” as the first Full Moon at the beginning of the year.

And of course there is a total lunar eclipse, although it is before dawn and while most of North America will see totality, western observers are favored. The entire event from beginning to end will be seen from Western Canada, Alaska, Hawaii, Australia and much of East Asia.

For most of the continent, the Sun rises and the Moon sets before the end of totality. Here is a table of timings derived from data courtesy of Fred Espenak and MrEclipse.comeclipsetable

For additional information, see this page on EarthSky:

The following is specifically for the Denver area. If you live East of Denver, you can adjust your times from the table above. Unfortunately, the farther east you go, the lower the Moon will be in the sky. It will already have gone down before the end of totality in most locations. For locations West of Denver, the Moon will be higher in the sky and those on the West Coast will be able (weather permitting) to see it through until the end of totality.

Specifically for the Denver area, the eclipse actually begins as the Moon enters the Earth’s outer shadow at about 3:51 am, but you won’t likely notice anything at that time. The better part of the eclipse begins with the partial phase, which begins at about 4:49 am. Shortly after this time you should be able to notice a darkening at the upper limb of the Moon. This darkening — the Earth’s inner shadow or umbra — will creep across the Moon until it is completely covered and totality begins at 5:52 am.

By the time of totality, the Moon will be low in the West-northwestern sky, only about 14 degrees high as seen from Denver. By “greatest” eclipse (essentially the mid-point) at 6:30 am, the Moon will be quite low in the West-northwest, hovering just above the mountains for some locations in the eastern part of the Denver area, but already lost behind the mountains for locations on the West side. Totality is over at 7:08 am, by which time the Moon is setting and the Sun is rising.

There will be several eclipses  — both solar and lunar – this year, but this is the only one visible from North America. The next eclipse visible for us will be January 21, 2019.


Carl Sagan quote taken from The Demon-Haunted World: Science as a Candle in the Dark. I should admit that I took it out of context a bit as Sagan was referring to religious beliefs. But I think it is appropriate here, too.

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Reflections of an Eclipse

05288-500Snappy title, huh? Actually, it should be, “Using a Mirror to View the Total Solar Eclipse,” but I thought that a bit dry.

(Image of the McMath Pierce Heliostat mirror at the Kitt Peak National Observatory. Credit: NSO/AURA/NSF )

If you can get past all the hype and hysteria, the August 21, 2017 total solar eclipse will be an event to remember, and it will be all the more special if you view it yourself.  Seems like some people are just out to make a buck, though, selling memorabilia and fake observing glasses. But even if you were lucky enough to get your genuine and safe viewing “glasses,” the image you will see will be very small. If you want to share with a group, you’ll want something bigger.

Here’s the latest solar image from NASA’s Solar and Heliospheric Observatory (SOHO). The mirror projection method described here will not provide such a large and detailed image as this (neither will it be yellow-orange!), but it will display the partial phases of the eclipse quite nicely. And at other times, you will be able to see large sunspots.

By the way, this is the basic method used at large solar observatories. The image at the top shows the mirror at the McMath Pierce Heliostat at Kitt Peak National Observatory in Arizona. It allows highly detailed images of the Sun. Our instructions call for a somewhat more modest mirror.

Pinhole projection, which you will find suggested in many places, is a common method. This is good, and it works, but the small size of the image is still a bit disappointing. Instead, you can make a nice image 3 or 4 inches across or even larger using a variation with a mirror. It’s the same basic physics, except that you reflect the light onto a wall instead of a small piece of cardboard. [Interestingly, the two methods show the same difference as that between the two major types of telescopes, refracting (which depends on a lens) and reflecting (which naturally depends on a mirror.)]

Here is a basic graphic showing how this works, and instructions based an excerpt from an activity I give to my students that involves projecting an image of the Sun:


You will need a very small, flat (non-magnifying) mirror. You need something roughly a quarter inch across. Since such small mirrors are rare, you can use a larger mirror, but you must block out all but a small hole. Make a small round hole (about 6 or 7 mm, roughly one quarter of an inch, is good) in black construction paper and mount this on the front of the mirror so that the mirror only shows through the hole. In a pinch you could use a large index card for this, but black construction paper is preferable.

Patti Sand Sun Mirror on TripodThe image on the left is from a former student, Patti Sand, for her class project in which she measured the diameter of the Sun, not observe an eclipse. She attached a flat compact mirror on a tripod, with paper blocking out all but a small hole exposing the mirror.

PattiSand3The image on the right shows how Patti reflected the image through an open door onto the wall  in a darkened room.

PattiSand4This last image shows what the Sun looked like on the way. Please note that it looks oblong because of the angle of the camera. There are also markings on the wall that were part of Patti’s project.

You could also use a dental mirror, which is what I used for this example, but you will need to project the image maybe 35-50 feet to get a good, well defined image. The larger the mirror, dentalmirrorthe father you have to reflect the image to get good resolution. The key is experimentation before hand.

Determine how you will mount the mirror in order to be able to aim the reflection of the Sun onto the wall. It is preferable that the mirror be located at approximately the same height above the ground as the reflection will be on the wall. Using a tripod as illustrated is an excellent way to do this, although there are many other way you could do it. The exact method is left to you. Holding by hand is of course one way, but you have to have a steady hand.

Find a suitable location to perform the observation. The easiest way to do this is to project onto a North-facing wall around noon. The wall onto which you project needs to be in shadow so that you can see the image well. Furthermore, it needs to be round in shape rather than oblong. If you follow the instructions carefully, you will get a round spot on the wall that is, in fact, an actual image of the Sun. It may not be terribly sharp and detailed, but it is an image as opposed to simply a reflection of the shape of the mirror or cut out.

Experiment with sizes and distances to find something that works for you. But keep in mind that the ratio of the size of the reflection distance (“l” in the graphic) to the size of the mirror cutout should be in the order of 1200 or 2500 to one. A 6 meter reflection from a 7 mm mirror fits the lower end of this ratio. That is about 23 feet distance for a quarter inch hole. These are just suggestions. The exact measurements are not terribly critical here, but you need to be close to this ratio and you do need to be projecting onto a light surface in a darkened room.

Experiment with sizes and distances to find something that works for you. But keep in mind that the ratio of the size of the reflection distance (“l” in the graphic) to the size of the mirror cutout should be in the order of 1200 or 2500 to one. That’s a fairly large range. When using a 6-7 mm (quarter inch) mirror or cutout, it’s best that you do not use reflection distances (“l”) of less than 7 meters (about 23 feet) or more than 15 meters (nearly 49 feet). The reason for this is simply that if the projection distance is too short, the image will be bright but too fuzzy (out of focus); if the distance it too great, the image will be sharply defined, but dim and difficult to see. With a 6-7 mm hole,  a distance of 7-15 meters is about the best range when projected onto a flat surface in the shade.

In general, use the shortest distance that provides you with an acceptable image. These are just suggestions. The exact measurements are not terribly critical here, but you need to be close to this ratio and you do need to be projecting onto a light surface in a darkened room.

 Again, the larger the mirror, the father you have to reflect the image to get good resolution.

Of course, standard precautions hold. Do not look directly into the reflection and be careful not to reflect it onto people or animals. This does not intensify the heat like a magnifying glass, but it is still bright sunlight and should not be observed directly.


mirrorprojectorFor the record, here is my quickly thrown together set up on Friday, August 17 using a tripod, a dental mirror and an index card cut out mask with a hole-punch hole (about a quarter inch). I reflected the sun from the tripod to the back of my garage onto a piece of white foam core. The distance was roughly 35 feet or approximately 10.5 meters.

sunAs you can see, there is a distinct circular image. Unfortunately, the sunspots currently on the Sun’s surface are not big enough to resolve with this method. This is, of course a fairly crude set up. Still I have seen large sunspots before using a set up like this. During the eclipse, the crescent shape of the partially eclipsed Sun will be quite distinct.

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Getting Past the Eclipse Hype

79eclipseConsidering the absurd level of hype and some of the more ridiculous exaggerations and crackpot  claims of mystical silliness, I am sorry to say that I will be glad when the whole thing is over.

Eclipses are amazing and beautiful. I witnessed the 1979 total eclipse in Williston, North Dakota, as well as partial eclipses before and since. . Such an event is worth your time and effort, and I am hopeful that this one will inspire an increased interest in science. That’s the good part.

But I am concerned that the reported traffic congestion, lack of accommodations and the hordes of hopeful eclipse watching pouring into small towns across the country will result in a less than happy experience. And instead of blaming the over-exuberant media that hyped it, disappointed observers will blame astronomers and science in general.

And then some will miss it altogether by the actions of  ill-informed and over-protective parents and school administrators. I know of schools here in Colorado where students will be prevented from even going outside during the eclipse, with or without the special glasses. I even heard the mother protesting these restrictions claiming that she wanted her child to see this amazing event because it would grow as dark as night, she claimed, even in our roughly 90% totality. As one who has seen a similar eclipse, I assure you that it does not grow “dark as night” even in the path of totality. (It will be like a fairly deep twilight, with brighter skies around the horizon.) Here in northern Colorado it will perhaps grow as dim as an overcast day, but hardly dark.  There is just so much misinformation and so much being taken out of context.

Let us hope that I am wrong and everyone has a good, educational experience..

But the really annoying aspect is coming from the wingnuts predicting the end of the world (again), the dangers of lizard men, massive power failures or even the appearance of the fictional planet Nibiru that supposedly will crash into Earth 33 days after the eclipse. Then there are less dire but no less absurd claims of a new level of cosmic consciousness or other such mystical woo woo.

Now, I am hopeful and even confidant that the majority of Americans won’t buy into this weak-brained nonsense, but given our current political situation it is very clear that many are swayed by sensational claims, vacuous promises and irrational ruminations.

So please folks, enjoy the eclipse, and help others realize that it is a perfectly natural and predictable event, useful for inspiration as well as scientific interpretation. It is not a religious sign, a mystical portent or anything to be feared. Let’s hope that people can all grow up a little.

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The Last Total Solar Eclipse in the USA

1979 Total Solar Eclipse by Larry C. SessionsI have seen references several times lately online, including an article in Popular Science, stating that the last total solar eclipse visible from the United States was in 1918. This is simply not true. There have been several total eclipses visible from portions of the US since then, including the last one on February 26, 1979. I can attest that this one was visible, as I personally witnessed it in Williston, North Dakota, with the crew from the Fort Worth Museum of Science and History.

Astronomers from the United States Naval Observatory planned to make observations during the 1918 eclipse to test Einstein’s recently minted General Theory of Relativity. Unfortunately, the observations in Oregon were clouded out, and the honor of successfully testing Einstein’s theory fell to British astronomer Arthur Eddington, based on observations of an eclipse in 1919, which did not cross North America. 

TSENorAm1901This map illustrates solar eclipse paths across the US in the early 20th Century.

Despite widespread pubic interest, no such major scientific import falls to the 2017 event. The next solar eclipse visible in the US is in April, 2024, which runs from Texas northeast to Maine. An even better opportunity comes on August 12, 2045, when a wide path of shadow (umbra) runs from Northern California to Florida. This path will pass right over my home town, but chances are, I will miss it.

TSENorAm1951This map charts solar eclipse paths including the February 26, 1979 event.

For the record, it is estimated that any specific location on Earth, a total solar eclipse can be observed on the average about once every 300 years. However, specific locations may not be so lucky.

20264870_1384030974965841_20876766761428793_nHere in Denver, the last total eclipse was the famed one mentioned above, on June 8, 1918. Although several not-quite-total annular eclipses will occur before then, the next full on total eclipse viewable from Denver will be on July 22, 2772. I think I will miss that one as well.


Thanks to Fred Espenak and NASA for the maps and predictions, the Central Arkansas Astronomical Society (CAAS) and The Denver Post for the clipping.

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