Greetings from Palmia Observatory
Well the Heavens-Above prediction for the latest batch of Starlink satellites was for magnitude 2 visibility for May 30, but our old nemesis, the clouds turned the blue skies to black.
As you can see in this 4 second exposure, nothing of magnitude 2 is going to show through.
|Lots of clouds, but no mag =2 Starlinks; DSLR, 18mm, 4 seconds (Source: Palmia Observatory)|
Ok, with the skies all blue during the daytime and obscured at night, we have an opportunity to return to a topic familiar with scientists and astronomers who rely on observation as part of the scientific method of gaining new knowledge about the world.
In one of our philosophy meetups, we reviewed some of the writings and thinking of 18th century philosopher, David Hume. I remembered one thing about Hume, prior to the meeting, and that was his discussion about the problem of induction. Recall that this problem had to do with how much credence we could place on patterns of observation that seemed to be directed by cause and effect, but that we could never be completely sure. It is just like the analogy of the pig, who becomes content with the farmer who has everyday in the past brought food to eat and the pig thinks that this will continue forever, until it doesn't, when the farmer this time brings a hatchet!
Anyway, Hume divided human knowledge into two broad categories: (1) Knowledge about the relationship between ideas, think of mathematics and geometry, and (2) Knowledge about matters of fact, which are entirely based on observation. He argues that we experience certain correlations, which we tend to generalize to cause and effect relationships, but we have to be careful here, as Hume points out. Humans develop a sense as to how reliable our senses are and how reliable expert testimony and eye witnesses are. We know that not all people are motivated by a singular desire to always speak the truth and get to the bottom of true understanding of the situations we face.
There is a lot to Hume and you can find out more by looking into his various writings, such as the pictured text, "An Enquiry Concerning Human Understanding." My copy on my Kindle app obviously shows a modern version with skyscrapers in the background. Check it out if you dare!
|Rereading Hume on the nature of human understanding (Source: David Hume)|
Ok, so given that introduction to the theory of epistemology and how we are able to learn anything about the world, what are we to make of some of the latest news flashes about the recent supposed evidence for UFO sightings. Have you been following any of this stuff on the Discovery Channel for example? Hmm, somehow, I don't think that is an actual photo of a flying saucer!
|The five UFO traits as shown on the Discovery Channel (Source: discovery.com)|
But followers of UFO events also claim that it is an observational science, just like astronomy. Here is the list of the five observables that are identified on the Discovery channel that apply to UFOs:
|The five UFO traits as shown on the Discovery Channel (Source: discovery.com)|
When we turn to astronomy and the types of observations that are possible and used to find new knowledge and understanding of the universe, beginning with Martin Harwit's book "Cosmic Discovery" is a good place to start. My first introduction to Harwit was at one of the recent Golden Webinar's presentations. Since that time, I purchased this book for review.
|Cosmic Discovery (Source: Martin Harwit)|
One of Harwit's conjectures is that the number of possible astronomical observations and objects or classes of objects is finite and limited. He identifies seven parameters associated with the available types of observations. Gravitational waves are included in the type of carrier category. We see by examining all of the possible messengers that bring us information, that they are all limited in terms of some performance criteria, like sampling rate, angular resolution, etc. All of these capabilities tend to increase as technology improves, but the capabilities are not infinite.
|Characteristics of Astronomical Observations (Source: Martin Harwit, "Cosmic Discovery")|
Harwit reviewed all of the current astronomical categories of objects and processes and that at the time he prepared the following chart, he assigned all known astronomical observations to 43 categories. The breakdown of observations into categories is arbitrary but it doesn't affect the final statistical calculation.
|Plot of common astronomical objects by discovery date (Source: Martin Harwit, "Cosmic Discovery")|
One of the characteristics of astronomical discoveries is that it can be many years after the first discovery of some astrophysical phenomena or observations that it is only then recognized as a new category. Consider this screenshot from Harwit that shows Arp's Diagram. This diagram illustrates how the discovery of the new class of objects was first thought to line up along a strip of observational space. Many objects like quasar 3C273 were observed way back in the 19th century, but it was only with the recent radio observations that the dim spot of optical light was recognized to be part of a new phenomenon. On the right of the strip of easily observed objects, there will be some new objects that are just too dim to be seen with current technology. So, sometimes the astronomical discovery is identifying a new classification of objects or observations that result from some common underlying physics.
|Arp's Diagram (Source: Martin Harwit, "Cosmic Discovery")|
Next, what Harwit does is to consider the statistics of the events and discoveries and estimates the number of remaining categories yet to be discovered. Wow, now this type of argument goes way beyond the argument from induction, which is all rely on, but which we know is not completely correct, but to argue from the list of observations that we have conducted so far, that the number of future types of observations is limited, is really going out on a limb. How can we estimate the unknown future of observations?
Well, Harwit argues that the number of angles that telescopes can be pointed and the time sequence of observations is finite and limited and so on and so on, so the sum total of possible astronomical observations is likewise limited and finite. We usually have the general feeling that knowledge will just keep increasing without bounds, but clearly it seems we are limited, so a limit to knowledge seems plausible too. How many of all of these possible observations have we made so far? Harwit plots the number of discoveries so far and then uses statistics to account for the conjectured finite future of possible observations. You can see his resulting estimate in the plot below where the number of observations peaks and then slowly declines and the cumulative total of observations slowly climbs and bends over and is limited.
So, without going into all of the statistical details, of which I am still trying to wade through, Harwit sets the finite limit for the total number of possible categories of astronomical observations at 130. A key parameter in the statistical calculation is the number of astronomical observations that have been detected with multiple types of messengers. Hmm, pretty neat, but at the same time we should keep Hume's discussion in mind and recognize that induction is not completely reliable.
|Discovery Rate of Observations projected into the future (Source: Martin Harwit, "Cosmic Discovery")|
In wondering about what some of the new observational categories that might show up in astronomy, it turned out that, just by chance, the latest Golden Webinar from the Institute of Astrophysics, Pontificia Universidad Catolica de Chile, in Santiago, Chile. Don't worry, all of the webinars are transmitted in both English and Spanish. The speaker this time was Harry (Hap) McSween, U. of Tennessee, whose topic was "Exploration of Asteroids by the Dawn Spacecraft: Turning Vesta and Ceres from Astronomical Objects into Geological Worlds."
For you that are still looking to photograph an asteroid, you can check out my lucky find of Ceres in this blog post from October 2, 2016 at: http://www.palmiaobservatory.com/2016/10/found-asteroid-pallas-but-what-is-that.html
The discussion of the findings from the Dawn spacecraft included one class of astronomical objects that come into our observation view. The discovery of a cryovolcano on Ceres was not expected and is pretty neat. This discovery can probably be counted as one of the new observational discoveries covered in Harwit's review of the probability of new classes of findings in astronomy. The discovery of the cryovolcano comes about from the increased resolution possible with spacecraft. It is an example of a new class of astronomical discovery.
|Observation of cryovolcano by Dawn Spacecraft (Source+: Hap McSween, Golden Webinar, 6/1/21)|
Until next time, here from our burrow, stay safe, as we recover more of our freedom,