The Learn Tracker
...life-long learning: structured, organized, searchable...
924
Lectures Watched
Since January 1, 2014
Hundreds of free, self-paced university courses available:
my recommendations here
Peruse my collection of 275
influential people of the past.
View My Class Notes via:
Receive My Class Notes via E-Mail:

VIEW ARCHIVE

Contact Me via E-Mail:
edward [at] tanguay.info
Notes on video lecture:
The Nature of Images
Notes taken by Edward Tanguay on December 22, 2014 (go to class or lectures)
Choose from these words to fill the blanks below:
tungsten, day, three, cosmic, astronomical, radiation, daguerreotypes, moon, visual, eerie, problematical, obtaining, light, Daguerre, register, second, photographs, photons, photographic, inundated, useful, light, output, models, darker, red, second, teeming, energy, intervals, blue
•
images
•
we are                    with images in our daily lives
•
enticing us to buy products
•
to remind us of an event
•
to please our artistic tastes
•
photographs
•
it's hard to imagine a time when people didn't have                       
•
1840
•
people were astonished to find that they could capture a              image of a moment in time in the minutest detail far surpassing any method that had ever come before
•
the first                              were called "the mirror with a memory"
•
photographs in astronomy
•
photographic images of one kind or another constitute almost the sole means of analyzing                          objects
•
it therefore behooves us to understand exactly what is involved in                    these images, how we perceive them, and what they can tell us
•
earliest photographs of astronomical objects
•
1851: the         
•
some of the early photos of the 19th century were distinctly           
•
street scene taken by Louis                  in 1838 of the Boulevard du Temple
•
a street always                with people and horse-drawn carriages
•
yet no one is to be seen except for a tiny figure at the lower left who is getting his shoes shined and was thus motionless for long enough to have his image appear on the                          plate
•
every other moving object could not                  on it
•
thus began a quest still with us today for speed, speed, and more speed so that we can capture progressively shorter and shorter time                    in our cameras, our telescopes and even out iPhones to be more and more sensitive to           
•
when they do become more sensitive, we can acquire an image in less time and we say we have increased the temporal resolution of observation.
•
today we can capture in 1/10000th of a              what took Daguerre hours to register on his camera
•
we cannot only record the        a photograph is taken
•
but we can time-tag each individual packet of light as they are received into our instruments
•
we call these packets of light               
•
these photons are the providers of almost all of our astronomical data
•
each photon provides
•
1. time of arrival
•
this allows us to see if the object we are looking at is changing its intensity or light              as a function of time
•
we can search for time variability of              sources
•
2. spatial position that each photon came from
•
how clear the image is
•
in color photographs we have energy information
•
blue light is more energetic than        light
•
x-rays are more energetic than          light
•
but black and white representations of objects can be more              than colored ones
•
e.g. you can see which parts are              than others
•
any representation of an x-ray source is going to be a bit                           
•
3. energy spectrum
•
the energy of each photon
•
how many photons of each energy gets emitted per             
•
a vital fingerprint for understanding the chemical composition of astronomical objects
•
give insights into the energy producing mechanisms governing their                   
•
just as florescent lamps work differently than                  light bulbs
•
so do cosmic sources have different ways to produce their             
•
therefore the energy spectrum can tell us what the object is made of and how it produces its           
•
and that's it, all we can glean from tiny pinpoints of light coming from distant light scattered about the universe are these            bits of data encoded into each photon
•
from these data we can construct              to understand the diverse inhabitants of the cosmos

Vocabulary:

daguerreotype, n. the first publicly announced photographic process and the first to come into widespread use during the early 1840s ⇒ ""The mind with a memory" are what the first daguerreotypes were called."

People:

######################### (1822-1891)
Early American photographer who pioneered astronomical and night photography known for his extraordinary early photographs of the moon
  • first in the United States to manufacture the chemicals used for daguerreotypes
  • first to produce images of stars other than the sun (Vega and Mizar-Alcor stellar system)

Spelling Corrections:

inticing ⇒ enticing

Ideas and Concepts:

Via this afternoon's Analyzing the Universe class: "Since photographic images of one kind or another constitute almost the sole means of analyzing astronomical objects, it behooves us to understand exactly what is involved in obtaining these images, how we perceive them, and what they can tell us."
On the last two centuries of increasing temporal resolution of observation, via this afternoon's Analyzing the Universe class:

"Some of the early photographs of the 19th century were distinctly eerie. For example, this street scene taken by Louis Daguerre in 1838 of the Boulevard du Temple in Paris shows a street that was always teeming with people and horse-drawn carriages, yet in the image no one is to be seen. However, if you look closely in the lower left-hand corner, you'll see a tiny figure who is getting his shoes shined, and was thus motionless for long enough to have his image appear on the photographic plate. Every other moving object could not register on it.

Thus began a quest still with us today for speed, speed, and more speed so that we can capture progressively shorter and shorter time intervals in our cameras, our telescopes, and even out smart phones. As these devices become more and more sensitive to light so that we can acquire an image in less time, we say we have increased the "temporal resolution of observation". Today we have reduced the temporal resolution of observation down to a point that we can record in 10000th of a second what took Deguerre hours to register on his camera."
On our limited source of data to study the cosmos, via this morning's Analyzing the Universe class:

"From the millions of tiny pinpoints of light scattered about the universe, we are only able to glean three bits of data encoded into each photon that reaches us:

1. TIME OF ARRIVAL:the changing intensity of light output as a function of time

2. SPATIAL POSITION:where exactly the photons come from

3. ENERGY CONTENT:how many photons of each type of energy gets emitted per second, a vital fingerprint for understanding the chemical composition of astronomical objects, since just as florescent lamps work differently than tungsten light bulbs, cosmic sources have different ways to produce their energy and the energy spectrum can tell us what the object is made of and how it produces its light

And that's it, these three bits of data are all we have to construct models that explain the diverse inhabitants of the distant cosmos."
On the difference between the words "cosmos" and "universe", via this morning's Analyzing the Universe class: "There's very little actually. Cosmos means "the universe seen as a well-ordered whole" and universe means "all existing matter and space considered as a whole, or the cosmos." The words can often be used synonymously, or you can use cosmos explicitly when you are referring to the well-ordered aspect of the universe. In addition, "cosmological" is used as the technical adjective, e.g. "cosmological redshift", since the adjective "universal" is often used in non-technical contexts and so a term such as "universal redshift" would be confusing."
The Nature of Images
Image Formation
Capturing Images of X-Ray Sources from Space