chapter 4 Flashcards
great informant by apparatus to father/refine light
electromagnetic radiation (EM)
wavelength, photon, infrared (IR), light, ultraviolet (UV), S-ray, gamma ray, atmospheric window
spectrum
spectrograph, ROY-G-BIV
telescope
optical, radio, intererometer, refracting, reflecting (Cassegrain), primary lens, primary mirror, prime focus, eye piece
power
light-gathering, resolving, magnifying, focal length, diffraction fringe, seeing, adaptive optics, sidereal tracking, photometer, change-coupled device (CCD)
geocentric universe model
Aristotle/Ptolemy (Greeks) “perfect” 55 spheres turing at different rates
Plato, philosopher, perfect motion (constant speed, perfect circles) uniform circular motion
Aristotle
student of Plato, philosopher
believed the heavens are perfect (circle/sphere) as first principle
first principle
natural phenomena appear obvious, explained with no further examination needed
Ptolemy
follower of Aristotle, mathematician
published 140 CE geometry model planets move in epicycle around a larger called the deferent solves planet big problem of retrograde motion
heliocentric universe model
Copernicus hypothesis
Sun-centered scientific revolution
adoption of new paradigm
Tycho Brahe
Tycho’s supernova seen in ‘unchanging starry sphere’ still of Aristotle’s view naked eye not see parallax
parallax
apparent motion of an object because of the motion of the observer
Johannes Kepler
Tycho’s assistant, 1606 figured Mars orbit is elliptical
elliptical
closed curve about two foci
Kepler laws
planet motion, empirical
- planet orbits are ellipses with the Sun at one foci
- line from planet to the Sun sweeps over equal areas in equal periods of time
- planet’s orbital period squared in proportional to its average distance from Sun cubed
empirical
described on observation only, without account for why occur
semi-major axis (a)
is half the longest diameter of ellipse
eccentricity (e)
is half the distance between the foci divided by the semi-major axis (1=long, 0=circular)
Galileo Galilei
used telescope lenses recreated in his workshop
moon not perfect (mountains that he calculated height of by shadows and imperfect ‘planet’)
later observed Venus go through complete set of Moon-like phases (confirmed by Copernican vs. Ptolemaic)
hypothesis
claim of guess that can be tested against reality wit observation and experimentation
theory
system of rules and principles applicable to many situations
law
many tests, refinements and confirmations such that great confidence as fundamental principle
speed
rate of movement (position change) is total distance moved divided by total time taken
velocity
is the speed and direction of an object (can change with change of speed and/or direction)
acceleration
rate of change of velocity with time, or turning (slowing is negative of deceleration)
Isaac Newton
studied math, physics, physical phenomena (light, gravity, etc.) developed math solutions
Newton’s three Laws of Motion
general laws that govern all bodies under action of external force
- body continues at rest, or in a uniform motion in straight like, unless acted upon by some force
- body’s change of motion is proportional to the force acting on it, and in the direction of the force
- body exerting force on a second body receives back an equal and opposite force from body contact
universal theory of gravitation
universal mutual gravitation
Moon in orbit
mass
matter making up an object
weight
force gravity exerts on an object, thus far from Earth have little or no force (~micro-gravity)
inverse square relation
strength of effect decreases in proportion as the distance squared increases
first noticed on light then gravity
centre of mass
objects orbiting each other actually revolve around a mutual point
circular velocity
velocity to keep circular orbit
above atmosphere
geosynchronous
eastward rotation with Earth
closed orbit
returns to starting point (ellipse or circle) making a circular orbit with escape velocity (velocity to escape planet) an open orbit will not return (parabola or hyperbola)
Earth’s tides
whole ocean bulge seen at coasts, by gravitational force from Moon and Sun (less so)
spring tide
neap tide
spring tide
new and full Moon align with Sun to create larger/extreme range (highest/lowest) tide
neap tide
smaller/milder tidal range at first and third quarter Moon
electromagnetic (EM) radiation
combination of electric and magnetic waves, spreads from source
wavelength
period between waves
light about 0.0005 mm
light is a particle
called photon, a quantum (smallest) bundle of electromagnetic waves
infrared (IR)
between 700 nm to about 1 mm
beyond range of human eyes, but felt as heat
light is a wave phenomenon
the visible portion of the EM spectrum (makes colours of rainbow)
ultraviolet (UV)
shorter than violet wavelength
x-ray
difficult to focus because they pass through most mirrors
gamma ray
higher frequency and shorter wavelength carries more energy
atmospheric window
wavelengths at which our atmosphere is transparent to ‘em’ radiation ozone layer at 30 km absorbs almost all UV, water vapour absorbs IR
speed of light
about 300000 km/s in space
true of all electromagnetic radiation
electromagnetic spectrum
the same phenomenon as light
spectrograph
spread light out according to wavelength into a spectrum for analysis
multiple prisms for maximum spread, photographic plate for record
nanometer (nm)
one-billionth of a meter (10^-9)
visible light wavelength between 400nm and 700nm
visual (indigo, violet, blue, green, yellow, orange, red)
optical telescope
lenses and/or mirrors are needed to gather light
radio telescope
gather intensity of radio radiation (energy) from a spot in the sky
interferometer
two or more telescopes combine to make diameter equal to distance between them
refracting
lens gathers and bends light to concentrate it to make an image
primary lens (objective lens)
is the main collecting lens (at front)
reflecting
mirrors gather and bounce light to concentrate it to make an image
primary mirror (objective mirror)
is the main collecting mirror (at bottom)
light continues up to focus within the prime focus cage or redirect
secondary mirror
redirect light down into hole on primary to instruments is Cassegrain focus smaller telescopes can direct with mirror to eyepiece on the side is Newtonian focus
eyepiece
a lens to magnify an image, a short focal length lens
telescope power
main function is to make faint things brighter (diameter most important, go larger)
light gathering power
diameter (light bucket), proportional to the area of t primary objective
resolving power
diameter of telescope objective to reveal fine detail, eliminate diffraction fringe blur fringe caused by wave property of light, 2m objective has fringes 1/2 as large as 1m
magnifying power
least important, ability to make image large
focal length of the primary divided by the focal length of eyepiece
focal length
distance from a lens or mirror to the formed image
seeing
condition of atmospheric turbulence that causes star twinkle, motion makes poor observing mountain location about atmosphere, avoid light pollution
light pollution
light from big cities and outdoor waste illumination
adaptive optics
are rapid computer controlled calculation and adjustment correcting for poor seeing
expensive, difficult compensation for distortion, partial correction
sidereal tracking
nonstop movement pointing telescope at stars as Earth rotates (from a clock drive)
photometer
measure brightness of individual objects, precise
charge-coupled device (CCD)
image recording device and photometer, chip, million+light detectors
array detector
size of postage stamp, digitized (numerical data), highly sensitive to bright and faint
can manipulate CCD camera data and create false-color images for different levels of intensity
