198 lines
5.9 KiB
Plaintext
198 lines
5.9 KiB
Plaintext
.SH
|
|
Annex: events
|
|
.LP
|
|
.BULLET
|
|
.UL "1665" ,
|
|
Isaac Newton
|
|
.BULLET
|
|
.UL "1784" ,
|
|
first observation of Cepheid variable star.
|
|
.BULLET
|
|
.UL "1908-1912" ,
|
|
Henrietta Swan Leavitt discovers a relation between Cepheid variable stars' brightness and period of their variation.
|
|
And this leads to knowing the distance between these stars: we now can make wild approximations on astonomic distances between us and stars.
|
|
.BULLET
|
|
.UL "1916, general theory of relativity" ,
|
|
a decade-long struggle to create a new theory of gravity by Albert Einstein.
|
|
.br
|
|
This work is also about space and time, and explains not only how objects move in the universe, but also how the universe itself might evolve.
|
|
.BULLET
|
|
.UL "1925" ,
|
|
Hubble publishes his study on spiral
|
|
.I nebulae ,
|
|
where he identified Cepheid variable stars in them (including the
|
|
.I nebulae
|
|
we currently know as Andromeda).
|
|
.BULLET
|
|
.UL "1925, Mount Wilson 100-inch Hooker telescope" ,
|
|
the world's largest at the time.
|
|
.FOOTNOTE1
|
|
We now make ten times bigger telescopes and hundred times bigger in area.
|
|
.FOOTNOTE2
|
|
.BULLET
|
|
.UL "1927" :
|
|
Lemaître shows that the Einstein's equations suggest an expanding universe.
|
|
.BULLET
|
|
.UL "1930" :
|
|
Lemaître proposes an universe beginning in a small point he called
|
|
.I "Primeval Atom" .
|
|
.ENDBULLET
|
|
|
|
.SH
|
|
Annex: vocabulary
|
|
.LP
|
|
.BULLET
|
|
.UL "perihelion" :
|
|
point of an orbit where the object (e.g.: a planet) is the closest from another object (e.g.: a star).
|
|
.BULLET
|
|
.UL "aphelion" :
|
|
opposite of perihelion, point of an orbit where the object is the farthest from another object.
|
|
.BULLET
|
|
.UL "precession" :
|
|
change in an angle over time.
|
|
This can be the angle of the ellipse formed by the orbital journey of a planet (apsidal precession).
|
|
Or this can be the movement of the rotational axis of an astronomical body, whereby the axis slowly traces out a cone (axial precession).
|
|
Finally, the precession can be a change in the
|
|
.I plane
|
|
of the orbital course (nodal precession), which can be caused by a third gravitational object.
|
|
.BULLET
|
|
.UL "nebulae" :
|
|
.I "fuzzy thing"
|
|
(or cloud) in latin.
|
|
Galaxies were named this way before we understood what we saw.
|
|
.BULLET
|
|
.UL "Cepheid variable" :
|
|
star whose brightness varies over some regular period, indicating a change in diameter and temperature.
|
|
.BULLET
|
|
.UL "Doppler Effect" :
|
|
a wave coming at you will be stretched if the source is moving away from you, or compressed if the source is coming toward you.
|
|
.ENDBULLET
|
|
|
|
.SH
|
|
Annex: people involved
|
|
.LP
|
|
.BULLET
|
|
.UL "Johannes Kepler" :
|
|
known for the first heliocentric model.
|
|
.BULLET
|
|
.UL "Isaac Newton" :
|
|
.BULLET
|
|
.UL "Christian Doppler" :
|
|
australian physicist, known for the "Doppler Effect".
|
|
.BULLET
|
|
.UL "Albert Einstein" :
|
|
.BULLET
|
|
.UL "Georges Lemaître" :
|
|
physicist and preist, first to suggest that the universe was expanding in 1927.
|
|
.br
|
|
He started as an engineer, then was a decorated artilleryman in WW1, switched to mathematics, and priesthood in early 1920s.
|
|
Then moved to cosmology and first studied with Sir Arthur Stanley Eddington before moving on to Harvard and receiving a second PhD in physics from MIT.
|
|
.BULLET
|
|
.UL "Arthur Stanley Eddington" :
|
|
astronomer.
|
|
.BULLET
|
|
.UL "Henrietta Swan Leavitt" :
|
|
Harvard College Observatory "computer".
|
|
Discovered the relation between Cepheid variable stars' brightness and period of vacation.
|
|
.BULLET
|
|
.UL "Edwin Hubble" :
|
|
former lawyer, became astronomer.
|
|
Made the first observation of the expansion of the universe.
|
|
.BULLET
|
|
.UL "Harlow Shapley" :
|
|
discovered the Sun wasn't at the center of the Milky Way, and that our galaxy was much larger than we previously thought.
|
|
.BULLET
|
|
.UL "Vesto Slipher" :
|
|
astronomer, he measured the spectra of light coming from several galaxies.
|
|
.ENDBULLET
|
|
|
|
.SH
|
|
Random explanations
|
|
.PP
|
|
|
|
Diffraction: behavior of waves when reaching an aperture.
|
|
|
|
.PS
|
|
reset
|
|
rad_large_circle = 0.6 # Size of circles.
|
|
rad_empty_space = 0.5 # Size of circles.
|
|
rad_light_source = 0.3 # Size of circles.
|
|
rad_aperture = 0.1 # Size of circles.
|
|
|
|
fill_large_circle = 0.1 # Represents light intensity.
|
|
fill_empty_space = 0.6 # Represents light intensity.
|
|
fill_light_source = 0 # Represents light intensity.
|
|
|
|
txt_x_shift = 0.05 # Shift from arrow start.
|
|
txt_y_shift = 0.05 # Shift from arrow start.
|
|
space_between_arrows_y = -0.25 # Allow space for text.
|
|
|
|
CIRCULAR_DIFFRACTION_FIGURE: [
|
|
circlerad = rad_large_circle
|
|
circle fill fill_large_circle
|
|
|
|
circlerad = rad_empty_space
|
|
move to last circle + (-circlerad, 0)
|
|
circle fill fill_empty_space
|
|
|
|
circlerad = rad_light_source
|
|
move to last circle + (-circlerad, 0)
|
|
circle fill fill_light_source
|
|
|
|
circlerad = rad_light_source
|
|
move to last circle + (-circlerad, 0)
|
|
LIGHT_SOURCE: circle fill fill_light_source
|
|
|
|
circlerad = rad_aperture
|
|
move to last circle + (-circlerad, 0)
|
|
APERTURE: circle fill fill_light_source dashed
|
|
|
|
# LEGEND.
|
|
|
|
move; move
|
|
arrow to APERTURE chop 0 chop rad_aperture
|
|
move to last arrow.s + (txt_x_shift,txt_y_shift)
|
|
"Aperture, where light can pass through" ljust
|
|
|
|
move to last arrow.s + (0,space_between_arrows_y)
|
|
arrow to LIGHT_SOURCE chop 0 chop rad_light_source
|
|
move to last arrow.s + (txt_x_shift,txt_y_shift)
|
|
"Main visible light source, very bright" ljust
|
|
|
|
move to last arrow.s + (0,space_between_arrows_y)
|
|
arrow to LIGHT_SOURCE chop 0 chop rad_empty_space
|
|
move to last arrow.s + (txt_x_shift,txt_y_shift)
|
|
"Empty space, very little light" ljust
|
|
|
|
move to last arrow.s + (0,space_between_arrows_y)
|
|
arrow to LIGHT_SOURCE chop 0 chop rad_large_circle
|
|
move to last arrow.s + (txt_x_shift,txt_y_shift)
|
|
"Halo, thin light" ljust
|
|
]
|
|
|
|
move to CIRCULAR_DIFFRACTION_FIGURE + (0, -1)
|
|
"Circular diffraction"
|
|
.PE
|
|
|
|
|
|
.\" Exponential: oldvalue + growth factor -> newvalue
|
|
.G1
|
|
GROWTHFACTOR=0.07
|
|
|
|
frame ht 2.5 wid 2.8
|
|
define expo { $1+$1*GROWTHFACTOR }
|
|
value = 1
|
|
draw LINEAR solid
|
|
for i from 1 to 100 by 1 do {
|
|
next LINEAR at i, i
|
|
times at i, value
|
|
value = expo(value);
|
|
}
|
|
line from 0,650 to 3,650
|
|
" linear curve" ljust at 1,650
|
|
" exponential curve" ljust at 1,600
|
|
times at 1,600
|
|
label top "Exponential curves: growth over time (7%)" up .2
|
|
.G2
|
|
|