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Transcript
Charting the Heavens
The gears in the big machine
The Universe is (according to the book) “…the totality of all space, time, matter and
energy”.
The Universe is (according to the book) “…the totality of all space, time, matter and
energy”.
As our understanding of what space, time, matter and energy are changes, we may need
to revisit this definition, and find one that is more appropriate.
The Universe is (according to the book) “…the totality of all space, time, matter and
energy”.
As our understanding of what space, time, matter and energy are changes, we may need
to revisit this definition, and find one that is more appropriate.
We should probably be able to tell how far away something is based upon a known
geometry.
1,000 kilometers
1,000,000 kilometers
1,000,000,000 kilometers
The Universe is (according to the book) “…the totality of all space, time, matter and
energy”.
As our understanding of what space, time, matter and energy are changes, we may need
to revisit this definition, and find one that is more appropriate.
We should probably be able to tell how far away something is based upon a known
geometry.
1,000 kilometers
1,000,000 kilometers
1,000,000,000 kilometers
This would be inconvenient, so we will be using scientific notation in many cases. Just
move the decimal point to the right (or left) to make the number larger (or smaller).
The Universe is (according to the book) “…the totality of all space, time, matter and
energy”.
As our understanding of what space, time, matter and energy are changes, we may need
to revisit this definition, and find one that is more appropriate.
We should probably be able to tell how far away something is based upon a known
geometry.
1,000 kilometers
1,000,000 kilometers
1,000,000,000 kilometers
This would be inconvenient, so we will be using scientific notation in many cases. Just
move the decimal point to the right (or left) to make the number larger (or smaller).
1,000 kilometers = 1.0 x 103 meters
1,000,000 kilometers = 1.0 x 106 meters
1,000,000,000 kilometers = 1.0 x 109 meters
Another quick and easy way to measure distance is to use the speed of light as a
constant, because it is, you know CONSTANT.
Another quick and easy way to measure distance is to use the speed of light as a constant,
because it is, you know CONSTANT.
A light-year is the distance light travels in one year. 4.2 light-years is approximatly the
distance to Alpha Proxima Centauri. This is the closest star to our Sun. It is a red dwarf,
which means it is not really all that hot (only red), and it is small (dwarf).
Another quick and easy way to measure distance is to use the speed of light as a constant,
because it is, you know CONSTANT.
A light-year is the distance light travels in one year. 4.2 light-years is approximatly the
distance to Alpha Proxima Centauri. This is the closest star to our Sun. It is a red dwarf,
which means it is not really all that hot (only red), and it is small (dwarf).
A light-second is the distance light travels in one second. The moon is 1.282 lightseconds away.
A final measurement unit that we will use a lot is the Astronomical Unit. This is the
average distance between the Sun and the Earth.
A final measurement unit that we will use a lot is the Astronomical Unit. This is the
average distance between the Sun and the Earth.
This is also about 8.25 light-minutes, or about 150,000,000 kilometers, or 1.5 x 108 km
The Celestrial Sphere
An imaginary sphere, that surrounds the Earth, that the stars are attached to.
The Celestrial Sphere
An imaginary sphere, that surrounds the Earth, that the stars are attached to.
Why, oh why, is the ecliptic (path of the Sun and planets), not on the Celestial
equator?
Movement of the Earth (Daily)
It ROTATES on its axis, which means it spins.
Relative to distant stars is a sidereal day.
Relative to the Sun is a solar day.
Movement of the Earth (Daily)
It ROTATES on its axis, which means it spins.
Relative to distant stars is a sidereal day.
Relative to the Sun is a solar day.
Which will be longer, a solar day or a sidereal
day?
Movement of the Earth (Seasonal)
Because the Earth is tilted (we will figure out why later), the Sun appears to rise and fall at
noon, from day to following day.
Movement of the Earth (Seasonal)
Because the Earth is tilted (we will figure out why later), the Sun appears to rise and fall at
noon, from day to following day.
Movement of the Earth (Seasonal)
Because the Earth is tilted (we will figure out why later), the days get longer and shorter.
Movement of the Earth (Seasonal)
Because the Earth is tilted (we will figure out why later), the days get longer and shorter.
The shortest and longest days are the solstices (December-winter, June-summer)
The days of equal length are the equinoxs (March-spring and September-fall)
Movement of the Earth (long term)
The Earth will move like a top, in a cycle called precession. This is a 25,000 year cycle.
Movement of the Earth (long term)
The Earth will move like a top, in a cycle called precession. This is a 25,000 year cycle.
**For all you Astrologers...the “ages” change as precession places the Earth’s axis at
different zodiac signs. We are in the “age of aquarius” because our axis most closely
points to aquarius.**
The Earth also moves from a tilt of 22.1º to 24.5º degrees each 41,000 years, and the
eccentricity of the orbit changes slightly over the course of 100,000 years (the
Milankovitch cycle).
The changes in the Earth’s orbit and rotation alter the climate characteristics of the Earth.
They are LONG term changes.
**For all you Astrologers...the “ages” change as precession places the Earth’s axis at
different zodiac signs. We are in the “age of aquarius” because our axis most closely
points to aquarius.**
Finding distances with triangulation.
Parallax is the apparent change in position, due to the movement of the observer.
Parallax terminology
Parallax is the apparent change in position of an object, due to the change in position of the
observer.
Arc is some movement around a circle
Degree is 1/360th of a circle
Minute of arc is 1/60th of a degree
Second is 1/60th of a minute
Par-sec is the distance from an object, such that the parallax from Earth would be one
second of arc.
The light-year is a measure of distance T F
The number 2 x 109 is equal to to billion T F
The stars in a constellation are physically close to one another T F
The star Polaris always lies precisely at the north celestial pole T F
Constellations are no longer used by astronomers T F
The solar day is longer than the sidereal day T F
The constellations lying along the ecliptic are collectively referred to as the zodiac T F
The seasons are caused by the precession of Earth’s axis T F
The vernal equinox marks the beginning of spring T F
The parallax of an object is inversely proportional to its distance T F
Rotation is the term used to describe the motion of some body around some
___________.
To explain the daily and yearly motions of the heavens, ancient astronomers imagined that
the Sun, Moon, stars and planets were attached to a rotating _________.
The solar day is measured relative to the Sun, the sidereal day is measured relative to the
bright and beautiful __________.
The apparent path of the Sun (and approximate path of most planets/moon) across the sky
is know as the ______________.
On December 21, known as the ______________________, the Sun is at its ____________
point on the celestial sphere.
Declination measures the position of an object north or south of the ______________ (see
page 14).
An arc second is ____________________ of an arc minute.
The average distance from the Earth to the Sun is an _____________________.
Between Alpha Centari Proxima (about 4 light years away), and Rigel (about 800 light years
away); ___________________________ would have the largest parallax.