Antonia Sherman Discussion Ch. 1
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Houston Community College *
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1304
Subject
Astronomy
Date
Dec 6, 2023
Type
docx
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2
Uploaded by ProfLightning103075
Antonia Sherman
ASTR 1304
10/19/2023
Professor Samuel
LO1 BP What does an astronomer mean by “the universe”?
a.
The totality of all space, time, matter, & energy.
LO1 BP Compare the size of Earth with that of the Sun, the Milky Way Galaxy, and the entire universe.
a.
The Earth -15,000 kilometers
b.
The Sun- 1,500,000 kilometers/0.5 light sec
c.
The Milky Way Galaxy- about 1,000 quadrillion kilometers/100,000 light-years
d.
The Universe/Galaxy Cluster-about 2,000,000 light-years
LO2 POS What is the scientific method, and how does science differ from pseudoscience?
a.
Scientific Method is methodical approach employed by scientists to explore the universe around
us in an objective manner.
b.
Science differs from pseudoscience by separating fact from fiction.
LO3 BP What is a constellation? Why are constellations useful for mapping the sky?
a.
A constellation is a human grouping of stars in the night sky into a recognizable pattern or
thousands of stars visible to the naked eye into patterns.
b.
some constellations served as navigational guides,
people used constellations to locate if
they were North or South , & Other constellations served as calendars to predict planting
and harvesting seasons.
LO4 How and why does a day measured with respect to the Sun differ from a day measured with respect
to the stars?
a.
The stars’ positions in the sky do not repeat themselves exactly from one night to the next. Each
night, the whole celestial sphere appears to be shifted a little relative to the horizon compared
with the night before. A sidereal day is Earth’s true rotation period—the time it takes for the
planet to return to the same orientation in space relative to the distant stars. A solar day is the
time from one noon to the next. The solar day is about 4 minutes longer than the sidereal day
because of Earth’s motion around the Sun.
LO4 What is precession, and what causes it? What effect does precession have on observations of stars?
A .
Precession is the slow change in direction of the rotation axis of a spinning object, caused by some
external gravitational influence. Precession changes its
direction
over the course of time.
LO5 Why are there seasons on Earth?
a.
Earth’s seasons result from the inclination of our planet’s rotation axis with respect to its orbit
plane.
LO6 How much of the Moon’s surface is lit by the Sun at any one time? why do we see different phases
of the Moon?
A. The moon’s surface is lit from waxing crescent to waxing gibbous.
b. the Moon orbits Earth, the visible fraction of the lunar sunlit face varies from night to night,
although the Moon always keeps the same face toward our planet.
LO6 What causes a lunar eclipse? A solar eclipse? Why aren’t there lunar and solar eclipses every
month?
a.
When the Sun and the Moon are in exactly
opposite
directions, as seen from Earth, Earth’s
shadow sweeps across the Moon, temporarily blocking the Sun’s light and darkening the
Moon; a celestial event during which the moon passes through the shadow of Earth,
temporally darkening it’s surface.
b.
The Moon passes directly in front of the Sun, briefly turning day into night; Celestial event
during which the New moon passes directly between Earth and the Sun, temporarily
blocking the Sun’s light.
c.
The answer is that the Moon’s orbit is slightly inclined to the ecliptic (at an angle of 5.2°), so
the chance that a new (or full) Moon will occur just as the Moon happens to cross the plane
of the ecliptic (with Earth, Moon, and Sun perfectly aligned) is quite low.
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