Science and The Universe Flashcards
What is our physical place in the universe?
Earth is part of the solar system, which is the Milky Way Galaxy, which
is a member of the Local Group of galaxies in the Local Supercluster.
How did we come to be?
The mater in our bodies came from the Big Bang, which produced hydrogen and helium.
All other elements were constructed from H and He in stars and then recycled into new star systems, including our solar system.
How can we know what the universe was like in the past?
When we look to great distances, we are seeing
events that happened long ago because light travels at a fnite speed.
Can we see the entire universe?
No. The observable porton of the universe is about 14-15 billion
light-years in radius because the universe is about 14-15 billion years old
Light travels at a fnite speed thus … ?
Thus, we see objects as they were in the past: The farther away we
look in distance, the further back we look in time.
Light year
The distance light can travel in one year. About 10 trillion km (6 trillion miles).
How big is Earth compared to our solar system?
The distances between planets are huge compared to their sizes
—on a scale of 1-to-10 billion, Earth is the size of a ball point and the Sun is 15 meters away
How far away are the stars?
On a scale of 1-to-10 the stars are thousands of km away.
How big is the milky way galaxy?
The Milky Way is one of about 100 billion galaxies.
How big is the universe?
10^11 stars/galaxy x 10^11 galaxies = 10^22 stars. It would take more than 3,000 years to
count the stars in the Milky Way Galaxy at a rate of one per second, and they are spread across 100,000 light-years
How many billion light years in radius is the observable universe
14 billion light years
How many galaxies does the observable universe contain?
100 billion
How do our lifetmes compare to the age of the universe?
On a cosmic calendar that compresses the history of the Universe into one year, human civilizaton is just a few seconds old, and a human lifetme is a fracton of a second
Distance of Earth moving in our solar system?
Earth orbits the Sun (revolves) once every year at an average distance of 1 AU ≈ 150 million km. Earth’s axis is tlted by 23.5º (pointng to Polaris).
Does Earth rotate in the same or a different direction then it’s orbit
Earth rotates in the same directon it orbits, counter- clockwise as viewed from above the North Pole.
How is our the stars in our solar system are moving in the Milky Way galaxy?
Stars in the Local Neighborhood move randomly relatve to one another but the stars are so far away that we cannot easily notce their moton
How is our solar system moving in the Milky Way galaxy? (focus on the sun)
Our Sun moves randomly relatve to the other stars in the local Solar neighborhood.
How fast does the sun move
typical relative speeds of more than 70,000 km/hr
How long does it take for the sun to orbit the milky way galaxy
Our Sun orbits the center of the Milky Way in about 230 million years.
How do galaxies move within the universe?
All galaxies beyond the Local Group are moving away from us with expansion of the Universe: the more distant they are, the faster they’re moving
Hubble discovered that:
All galaxies outside our Local Group are moving away from us.
The more distant the galaxy, the faster it is racing away.
What can we conclude from Hubble’s discovery that all the galaxies are moving away from us?
Our galaxy is expanding
How many stars can we see with out naked eye?
We can see over 2,000 stars and the Milky Way with our naked eyes
each positon on the sky belongs to one of (how many) constellatons?
88
How can we specify the position of an object in the local sky?
We can specify the positon of an object in
the local sky by its alttude above the horizon and its directon along the horizon
Constellation
a constellaton is a region of the sky
Can we say that the stars in the same constellaton are nearby?
no
Why is it hard to notice the motion of the stars?
Because they are so far away
Why do stars rise and set?
Because of Earth’s rotaton. Stars near the north celestal pole are circumpolar and
never set. All other stars (and Sun, Moon, planets) rise in east and set in west.
Earth rotates west to east, so stars appear to circle from east to west
What is a circumpolar star?
Stars near the north (south) celestal poles are circumpolar and never set. All other
stars (and Sun, Moon, planets) rise in east and set in west. Circumpolar stars rotate in counterclockwise directon
around North celestal pole in the Northern Hemisphere.
What is the ecliptic plane?
Ecliptic is Sun’s apparent path through the celestial sphere.
The sky varies as Earth orbits the Sun
As the Earth orbits the Sun, the Sun appears to move eastward along the ecliptic.
At midnight, the stars on our meridian are opposite the Sun in the sky.
Why do the constellatons we see depend on lattude and tme of year?
The constellatons we can see depend
on lattude because your positon on Earth determines which constellatons remain below the horizon and hidden
by Earth. They depend on tme of year because Earth’s orbit changes the apparent locaton of the Sun among
the stars. We can’t see the stars during the day!
Altitude:
An object’s altitude (above horizon) and direction (along horizon) specifies its location in your
local sky
Zenith:
The point directly overhead
Horizon:
All points 90° away from zenith
Meridian:
Line passing through zenith and connecting N and S points on horizon
Stars near the _________ pole are circumpolar and never set.
north celestial
Polaris Alttude and our locaton on Earth.
For an observer Polaris alttude will be the same as a person’s lattude on Earth.
What makes the North Star, Polaris, special?
Some stars travel a great distance over the course of the night. Polaris is different. Because it’s so close to the celestial pole, it traces out a very small circle over 24 hours. So Polaris always stays in roughly the same place in the sky, and therefore it’s a reliable way to find the direction of north
Astronomy def
the study of the objects that lie beyond our planet Earth and the processes by which these objects interact with one another.
1st step in the method of learning about Astronomy
Observing things over time
. The most straightforward approach to such testing in science is to ______________.
perform an experiment
What do astronomers do?
sift through and organize the evidence to test various hypotheses about what actually happened.
scientific laws
the “rules” of the game that nature plays.
A reason why astronomers strive to build telescopes that collect the faint light in the universe
On average, fainter objects are farther away and can, therefore, tell us about periods of time even deeper in the past.
Our nearest astronomical neighbor is ______
the moon
If we travel around the sun in one year how fast do we travel in an hour?
110,000 kilometers per hour.
Why are we able to see planets?
They reflect the light of the sun?
How do stars produce vast amounts of energy
by nuclear reactions deep within.
What makes stars considered “triplets or doubles”
If they revolve around each other
Magellanic Clouds
Two dwarf galaxies
Andromeda galaxy
The nearest galaxy to us
Our “address” in the universe
you, Earth, solar system, Milky Way, Local Group, Local Supercluster
Suppose we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest? The one farther away or closer?
Farther away
What’s larger, a light year or the size of a typical galaxy
the size of a typical galaxy
What is the meaning of the word cosmos?
the sum total of all matter and energy, that is, everything within and between all galaxies
Suppose we imagine the Sun to be about the size of a grapefruit. How big an area would the orbits of the eight planets of the solar system cover?
the size of a typical campus
