Unit 6

Question 1

what is day and night caused by

Answer 1

the earth spinning on its axis
one revolution takes 24 hours

Question 2

which way does the sun travel across the sky

Answer 2

the earths rotation causes the sun to go east to west
(rise in the east)

Question 3

why do the seasons change

Answer 3

due to the motion of the earth
due to the tilt of the earth

Question 4

how does the tilt of the earth change the seasons

Answer 4

the tilt is 23.5
during spring and summer, the northern hemisphere is tilted towards the sun so that the hours of daylight are greater. it recieves more solar radiation making it warm

during winter and autumn, the southern hemispher is tilted towards the sun

Question 5

what is the moon

Answer 5

a satellite of the earth that travels in an approximately circular orbit
rotates on its own axis and orbit takes around a month

Question 6

why does only one side of the moon show at all times

Answer 6

because it revolves on its own axis

Question 7

why can we see the moon

Answer 7

due to reflected sunlight
doesnt produce any light by itself

Question 8

how to find average orbital speed

Answer 8

circumference of the orbit/ time
2 x pi x radius
———————
time

Question 9

what way does the moon rise

Answer 9

in the east and sets in the west

Question 10

what does the solar system consist of

Answer 10

1 star(sun) and eight planets

Question 11

what are the 4 inner planets

Answer 11

mercury, venus, earth, mars

Question 12

what are the 4 outer planets

Answer 12

jupiter, saturn, uranus, neptune

Question 13

what are all the planets in order, from the sun

Answer 13

mercury, venus, earth, mars, jupiter, saturn, uranus, neptune

Question 14

features of the inner planets

Answer 14

they are small, solid and rocky.
also have high densities

Question 15

features of the outer planets

Answer 15

large, cold and mainly consist of gases
density is low
have many moons and satellites

Question 16

what are dwarf planets

Answer 16

like pluto
generally low density and thought to be composed of rock and ice

Question 17

what are asteroids

Answer 17

rocks of various sizes which mostly orbit the sun between mars and jupiter
density is similar to that of inner planets

Question 18

what is the accretion process

Answer 18

as material continued to rotate around the sun, gravitational attraction between small particles cause them to join together and grow in size

Question 19

how was the sun formed

Answer 19

when gravitational attraction pulled together swirling clouds of hydrogen and gas( known as nebulae) in a region of space where the density is high

Question 20

why are the inner planets made up of materials with high melting temperatures

Answer 20

as the sun grew in size , it became hotter and lighter molecules such as hydrogen wont be able to exist in a solid state

Question 21

why are the outer planets less dense

Answer 21

because theyre further away from the sun, light molecules can exist in a solid icy form

Question 22

what does the gravitational field strength of a planet depend on

Answer 22

the mass of the planet
the distance of the object from the planet

Question 23

what happens when distance from the sun inreases

Answer 23

suns gravitational field decreases
orbital speeds of the planets decrease

Question 24

why do planets orbit the sun

Answer 24

because the sun contains most of the mass of the solar system

Question 25

how do objects with large elliptical orbits change speeds as they move around the sun

Answer 25

speed increases as it approaches the sun and decreases as it moves further away some of the kinetic energy it has is transferred into potential energy as it moves away

Question 26

features of the sun

Answer 26

a medium sized star, consisting mostly of hydrogen and helium. It radiates its energy in the infrared, visible and ultraviolet regions of the electromagnetic specrtum

Question 27

how are stars powered

Answer 27

through nuclear reactions that release energy and in stable stars, nuclear fusion of hydrogen into helium occurs

Question 28

what are galaxies made up of

Answer 28

many billions of stars

Question 29

what is our galaxy known as

Answer 29

the milky way

Question 30

what are light years

Answer 30

they are the distance traveled in space by light in one year used to measure astronomical distances

Question 31

how much is one light year

Answer 31

9.5 x 10^15 m

Question 32

what are stars formed from

Answer 32

interstellar clouds of gas and dust that contain hydrogen

Question 33

what is a protostar

Answer 33

an interstellar cloud collapsing and increasing in temperature as a result of its internal gravitational attraction

Question 34

when do protostars become stable stars

Answer 34

when the inward force of gravitational attraction is balanced by an outward force due to the high temperature in the center of the star

Question 35

what happens when the star eventually runs out of hydrogen

Answer 35

there is no more energy for nuclear reactions most stars expand to form red supergiants when most of the hydrogen has been converted to helium

Question 36

what happens if a red giant is formed with a less massive star

Answer 36

a planetary nebula with a white dwarf star in the center is formed

Question 37

what happens to red supergiants

Answer 37

it explodes as a supernova, forming a nebula containing hydrogen and new heavier elements, leaving behind a neutron star or a black hole

Question 38

what is the diameter of the milky way

Answer 38

apporximately 100000 light year

Question 39

what is redshift

Answer 39

an increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies light emitted from distant galaxies appear redshifted in comparison to light on earth

Question 40

what does redshift help prove

Answer 40

it provides evidence that the universe is expanding and supports the big bang theory

Question 41

what is Cosmic Microwave Background Radiation

Answer 41

microwave radiation of a specific frequency that is observed at all points in space around was produced shortly after the Universe was formed

Question 42

how can the speed of which a galaxy is moving away from earth be found

Answer 42

from the change in wavelength of the galaxy's starlight due to redshift

Question 43

how can the distance of a far galaxy be determined

Answer 43

using the brightness of a supernova in that galaxy

Question 44

what is the hubble constant

Answer 44

the ratio of the speed at which the galaxy is moving away from the earth to its distance from the earth can be found with : speed of galaxy moving away(v) / distance of galaxy(D)

Question 45

what is the current estimate of the hubble constant

Answer 45

2.2 x 10^-18

Question 46

equation that estimates the age of the universe

Answer 46

d/v = 1/ hubble constant