Gravity
_____________is a force that pulls objects on or near Earth's surface toward Earth's center.
gravity
sun's gravity is strong enough to make Earth
follow an orbit around the sun
Stars give off energy in the form of____________
light
A light-year is a measurement of ______________
distance
An imaginary line running through its North and South pole
axis
Objects__________to the ground because of gravity's force.
fall
A __________ is used to measure weight
scale
A star's light spreads out in ________ _____________. As the light moves away from a star, it spreads out over more and more ___________.
all directions
space
The__________ __________ of a star is a measure of how bright it looks from Earth.
apparent brightness
Day and night are caused by Earth's _______________
rotation on its axis
What many people think of as “down” is actually the direction that gravity is _______________.
pulling
Astronauts that go to the moon experience weight changes as they travel
Their weight goes down to zero once they get very _____ from Earth. But their weight goes back up as they get to the moon because it has_________.
far
gravity
When a star is very far away, ______________ amount of its light reaches Earth
only a tiny
Three factors that affect a star's apparent brightness are _________________
size
temperature
distance from Earth
There are ____________ time zones in the world, _______of which are in the United States.
24
6
What happens when a meteoroid in space comes close enough to Earth?
Gravity pulls it toward Earth.
Meteoroids heat up and give off light.The streaks of light are meteors.
Those that do not burn up sometimes land on Earth's surface and are called meteorites.
All objects have _________ that pulls other objects toward their _________.
gravity
center
The __________ looks bigger and brighter than other stars because it is _________ to Earth.
sun
closer
Blue stars are the ____________, and red stars are the _____________.
hottest
coolest
The time in each time zone is based on the pattern of the_______ ________ in the sky. In each time zone, the sun is at or near its ________ point at 12:00 p.m.
sun's position
highest
Earth's gravity is strongest at Earth's_____________. So, it pulls the most on objects at ______________.
surface.
sea level.
The moon's gravity is noticeable on objects that are _____________.
close to it
Distances between the sun and other stars are measured in units called______________
light years
A star's size is described as its radius, or its ____________________
distance from its center to its outside
Spring and fall have about the same number of daylight hours. It is daytime for the longest during the ________, and it is daytime for the shortest during _______.
summer
winter