Moon 101

Transcript

Over 150 moons orbit the solar system’s planets.
 
And one of those moons calls Earth home.
 
The moon was formed about 4.5 billion years ago when, according to one theory, the Earth slammed into another early planet.
 
Debris from this collision began to orbit Earth, and accumulated, forming today’s moon.
 
The moon is the fifth largest natural satellite in the solar system, with a diameter just under the width of China.
 
It’s composed of an iron rich core, plus a mantle and crust containing minerals made of magnesium, oxygen and silicon.
 
The moon’s surface was once geologically active and covered in an ocean of magma.
 
But today, apart from traces of water ice, the surface is completely covered in dust and rocky debris.
 
Countless craters dot the moon’s surface.
 
Each formed by objects such as meteroids, comets and asteroids crashing onto the moon.
 
The largest crater, the South Pole Aitkin basin, spans across a quarter of the moon’s surface, and is nearly deep enough to fit Mount Everest inside.
 
The moon orbits our planet at an average distance of 30 Earths.
 
It rotates at the same rate that it revolves.
 
So as it revolves around our planet, the same side of the moon faces the Earth at all times.
 
From the Earth’s surface, we can observe eight distinct traditionally recognized stages of the moon’s illumination, called lunar phases.
 
They have been observed for thousands of years, and even provided the basis for the earliest calendars.
 
For most of human history, the moon could only be studied from afar.
 
But on July 20th, 1969, humans were able to close that distance with the American spaceflight mission Apollo 11.
 
It placed humans on the moon for the very first time.
 
Bringing our understanding of Earth’s only natural satellite one step closer.

Vocabulary List

orbit
(verb) to move around something else in a curved path
 
slam
(verb) to hit something with great force
 
debris
(noun) broken or torn pieces of something that has been destroyed
 
collision
(noun) an instance of two or more things coming together with force
 
mantle
(noun) the layer of hot, solid rock that makes up the largest part of Earth’s interior
 
crust
(noun) the outermost layer of Earth’s solid surface
 
countless
(adjective) too many to be counted
 
crater
(noun) a large round hole in the ground or on a surface, typically caused by the impact of a meteorite or bomb
 
dot
(verb) to be spread over an area
 
span
(verb) to extend over a certain distance or period of time
 
revolve
(verb) to move around something else in a circle or oval.
 
distinct
(adjective) clearly different from something else
 
afar
(adverb) at a great distance

Grammar Lesson

In this lesson, we will learn:
  • how to use once
 
ONCE
The moon’s surface was once geologically active and covered in an ocean of magma.
 
Once is:
  • an adverb
  • a conjunction
 
Once (1)
(adverb)
on one occasion only; one time
 
subject + verb + object + once
I met him once.
 
subject + verb + object + only + once
I met him only once.
 
subject + verb + object + once + duration
I met him once a week.
 
subject + verb + object + once + before
I met him once before.
 
Once (2)
(adverb)
at some time in the past, but not now
 
subject + once + verb
He once lived in Japan.
 
subject + verb be + once + adjective phrase
He was once very popular.
 
Once (3)
(adverb)
at any one time (used in negative sentences or questions)
 
subject + auxiliary verb + not + once + base form
He didn’t once thank me.
= He didn’t thank me at all.
 
subject + never + once + verb
He never once thanked me.
= He didn’t thank me at all.
 
Once (4)
(conjunction)
as soon as
 
once + dependent clause + comma + main clause
once + subject + verb (+ object) + comma + subject + verb (+ object)
Once he gets a job, he’ll be fine.
= As soon as he gets a job, he’ll be fine.
 
main clause + once + dependent clause
subject + verb (+ object) + once + subject + verb (+ object)
He’ll be fine once he gets a job.
= He’ll be fine as soon as he gets a job.
 
Remember:
  • If a subordinating conjunction starts a sentence, we need a comma after the dependent clause.
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