Video Transcript
Approximately, how long ago did the
solar system start to form? (A) 500000 years ago, (B) five
million years ago, (C) five billion years ago, (D) 14 billion years ago, (E) three
trillion years ago.
This question can be a bit tricky
if we don’t already know the answer off the top of our heads. Fortunately, we can use some dates
that we already know to work out the most likely answer.
Let’s start by looking at option
(D), 14 billion years ago. The universe itself is
approximately 14 billion years old. The early universe was very
different from the universe today. And the materials needed to form
the solar system weren’t around back then. So option (D) cannot be the
answer.
Now let’s think about option (E),
three trillion years ago. Three trillion years ago is much,
much longer than 14 billion years ago. Even the universe itself hadn’t
formed three trillion years ago. So option (E) cannot be the
answer.
Now lets look at options (A) and
(B). Although 500000 years ago, and even
five million years ago, sound like really long times, this is not long enough ago
for the solar system to be just beginning to form. Life already existed on Earth long
before these times, so the solar system must have already finished forming by
then. We can rule out options (A) and
(B).
This leaves us with only one
possibility left: option (C), five billion years ago. This must be the correct
answer.
