Video Transcript
Which of the following diagrams
correctly shows how the Sun and the planets formed from a hot, rotating disk?
This question asks us to recall the
order in which the solar system was formed. To do this, we can look at the
diagrams we’re given and decide what seems most reasonable.
Look at answer choice (A), for
example. The first caption describes the
picture by saying the cloud of gas and dust continues to contract and heat up,
forming a rotating disk. Notice that this is the same as the
first picture in answer choice (B). So far, we haven’t been able to
eliminate either choice. So far, they’re the same.
When we move on to the middle
picture, however, we have to start thinking outside the box. What was happening as the cloud of
dust and gas contracted? Recall that as a result of the
force of gravity, the particles in the cloud got closer together. Because they were closer together,
they began to collide or bump into each other more often. This caused the temperature of the
cloud to increase. It’s kind of similar to the heat
you generate when you rub your hands together. As a result of lots of quick
contact between the particles that make up your palms, heat is generated.
As the cloud kept contracting, it
got hotter and denser. Eventually, the center of the cloud
got so hot and dense that it formed a core, where the Sun began to form. This leads us to our third
picture. Did the planets form like the Sun
did from a cloud of dust and gas? Or were they attracted from other
parts of the universe?
If we explore this last idea, that
they were captured from nearby star systems, we have to ask this question. How were those planets formed to
begin with? And what happened to the dust and
gas that were not part of the core that formed the Sun? Did they just disappear in the vast
expanse of space? Add that to the fact that planets
generally don’t just zoom across the universe. This line of questioning sort of
leaves us back at square one.
When the core of the cloud heated
up and formed the Sun, the particles on the outer edges of the rotating disk also
experienced some change. They bumped into each other and
sometimes stuck together. Eventually, these clumps collided
and formed big objects. Those big objects ran into other
big objects to form even bigger objects. This is how the planets began to
form.
We can conclude then that answer
choice (A) does not provide enough information to make a sensible theory. Answer choice (B) illustrates how
the Sun and planets formed from a circular, rotating disk. (B) is the correct answer.
