Video Transcript
Fill in the blank. The solar system started as a large
cloud of gas and dust in space. This cloud began to blank. (A) Contract, (B) expand.
The solar system began as a very
large cloud of dust and gas called a nebula. This question asked us what
happened to the cloud of gas and dust to make it eventually form our solar
system.
Let’s look at option (A). Based on the evidence they have,
scientists theorize that the cloud began to contract, or get smaller, due to the
force of gravity. Gravity is a force that attracts
objects that have mass. Gravity pulled the particles of
dust and gas towards each other, causing the cloud to contract. Once the cloud contracted, it
heated up, and the Sun and planets began to form. Gravity has an important role in
the solar system today, so it seems logical that gravity was an important player in
the formation of our solar system, too.
Now let’s look at option (B). You might have heard that
scientists theorize that the universe itself is expanding, or getting larger. This expansion causes the distance
between objects in space to increase. However, when things are already
pretty close together, the force of gravity has a greater effect on the distance
between them than the expansion of the universe. In the cloud of dust and gas, the
particles were already close together. So gravity still caused the cloud
to contract, even though the universe itself was expanding. So we have seen that the dust and
gas cloud that eventually formed our solar system contracted, heated up, and formed
the Sun and planets we know and love today. The answer to this question must be
option (A).
