Video Transcript
Which of the following is at the
center of the solar system? (A) The Moon, (B) Earth, (C) the
Sun, (D) Mars, or (E) Jupiter.
This is a question about the layout
of the solar system. We are given a list of objects and
need to identify which one of them is at the center of the solar system. We will look at each option,
starting with option (A). We often see the Moon in the
sky. We know that the Moon orbits the
Earth. This means that the Moon cannot be
at the center of the solar system.
The Sun is the object on the list
we see every day. It appears to move across the sky,
rising above the horizon in the East and moving below the horizon in the West. This makes it seem like the Sun
moves around the Earth. But actually, it is the Earth’s
spin that causes this apparent movement of the Sun in the sky. The Sun is not in motion during the
day; the Earth is. While the Earth appears flat, this
is only because we are very small and very close to the surface. The Earth is a sphere. It is the spinning or rotation of
this sphere that causes the Sun to appear to move across the sky.
This sketch is not to scale, but it
will help to show how the Earth’s rotation leads to the apparent movement of the Sun
in the sky. In this drawing, the person
initially sees the Sun directly above. As the Earth rotates, the apparent
position of the Sun will change. The person rotates with the Earth,
and from their perspective, it is the Sun that has moved position in the sky. The Sun sets when the Earth rotates
so that the person can no longer see the Sun. This defines a day on Earth. When we are on the night side of
this day–night line, it is nighttime. So we have established that the Sun
does not move around the Earth. It is only the Earth’s rotation
that causes this apparent motion of the Sun in the sky.
As well as this rotation, or spin,
the Earth orbits around the Sun. Its orbit is nearly circular. One full orbit is one year on
Earth. Since the Earth orbits the Sun, we
know that it cannot be at the center of the solar system. So option (B) is incorrect.
As well as the Earth, all the other
planets orbit around the Sun in circular orbits. Three of the options are
planets. There is Earth as well as Mars and
Jupiter. We can sometimes see Mars and
Jupiter at night as bright points of light that move slowly across the sky. Both Mars and Jupiter orbit around
the Sun. Hence, we know that the Sun is at
the center of the solar system, as all of the planets orbit around it, including
Mars and Jupiter.
This sketch of the solar system is
not to scale. The planets are much smaller than
the Sun. And the distances between the
planets are also not drawn to scale. The Sun is at the center of the
solar system because it is much, much bigger than the planets. So option (C) is the correct
answer. The name “solar system” is
referring to the Sun, where the word “solar” refers to our Sun. This can help us remember that the
Sun is at the center of the solar system.
