by Emmanuel Agyemang
The stars you see today appear as they
existed many years ago.
Have you ever felt fascinated by the lights that
array themselves in the sky at night? Some
take the shape of animals, so much so that
we have named the stars after these animals.
Ursa Major, a constellation in the Northern
hemisphere, for example, has been named the
Great She Bear as its form looks like a bear.
The Andromeda galaxy, the closest galaxy
to our Milky Way, can leave us in awe as we
marvel at how insignificant we seem relative
to such majesty.
Yet beyond the beautiful sky at night,
what exactly are we looking at? Many think
we are looking at the stars as they are in
the present. Yet on the contrary, we actually
are looking at them as they were hundreds,
thousands or even millions of years ago.
Light travels at a constant speed of 186,000
miles per second. At that speed, one can
circumnavigate the earth’s equator seven and
a half times in a single second—or travel six
trillion miles in one year. The name for that is a
“light year,” and that is the metric at which the
universe is measured.
For example, the North Star, Polaris, is
about 323 light years away from Earth. That
means the light that leaves Polaris today will
reach Earth in 323 years. Therefore, the light
that we see tonight from the North Star left
that star 323 years ago. Which means if there
was an alien with a telescope powerful enough
to view the Earth from the North Star, they
would see the events that took place on Earth
323 years ago. And this same concept applies
to all the other stars and galaxies we see in the
sky. We are seeing the Andromeda galaxy as it
was 2.5 million years ago, since it is 2.5 million
light years away from us and its light is just
reaching us today.
Our sun, a type G star which burns
around 5,000 degrees Kelvin, is about eight light
minutes away from the Earth. Consequently,
we see the sun as it was eight minutes in the
past, and not as it is. So, if the sun disappeared,
we would not know until about eight minutes
later. The further away stars are, the further
back in time they are. For example, if you are
speaking to a friend who is about a meter away,
the light from the friend’s face takes about
3.666 nanoseconds to reach you. Therefore, if
you look around you, according to the concept
of time measured in light years, you are looking
into the past; it only depends on how far in time
you are looking. Whether three nanoseconds
into the past or millions of years into the past,
you only need to look around.
The Peoria planetarium provides an
in-depth understanding of the stars and the
universe by simulating the stars and other
heavenly bodies. Visit the Peoria Riverfront
Museum to learn more about the cosmos.
About Emmanuel Agyemang
Emmanuel Agyemang is an international student from Ghana
and a recent graduate of Bradley University with a degree in Political
Science. He has an interest in pursuing law in the near future.
About Sophie Liu
Sophie Liu is a senior at Dunlap High School who has won numerous art prizes such as the Scholastic Art and Writing Gold Key Award and several honorable mentions. As someone who also values academics, business, and volunteering, she has participated in and led many activities in her community. Her volunteering contribution has awarded her the Gold President’s Volunteer Service Award. She is one of the club leaders of her school’s Interact Volunteering Club. During her summers, Liu has participated in several business camps such as Kelley Business’s Young Women’s Institute, where she has gained knowledge and experience in her passion. She also runs her own online art business where she creates commissioned art pieces and gains firsthand business experience. Liu plans to continue her love of business, volunteering, and art in college, where she will major in either Marketing or Business Analytics and minor in art.