“The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge”,
Stephen Hawking.
The universe is a vast, apparently endless wonder of existence.
Over the last century, we've learned that the universe extends beyond our Milky Way's
billions of stars, spanning tens of billions of light-years and holding about a trillion
galaxies in total.
That is, however, only the observable universe!
There are compelling grounds to assume that the universe extends beyond our ability to
observe it; the question is, how far does it extend?
Forever?
Or does it eventually collapse in on itself?
The closer an object is to the observer in the universe, the easier it is to measure
its distance.
Simply shine a beam of light skyward and time how long it takes for the beam to bounce off
the celestial object and return to Earth.
The most distant objects in our galaxy, on the other hand, are more difficult to comprehend.
After all, a powerful beam of light would be required to reach them.
Even if we had the technological capability to send a beam that far, who has thousands
of years to wait for it to bounce off the universe's farthest exoplanets and return
to us?
In 2013, the Planck space mission of the European Space Agency revealed the most accurate and
complete map of the universe's oldest light.
According to the map, the universe is 13.8 billion years old.
Planck figured out how old the universe was by looking at the cosmic microwave background.
The cosmic microwave background light is a distant and long-ago traveler.
When it arrives, it tells us about our universe's entire history.
Scientists can stare at an area of space that is 13.8 billion light-years away because of
the relationship between distance and the speed of light.
Astronomers on Earth can tilt their telescopes to stare 13.8 billion light-years in every
direction, similar to a ship on an empty ocean, putting Earth inside an observable sphere
with a radius of 13.8 billion light-years.
The phrase "observable" is crucial; the sphere restricts what scientists can observe, but
not what actually exists.
However, despite its apparent diameter of about 28 billion light-years, the sphere is
much larger.
The universe is expanding, so while astronomers may be able to see a place 13.8 billion light-years
away from Earth at the time of the Big Bang, the universe has continued to expand throughout
time.
If inflation continued at a constant rate throughout the lifetime of the universe, that
same place would be 46 billion light-years away now, making the diameter of the observable
universe a sphere of about 93 billion light-years (28 billion parsecs).
Some scientists have used that number to try to figure out what lies beyond the observable
universe.
Astronomers can look at the patterns we see in the observable universe and use models
to estimate how far the rest of the universe extends based on the premise that the universe
has a curved form.
According to one study, the actual universe could be at least 250 times larger than the
observable universe.
However, there is no proof that the cosmos is finite.
It might carry on indefinitely.
Although scientists disagree on whether the cosmos is finite or infinite, they agree that
it is quite vast.
Unfortunately, we'll only be able to see the small portion that we see now for the rest
of our lives.
The furthest borders of our observable universe are rushing outward faster than the speed
of light because the universe is expanding at an increasing rate.
This means that our universe's edges are moving away from us faster than their light can reach
us.
It may appear that centering a sphere on Earth's position in space places humanity at the center
of the universe.
We, like that same ship in the ocean, have no way of knowing where we are in the vastness
of the universe.
We are not at the center of the ocean just because we can't see land; we are not in the
center of the cosmos just because we can't see the edge of the universe.
The vastness of the universe, and the vastness of what we can't see, is humbling.
But that doesn't stop scientists from looking for answers, although they could fail to figure
it out.
It could be seen as aggravating, but it also adds to the excitement.
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