What’s Really at the Center of the Universe?
Vast, mysterious, shapeless and most likely infinite; it feels almost impossible that
we’ll ever fully explore the universe. We once thought that we were at the centre of
it all, but is there actually any truth to the idea that everything revolves around humanity?
This is Unveiled, and today we’re answering the extraordinary question; what’s really
at the centre of the universe?
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For centuries, the geocentric model ruled popular and academic thought when it came
to understanding our own place in the universe. Also called the Ptolemaic system after the
Roman astronomer Ptolemy, it was an ancient belief that planet Earth was truly the centre
of everything. It was such a widespread and accepted explanation that even Aristotle helped
to popularise it.
According to this model, a fixed, spherical Earth existed at the centre of every imaginable
construct. The moon, stars and sun all orbited around it. Out beyond the planets were the
heavens and other “realms” we now generally assume don’t exist – or if they do, they’re
probably not hiding behind any planets in outer space. Because of this model, people
believed that Earth lay at the centre of the universe itself. And, in even earlier flat
Earth belief systems, similar theories persisted with the flat Earth in the middle of all existence.
Today, it’s easy to dismiss these ideas thanks to centuries of study proving that
the Earth is a globe which belongs to the solar system, orbiting the sun. However, the
basic idea that the Earth really is at the centre of our universe might not be as ludicrous
as it seems. In fact, it’s essentially true. The earth is, as much as anywhere else can
be.
And that’s because, according to the cosmological principle, there isn’t actually a centre
of the universe at all - which, from another perspective, also means that everywhere is
the centre. To have a centre, the universe would need to have an observable edge, or
even a shape; which it doesn’t. And, while it’s true we can only observe so much thanks
to the speed of light, this isn’t the same as having a defined edge at all.
In general, we tend to imagine a ‘universal centre’ because common ideas about the Big
Bang are actually wrong - or at least, according to contemporary science. The general assumption
is that the Big Bang was an enormous explosion at the dawn of all existence, which created
everything in the universe. But, there are plenty of physicists who doubt that this is
true. To them, though the name is a bit misleading, the Big Bang wasn’t an explosion at all,
but rather a rapid inflation of space itself. Once, at the beginning, the universe was impossibly
small and finite, and when the Big Bang happened it began to expand.
The best way to understand this is through a famous balloon analogy, first told in the
1930s. It says that the universe is like a balloon with dots already drawn onto it. Those
dots stand in for galaxies, celestial bodies, various points of interest… And, as the
balloon is inflated, the dots grow further and further apart - and that’s expansion.
If you were miniscule and you stood on the surface of that balloon, the ‘centre’
could be anywhere.
The Big Bang happened everywhere at once simultaneously and is actually still happening today - because
the universe is still expanding. Another way to understand this is to consider that everything
in the universe right now also existed when the Big Bang happened… It’s just that
as the years roll by, the universe gets less and less dense and things spread out.
In terms of concrete, scientific evidence to prove this, we have redshift. First observed
by renowned astronomer Edwin Hubble in the 1920s, redshift is the light-wave equivalent
of a soundwave phenomenon that’s much easier to observe. The soundwave version is called
the Doppler effect, and refers to how sounds (perhaps sirens) change pitch the closer or
further away from you they are. We’re more easily able to perceive the Doppler effect
rather than redshift (the same thing, but for light-waves) because sound travels so
much slower than light.
Regardless, both of these effects happen because of how waves change over a distance; sound
waves are shorter, and therefore higher, the closer they are to you; While light waves
are longer and therefore redder, the further away the object being observed is. Distant
planets and galaxies appear further on the ‘red-end’ of the visible light spectrum,
and get more and more red until eventually becoming infrared and invisible to the naked
eye. From our position, this is happening to all celestial bodies, and it’s how we
know that the expansion of the universe is ongoing. Like the dots on the surface of the
balloon, everything is infinitely spreading out… Only, it’s moving further and further
on a scale so huge it’s almost impossible to imagine.
But how do we know that everything (centre, or no centre) was once held in a much smaller
area of space? How do we know the Big Bang happened at all, or when it happened? And
can we be sure that objects drifting away from each other were once much, much closer
together? These are questions with another reasonably simple answer: cosmic microwave
background radiation.
This radiation is present throughout the universe, and can be traced back to about 400,000 years
after the Big Bang. Where once it was staggeringly hot… today, 13.8 billion years later, CMB
has cooled to around 2.7 degrees above absolute zero, making space a very cold place to be.
But, the most interesting part is that CMB is always this temperature no matter where
you look in the sky. It’s been said that if the radiation was made of visible waves
rather than microwaves, then the entire universe would be illuminated identically in any possible
location. Because the universe is uniform like this, we know that it was once smaller
and closer and, again, we know that expansion is happening everywhere.
Of course, though, science could be wrong. Perhaps our understanding of the universe
is just as ludicrous when compared to the elusive truth as our previous beliefs about
the sun orbiting the earth now seem. Maybe we just don’t have the instruments, the
knowledge, or the comprehension to really understand space, let alone put a pin in its
‘middle’. Perhaps, somewhere, there really is a universal centre. But, if there was,
it’s incredibly unlikely that it would be anywhere near Earth at all - it’d be a ‘law
of averages’ almost impossibility, because the universe is just too huge.
Think about it… If expansion really did occur from a singular point and the Big Bang
was a specific explosion, then we’d most probably never be able to observe the mythical
centre or travel to it. So, in that sense, it’s much better to accept what modern science
tells us: that we really do belong at the centre of existence, but so does everything
else.
Because of the constant expansion of the universe over the last 14 billion years, everywhere
and nowhere is simultaneously at the heart of all existence. And that’s what’s really
at the centre of the universe.
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