It’s a calm, clear night, and you’re lounging on the grass, staring up at the twinkling
stars, wondering about the vastness of space and the mysteries of the universe.
As you stare in awe at the cosmos, your mind is filled with questions about the universe
and our place in it.
How many stars are there?
How much of space can we even observe?
Are we really alone in the universe?
It may seem like we’re well on our way to understanding the cosmos, but in reality we’ve
explored less than zero-point-one percent of the entire known universe, and there are
still countless mysterious space events that astronomers can’t explain.
Humans have been watching the skies for millenia, observing cosmic events and trying to interpret
and predict their effect on events on earth.
After centuries of stargazing, we now know more about space than our ancestors ever could
have dreamed - we know that earth is a planet in the solar system that orbits our sun; we
know that our solar system exists in the Milky Way galaxy; and we know that there are countless
other galaxies, stars, and planets in the universe.
We know that stars can “die” in spectacular ways, and we know that our universe is constantly
expanding.
Perhaps most importantly, though, we know how little we actually know about the universe,
and we know that we will never know everything about the cosmos.
As impressive as humanity’s knowledge of the universe is, there are many more space
mysteries than cosmic answers when it comes to our universe.
Take, for example, the recent discovery of The Cow, a mysterious explosion in deep space
first observed in 2018.
Astronomers and hobbyists alike were mystified when they looked into their telescopes on
June sixteenth and saw an unusually bright glow in the sky that definitely hadn't been
there the day before.
Even seasoned astronomers thought this was “super weird”.
At first, experts thought they were looking at a fairly common event somewhere in our
galaxy - perhaps a white dwarf, the burnt-out remains of a star that was consuming material
from a nearby star, causing it to flare up.
But, once astronomers analyzed The Cow’s light spectrum, they realized that the thing
they were seeing was not in our galaxy at all - it was actually much farther, up to
two-hundred million light years away!
A white dwarf would never be visible from that distance, and the object wasn’t displaying
the hallmark changes in brightness that we’d expect from a supernova.
Experts were transfixed - The Cow didn’t behave like any space events they were used
to - it just appeared one day, and continued to burn hot for nearly three whole weeks.
The unusually long and steady duration of the light pointed to some sort of massive
explosion deep in space - we just have no idea what caused it.
Some think it was an unusual kind of supernova where the star’s core collapsed inward after
it exploded.
Others think it was a tidal disruption event - a star being ripped apart by a black hole.
But, black holes big enough to tear apart a star are usually only found at the centre
of a galaxy, and the bright lights of The Cow were coming from the outer edge of the
galaxy’s spiral arm, leading some to theorize that a smaller black hole is responsible - but
we’re not sure if those kind of black holes even exist!
Anna Ho, a researcher from the California Institute of Technology, finally decided to
try observing The Cow using a submillimeter array, which sends short frequency radio waves
into space.
This wouldn’t normally work, because the phenomenon we’re trying to observe usually
disappears before the radio waves can reach it.
But The Cow’s unusually long and bright existence gave the waves enough time to reach
it, allowing researchers to monitor the event for several days before the signal dramatically
dropped off.
Based on this data, Anna theorized that the light we could see was the result of the shockwave
from some unknown giant explosion travelling through a cloud of dust and gas, emitting
light as the gasses heated.
If you’re surprised by the fact that scientists can’t agree on an explanation for an event
that we can clearly see with our own eyes, you may be wondering what else we don’t
know about space.
It turns out, there’s plenty we don’t know.
Take, for example, black holes.
Common in both sci-fi and real scientific theories, you might think we have them all
figured out, but it’s actually shocking how little we know about black holes.
Black holes are giant masses of cosmic quicksand that are formed when a giant star collapses
and all of its mass implodes into a tiny area of such intense gravity that even light gets
sucked in.
Because no light can escape from a black hole, we can’t see them with our own eyes.
We only know that they exist because we can observe how the stars and gasses closest to
them behave.
The black hole’s super strong gravitational force pulls any nearby objects towards it
- when a star is close to a black hole, it also creates a type of high-energy light that
can’t be seen with the naked eye, but can be detected using special satellites and telescopes.
The types of black holes caused by an imploding star are called stellar black holes, and they
can be up to twenty times more massive than our sun.
Some black holes are as small as a single atom, but have the mass of a large mountain.
At the centre of each galaxy in the universe is a supermassive black hole, which scientists
believe were created at the same time as the galaxy they are in.
Sagittarius A is the name of the supermassive black hole at the centre of our galaxy, the
Milky Way, and it has a mass greater than four million of our suns.
Before you start panicking about how the Earth is slowly being sucked into the black hole
at the centre of our galaxy, let’s move on to some other, less stressful space mysteries.
We talk a lot about all of the different stuff that makes up the universe -the planets and
stars and solar systems and galaxies - but we don’t often think about the absence of
stuff in space.
During the Big Bang, all of the matter in the visible universe that had been compressed
into a single point began rapidly expanding outwards.
More than thirteen billion years later, what started out as small variations in the density
of matter have turned into huge, empty voids in space.
The largest one that we know of, the Great Void, is one and a half billion light years
away from us, and measures more than one point three billion light years across.
To be fair, these voids aren’t totally empty - they are filled with dust, gas and even
dark matter - but the density of matter in a void is less than a tenth of the average
for the rest of the universe, making them quite unusual.
So, what is this Dark Matter that’s floating around in these space voids?
With all the talk about dark matter and energy in recent years, it may seem like we’re
well on our way to understanding these dark forces, but much like black holes, we can’t
actually see dark matter or dark energy, and what little we do know about them is purely
guess work.
We know that the universe has been expanding since the Big Bang, and for decades astronomers
theorized that the rate of expansion was slowing over time due to the effects of gravity.
However, all their theories went out the window in nineteen ninety-eight when the Hubble Space
Telescope made a shocking discovery.
By observing a very distant supernova, the Hubble proved that the universe had been expanding
more slowly in the past than it was today, meaning that the expansion of space was actually
speeding up, not slowing down.
This discovery stumped the experts.
No one was sure exactly why the expansion was accelerating - perhaps it was a problem
with Einstein’s theory of gravity, or the existence of some unknown energy fluid in
space?
Even though astronomers couldn’t explain this phenomenon, they gave it a name - Dark
Energy.
We know that Dark Energy exists - and how much of it there is - by how it affects the
universe’s expansion.
Scientists have estimated that up to sixty-eight percent of the universe is made up of dark
energy.
Some experts also theorize that dark energy is evenly distributed through both space and
time - meaning that as the universe expands, it creates more dark energy.
Dark energy does not have its own local gravity, but instead has a repulsive effect on the
universe as a whole, causing the expansion of the universe to accelerate.
Scientists need much more and better data to make any headway in understanding dark
energy.
If Dark Energy makes up sixty-eight percent of our universe, dark matter makes up another
twenty-seven percent.
That means that all of the so-called “normal” matter that we can see and observe, even with
our most sensitive equipment, makes up only a measly five percent of the entire universe!
That’s a little bit unnerving to think about...
Like dark energy, dark matter is invisible.
It does not interact with electromagnetic forces - it doesn’t absorb, reflect or emit
light - so the only way we know it exists is by observing the effects of its gravitational
pull on other matter.
If dark matter were created during a controlled particle collision at CERN’s Large Hadron
Collider, the dark matter would escape undetected by their equipment.
But, scientists could infer its existence by measuring the amount of “missing” energy
after the collision.
One of the most interesting theories about dark matter is the existence of a “Hidden
Valley” - a parallel world made entirely of dark matter.
If imagining an entire parallel world made of dark matter is making you uneasy, wait
until you hear about the evil twins of outer space.
Subatomic particles like protons, electrons and neutrons all have an evil twin - antimatter.
Antimatter particles have the same mass as normal particles, but the opposite electrical
charge.
As a result, antimatter destroys normal matter on contact.
That sounds terrifying, but don’t worry - there’s very little antimatter in the
universe, and it can actually be harnessed for good.
PET scanners work by creating anti-electrons and using the energy that’s released when
they are destroyed to create sophisticated images.
Even more wild than evil twins is the theory of Quantum Entanglement.
In quantum entanglement, two particles in completely different parts of the universe
can actually be linked to one another, and will mirror the state and behaviour of their
partner over great distances.
At first, this seemed to break some pretty fundamental laws of physics, since they thought
that the signals sent between particles would have had to travel faster than the speed of
light.
But eventually, as scientists began to unravel the puzzle of quantum mechanics they started
to understand how this “spooky action at a distance”, as Einstein called it, actually
works.
It would take a whole other video to begin to explain quantum mechanics, but the basic
idea is that unobserved particles exist in all states simultaneously, and takes on one
state only when it’s observed and measured.
It’s like that old riddle - if a tree falls in the forest and no one’s around to hear
it, does it make a sound?
As you lay back on the grass and take in the marvel above you, there’s still one space
mystery tugging at your curiosity - are we really alone in the universe?
This is yet another mystery of space that continues to stump scientists.
According to the Fermi Paradox, the universe is so massively huge and so unimaginably old
that all probability points to a high likelihood of extraterrestrial life.
And yet, we have no evidence of life outside our own planet.
Enrico Fermi, the Italian physicist credited with sparking this debate, theorized that
any civilization with modest rocket technology could colonize an entire galaxy within the
span of ten million years - the blink of an eye in the timeline of our universe.
It’s entirely possible that life has existed outside earth, and that the lack of evidence
is more of a problem of “right place, wrong time” than proof that we truly are alone.
If you really want to have your mind blown as you gaze in wonder at the stars, consider
the Multiverse Theory - the possibility that our universe is just one of many, possibly
infinite universes.
The fact that this is a valid theory currently being studied by renowned scientists just
goes to show you how little we really understand about the nature of the universe.
As fascinating as space mysteries are, the lack of definitive answers can be frustrating.
Your best bet is to just enjoy your time laying in grass, staring at the cosmos.
And, if you’re lucky enough to see a shooting star, maybe you can wish for an answer to
these space mysteries that astronomers can’t explain!
If you thought this video was crazy, you have to check out “What If You Die In Space?”,
or this other great video.