What Is Hidden In The Darkness At The Beginning Of Time?

Close your eyes and imagine yourself within a supervoid.

Darkness envelops you, holding you captive and isolated.

With your eyes, even with any amateur telescope, you see nothing, no stars,

no hint of the fuzzy smudges we now know as our own neighbouring galaxies.

To you, the Universe is empty. The Boötes void is a spherical

region 330 million light years across, approximately 0.2% the diameter of the

entire observable cosmos/universe. The Milky Way could fit inside it millions of times over,

and yet within a volume of about one million cubic Mpc, where there should be thousands of galaxies,

we have observed only 60 - spiral galaxies, blue with the light of new star formation.

To quote astronomer Greg Aldering: "If the Milky Way had been in the center

of the Bootes void—we wouldn't have known there were other galaxies until the 1960s."

Indeed, were Earth to rest on one edge of this void, observers on the other

side would only now be receiving light from a time when amphibians dominated the earth,

before even the age of the dinosaurs. Even now, we do not fully understand how such

a void came to be. The age of the Universe sets a limit for the maximum size of any structure,

galaxy clusters, and indeed the voids in between. There should be no single

structure in the Universe that is already greater than tens of millions of light years across.

The Great Nothing, as the void is known, shatters this limit.

Though its absence of structure does give us an insight into the growth of structure

at the earliest of times - the few galaxies observed within the void following a tube shape,

perhaps the crumbled remnants of a wall between two voids. Individually,

these voids would each fit in with the growth limit, but together they form a supervoid.

And so even here, in the “Great Nothing”, one of the darkest places in the Universe,

there is the light of galaxies, unveiling their secrets to us through the visible spectrum.

To find true darkness, we have to look farther than the Boötes void, farther back in time.

We can only find complete oblivion in the time before stars and galaxies and

planets existed - forebodingly known as the Cosmic Dark Ages.

Here, the darkness was total, and long-lived. Although for about 200 million years after the

Big Bang the Universe contained a variety of ingredients that could produce the first stars,

none formed. There was no visible light at all.

But why was the cosmos dark for so long?

What does this mean for the stars and galaxies we see around us today?

And how can we possibly hope to shed any light on an era when there was only darkness?

In 1543, Nicolas Copernicus showed the earth isn´t the centre of the solar system, in the 1920s Jon

Oort discovered the sun wasn´t in the centre of our galaxy, and in that same decade Hubble

discovered our galaxy was just one of countless others. Cosmologically we arent the centre of

anything - and that is a sobering realization. This video has been kindly sponsored by

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In 1995, the then-director of the Hubble Space Telescope Bob Williams

had ring-fenced some personal observing time.

He was the envy of the scientific world, holding precious hours on the world’s greatest telescope,

able to look at anything he wanted. At the time Hubble was in the spotlight - but

not for the right reasons, having used up billions of dollars of public funds only to require a

crewed space mission to correct a near-fatal flaw in the system's optics. The mirror which

reflects gathered light into the instruments needed to be extraordinarily smooth in order

for the image to be in focus. Hubble’s mirror was very smooth indeed, but the first images had been

disappointingly blurry, a devastating blow to the intended science aims of the mission.

It was determined that the mirror had an aberration less than a fiftieth of the width

of a human hair that was causing the incoming rays of light to focus at different points,

clouding our view of the cosmos. For most space missions, this would have been fatal,

but Hubble was in low-Earth orbit, making a repair mission not unrealistic.

Astronauts installed several clever adaptations and replacements,

correcting Hubble’s eyesight to perfection. But now, Williams was under pressure to produce

something of worth, something that would dispel the naysayers in politics, press,

and even within the corridors of NASA. And so he decided to look at nothing.

Against the counsel of his colleagues, Williams and his students steered the

eye of the billion-dollar machinery such that it looked past the planets, sidestepped the stars,

and away from the galaxies. Hubble instead settled its sights on a tiny patch of sky

only 1/30th the diameter of the Moon. And there, it stared, for ten whole days.

To our eyes, and any other telescope that had come before, this patch was barren of

structure - but this technology was a giant leap forward in astronomy - and

the fine resolution and sensitivity of the Hubble Space Telescope revealed shapes in the darkness.

Over a long exposure, the new Hubble could slowly gather photons coming

from the farthest and faintest objects in the Universe - and distant galaxies of every size,

shape and colour emerged from the darkness. We now know this as the Hubble Deep Field,

one of the most iconic images in astronomy. As with any photograph, this image is a 2D

projection of a 3D landscape - galaxies far removed in distance appear to be neighbours.

It is also a projection of time. Photons from the farther galaxies have travelled for longer,

and so we see those galaxies as they were farther back in time. Galaxies

can even appear to be colliding, when they existed as pictured billions of years apart.

To understand why, let us consider the observable universe as

constructed of a series of shells around us. The shell closest us to us is easy to observe

because the light travels to our telescopes almost instantaneously. Light from the Sun takes about

eight minutes to arrive to Earth. Move a shell outwards, perhaps to our nearest neighbouring

galaxy, Andromeda, and from here, the light we see today has taken 2.5 million years to get to us,

released when one of humanity’s earliest ancestors, Homo Habilis, walked the Earth.

This may be a long time for us, but it is still a short time in terms of the

cosmological timeline of 13.8 billion years. As we consider the light from even farther shells,

the photons we receive get progressively more ancient, and so we can see further back in time.

And so with Hubble we could finally observe light from galaxies as they

were only hundreds of millions of years after the Big Bang,

so faint and poorly resolved that they are mere red smudges in the sky - just as our closest

galaxies were once smudges on the sky for the astronomers of the last century and before.

We have the means to pick apart the light that we observe, working out the composition of that

galaxy and comparing known element markers to work out the distance to, and age of,

the galaxies we see. This method uses the same principle that causes a fire engine’s siren to

change pitch as it approaches and passes you on the street. As the fire engine approaches,

the wavefronts of sound pile up, and we perceive a sound of shorter wavelength,

or higher frequency. Conversely, as the fire engine recedes, the wavefronts are increasingly

spaced out, and we hear a lower pitch. The inherent siren pitch remains the same,

but it is the relative movement between the source and the listener that causes a shift.

Now imagine a galaxy as our siren, except instead of listening for the sound, we observe the siren

light. This light is a specific colour, blue, and does not change. As the galaxy recedes from us,

however, the light wavefronts stretch out and we observe a longer wavelength light:

the siren gets redder. We call this shifting of the light spectrum redshift.

Certain chemical elements are natural siren lights in the spectrum, producing a clear emission line

at a known frequency. By measuring how much that line has shifted in a galaxy’s spectrum,

we can calculate the speed at which it is travelling away from us. Edwin Hubble, the famous

astronomer for whom the telescope was named, observed that the farther the galaxy, the faster

it appeared to be travelling away: a keystone of the Big Bang theory. As a rule of thumb,

the oldest light is the most redshifted. In this way, we prise apart the thousands of galaxies that

appear tangled in the deep field images, and brush away layers of young galaxies, until we are left

with only the oldest, the first of their kind. The latest deep field image from the James Webb

Space Telescope covers the area of just a grain of sand in the sky and yet still,

thousands of galaxies emerged from the darkness - pushing back the cosmic frontier to only a few

hundred millions of years after the Big Bang. We are finally reaching a time in the Universe

where there was no visible light at all, a time that even JWST is blind

to - the frontier of the First Stars. But does this mean we can go no further?

Are we forever closed off from the darkness that lay before?

In the beginning, light ruled the Universe.

The energy density of radiation far outweighed the energy density of matter, and interactions between

the two were commonplace. So much so that photons of light quickly broke apart any atoms that formed

and, as a result, the photons could not travel freely in this super-hot dense plasma of matter.

This soon changed however. While both densities reduced as the

volume of the Universe increased, radiation fell faster because of an extra factor: the

stretching of light into the longer wavelengths as the universe expanded, and lower equivalent

temperatures - cosmological redshift. After around 380,000 years of expansion,

the energy density of radiation had fallen below that of matter, and the dominion of light in the

cosmos was long over. The temperature of the plasma had in fact cooled to such an

extent that atomic nuclei could now reliably combine with electrons into simple atoms.

Though light was now no longer the dominant force in the universe, there was an upside - the

creation of atoms now meant photons had space to travel, having their paths diverted only

occasionally through interactions with matter. And so light was free - but what would you have

actually been able to see? The answer is hard to know

for certain - but we can estimate what the Universe would have looked like.

The radiation at the point of recombination emitted as a blackbody: an object that emits

radiation across the wavelengths with a predictable shape, as long as you know

its temperature. To an onlooker, the Universe would have seemed to have a warm orange glow.

Over the next few hundred million years, as the Universe expanded further, the dropping

temperatures lead that glow to redden with time. Finally, it cooled such that there was no longer

radiation emitted in the visible part of the electromagnetic spectrum at all. The embers

of the Big Bang faded entirely into the infrared, microwave and radio wavelengths. Darkness fell.

In the midst of the black, though, all was not quiet.

For another kind of matter was created in the Big Bang, a kind of matter that

is still mysterious to us today: dark matter. In the 1960s, scientists Kent Ford and Vera Rubin

measured the orbital velocities of stars in spiral galaxies and found that something didn’t add up.

Orbital velocity, the speed that stars orbited the galaxy,

is a fine balance. Too slow and gravity causes the star to spiral inwards, too fast, and the

star overcomes gravity and flies out of orbit. The astronomers carefully estimated the stellar

mass, and hence gravitational pull, of a variety of galaxies and found that stars were simply

moving far too fast. Observation after observation pointed to an uncomfortable truth: there must be a

hidden component of mass keeping them in orbit. And that hidden mass was known as “dark matter.”

Calculations show that this ‘dark matter’ makes up four-fifths of all matter in the Universe,

yet it still evades our direct detection and capture today.

The matter we see around us interacts with the Universe both gravitationally

and electromagnetically. Dark matter, in contrast,

only interacts with the gravitational field. It cannot absorb or emit photons and so has

no imprint on a spectrum in the same way chemical elements do. It does possess a gravitational pull,

however, and so high-density areas of dark matter can grow

and collapse through accretion. But only up to a certain point.

And this is key - there can be no stars or planets made of dark matter.

As a cloud of matter collapses, the pressure of the particles in the cloud fights back.

Pressure is linked to temperature: the denser the particles, the hotter they are, and the more

kinetic energy they have to more effectively create an outward-acting pressure force.

Normal matter can convert thermal and kinetic energy into electromagnetic radiation via the

excitation of electrons in colliding atoms. The atoms move apart at a slower pace and

when the electrons naturally return to their ground states, they emit photons

which carry away the parcel of energy from the cloud. The pressure is reduced permanently.

But dark matter does not interact electromagnetically and so cannot

emit photons. There is no escape valve. This means that once the outwards thermal pressure

of the system balances the inwards gravitational pressure, the collapse is simply halted.

And so instead dark matter collapses into filaments, connecting at their densest

points into halos. Unable to emit light, our Big Bang observer could not see this vast background

web of dark matter, behind the uniform orange or red glow of the gas. Even in the total darkness

that followed as the radiation shifted out of the visible, the dark matter remained hidden.

For close to two-hundred million years, this remained the state of play - a web of

dark matter that was doomed to darkness forever, and a mist of gas too dilute to ignite fusion.

And so how could the Universe ever form a star to break the impasse?

And hidden as the evidence is in the total darkness at the

beginning of time - how could we ever know what happened?

On 6th May 1937, flames viciously engulfed the German airship Hindenburg as it attempted to dock

with its mooring mast in New Jersey. Bystanders could only look on in horror. Pride of the fleet,

the ship regularly carried passengers across the Atlantic Ocean at a stately 80 miles per hour.

This journey had been no different until the very last moment, when the hydrogen cells filling the

balloon ignited one by one, causing explosive damage as the fuel tanks erupted. Remarkably,

just under two-thirds of the passengers and crew survived,

thanks only to its proximity to the ground and the extended duration of the disaster. Most victims

however were severely burnt, and grief ripped through the families of the 35 lost souls.

Airships had been a regular sight across city skies, carrying army personnel, passengers and

freight across and between continents. Most airships utilised hydrogen as a way of filling

the balloon, as its buoyancy is well above that of air - but hydrogen also boasts another property:

it is extremely flammable.

Most evidence points to the cause of the Hindenburg disaster as a hydrogen leak

in the fuel tanks. When this hydrogen mixed with oxygen in the air, the gas holding up the balloon

became ready to blow, and it is thought that a simple flash of static electricity provided

the source of ignition, thus ending the era of airships with almost immediate effect.

Hydrogen. One proton, one electron. Simplicity itself.

This most basic atomic structure is odourless and tasteless, and it will combust when exposed

to even the lowest concentrations of air and an ignition, as seen in the Hindenburg incident.

But even that fatal destruction is far from the full power held within this small orbital system.

Nagasaki. Hiroshima.

These cities act as reminders of the horror that humankind can unleash upon