The Universe-2.
Without realising it, we are all travelling back in time by the most minuscule amount.
The consequences of light travelling fast, but not infinitely fast,
is that you see everything as it was in the past.
In everyday life the consequences of the strange fact are intriguing but irrelevant.
When we lookup at the moon we are looking at our closest neighbour a second into the past.
The moon is 380,000 kilometres from Earth.
When we look at the Sun, we are beginning to bathe in the past.
The Sun is 150 thousand kilometres away.
When we see the Sun, it is 8 minutes into the past.
Because the speed of light is actually the maximum speed,
at which any influence in the Universe can travel, this delay applies to gravity as well.
As we look at the planets in our solar system we move further and further into the past.
The light from Mars takes between 4 and 20 minutes to reach Earth,
depending on the relative positions of Earth and Mars.
This has a significant impact on the way we design and operate vehicles,
on the surface of Mars.
When Mars is at its furthest point from Earth,
it would take 40 minutes to communicate with it.
So the Mars rover has to take some decisions by itself.
As we travel further, it takes longer.
Light from Neptune takes 4 hours to reach the Earth.
If we look beyond our solar system, the time for light to travel from our neighbouring stars,
is measured in years.
Light from the nearest star Alpha Centauri takes four years to reach us.
As cosmic distances increase the time for light’s journey to reach us,
becomes longer and longer.
If we look into the sky on a clear and dark night,
every single point of light have their origin a star in our own galaxy,
or the misty clouds known as the Magellanic clouds.
These are two dwarf galaxies in orbit around the Milky Way.
To find another one, we need to recognise the W shape of the constellation of Cassiopeia.
It sits on the opposite side of Polaris, the North Star, towards the constellation Ursa Major,
also known as the Great Bear.
Cassiopeia, being so close to Polaris, is a constant feature in the northern skies.
It simply rotates around the pole every 24 hours, and never sets below the horizon,
at high altitudes.
Beneath the W of the Cassiopeia, we can see quite a large, faint misty patch in the sky.
It is comparable in brightness to most of the stars surrounding it,
although dimmer than the bright stars of Cassiopeia.
This unremarkable little patch, is the most intellectually stunning object,
you can see with a naked eye.
It is an entire galaxy beyond the Milky Way.
It is called Andromeda.
It is our nearest galactic neighbour.
It is home to a trillion stars.
It is 25 into 10 to the power of 18 kilometres away,
or 2.5 million light years away.
With a naked eye, we can travel back in time by a mere 2.5 million light years.
Until recently Andromeda was the furthest we could look back unaided.
Modern more powerful telescopes now enable us to see deeper and deeper into space.
In the history of astronomy, no telescope since Galileo’s original,
has a greater impact than the Hubble Space Telescope.
It is named after Edwin Hubble, the scientist who discovered that the Universe is expanding.
In 1990 Hubble was launched into an orbit 600 kilometres above Earth.
The promise of Hubble was simple.
It would provide images from the depths of space unaffected,
by the distorting effects of Earth’s atmosphere.
After launching it was discovered that Hubble’s shining retina,
was 2.2 thousandths of a millimetre out of shape.
Hubble was designed to be the first, and only telescope to be serviceable by astronauts,
in space.
In 1993, astronauts spent 10 days refitting the telescope with new corrective equipment.
In 1994, NASA opened Hubble’s corrected eye to the Universe.
It opened our eyes to the extraordinary beauty of the Cosmos.
For two decades the Hubble Space Telescope has captured the faintest lights,
and provided a window onto places billions of years ago.
There is one Hubble image that has done more than any other to reveal the scale,
depth and beauty of our Universe.
It is known as the Hubble Ultra Deep Field.
It was taken over a period of eleven days in 2004.
During this period Hubble focused two of his cameras-,
The Advanced Camera For Surveys or ACS,
and Near Infrared Camera and Multi Object Spectrometer or NICMOS-,
on a tiny piece of sky in the southern constellation, Fornax.
By using its million second shutter speed, Hubble was able to capture images,
of unimaginably faint, distant objects in the darkness.
The dimmest object in the image were formed by a single photon of light,
hitting Hubble’s camera sensors every minute.
Almost every one of these points of light is a galaxy.
Each galaxy is an island of hundreds of billions of stars.
Over 10000 galaxies were visible.
If we extend that to the entire sky, it means there are over 100 billion galaxies,
in the observable Universe, each containing 100’s of billions of stars.
There is something remarkable about this invention than mere scale.
The image captures thousands of galaxies, all at different distances from Earth.
It makes the image 3D in a very real sense.
But the 3rd dimension is not spatial, it is temporal.
When we look at Hubble’s masterpiece we are looking back in time; deep time,
time beyond human comprehension.
The Hubble’s Ultra Deep Field transports us back through the history of Universe.
The photograph contains images of galaxies of various ages, sizes, shapes and colours.
Some are relatively close to us, some incredibly far away.
The nearest galaxies which appear larger, brighter,
and have well defined spiral and elliptical shapes, are only a billion light years away.
Some would have formed soon after the Big Bang, they are around 12 billion years old.
However, it is the small, red, irregular galaxies that are the main attraction.
There are about 100 of these galaxies in the image.
They are the most distant objects we have ever seen.
Some of these faint red blobs are well over 13 billion light years away.
This means that when their light reaches us,
it has been travelling for almost the entire 13.75 billion year history of the Universe.
The most distant galaxy in the Deep Field, is over 13 billion light years away.
It is hard to grasp these vast expanses of space and time.
The image of the ancient galaxy was created by a handful of photons of light.
When they began their journey, released from hot, primordial stars, there was no Earth,
no Sun, and only an embryonic and chaotic mass of young stars and dust,
which would eventually evolve into the Milky Way.
When these little particles of light had completed almost 2/3rd of their journey,
to Hubble’s cameras, a swirling cloud of interstellar dust collapsed to form our solar system.
They were almost here when the first complex life on Earth arose.
They were within a cosmic heartbeat of their final destination,
when the species that built the Hubble first appeared.
The story hidden within the Hubble Ultra Deep Field image is ancient and detailed.
How can we infer so much from a photograph?.
The answer lies in our interpretation of the colours of these distant, irregular galaxies.
Scientists have attempted to understand rainbows since the time of Aristotle.
They tried to explain how white light is apparently transformed into colour.
The scientist Ibnal-Haytham was the first one to attempt to explain,
the physical basis of a rainbow in the 10th century.
He described them as the light from the Sun as it is reflected by a cloud,
before reaching the eye.
The basis of our modern understanding was given by Newton.
Newton observed that white light is split into its component colours,
when passed through a glass prism.
He correctly surmised that white light is made up of light of all colours, mixed together.
The physics behind the rainbow is essentially the same as that of the prism.
Light from the Sun is a mixture of all colours.
Water droplets acts like tiny prisms, splitting up the sunlight again.
But why the characteristics arc of the rainbow?
The first scientific explanation was given by Descartes, in 1637.
Water droplets in the air are essentially little spheres of water.
Descartes considered what happens to a single water droplet.
The light ray from the Sun enters the face of the droplet and is bent slightly.
This is known as refraction.
Light gets deflected when it crosses a boundary between two different substances.
Then the light ray gets to the back surface of the raindrop.
It is reflected back into the raindrop.
It finally emerges out of the front again, where it gets bent a little more.
The light ray then travels from the raindrop to our eye.
The key point is that there is a maximum angle through which light enters the raindrop,
and gets bounced back.
Descartes calculated this angle to be 42 degrees for red light.
For blue light the angle is 40 degrees.
Colours between blue and red in the spectrum have maximum angles of reflection,
between 42 and 40 degrees.
No light gets bounced back with angles greater than this.
It turns out that most of the light gets reflected back at this special, maximum angle.
This is the explanation for the rainbow.
When you look up at the rainbow, imagine drawing a line between the Sun,
which must be behind you, through your head and on to the ground in front of you.
At an angle of 42 degrees to this line, you will see the rainbow.
At an angle of 42 degrees you see ray of red light.
At an angle of 40 degrees you will see a ray of blue light.
All the colours of the rainbow will be in between.
There is some light reflected to your eye through shallower angles.
This is why the sky is brighter below the arc then above it.
You don’t see the colours below the arc because all the rays merge to form white light.
Raindrops separate the white light into a rainbow because each of the constituent colours,
gets reflected back to your eye at a slightly different maximum angle.
But why the arc ?
In fact rainbows are circular.
Think of the imaginary line between the Sun, your head and the ground.
There isn’t just one place between this line and the sky which is 42 degrees.
There is a whole circle of points surrounding this light.
The reason you cannot see a complete circle is that the horizon cuts it off.
So you see only the arc.
This is also why you tend to see rainbows in the early mornings or late afternoon.
As the Sun climbs in the sky, the line between the Sun and your head steepens,
and the rainbow which is centred on this line drops closer and closer to the horizon.
At some point it will vanish below the horizon.
The colours hidden in white light are not only revealed in rainbows;
wherever Sunlight strikes an object,
the different colours, are bounced around or absorbed in different ways.
The sky is blue because the blue components of sunlight,
are more likely to be scattered off air molecules then the other colours.
As the Sun drops towards the horizon,
and the sunlight has to passthrough more of the atmosphere,
the chance of scattering yellow and red light increases.
This turns the evening skies redder.
Leaves and grass are green because they absorb blue and red light from the Sun,
which is used in photosynthesis, but reflect back the green light.
What is the difference between the colours that makes them behave so differently?
The answer lies in understanding of light as an electromagnetic wave.
Blue light has the shorter wave length than red light.
Our eye has evolved to discern about 10 million different colours.
This means our eye can differentiate between 10 million subtle variations,
in the wavelength of electromagnetic waves.
This simple concept is all we need to read the story of the Hubble Ultra Deep Field image.
How do we know that the irregular, messy galaxies in the Hubble image,
are billions of light years away?
The image shows some of the most distant galaxies we have observed.
The most obvious thing about them is that they are all red.
During the 1920s, Edwin Hubble was using what was then the world’s most powerful telescope,
at the Mount Wilson observatory, California to observe stars called Cepheid variables.
Cepheid variables are stars whose brightness varies regularly over a period of days or months.
They are astonishingly useful to astronomers,
because of the period of their brightening and dimming,
is directly related to their intrinsic brightness.
In other words it is a simple matter,
to work out exactly how bright a Cepheid variable star actually is,
just by watching it brighten and dim for a few months.
If we know how bright something really is, then measure how bright it looks to you,
you can workout how far away it is.
Edwin Hubble’s research project was simply to search for Cepheid variables,
and measure their distance from Earth.
During this observation he discovered two remarkable things.
Firstly, he determined the Cepheid variables in the so called spiral nebulae,
were in fact well outside our galaxy.
At that time the spiral nebulae were thought to be clouds of glowing gas within the Milky Way.
For the first time, Hubble showed that there are other galaxies in the Universe,
millions of light years away.
Hubble’s second observation was of even greater scientific importance.
While he and others were measuring the spectrum of the light from the stars,
in the spiral nebulae, which thanks to Hubble were now understood to be other galaxies,
beyond the milky way, they observed that many of the galaxies appeared to be emitting light,
that was redder than it should be.
Hubble quantified the amount of reddening in each galaxy as a number called redshift.
Red light has a longer wavelength, than blue light.
Seeing light redshifted simply means the wave length is longer than expected.
Hubble made his second great discovery by plotting a graph of the redshift of the light,
from distant galaxies against their distance.
He calculated the distance from his observation of the Cepheid variables.
To his great surprise, Hubble noticed that his graph was approximately a straight line.
This is because the further away a galaxy is, the greater is the redshift.
That is the further away the galaxy is, the more its light is stretched.
There is a very simple relationship between the distance and the redshift.
The interpretation of Hubble for the reason for this is quite remarkable.
The more distant the galaxy, the further the light has travelled across the Universe to reach us.
Also, the further it has travelled, the more it has been stretched.
This relationship between distance travelled and amount of stretching occurs,
when something very simple but surprising is happening in the Universe.
The Universe is expanding !
In other words, over the hundreds of millions of years,
during which the light has been travelling ,
space itself has been stretching at a relatively constant rate.
This has stretched the wave length of the light,
in direct proportion to the distance it had to travel.
This is why the most distant galaxies have the largest redshift.
Their light has travelled through our expanding Universe for longer,
and therefore become more stretched.
Hubble’s discovery of this ‘cosmological redshift’ was one of the greatest intellectual moments,
in 20th century science.
Hubble discovered we live in a expanding Universe.
There is a vast amount of information contained within Hubble’s simple graph.
Redshift can be expressed as the amount of stretching you would see,
if something were flying away from you at a particular speed.
The ratio of the redshift expressed in this way to the distance of the galaxy -
which is the gradient of the line on Hubble’s graph - is called the Hubble’s constant.
Its value as measured today is 68 kilometres per second, per megaparsec.
A megaparsec is a measure of distance commonly used by astronomers.
One megaparsec is 3.3 million light years.
So another way to think of Hubble’s law is that a galaxy 3.3 million light years away,
will be receding from us at a velocity of about 70 kilometres per second.
That is pretty slow.
A galaxy that is 6.6 million light years away will be receding,
at about 140 kilometres per second, and so on.
And further, if you simply invert Hubble’s constant,
then you get a number with the units of time.
For a Hubble’s constant of 70 kilometres per second, per megaparsec,
this corresponds to 14.3 billion years.
This can be interpreted as the age of the Universe.
We notice that our current best measurement of the Universe,
is slightly lower at 13.75 billion years.
This is because precise measurements over the last few decades have shown us,
that the expansion of the Universe is not in strict accord with Hubbles simple law.
The best data we have today tells us that the Universe is accelerating in its expansion,
due to the presence of something called dark energy.
The conclusion is simple and profound.
The reddening of the distant galaxies tells us that the Universe is expanding.
This means that the galaxies we see in the sky today,
must have been closer together in the past.
If we keep winding back time, and watch the galaxies getting closer and closer together,
at the time given by the inverse of the Hubble constant,
we will find they must have all been on top of each other.
In other words the Universe we see today must have been incredibly tidy.
This all happened 14 billion years ago, and that event is what we call the Big Bang.
So, Hubble’s remarkable observation is direct evidence,
that the Universe began with a Big Bang, around 14 billion years ago.
The Big Bang is difficult to visualise.
It is easy to think of it as a vast explosion that flung matter out into a pre-existing void.
But this is wrong.
The currently accepted view is that all of space came into existence at the Big Bang.
In fact, the sprit of Einstein, we should more correctly say,
that all of space time came into existence at the Big Bang.
This means that the Big Bang didn’t just happen out there in the Universe.
It happened at every point in the solar system and inside the most distant galaxies.
In other words, it happened at every point in the Universe.
All of space was there at the Big Bang, and all it has done is stretch ever since.
This has the rather mind bending consequence that if the Universe is infinite today,
it was born infinite.
Every where that is here now was there then, but just squashed a lot!
When we look at the distant galaxies and we see them all flying away from us,
this is not because they were flung out in some massive explosion at the beginning of time.
It is because space itself is stretching since the Big Bang.
The Hubble expansion is one piece of evidence for the Big Bang.
There is another perhaps more remarkable finger print,
of the Universe’s violent beginning delivered to us by the most ancient light in the Cosmos.
Every second, light from the beginning of time is raining down,
on Earth’s surface is a ceaseless torrent.
Only a fraction of the light present in the Universe is visible to the naked eye.
If we could see all of it, the sky would be ablaze with this primordial light both day and night.
However some of this hidden light is not quite a featureless glow.
The long wave length Universal glow known as the Cosmic Microwave Background or CMB,
in fact displays minute variations in its wave length.
The CMB carries with it an image of our Universe as it was just after its birth.
This discovery has provided key evidence that the beginning really did start with the Big Bang.
Visible light is a tiny fraction of the light in the Universe.
Beyond the red, the electromagnetic spectrum extends to wavelengths,
too long for our eyes to detect.
We did not evolve to see it.
Scientist calls some of it infrared light.
The only difference between infrared and visible light is the wavelength.
Infrared has a longer wavelength than visible light.
If we move further along the spectra, past infrared, we arrive at microwaves.
These have wavelengths about the size of a microwave oven.
The spectrum then seamlessly slides into the region, with wavelengths the size of mountains.
Through out most of human history we have been blind to these more unfamiliar forms of light.
To detect them all we need is just a radio.
When tuning into a radio, we are not tuning into a sound wave.
We are picking up information encoded in a wave of light.
Most of the radio waves we are familiar with are artificially created,
and used for communication and broadcasting.
There is plenty of visible light in the Universe that isn’t man made.
There are naturally occurring microwaves and radio waves too.
Just like the visible photons from the most distant galaxies,
the microwave and radio photons are messengers.
They carry detailed information about distant places and times across the Universe,
and into our technologically created instruments.
When we tune a radio, we can listen to the static between the stations.
About 1% of this is music to the ears of a physicists,
because it is stretched light that has travelled from the beginning of time.
Deep in the static is the echo of the Big Bang.
These radio waves were once visible light.
But it is light that originated 400 thousands years after the Big Bang.
Prior to that, the observable Universe was far smaller and hotter than it is today.
At 273 million degrees Celsius, this is an order of magnitude hotter than the centre of a star.
It is so hot that the hydrogen and helium nuclei then present in the Universe,
could not hold on to their electrons to form atoms.
The Universe was a super heated ball of naked atomic nuclei and electrons known as plasma.
Light cannot travel far in dense plasma,
because it bounces off the electrically charged subatomic particles.
It was only when the Universe had expanded and cooled down enough for the electrons,
to combine with the hydrogen and helium nuclei to form atoms, that light was free to roam.
This point in the evolution of the Universe, known as recombination,
occurred around 400,000 years after the Big Bang.
By this time the Universe had cooled to 3000 degrees Celsius.
The Universe was then one thousandth of its present size.
3000 degree Celsius is close to the surface temperature of red giant stars.
So the whole Universe would have been glowing with visible light like a vast star.
The Universe has become cooler and more diffuse since then.
So this ancient light has been free to fly through space.
It is some of these wandering messengers we collect with a detuned radio today.
However as the Universe has expanded, space has stretched and so too has the light.
It is stretched so much that the light is no longer in the visible part of the spectrum.
It has moved beyond even the infrared, and is now visible to us only in the microwave,
and radio parts of the spectrum.
This faint, long, wavelength universal glow,
is known as the Cosmic Microwave Background or CMB.
Its discovery in 1964, by Aron Penzias and Robert Wilson,
was key evidence in proving that the Universe began in a Big Bang.
In 2001, the Wilkinson Microwave Anisotropy Probe, known as WMAP was launched,
from the Kennedy Space Centre in Florida.
This highly specialised telescope was built with a single purpose:
to capture the faint glow of the CMB,
and create the earliest possible photograph of the Universe.
After 9 years of service, WMAP was retired.
But its photograph is still the object of frenzied research.
This is because it contains so much rich detail about the early Universe,
and its expansion and evolution ever since.
This much studied image is probably the most important picture of the sky ever taken.
It contains a vast amount of information about the history of our Universe.
The raw image from WMAP shows the glow of our Milky Way galaxy,
as it creates a hot bright band across the sky.
Once this detail, have other observational side effects removed,
we are left with a simplified, but equally important picture.
This photograph of the night sky documents in extraordinary detail,
the structure of the Universe at the time of recombination.
Over the nine years in which WMAP was in service , the detail has been repeatedly refined.
This in turn reveals more and more detailed information encoded in the primordial light.
The WMAP data presence a temperature map of the sky.
The wavelength of the detected light at any particular point corresponds to a temperature.
Shorter wavelengths are higher temperatures.
Longer wavelengths are lower temperatures.
The red areas are hotter than the blue, but only by .0002 degrees.
The average temperature of the CMB is 2.725 degrees above absolute zero.
That is 2.2725 K, or minus 270.425 Celsius.
Despite being incredibly tiny, these temperature differences are overwhelming importance,
because they tell us that in the very first moments of our Universe’s life,
there were regions of space that were slightly denser than others.
These virtually imperceptible differences might not seen much,
but without them we would not exist.
That’s because these little blips in the CMB are the seeds of the galaxies.
The red spots in the CMB corresponds to parts of the Universe,
that were on average half an percentage denser than the surrounding areas,
at the time of recombination.
As the whole Universe expanded, these areas would have expanded,
slightly more slowly than their surroundings because of their higher density.
Effectively, their increased gravity due to their higher density would have slowed the expansion.
This would have caused their density to increase further relatively to the space around them.
By the time the Universe was 1/5th its present size, just over a billion years after the Big Bang,
these regions would have been twice as dense as their surrounding.
By this time the matter in these regions was dense enough and cool enough,
to begin to collapse under its own gravity.
This led to the first star formation at the emergence of the cores of the galaxies,
including our Milky Way.
This is the cosmic epoch we see in the most redshifted Hubble telescope data.
It reflects the formation of the first galaxies.
The seeds for the firsts galaxies are the minute fluctuations,
in the Cosmic Microwave Background Radiation.
The rest as they say, is history.
Across the Cosmos countless stars began to switch on and fill the Universe with light.
For billions of years, generations of stars lived and died.
Nine billion years after it all began, in an unremarkable piece of space,
known as the Orion Spur, of the Perseus Arm of a galaxy called the Milky Way,
a star was born that became to be known as the Sun.
This is the story of how our solar system
as its ultimate origin in those dense areas of space,
that appeared in the first moments of our Universe’s life.
But what is the origin of those tiny fluctuations in density that we see in the CMB?
This is perhaps the most remarkable piece of physics of all.
The most popular current model for the very very early Universe is known as inflation.
The idea is that, that around 10 to the power of minus 36 seconds after the Big Bang,
the Universe went through an astonishingly rapid phase of expansion.
During this phase the Universe increased its volume by a factor of 10 to the power of 78!
It was all over by 10 to the power of minus 32 seconds.
Before inflation, the part of the Universe we now observe,
all the hundreds of billions of our galaxies, would have been far,
far smaller than a single subatomic particle.
At these minute distance scales, quantum mechanics reigns supreme.
Tiny quantum fluctuations before inflation would have been magnified,
by the rapid expansion to form the denser regions,
in the Cosmic Microwave Background spectrum.
If inflation theory is correct, the CMB is therefore a window,
into a time in the life of the Universe far earlier than 400,000 years after the Big Bang.
We are seeing the imprints of events in the first 10 to the power of minus 30 seconds,
after it all began.
This is the most astonishing idea in all of science.
From a vantage point of 13.7 billion years,
we are able to understand the evolution of the Universe, and speculate intelligently,
about the very beginning of time itself.
We do this by decoding the messages carried to us across the Cosmos on beams of light.
There is one last twist to this story.
Through out our journey, light has been the messenger.
It carried stories of far flung places and the distant past to us.
But there is evidence from one of the ancient sites on our home planet,
that light may have played a far more active role in our history than mere muse.
Hidden in the high rocky mountains in Canada,
is one of the most important and evocative scientific sites on Earth.
It is where the story of light and our lives begins.
505 million years ago, when this whole area,
lay deep behind beneath the surface of a primordial ocean, it was hit by a huge mudflow.
The mud created a snap shot of a remarkable time in the evolution of life on Earth.
A whole ancient ecosystem was frozen and preserved intact in the mud.
For hundreds of millions of years, this ancient treasure trove was locked away.
In 1909, it was uncovered, and now known as the Burgess Shale.
The Burger Shale is one of the most important fossil site in the world.
It is not just the number and diversity of the animals found there, it is their immense age.
Before 540 million years ago, there is no fossil fuels of complex life forms,
found anywhere in Earth.
We know that there was life before this period.
But the animals were very simple creatures that didn’t possess skeletons of any kind.
This means they don’t show up in the fossil record.
The period of time immortalised in the Burgess Shale, is known as the Cambrian Era.
It appears that a vast range of complex multi cellular life emerged on the planet at this time.
Biologists call it the evolutionary Big Bang, or the Cambrian explosion.
What triggered the evolution of complex life?
There is a clue in the Burgess Shale.
One form of life found there is the trilobites, now long extinct.
They had external skeletons, jointed limbs, and most strikingly had complex, compound eyes.
These pre historic predators see shapes, detect movements,
and use their eyes very effectively to chase their prey.
The ability to see made these trilobites very successful animals.
In fact they survived for 250 million years.
They vanished 250 million years ago in the Permian mass extinction .
One current theory for the origin of the Cambrian explosion,
is the emergence of the eye in animals.
Once a predator possess’s eyes which will help chase its prey,
a new force in natural selection is immediately introduced.
Once one predatory species develops eyes, there is a powerful selection mechanism,
in favour of others developing and refining eyes.
In turn this selects for more sophisticated predators and so on.
This in a sense sets off an evolutionary arms race.
The pressure of natural selection leads more and more complex life to develop.
These early creatures immortalise in the Burgess Shale, were among the first to harness light.
Before them, the rising and setting of the Sun and stars went unnoticed.
These creatures are our ancestors.
In fact there is evidence at Burgess Shale,
that we humans exist because of one particular adaption in a strange,
warm like creature called the Pikaia.
This may be one of the most important animals ever discovered.
Some evolutionary biologists think that the Pikaia is the earliest known ancestor,
of modern vertebrates.
This is a branch of life that we humans are categorised in.
It could be that the Pikaia is our earliest known ancestor.
What is also fascinating about Pikaia is that it may have had light sensitive cells,
that allowed to evade predators and survive in the Cambrian seas.
These cells may have evolved over hundreds of millions of years into our eyes.
Understanding the Universe is like reading a detective story.
The essential evidence we need to understand it has been carried to us,
across the vast expenses of space and time by light.
We have been able to capture the light from the beginning of time.
We have glimpsed within it the seeds of our own origins.
We have seen stars being born in distant realms,
and galaxies lost in time at the very edge of the visible Universe,
and our cosmos just moments after it all began.