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Cosmic Journeys: Cosmic Energy Powers of 10
Poziom:
Temat: Nauka i technologia
All across the immense reaches of time and
space, energy is being exchanged, transferred,
released, in a great cosmic pinball game we
call our universe.
To see how energy stitches the cosmos together,
and how we fit within it, we now journey through
the cosmic power scales of the universe, from
atoms nearly frozen to stillness.
To Earths largest explosions. From stars colliding,
exploding, to distant centers of power so
strange, and violent, they challenge our imaginations.
Today, energy is very much on our minds, as
we search for ways to power our civilization
and serve the needs of our citizens.
But what is energy? Where does it come from?
And where do we stand within the great power
streams that shape time and space?
Energy comes from a Greek word for activity
or working. In physics, it is simply the property
or the state of anything in our universe that
allows it to do work. Whether it is thermal,
kinetic, electro-magnetic, chemical, or gravitational.
The 19th century German scientist Hermann
von Helmholtz found that all forms of energy
are equivalent, that one form can be transformed
into any other. The laws of physics say that
in a closed system - such as our universe
- energy is conserved. It may be converted,
concentrated, or dissipated, but it is never
lost.
James Prescott Joule built an apparatus that
demonstrated this principle. It had a weight
that descended into water and caused a paddle
to rotate. He showed that the gravitational
energy lost by the weight is equivalent to
heat gained by the water from friction with
the paddle.
That led to one of several basic energy yardsticks,
called a joule. Its the amount needed to lift
an apple weighing 100 grams one meter against
the pull of Earth's gravity.
In case you were wondering, it takes about
one hundred joules to send a tweet, so tweeted
a tech from Twitter.
The metabolism of an average sized person,
going about their day, generates about 100
joules a second, or 100 watts, the equivalent
of a 100-watt light bulb. In vigorous exercise,
the power output of the body goes up by a
factor of ten, one order of magnitude, to
around a thousand joules per second, or a
thousand watts.
In a series of leaps, by additional factors
of ten, we can explore the full energy spectrum
of the universe. So far, the coldest place
observed in nature is the Boomerang Nebula.
Here, a dying star ejected its outer layers
into space at 600,000 kilometers per hour.
As the expanding clouds of gas became more
diffuse, they cooled so dramatically that
their molecules fell to just one degree above
Absolute Zero, one degree above the total
absence of heat. That is around a billion
trillionths of a joule, give or take.
That makes the signal sent by the Galileo
spacecraft, as it flew around Jupiter, seem
positively hot. By the time it reached Earth,
its radio signal was down to 10 billion billionths
of a watt. Now jump all the way to 150 billionths
of a watt.
That is the amount of power entering the human
eye from a pair of 50-watt car headlamps a
kilometer away. Moving up a full seven powers
of ten, moonlight striking a human face adds
up to three hundred thousandths of a watt.
That is roughly equivalent to a crickets chirp.
From there, it's a mere five powers of ten
to the low wattage world of everyday human
technologies.
Put ten 100-watt bulbs together. At 1000 joules
per second, 1000 watts, that roughly equals
the energy of sunlight striking a square meter
of Earth's surface at noon on a clear day.
Gather 200 bulbs. 20,000 watts is the energy
output of an automobile. A diesel locomotive:
5 million watts. An advanced jet fighter:
75 million watts. An aircraft carrier: almost
two hundred million watts.
The most powerful human technologies today
function in the range of a billion to 10 billion
watts, including large hydro-electric or nuclear
power plants. At the upper end of human technologies,
was the awesome first stage of a Saturn V
rocket. In five separate engines, it consumed
15 tons of fuel per second to generate 190
billion watts of power.
How much power can humanity marshal? And how
much do we need?
Long before the launch of the space age, visionaries
began to imagine what it would take to advance
into the community of galactic civilizations.
In the 1960s, the Soviet scientist, Nicolai
Kardashev, speculated that a Level 1 civilization
would acquire the technology needed to harness
all the power available on a planet like Earth.
According to one calculation, we are .16%
of the way there. This is based on British
Petroleum's estimate of total world oil consumption,
some 11 billion tons in 2007. Humans today
generate about two and a half trillion watts
of electrical power.
How does that stack up to the power generated
by planet Earth? Deep inside our planet, the
radioactive decay of elements such as uranium
and thorium generates 44 trillion watts of
power. As this heat rises to the surface,
it drives the movement of Earths crustal plates,
and powers volcanoes.
Remarkably, that is just a fraction of the
energy released by a large hurricane in the
form of rain. At the storms peak, it can rise
to 600 trillion watts. A hurricane draws upon
solar heat collected in tropical oceans in
the summer.
You have to jump another power of ten to reach
the estimated total heat flowing through Earths
atmosphere and oceans from the equator to
the poles, and another two to get the power
received by the Earth from the sun, at 174
quadrillion watts.
Believe it or not, there's one human technology
that has exceeded this level. The AN602 hydrogen
bomb was detonated by the Soviet Union on
October 30, 1961. It unleashed some 1400 times
the combined power of the Nagasaki and Hiroshima
bombs.
With a blast yield of up to 57 million tons
of TNT, it generated 5.3 trillion trillion
watts, if only for a tiny fraction of a second.
That's 5.3 Yottawatts, a term that will come
in handy as we now begin to ascend the power
scales of the universe.
To Nikolai Kardashev, a Level 2 civilization
would achieve a constant energy output 80
times higher than the Russian superbomb. That
is equivalent to the total luminosity of our
sun, a medium-sized star that emits 375 yottawatts.
However, in the grand scheme of things, our
sun is but a cold spark in a hot universe.
Look up into Southern skies and you'll see
the Large Magellanic Cloud, a satellite galaxy
of our Milky Way. Deep within is the brightest
star yet discovered. R136a1 is 10 million
times brighter than the sun.
Now if that star happened to go supernova,
at its peak, it would blast out photons with
a luminosity of around 500 billion yottawatts.
To advance to a level three civilization,
you have to marshal the power of an entire
galaxy.
The Milky Way, with about two hundred billion
stars, has an estimated total luminosity of
3 trillion yottawatts, a three followed by
36 zeros. The author Isaac Asimov imagined
a galaxy-scale civilization in his Foundation
series. Galaxia, he called it, is a super-organism
that surpasses time and space to draw upon
all the matter and energy in a galaxy.
But who is to say that is the upper limit
for civilizations? To boldly go beyond Level
3, a civilization would need to marshal the
power of a quasar. A quasar is about a thousand
times brighter than our galaxy.
Here is where cosmic power production enters
a whole new realm, based on the physics of
extreme gravity.
It was Isaac Newton who first defined gravity
as the force that pulls the apple down, and
holds the earth in orbit around the sun. Albert
Einstein redefined it in his famous General
Theory of Relativity. Gravity isn not simply
the attraction of objects like stars and planets,
he said, but a distortion of space and time,
what he called space-time.
If space-time is like a fabric, he said, gravity
is the warping of this fabric by a massive
object like a star. A planet orbits a star
when it is caught in this warped space, like
a ball spinning around a roulette wheel. Some
scientists began to wonder if matter became
dense enough, could it warp space to such
an extreme that nothing could escape its gravity,
not even light?
With so much power being emitted from such
a small area, scientists suspected that quasars
were actually being powered by black holes.
How a totally dark object can do this has
been narrowed by decades of observations and
theory.
If a black hole spins, it can turn into a
violent, cosmic tornado. Gas and stars begin
to flow in along a rapidly rotating disk.
The spinning motion of this so-called "accretion
disk" generates magnetic fields that twist
up and around.
These fields can channel some of the inflowing
matter out into a pair of high-energy beams,
or jets. Gas and dust nearby catch the brunt
of this energy, growing hot and bright enough
to be seen billions of light years away.
Amazingly, the power of a black hole can rise
to even greater extremes at the moment of
its birth. As a giant star ages, heavy elements
like iron gradually build up in its core.
As its gravity grows more intense, the star
begins to shrink, until it reaches a critical
threshold. Its core literally collapses in
on itself.
That causes the star to explode, in a supernova.
And now, in death, the star can unleash gravitys
true fury.
In the violence of the star's death, gravity
can cause its massive core to collapse to
a point, forming a black hole.
In some rare cases, the new-born monster powers
a jet that accelerates to within a tiny fraction
of the speed of light. For a few minutes,
these so-called gamma ray bursts are known
to be the brightest events since the big bang,
three orders of magnitude above a quasar at
a billion billion yottawatts, a ten with 42
zeros.
Remarkably, they are still not the most powerful
events known. Albert Einstein's equations
contained an astonishing prediction, that
when massive bodies accelerate or whip around
each other, they can stir up the normally
smooth fabric of space-time.
They produce a series of waves that move outward
like ripples on a pond. Scientists are now
hoping to detect these gravitational waves,
and verify Einsteins prediction, using precision
lasers and some of the most perfect large-scale
vacuums ever created.
At the Laser Interferometry Gravitational
Wave Observatory, known as LIGO, they are
hoping to record the collision of ultra-dense
remnants of dead stars known as neutron stars
and of black holes.
According to computer simulations, as two
black holes spiral into a fateful embrace,
the energy carried by each gravity wave rises
five orders of magnitude above a gamma ray
burst to a hundred billion trillion times
the power of our sun.
Does the collision of black holes define the
known power limits of our universe? Perhaps
not.
As turbulent as the environment of a black
hole might be, its true power may well lie
deep in its core. A black holes mass is enshrouded
within a dark sphere called the event horizon.
Since the 1920s, scientists have described
the mathematics of the event horizon as the
equivalent of a waterfall. It's the point
of no return, beyond which water falls freely
into the gorge.
At the event horizon of a black hole, space
itself falls freely in at the speed of light.
If the black hole is spinning, then the flow
spirals down and around an inner horizon that
envelops the singularity. That's the central
region where space-time becomes infinitely
warped.
Any matter that rides this river of space
whips around the inner horizon so fast that
centrifugal force tends to fling it back out.
As that happens, it collides with matter that's
streaming in, whipping up a ferocious cosmic
storm.
The energy of the colliding streams feeds
upon itself, rising to what may well be a
limit imposed by nature. It dissipates only
as it falls into the singularity and disappears.
Fortunately, for us, gravity walls off such
energy extremes behind the event horizon where
they cannot affect the rest of the universe.
And so here we sit. Our world is nestled within
a vast stream of cosmic energy, somewhere
between the spin of an electron and the maelstrom
of a black hole.
There's no telling whether a future Earth
civilization will be able harness enough energy
to advance into the cosmos.
For now, as we tap into the tiny morsels of
power at our disposal, we venture a closer
look at a universe blazing with activity.
We are its product, and its star struck admirer.
