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.