Why are atoms so small? ... Many examples have been devised to bring this fact home to an audience, none of them more impressive than the one used by Lord Kelvin: Suppose that you could mark the molecules in a glass of water, then pour the contents of the glass into the ocean and stir the latter thoroughly so as to distribute the marked molecules uniformly throughout the seven seas; if you then took a glass of water anywhere out of the ocean, you would find in it about a hundred of your marked molecules.

But many of our imaginations and investigations of nature are futile, especially when we see little living animals and see their legs and must judge the same to be ten thousand times thinner than a hair of my beard, and when I see animals living that are more than a hundred times smaller and am unable to observe any legs at all, I still conclude from their structure and the movements of their bodies that they do have legs... and therefore legs in proportion to their bodies, just as is the case with the larger animals upon which I can see legs... Taking this number to be about a hundred times smaller, we therefore find a million legs, all these together being as thick as a hair from my beard, and these legs, besides having the instruments for movement, must be provided with vessels to carry food.

Take water. It's simple, common, and vital. There are more molecules of water in an eight-ounce cup of the stuff than there are cups of water in all the world's oceans. Every cup that passes through a single person and eventually rejoins the world's water supply holds enough molecules to mix fifteen hundred of them into every other cup of water in the world. No way around it: some of the water you just drank passed through the kidneys of Socrates, Genghis Khan, and Joan of Arc.

How about air? Also vital. A single breathful draws in more air molecules than there are breathfuls of air in Earth's entire atmosphere. That means some of the air you just breathed passed through the lungs of Napoleon, Beethoven, Lincoln, and Billy the Kid.

When I pause and reflect on our expanding universe, with its galaxies hurtling away from one another, embedded within the ever-stretching, four-dimensional fabric of space and time, sometimes I forget that uncounted people walk this Earth without food or shelter, and that children are disproportionately represented among them.

When I pore over the data that establish the mysterious presence of dark matter and dark energy throughout the universe, sometimes I forget that every day—every twenty-four-hour rotation of Earth—people kill and get killed in the name of someone else's conception of God, and that some people who do not kill in the name of God kill in the name of their nation's needs or wants.

When I track the orbits of asteroids, comets, and planets, each one a pirouetting dancer in a cosmic ballet choreographed by the forces of gravity, sometimes I forget that too many people act in wanton disregard for the delicate interplay of Earth's atmosphere, oceans, and land, with consequences that our children and our children's children will witness and pay for with their health and well-being.

And sometimes I forget that powerful people rarely do all they can to help those who cannot help themselves.

I occasionally forget those things because, however big the world is— in our hearts, our minds, and our outsize atlases—the universe is even bigger. A depressing thought to some, but a liberating thought to me.

In fact, a physics colleague, Mark Srednicki of U.C. Santa Barbara, brought to my attention a much greater gaffe in one episode, in which sound waves are used as a weapon against an orbiting ship. As if that weren't bad enough, the sound waves are said to reach “18 to the 12th power decibels.” What makes this particularly grate on the ear of a physicist is that the decibel scale is a logarithmic scale, like the Richter scale. This means that the number of decibels already represents a power of 10, and they are normalized so that 20 decibels is 10 times louder than 10 decibels, and 30 decibels is 10 times louder again. Thus, 18 to the 12th power decibels would be 10 (18)^12 , or 1 followed by 11,568,313,814,300 zeroes times louder than a jet plane!

2. 
   1.How faint are the farthest objects?

The Hubble observations detected objects as faint as 30th magnitude. The faintest objects the human eye can see are at sixth magnitude. Ground-based telescopes also can detect 30th-magnitude objects. Those objects, however, are so dim they are lost in the glare of brighter, nearby galaxies.

Searching for the faintest objects in the Ultra Deep Field is like trying to find a firefly on the Moon. Light from the farthest objects reached the Hubble telescope in trickles rather than gushers. The orbiting observatory collected one photon of light per minute from the dimmest objects. Normally, the telescope collects millions of photons per minute from nearby galaxies.

It took 400 orbits to make the observations.

The Hubble telescope's Advanced Camera for Surveys' wide-field camera snapped 800 exposures, which equals two exposures per orbit. The exposures were taken over four months, from Sept. 24, 2003 to Jan. 16, 2004.

The 800 exposures amounted to about 1 million seconds or 11.3 days of viewing time. The average exposure time was 21 minutes.

The image yields a rich harvest of about 10,000 galaxies.

The colors used were blue, green, red, and near-infrared. The observations were taken in visible to near-infrared light.

The whole sky contains 12.7 million times more area than the Ultra Deep Field. To observe the entire sky would take almost 1 million years of uninterrupted observing.

The Hubble Ultra Deep Field is called a "pencil beam" survey because the observations encompass a narrow, yet "deep" piece of sky. Astronomers compare the Ultra Deep Field view to looking through an eight-foot-long soda straw.

The Ultra Deep Field's patch of sky is so tiny it would fit inside the largest impact basin that makes up the face on the Moon. Astronomers would need about 50 Ultra Deep Fields to cover the entire Moon.

Hubble's keen vision (0.085 arc seconds.) is equivalent to standing at the U.S. Capitol and seeing the date on a quarter a mile away at the Washington monument.

Here we go again, one of the epic documents of our time, the Hubble Ultra Deep Field (UDF) photograph, the deepest look into space ever. A random part of the sky, so small it could be covered by a pinhead held at arm's length. A part of the sky -- as NASA says -- that you'd see looking through an eight-foot-long soda straw. A photo exposed over 400 orbits of the Hubble, a total exposure of 11.3 days. The telescope pointing precisely to the same point in space even as it whizzes around the Earth.

Here's another way to think of it. The image on your computer screen is about 10x10 centimeters. Imagine the image as a tile of that size. A survey of the whole sky -- the whole visible universe from Earth -- would encompass 12.7 million tiles, enough to cover 18 footfall fields!

And each tile shows something like 10,000 galaxies.

A typical galaxy contains as many stars as there are grains of salt in 10,000 one-pound boxes of salt. We are potentially seeing the light of more than 1,000,000,000,000,000 stars. Most, or all, of which have planets.

We've been over this before, but it's worth coming back to. It's not easy to get one's head around. Surely, discovering the scale of the universe is the greatest intellectual achievement in human history, and one of the least appreciated. We live in a universe of at least 10 billion galaxies -- maybe an infinite number -- and we go on worshiping the gods of our cave-dwelling ancestors. Gods with human faces, human qualities, human actions.

Perfectly natural to do so. The familiar is always more consoling than the unfamiliar. As for myself, I stare into those vast and almost unimaginable depths of space and I'm humbled into silence. Stunned. Ecstatic. Curious. Proud of what we have discovered. Knowing that future generations will consider our knowledge fragmentary and naive.