"We've been through this over and over again," he started, "This is part of my job. You can't expect me to spend eight years designing the ship and then not participate in the mission. Think what this will mean for Sandstone!"

"I don't care," she said, "No one who has set out to find the Boundary has ever survived, and plenty have tried. A lot of scientists don't even believe in the theories on which all your research is based." The artificial light in the room reflected off the shell of a tiny arthropod that floated by, probably missed on its first pass through the filtration system.

"Nothing is going to happen to me. This ship is far more sophisticated than the ones that were used on prior missions. Fully reinforced double hull enhanced with a force field to improve structural integrity. Advanced sensors, extended-range sonar, and almost infinitely adjustable viewing systems. Any sign of trouble and we would turn around immediately. You know I've dreamed of this for years."

"I know," she said, realizing that she was losing this battle, as she always knew, deep down inside, that she would, "But I'm frightened. What if you don't come back? What about our children? It will only be a few weeks now."

Raz's heart rate accelerated at the mention of his children. This was the first time he would become a father, and he was overcome with emotion at the thought of his home filled with little ones, darting about.

"I promise, I'll be fine," he said, "We'll even be able to keep in touch by radio if necessary, at least for the first part of the trip." He knew in the end that she would give in, because she realized just how important this mission, and its implications for the future, was to him.

Raz had a great deal of trouble sleeping the night before the launch. He had turned the temperature down in his chamber in an effort to slow his metabolism and induce sleep, but it was useless - he was too excited. So many years of preparation and it all came down to just one crucial day. He left his chamber and went quietly into the nursery, where it was much warmer due to the carefully controlled environmental temperature. He looked at the nest containing exactly thirty-eight perfect, spherical, translucent eggs (he had already counted them no less than fifty times). Already he could see tiny embryos actively moving inside most of them, but he refused to give in to the sudden twinge of fear he felt about the mission. There was an entire world depending on him, and the newly built Edge of the Universe.

Raz and his crew were already in the ship when the rest of Sandstone's thirty million inhabitants awoke. They were to get underway as soon as possible, initially following the same course as the last failed voyage. Very early expeditions had discovered that the city, which rested on a solid sandstone foundation and had been initially established by long-forgotten, ancient ancestors countless thousands of years before, was actually built in a huge crater surrounded by rock. You could travel across land for one hundred kilometers in some directions, two hundred in others, but eventually, whatever direction was chosen, a towering stone wall was encountered.

Many had tried to scale those heights, but none had ever reached the top. Later, ships like the Edge of the Universe, but far less refined, had tried to ascend to heights never before achieved, but all were destroyed before reaching the top of the stone wall. The Edge of the Universe would be the first to climb beyond the top of the rock face, hopefully to the Boundary after which the magnificent ship was named. The entire concept of an alternate universe, a world beyond their atmosphere, was only a theory, but there was extensive circumstantial evidence of its existence, and Raz wanted to be the one to prove the skeptics wrong.

After all systems were checked and found to be in normal working condition, Raz gave the order and the ship was launched. It was a fairly large ship, heavy with visual processing equipment, sensors, and recording devices, but it's size was deceiving due to the two huge tanks which would allow for the necessary buoyancy. Highly purified dihydrogen oxide stored in the tanks was converted, as needed, to hydrogen and oxygen gas. As the percentage of hydrogen and oxygen in the tanks grew, the ship's buoyancy would increase, and it would rise. Maneuvering thrusters were used for lateral movement. Raz had designed this unique system himself, and was subsequently granted command of the Edge of the Universe as a reward for his success.

As the tanks began to fill, the ship rapidly rose over the sprawling city, already flooded with artificial light for the start of the workday. Within ninety minutes, the city had shrunk on the viewscreen to a small circle of light.

"Status report!" Raz asked Spike, his second in command, and helmsman.

"Everything looks great," Spike replied, "We're two kilometers above the city, rising at a rate of about one kilometer every hour, as planned. The atmosphere is cloudy with debris, but visibility is adequate. All systems are functioning normally. The nuclear batteries are fully charged and we have full power to the shields."

Raz knew that the biggest danger they faced, by far, was a loss of hull integrity, and the subsequent explosion that would occur due to the differences in internal and external pressures. But he had helped design the shielding system himself, and he knew it should theoretically hold to at least seven kilometers. Still, he wasn't taking any chances.

"Very well," Raz said, "I want the shields checked every fifteen minutes, and we'll vent the tanks of gas the instant there's any problem. Got that?"

"Yes, sir," Spike replied.

"Sir," Angel said later, as he monitored the input from the ship's sensor system, "We're five hundred meters past the point where contact was lost with the last expedition. Look at this!" He directed the sensor input to the large viewscreen located near the front of the ship.

As the screen came to life, Raz was mesmerized by the view. There were hundreds of different species of small fish, so many that at times their sheer number blocked his view. None of the species were familiar - all were different from those that could be found surrounding the city's controlled environment.

"Altitude?" he asked.

"Four point five kilometers," Spike replied.

"Amazing. Make sure all of this is recorded, and collect a sample of the atmosphere here. Use a pressurized sample container, I don't want anything destroyed by pressure changes before our team's scientists can have a look at this. Too bad we don't have time to obtain some specimens of the life here," he lamented.

Gradually the giant tanks filled with gas, and at five point five kilometers, about ten minutes after radio contact was lost with their counterparts in Sandstone, came the discovery for which they were waiting.

"Sir!" Angel shouted, "It's gone!"

"What's gone?" Raz asked.

"The stone wall, Sir. Enhanced sonar now shows only open atmosphere for at least a thousand kilometers in each direction!"

"Shield status?"

"Still holding," Spike replied.

"Well," Raz said, "I'd love to explore laterally, but I guess we'll have to leave that to a future expedition. We've proven that there is a limit to the height of the rock face that surrounds the city. Let's complete our mission as planned. Continue increasing altitude."

An hour later Raz noticed that Spike's gills were flapping rapidly, and his tail was swishing back and forth in concern. "Is there a problem?" He asked.

"Not that I can tell," Spike replied, "The shields seem to be holding. But we're at six point three kilometers, the tanks are almost completely full of gas, and we haven't reached the Boundary yet. Once we hit seven kilometers the shields will have reached their design limitations. Maybe the Boundary doesn't exist. Maybe our atmosphere does extend forever."

"This is no time for pessimism. We go on until we reach seven kilometers or a problem develops. That's our mission. If we don't reach the edge of the universe, than we return home, redesign the ship, and take a second expedition, and a third if necessary, until we do."

"Yes, sir," Spike replied.

At six point five kilometers, warning bells sounded from the sensor panel.

"What is it?" Raz demanded.

"My God," Angel replied, "Look!"

He transferred the image to the viewscreen, but at first the crew was blinded by the sudden, intense white light. Angel enhanced the image using polarizing filters, and they all gaped at the sight before them.

The first thing they noticed was the light. Bright, blinding, unbelievable light, coming from above. Sandstone's entire artificial lighting system in the middle of a workday couldn't produce a fraction of the light they were seeing.

Then, as the image was processed further and continued to improve, they all saw it. Shimmering, not half a kilometer above them, was what appeared to be a boundary layer - the end of their universe and the start of, well, who knew what?

Its crew enthralled by the sight before them, the Edge of the Universe continued to slowly rise, and then stopped.

"What happened?" Raz asked.

"That's it," Spike replied, "We're at seven kilometers. Outside pressure is so low that it's barely measurable. The tanks are now filled to capacity with gas. We are unable to go further."

"But that's ridiculous!" He shouted, "The Boundary is only a couple hundred meters farther. I helped design the shielding system, and believe me, seven kilometers was a conservative estimate. Surely just two or three hundred meters more would be tolerable!"

"I want to see what's beyond the Boundary too," Spike replied, "But you can't argue with the laws of physics. The tanks are completely filled, the ship simply won't go any higher."

Raz was deeply frustrated. To come so far and have to turn back was intolerable. Then he was struck with an idea.

"The tanks contain two-thirds hydrogen and one third oxygen, correct?"

"Yes," replied Spike, "What are you getting at?"

"The tanks are designed to withstand even higher pressures than the ship itself. Is there any way to selectively bleed off the oxygen molecules and leave the hydrogen behind?"

"I'm not sure. It might take a couple hours, but I think so. Why?"

"Hydrogen atoms are of much smaller mass than oxygen atoms. If the tanks were filled only with hydrogen gas, especially if its density was decreased by removing the oxygen, it might give us just enough lift to reach the Boundary."

"Of course!" Spike said, "I'll get started right away."

Two hours later they were ready try the alterations Spike had made. Slowly, the oxygen was filtered out of the ship's tanks, and after about thirty minutes the Edge of the Universe slowly rose. Higher and higher it went, approaching the Boundary between universes.

"It's working!" Spike cried, "We're almost there!"

Raz's heart was pounding in his chest. "Brace for impact!" he warned.

The ship reached the boundary layer, broke though, and floated on the surface.

"Viewscreen!"

""I'll do the best I can," Angel replied, "But there's so much light that it's interfering with our viewing system. It's going to be very bright even with the polarizing filters on maximum." Then they all looked on in silence as the scene appeared before them. Everything was awash in bright, harsh, unbearable light. There was a huge, glowing ball of incredibly intense yellow light, hanging motionless in the distance, above the boundary layer between the universes. Above them, all that could be seen was a huge expanse of blue, accented by what appeared to be bright white puffs of steam. The Boundary was volatile, and its undulations rocked the ship.

"My God, where are we?" Raz asked.

"Sir!" Angel shouted, "There's a huge object right behind us!"

"Turn the ship to face it!"

As the Edge of the Universe turned to face the unknown object, the crew was shocked to see what looked like a giant vessel of some type, floating on the Boundary. It was long and flat, and appeared to have many tiny, cross-shaped metallic vessels on its surface. As Angel adjusted the camera and focused on the upper edge of the great vessel, they could see creatures - strange, finless beings, obviously alive in spite of the lack of atmosphere to breathe, moving back and forth. They seemed to be covered with some type of strange, colored fabric, and they moved using two appendages attached to the lower half of their bodies.

The shrieking alarm bell broke Raz's concentration.

"The shields are weakening, sir!" Spike shouted over the din of the alarms, "Pressure outside reads zero! The ship can't take anymore! Explosion is imminent!"

"Emergency descent!" Raz ordered, "Reverse engines!"

The Edge of the Universe reentered its own realm and began to descend quickly as the hydrogen was vented from the tanks and replaced with atmosphere, which was then pressurized to match the pressure of Sandstone's atmosphere. Spike called off the readings, "Six point five kilometers, six point three kilometers, six kilometers. Okay, the shield's have stabilized, but I think we should continue to descend as quickly as possible."

"Okay," Raz replied, regaining some of his composure, "What do you two make of what we saw up there?"

Spike spoke first. "So much light, and no atmosphere at all. But there's no doubt that we left our own universe, and that alien beings somehow survive in the universe next to ours."

"I agree," Angel said, "But even though they appeared so different from us, maybe we can try to contact them, to communicate with them. Certainly they were intelligent beings, having built a ship of their own. And imagine how much more we'll know once our scientists have gone through all the data we collected!"

The ship continued to descend, and before long they could see the lights of the city in the distance. Raz wondered if, someday, his children would travel between universes as easily as he traveled back and forth to his laboratory. One thing, however, was certain, Raz thought - we no longer have the luxury of believing we are alone.

About the author, Jeffrey A. Katt:
Jeffrey A. Katt lives with his wife in Southeastern Wisconsin. In his limited free time he enjoys a glass of fine vintage port, listening to classical or jazz music, cultivating native Wisconsin wildflowers, and writing articles, fiction, and poetry. He began writing in 1999, and has been (or soon will be) published in Black Petals, Redsine, The Door to Worlds Imagined, Anotherealm, Mindmares, The Inditer, Blood Coven, In Buddha's Temple, Millennium Science Fiction & Fantasy, Topsite, At The Brink of Madness, Zombie Horrors!, Pablo Lennis, Bloody Muse, The Roswell Literary Review, Quicker, and Pillow Screams, among others. He hopes to begin a novel near the turn of the century.