Scuba Diving Gear

Spare Air

Is it ok to burn my bra on a Spare The Air day?

NO, do you know what bras are made of, you could make yourself sick from the fumes.

Career 300 Spare Magazine Spring $3.59 Spare spring for Career 300 magazines.

Airforce Edge Spare Tank & Buttstock Assembly, Fits Airforce Edge Air Rifles $164.34 Airforce Edge tank & buttstock assembly Fits Airforce Edge air rifles The Edge Spare Tank with Buttstock assembly provides complete back up for the big match or an extended shooting session.

Spare Shells for UHC UG134, UG135, UA933 & UA934 Revolvers $8.34 Spare Shells for UHC Gas & Spring Revolvers, 8pc to a set. Not compatible with UHC Spring Revolver Models UA937, UA938 & UA941. Use for UG134 & UG135 Gas and UA933 & UA934 Spring Revolvers.

Surround Air S5000PH Replacement Filter $32 Keep your S5000 purifying at optimal performance with Surround Air's S5000PH S Series spare photocatalytic filter.

Surround Air S5000UV Replacement Bulb $19 Keep your S5000 air purifier running smoothly and fighting germs with Air Surrounds S5000UV S Series spare UV lamp.

Surround Air S5000SF Replacement HEPA Filter $52 Ensure that your S5000 air purification system is always running at its peak output with the Surround Air S5000SF S Series spare HEPA and pre-filter.

TSD SD700 Series Rifle Spare Magazine $8.34 Replacement magazine for TSD SD700. Holds 30 rounds.

Replacement Air Reservoir, Fits Feinwerkbau P70 & P700 Air Rifles $387.46 Feinwerkbau replacement air reservoir Built-in manometer (air pressure gauge) 2900 psi max air pressure (200 bar) Fits Feinwerkbau P70 & P700 PCP air rifles Instead of carrying a bulky fill tank or a hand pump, take along a spare air reservoir. Fill it up before your match and avoid lugging extra baggage. Same high-quality construction as the original tank that came with your FWB P70 or P700 air rifle.

AirForce Quick-Detach Air Tank, Fits TalonP Air Pistols $159.6 Quick-detach air tank Fits TalonP air pistols Can be used with compressed air or dry nitrogen gas only 6.125" long Need some extra air? Don't carry refill equipment! Get a spare tank, fill it up at home & take it with you. Simply swap the filled tank for the empty one, and you're good to go.

Weihrauch Magazine for HW100 target air rifle - .177 caliber $33.59 Spare 14 shot magazine for Weihrauch/Beeman HW100 .177 cal

Weihrauch Magazine for HW100 target air rifle - .22 caliber $33.59 Spare 14 shot magazine for Weihrauch/Beeman HW100 .22 cal

Surround Air S5000CF Replacement Carbon Filter $26 Get the most out of you S5000 and remember to replace the carbon filter with Surround Air's S5000CF S Series Spare Carbon Filter every six to twelve months.

AllerAir A3FH0410 Replacement HEPA Filter $79.98 The A3FH0410 is the spare HEPA filter for the AllerAir Air Tube Home Air Purifier.

Cybergun Spare 28rd Mag for Taurus PT99 CO2 Pistol $35.99 28rd Mag Fits the Taurus PT99 CO2 Pistol (item # CG21525)

Cybergun Schmeisser MP44 AEG 430 rd Magazine $23.94 Spare mag for the Schmeisser MP44 AEG!

Walther PPQ Air Pistol BB Magazine, 8 Rds, 3ct $11.94 PPQ air pistol BB magazine 3 clips 8 rds each Carrying spare air gun magazines lets you spend more time shooting and less time reloading. This 8-rd clip by Walther comes in packs of 3 and fits the PPQ CO2 pistol. The PPQ owner's manual incorrectly states how the BBs should be loaded. The correct way to load the magazines is from the side that does not have the ratchets.

Crosman Assembled Piston with Spring Guide $19.19 Spare part for Legacy 1000 full power version.

DPMS Spare 300 Rd Airsoft Metal Magazine for Mod4 and Mod16 AEG Guns $27.54 300-Round Mod4/Mod16 high metal capacity magazine. Fits on DPMS Panter Carbines 17927, 17928, 17929, 17930. Compatible with Echo 1, JG, ICS, DBoys, G&G, Classic Army and TM Model4/Mod16 AEGs.

Air Venturi G4 Hand Pump, Hose with 1/8" BSPP Threads $238.8 G4 hand pump Pumps to 3,335 psi/230 bar (use only the correct pressure rated for your gun) 23" hose ends in 1/8" BSPP threads Tube lock prevents separation during transport Moisture filter Ergonomically designed handle Compartment in handle holds spare parts 1/8" BSPP threads Wide footplate with adjustable pumping angle

HFC Metal Shells for G132 & 133 Gas Revolvers $15.54 Spare Shells for HFC HG-132 & HFC HG-133 Gas Revolvers, 6pc to a set.

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Spare Air Demo

An Ocean of Air

Nearly four hundred years ago, in a patchwork of individual fiefdoms that we now call Italy, a revolution of ideas was struggling to take place. The traditional way to understand the workings of the world -- through a combination of divine revelation and abstract reasoning -- had begun to come under attack from a new breed. These people called themselves “natural philosophers,” because the word “scientist” had not yet been invented. To find out the way the world worked, they didn’t sit around and talk about it. They went out and looked. This was not an approach that was likely to find favor with the Church, home of received wisdom, or with its instruments -- the whispering Inquisitors, with their hotline back to Rome. Now, a certain natural philosopher had fallen very foul of those Inquisitors and been forced to stop his investigations into the structure of the heavens. His name was Galileo Galilei, and our story begins with him.

Convent of Minerva, Rome

June 22, 1633

I, Galileo Galilei, son of the late Vincenzo Galilei, Florentine, aged seventy years, arraigned personally before this tribunal, and kneeling before you, most Eminent and Reverend Lord Cardinals, Inquisitors general against heretical depravity throughout the whole Christian Republic . . . have been pronounced by the Holy Office to be vehemently suspected of heresy, that is to say, of having held and believed that the sun is the center of the world and immovable, and that the earth is not the center and moves:

Therefore, desiring to remove from the minds of your Eminences, and of all faithful Christians, this strong suspicion, reasonably conceived against me, with sincere heart and unfeigned faith I abjure, curse, and detest the aforesaid errors and heresies . . . and I swear that in the future I will never again say or assert, verbally or in writing, anything that might furnish occasion for a similar suspicion regarding me.

As the great Galileo rose from his knees at the end of this infamous, and forced, recantation, he is said to have muttered “Eppur si muove!” (“And yet it moves!”). He knew in his heart that Earth moves around the sun, in spite of what the Inquisitors had made him say. Still, devoutly religious as he was, he had no taste for defying his own church. Nor had he any desire to share the fate of the unfortunate monk Giordano Bruno, who a few decades earlier had been publicly burned for holding similar views. Galileo may have been the most famous philosopher in all Italy, but he knew that in itself wouldn’t save him from the fire.

And though he was now seventy years old, frail, and steadily losing his sight, he was not yet ready to die. He had damaged his eyes by staring through a telescope at wonders he himself had discovered: blemishes that appeared periodically on the surface of the sun; craters on the moon; distant but distinct moons circling the planet Jupiter (who would have thought that other planets could have moons of their own?), and stars that nobody knew existed. Now, before the cataracts and glaucoma finally clouded his sight, in secret, if necessary, he had one last task to complete. Galileo had seen this “trial” coming; he’d known for some time that he couldn’t continue his study of the heavens. So for some years he had been discreetly changing tack, turning his attention inwards to Earth itself. And, failing eyesight notwithstanding, he was about to change the way we see the most apparently ordinary substance in the world: air.

The Inquisitors knew nothing of this. They were satisfied with his recantation, and decided, graciously, to spare his life. He would be allowed to return to his villa at Arcetri in Florence, though he should understand that he was still considered dangerous and would therefore be held under house arrest. There would be no visitors, save those given prior permission by the Church. Meanwhile, Galileo himself was to spend his time reciting the holy psalms as penance, and praying for his immortal soul.

Galileo returned to his villa as instructed and performed his penance diligently. But the Inquisitors had also obliged him to swear never again to publish work that might offend the Holy Office, and he had no intention of complying. For with him to Arcetri he had taken a certain manuscript that was already nearly finished.

He had started the experiments it described while awaiting his summons to Rome. Having turned away from his telescope, Galileo had become fascinated instead by the different ways that objects move through the air. The result was to become his masterpiece. The manuscript already recounted findings that would become just as famous as the moons of Jupiter. For instance, Galileo had made the surprising discovery that Earth’s gravity doesn’t care in the least how much something weighs. Drop a cannonball and a pebble from a high tower, and both will reach the ground at exactly the same moment.

But within its pages was another discovery that would prove to be less famous yet no less significant. Galileo had measured the weight of air.

This might seem like a bizarre notion. How can something so insubstantial as the air weigh anything at all? In fact our planet’s air is constantly pushing down on us with great force. We don’t notice this because we’re used to it, like lobsters sauntering along on the seafloor, unaware of the crushing weight of the ocean of water above them. We give our own overlying air-ocean so little respect that we even describe anything that’s full of air as being “empty.”

Back in Galileo’s time, notions about air were similarly hazy. Most people accepted the idea put forward by Aristotle in the fourth century b.c. that everything in the world was made up of four elements: earth, air, fire, and water. Earth and water were obviously pulled downward by gravity. Fire was obviously weightless. But air was the problem child. Was it heavy enough to be dragged to the ground, light enough to rise like flames do, or did it simply ignore Earth’s gravitational tug and hover?

Galileo believed that air is heavy and had set about testing his idea. The experiments he performed were typically ingenious. First, he took a large glass bottle with a narrow neck and a tight leather stopper. Into this stopper he inserted a syringe attached to a bellows and by working vigorously managed to squeeze two or three times more air into the bottle than it had previously contained. Next, he weighed the glass bottle most precisely, adding and subtracting the finest of sand to his scales until he was satisfied with the answer. Then, he opened a valve in the lid. Immediately, the compressed air rushed out of its confinement, and the bottle was suddenly a handful of grains lighter. The air that had escaped must account for the missing weight.

This showed that air is not the insubstantial body we usually take it for. But now Galileo wanted to know how much air corresponded to how many grains of sand. For that he would somehow need to measure both the weight of the escaping air and its volume.

This time, he took the same glass bottle with its long, narrow neck. However, instead of pumping it full of extra air, he forced in some water. When the bottle was three-quarters full of water, its original air was squeezed uncomfortably into a quarter of its original space. Galileo weighed the bottle accurately, opened the valve, allowed this pressurized air to escape, and then weighed the bottle again to find out how much air he had lost. As for the volume, Galileo reasoned that the portion of air that had been forced to leave the bottle had been pushed aside by the water he had squeezed in, so the volume of air that had fled must be exactly the same as the volume of water that remained. All he had to do was pour out the water and measure its volume and voilà, he had found the weight for a given volume of air.

The value Galileo came up with was surprisingly large: Air seemed to weigh as much as one four-hundredth the weight of an equivalent amount of water. If that doesn’t sound like much, consider this. Picture a particular volume of air for a moment -- such as the “empty” space inside Carnegie Hall in New York. How heavy would you expect that amount of air to be? Would it weigh ten pounds? Or a hundred? Or maybe even five hundred?

The answer is somewhere in the region of seventy thousand pounds.

The weight of air is so extreme that even Galileo didn’t see the whole story. He never considered the question of how we can shoulder such a crushing, overwhelming burden, for the simple reason that he didn’t realize the air above us is still heavy. He had measured the weight of air in his bottle, but he was convinced that the moment this air was released back into its natural element, the sky, it immediately ceased to weigh anything at all.

Galileo believed that our atmosphere as a whole is incapable of pushing. It was one of the few occasions when the great man was wrong.

In spite of the Church’s opposition Galileo finished his manuscript -- and published it. After fruitless efforts to convince publishers in Florence, Rome, and Venice to defy the Inquisitors, Galileo finally smuggled the manuscript out to a printer in the Netherlands. Four years later, as he approached the end of his life, a few copies began filtering back to Italy. Each bore a disingenuous disclaimer by Galileo himself, who wrote how astonished he was that his words had somehow found their way to a printer’s in spite of his obedience to the Papal diktat.

And although Galileo was wrong about the way our air behaves aloft, the experiments his great work contained would influence two very different people to discover the truth.

The above is an excerpt from the book An Ocean of Air

by Gabrielle Walker

Published by Harcourt, Inc.; August 2007;$25.00US; 978-0-15-101124-7

Copyright © 2007 Gabrielle Walker

Author

Gabrielle Walker is an award-winning science writer who has a Ph.D. in chemistry from Cambridge and has presented many programs for BBC radio. She has served as a climate-change editor at Nature, features editor at New Scientist, and visiting professor at Princeton University. She lives in London.

About the Author

For more information, please visit www.GabrielleWalker.com.