Monday, March 30, 2009
Gardener on the Moon
A greenhouse to grow mustard flowers will piggyback on a lunar lander being developed by Odyssey Moon, a competitor in the Google Lunar X Prize contest (Illustration: Paragon Space Development)
Thursday, March 12, 2009
Astronaut John Glenn, the first American to orbit Earth, is shown here in NASA's first spacesuit, designed for the Mercury programme (1958-1963).
The suits were adapted from US Navy pressure suits for high-altitude flights and not designed to be worn on spacewalks. That's because the suits folded in on themselves at the joints, decreasing the volume in the suit. That increased the pressure in the rest of the suit, making it hard for astronauts to bend their legs or arms. As a result, the suits were used only as protection against emergency losses of pressure. (Image: NASA Headquarters)
Spacesuit design took a step forward during NASA's Gemini programme, which featured the agency's first spacewalk on 3 June 1965. To insulate astronauts from the low pressures and temperature extremes of space, Gemini suits boasted extra layers and balloon-like "bladders" filled with gas to maintain pressure, while also maintaining flexibility.
Gus Grissom (left) and John Young, the crew of the first manned Gemini mission, a five-hour orbital flight on 23 March 1965, are shown here in the suits, which are attached to portable air conditioners to keep the astronauts cool. (Image: NASA Johnson Space Center)
The acid test for the Gemini spacesuit came on 3 June 1965, when astronaut Edward White ventured from the capsule for a 23-minute spacewalk - the first such foray for a US astronaut.
White used a gas-powered gun to manoeuvre in space. Oxygen was provided through an 8-metre 'umbilical' cord connected to the Gemini 4 spacecraft. (Image: NASA Johnson Space Center)
To allow lunar explorers greater flexibility, the Apollo suits were built with bellow-like rubber joints at the shoulders, hips, elbows and knees.
Here engineer Bill Peterson fits test pilot Bob Smyth in an early incarnation of the Apollo suit in 1964. The dark straps are part of a restraint harness for the Lunar Excursion Module. (Image: NASA Johnson Space Center)
By the time of the first Moon landing in 1969, the Apollo suits boasted a backpack that provided enough oxygen for breathing, ventilation and suit pressure for 7 hours of Moon walking. Astronaut Buzz Aldrin is pictured here exploring the lunar surface during the Apollo 11 mission. Although the suits performed well in the six missions to land on the Moon, lunar dust became a worry. Astronauts reported that sharp, abrasive lunar dust damaged the suits, wearing through layers and infiltrating seals.
The Apollo suit had to be relatively light so that astronauts could move around in the Moon's gravity and weighed about 82 kg (180 pounds), including its backpack. Later space shuttle suits, by comparison, were more than 1.5 times as heavy - but they were worn in the weightless environment of low-Earth orbit. (Image: NASA Kennedy Space Center)
NASA astronauts now use a two-piece spacesuit for spacewalks called the Extravehicular Mobility Unit (EMU). Unlike the Apollo suits, which were custom-made to fit each astronaut, the EMU has interchangeable parts that can be used to accommodate a range of body sizes.
The EMU is pressurised at about a third of atmospheric pressure, so astronauts must camp out in a relatively low-pressure airlock before spacewalks to remove nitrogen dissolved in the blood and tissues. Moving too quickly to lower pressures can cause that nitrogen gas to create bubbles and obstruct blood flow, which can sometimes be fatal. The suit can weigh about 180 kg (400 lb) and operate for about 8 hours in space. It has a lifetime of 30 years. (Image: NASA Johnson Space Center)
NASA's EMU suits are not the only gear used for spacewalks. Here, astronaut Mike Fincke wears a Russian Orlan suit while performing work outside the International Space Station during the six-month Expedition 9 mission in 2004. (He and cosmonaut Gennady Padalka were originally going to use US suits but discovered problems with the suits, including a failed cooling unit.)
Unlike NASA's EMU suits, which have separate pants and torso sections, Orlan suits are entered through a hatch at the back. That allows astronauts to get into and out of them quickly without assistance. The suit weighs nearly 110 kg (240 pounds), can spend 7 hours in space and is designed to last for 12 spacewalks. (Image: NASA)
China's Feitan suit had a public debut in September 2008, when one of the astronauts aboard the Shenzhou 7 performed the country's first spacewalk.
The spacesuit is reportedly modelled after Russia's Orlan suit. Here one of the Shenzhou 7 crew members emerges from the spacecraft after landing in north China. (Image: China National Space Administration)
Gloves are possibly the most important part of the spacesuit from an astronaut's perspective. In addition to cranking levers and handling power drills, astronauts use their hands - rather than their feet - as their primary mode of "walking" around their spacecraft during spacewalks. The gloves are pressurised, making it difficult for astronauts to move their fingers.
The Apollo spacesuits used two sets of gloves - an inner layer (left) consisting of cloth-covered pressure bladders, and an outer layer made of cloth, Mylar and a metallic mesh. The outer gloves were used on spacewalks to protect against micrometeorites, scratches and heat. (Image: NASA-JSC)
In May 2007, engineer Peter Homer of Southwest Harbor, Maine, won $200,000 when his design for a spacesuit glove beat NASA's in an agency-sponsored competition. His company, Flagsuit LLC, is building on that design and is working with the firm Orbital Outfitters on spacesuits for suborbital tourist trips.
Homer says that unlike current gloves, which are pleated in a way that causes the fingers to curve like a banana, his gloves bend at the same points where our fingers do. That makes it easier for astronauts to move their fingers - important since spacewalks are so labour-intensive that they often leave astronauts' hands bruised and their fingernails bent backwards. (Image: Flagsuit.com)
For decades, NASA has been working intermittently on a next-generation spacesuit that will offer more flexibility and could be used at higher pressures, to eliminate the need for camping out before spacewalks, or breathing in pure oxygen to avoid decompression sickness, or the bends. The Mark III suit (left), one prototype that began development in the late 1980s, boasts a rear-entry system and bearings at the joints to allow astronauts the ability to kneel and perform other tasks.
In the push to return to the Moon, NASA signed a contract in February 2009 with the firm Oceaneering International, Inc, to develop suits for the crew of the shuttle's replacement, the Orion capsule, which is set to fly as early as 2015. Long-time spacesuit developer Hamilton Sundstrand contested the award, but the two firms now plan to work together on the suits, which are intended to share components with a future suit to be designed for the Moon (right). (Image and illustration: NASA)
The suit is patterned with stiff lines that do not extend when an astronaut moves a part of their body. These "lines of non-extension" provide a stiff skeleton but do not restrict an astronaut's movement. The team expects it will take several more years of development before the suits can be used in space. Other researchers are developing high-tech spacesuit materials that could one day heal themselves, generate electricity and kill germs. (Image: Donna Coveney)
Given enough notice of a possible collision, the space station can fire thrusters to move out of the way - eight such 'avoidance manoeuvres' have been made in the past. But on Thursday, the threat of a collision was discovered too late to move the station, so the crew took shelter in a docked Soyuz spacecraft (Image: NASA)
Display model of Soyuz Module
In about three weeks, we will lose a brilliant luminary that has been so much a part of our evening sky since the end of last summer.
The planet Venus, which shone so high and bright in the western sky during February, is now moving steadily lower with each passing night; it has begun its plunge down toward the sunset, soon to make its most dramatic exit from the evening sky since 2001.
Currently Venus is setting just under three hours after the sun in a dark sky. You can't miss it. Simply go out just after sunset and look West.
By March 12, Venus will follow the sun by only about two hours and on March 21 by just an hour. And by March 25 it will lie only 9-degrees to the upper-right of the setting sun (your clenched fist measures roughly 10-degrees at arm's length) and follows it down by only about a half an hour.
Sweeping toward Earth
The reason for Venus' rapid fall toward the sun is that the planet will pass inferior conjunction on March 27. That means Venus, which orbits the sun well inside Earth's orbit, will be between us and the sun [Video].
The first public appearance of China's military space station concept. The space station design was unveiled on a live broadcast to celebrate the Chinese New Year. Credit: CCTV
China is aggressively accelerating the pace of its manned space program by developing a 17,000 lb. man-tended military space laboratory planned for launch by late 2010. The mission will coincide with a halt in U.S. manned flight with phase-out of the shuttle.
The project is being led by the General Armaments Department of the People's Liberation Army, and gives the Chinese two separate station development programs.
Shenzhou 8, the first mission to the outpost in early 2011 will be flown unmanned to test robotic docking systems. Subsequent missions will be manned to utilize the new pressurized module capabilities of the Tiangong outpost.
Importantly, China is openly acknowledging that the new Tiangong outpost will involve military space operations and technology development.
Also the fact it has been given a No. 1 numerical designation indicates that China may build more than one such military space laboratory in the coming years.
"The People's Liberation Army's General Armament Department aims to finish systems for the Tiangong-1 mission this year," says an official Chinese government statement on the new project. Work on a ground prototype is nearly finished.
A closeup of the replacement urine and body-fluid distillation assembly for the International Space Station's (ISS). The new water recycling system is being checked out in the Space Station Processing Facility at NASA's Kennedy Space Center in Florida. The unit will be flown to the station aboard space shuttle Discovery on the STS-119 mission.
I am sure the crew will be relieved to see it. The previous urine recycling unit (URU) experienced a series of malfunctions after installation. The thought of which just leaves a bad taste in the mouth but it does demonstrate how close the partnership and bond is, between the crew inside the ISS. Cheers team!
Wednesday, March 11, 2009
Power comes from the user, who has to pull the printer head back and forth as the paper is pulled through. Cleverly, the printer also does away with expensive ink cartridges, instead making use of waste coffee.
The printed product definitely smells of coffee, which some evidence suggests could help reverse the effects of sleep deprivation. And there's no word on how permanent a coffee-printed document is.
Sunday, March 8, 2009
Oliver Knickel, a mechanical engineer in the German army (second from right), and airline pilot Cyrille Fournier from France (right) were selected as the two European participants in a 105-day isolation study. They joined three Russians on a three-day survival exercise in the woods near Star City, the Russian centre for cosmonaut training near Moscow.
To better understand how astronauts on a journey to Mars might cope with the confinement on the 520-day trip to Mars, the Institute for Biomedical Problems in Moscow, Russia, and the European Space Agency have set up such an experiment.
From 31 March, French airline pilot Cyrille Fournier, German engineer Oliver Knickel and four Russians - cosmonauts Oleg Artemyez and Sergei Ryazansky, Alexei Baranov, a doctor, and Alexei Shpakov, a sports physiologist - will be stuck in a simulated Mars spacecraft. Their communications with the outside world will be delayed by 20 minutes to simulate the radio lag between Mars and Earth.
Conflict arises easily in such crowded environments, says Pascal Lee, a planetary scientist who once did a 402-day stint in a French research station in Antarctica. The results will help design an experiment of full Mars-mission duration.
All the other moons - and there could have been 20 or more - were devoured by the planet in the early days of the solar system.
The four Galilean moons have played a key role in the history of science - their discovery by Galileo 400 years ago provided irrefutable evidence that not all bodies orbited the Earth. But until recently, nobody had suspected that Jupiter had once had many more moons.
Astronomers have long been aware of a mystery thrown up by simulations of the way Jupiter and its moons formed. These models indicate that the mass of the debris disc around Jupiter, from which the moons formed, was several tens of a per cent of the mass of giant planet. And yet only 2 per cent is enough to make the moons we see today.
Now we believe we know why. The extra mass can be explained if other moons formed while the debris disc was still present (www.arxiv.org/abs/0812.4995). A key process is therefore the interaction between the growing moons and the disc material still flowing in from the solar system. This interaction would have caused the early moons to spiral in towards Jupiter and eventually be "eaten".
This would explain the discrepancy in the earlier simulations: as one set of moons was swallowed, a new set immediately began to form. There could have been five generations of moons. The current Galilean moons formed just as the inflow of material into the disc from the solar system choked off, so they escaped the fate of their unfortunate predecessors.
In each generation the total mass of the moons was the same, but the number of moons could have varied. Something similar happened around Saturn, where the last generation contained one giant moon - Titan.
This could have implications for the solar system as a whole. Rocky planets may take as long as 10 million years to aggregate, chunk by chunk. The process continues long after the debris disc around the sun has blown away, so these planets would not have been at risk of spiraling inwards.
In contrast, the gaseous cores of gas giants like Saturn and Jupiter condense out of the solar debris disc very quickly via gas shrinkage. This means they would have had time to interact with the debris disc. It is entirely conceivable that the sun may have swallowed numerous gas cores before the current stable configuration of the solar system emerged.
Friday, March 6, 2009
Time. There is nothing with which we are so familiar, and yet when you try to pin it down you find only a relentless torrent of questions. Why does time appear to flow? What makes it different from space? What exactly is it? It's enough to make your neurons misfire, then sizzle and smoke.
You are not alone. Physicists have long struggled to understand what time really is. In fact, they are not even sure it exists at all. In their quest for deeper theories of the universe, some researchers increasingly suspect that time is not a fundamental feature of nature, but rather an artefact of our perception. One group has recently found a way to do quantum physics without invoking time, which could help pave a path to a time-free "theory of everything". If correct, the approach suggests that time really is an illusion, and that we may need to rethink how the universe at large works.
For decades, physicists have been searching for a quantum theory of gravity to reconcile Einstein's general relativity, which describes gravity at the largest scales, with quantum mechanics, which describes the behaviour of particles at the tiniest scales. One reason it has been so difficult to merge the two is that they are built on incompatible views of time. "I am more and more convinced that the problem of time is key both to quantum gravity and to issues in cosmology," says Lee Smolin of the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada.
According to general relativity, time is stitched together with space to form four-dimensional space-time. The passage of time is not absolute - no cosmic clock ticks away the hours of the universe. Instead, time differs from one frame of reference to the next, and what one observer experiences as time, another might experience as a mixture of time and space. For Einstein, time is a useful measure of things, but nothing special.
Not so in quantum mechanics. Here time plays a key role, keeping track of the ever-changing probabilities that define the microworld, which are encoded in the "wave function" of a quantum system. The clock by which the wave function evolves records not just the time in one particular frame of reference, but the absolute time that Einstein worked so hard to topple. So while relativity treats space and time as a whole, quantum mechanics splits the universe into two parts: the quantum system being observed and the classical world outside. In this fractured universe, a clock always remains outside the quantum system (see Diagram).
Something has to give. The fact that the universe has no outside, by definition, suggests that quantum mechanics will be the one to surrender - and to many, this suggests that time is not fundamental. In the 1990s, for instance, physicist Julian Barbour proposed that time must not exist in a quantum theory of the universe. All the same, physicists are loath to throw out quantum theory, as it has proven capable of extraordinarily accurate predictions. What they need is a way to do quantum mechanics in the absence of time.
Single quantum event
Carlo Rovelli, a physicist at the University of Marseille in France, has found just that. In the past year, he and his colleagues have worked out a method to compress multiple quantum events in time into a single event that can be described without reference to time (Physical Review D, vol 75, p 084033).
It is an intriguing achievement. While Rovelli's approach to dealing with time is one of many, and researchers working on other models of quantum gravity may have different opinions on the matter, nearly every physicist agrees that time is a key obstacle to finding an ultimate theory. Rovelli's approach seems tantalisingly close to surmounting that obstacle. His model builds upon research into generalising quantum mechanics by physicist James Hartle at the University of California, Santa Barbara, as well as Rovelli's earlier work on quantum systems.
The idea is this: suppose we have an electron characterised by its spin, a quantum property that is either "up" or "down" along whatever direction you measure it. Say we want to make two consecutive measurements of its spin, one in the x direction and one in the y direction. The probabilities of the possible outcomes will depend on the order in which we perform the measurements. That's because a measurement "collapses" the indeterminate state of the wave function, forcing it to commit to a given state; the first measurement will change the particle's state, which affects the second measurement.
Say we already know the electron's spin is up in the x direction. If we now measure the spin in the x direction followed by the y direction, we will find the x spin up - no change there - and then there is a 50:50 chance of finding the y spin up or down. But if we begin by measuring the y spin, that disturbs the spin in the x direction, creating a 50-50 probability for both measurements.
If reordering the measurements in time changes the probabilities, how can we calculate the probabilities of sequences of events without reference to time? The trick, says Rovelli, is to adjust the boundary between the quantum system under observation and the classical outside world where measuring devices are considered to reside. By shifting the boundary, we can include the measuring device as part of the quantum system.
In that case we no longer ask, "What is the probability of the electron having spin up and then spin down?" Instead we ask, "What is the probability of finding the measuring devices in a particular state?" The measuring device no longer collapses the wave function; rather, the electron and the measuring device together are described by a single wave function, and a single measurement of the entire set-up causes the collapse.
Where has time gone? Evolution in time is transformed into correlations between things that can be observed in space. "To give an analogy," Rovelli says, "I can tell you that I drove from Boston to Los Angeles but I passed first through Chicago and later through Denver. Here I am specifying things in time. But I could also tell you that I drove from Boston to LA along the road marked in this map. So I can replace the information about which measurement happens first in time with the detailed information about how the observables are correlated."
That Rovelli's approach yields the correct probabilities in quantum mechanics seems to justify his intuition that the dynamics of the universe can be described as a network of correlations, rather than as an evolution in time. "Rovelli's work makes the timeless view more believable and more in line with standard physics," says Dean Rickles, a philosopher of physics at the University of Sydney in Australia.
With quantum mechanics rewritten in time-free form, combining it with general relativity seems less daunting, and a universe in which time is fundamental seems less likely. But if time doesn't exist, why do we experience it so relentlessly? Is it all an illusion?
Yes, says Rovelli, but there is a physical explanation for it. For more than a decade, he has been working with mathematician Alain Connes at the College de France in Paris to understand how a time-free reality could give rise to the appearance of time. Their idea, called the thermal time hypothesis, suggests that time emerges as a statistical effect, in the same way that temperature emerges from averaging the behaviour of large groups of molecules (Classical and Quantum Gravity, vol 11, p 2899).
Imagine gas in a box. In principle we could keep track of the position and momentum of each molecule at every instant and have total knowledge of the microscopic state of our surroundings. In this scenario, no such thing as temperature exists; instead we have an ever-changing arrangement of molecules. Keeping track of all that information is not feasible in practice, but we can average the microscopic behaviour to derive a macroscopic description. We condense all the information about the momenta of the molecules into a single measure, an average that we call temperature.
According to Connes and Rovelli, the same applies to the universe at large. There are many more constituents to keep track of: not only do we have particles of matter to deal with, we also have space itself and therefore gravity. When we average over this vast microscopic arrangement, the macroscopic feature that emerges is not temperature, but time. "It is not reality that has a time flow, it is our very approximate knowledge of reality that has a time flow," says Rovelli. "Time is the effect of our ignorance."
It is not reality that has a time flow, but our very approximate knowledge of reality. Time is the effect of our ignorance
It all sounds good on paper, but is there any evidence that the idea might be correct? Rovelli and Connes have tested their hypothesis with simple models. They started by looking at the cosmic microwave background (CMB) radiation that pervades the sky - relic heat from the big bang. The CMB is an example of a statistical state: averaging over the finer details, we can say that the radiation is practically uniform and has a temperature of just under 3 kelvin. Rovelli and Connes used this as a model for the statistical state of the universe, tossing in other information such as the radius of the observable universe, and looked to see what apparent time flow that would generate.
What they got was a sequence of states describing a small universe expanding in exactly the manner described by standard cosmological equations - matching what physicists refer to as cosmic time. "I was amazed," says Rovelli. "Connes was as well. He had independently thought about the same idea, and was very surprised to see it worked in a simple calculation."
To truly apply the thermal time hypothesis to the universe, however, physicists need a theory of quantum gravity. All the same, the fact that a simple model like that of the CMB produced realistic results is promising. "One of the traditional difficulties of quantum gravity was how to make sense of a theory in which the time variable had disappeared," Rovelli says. "Here we begin to see that a theory without a time variable can not only still make sense, but can in fact describe a world like the one we see around us."
What's more, the thermal time hypothesis gives another interesting result. If time is an artefact of our statistical description of the world, then a different description should lead to a different flow of time. There is a clear case in which this happens: in the presence of an event horizon.
When an observer accelerates, he creates an event horizon, a boundary that partitions off a region of the universe from which light can never reach him so long as he continues to accelerate. This observer will describe a different statistical state of the universe from an observer who doesn't have a horizon, since he is missing information that lies beyond his event horizon. The flow of time he perceives should therefore be different.
Using general relativity, however, there is another way to describe his experience of time. The geometry of the space-time he inhabits, as defined by his horizon, determines a so-called proper time - the time flow he would register if he were carrying a clock. The thermal time hypothesis predicts that the ratio of the observer's proper time to his statistical time - the time flow that emerges from Connes and Rovelli's ideas - is the temperature he measures around him.
It so happens that every event horizon has an associated temperature. The best known case is that of a black hole event horizon, whose temperature is that of the "Hawking radiation" it emits. Likewise, an accelerating observer measures a temperature associated with something known as Unruh radiation. The temperature Rovelli and Connes derived matches the Unruh temperature and the Hawking temperature for a black hole, further boosting their hypothesis.
"The thermal time hypothesis is a very beautiful idea," says Pierre Martinetti, a physicist at the University of Rome in Italy. "But I believe its implementation is still limited. For the moment one has just checked that this hypothesis was not contradictory when a notion of time was already available. But it has not been used in quantum gravity."
Others also urge caution in interpreting what it all means for the nature of time. "It is wrong to say that time is an illusion," says Rickles. "It is just reducible or non-fundamental, in the same way that consciousness emerges from brain activity but is not illusory."
So if time really does prove to be non-fundamental, what are we to make of it? "For us, time exists and flows," says Rovelli. "The point is that this nice flow becomes something much more complicated at the small scale."
At reality's deepest level, then, it remains unknown whether time will hold strong or melt away like a Salvador Dali clock. Perhaps, as Rovelli and others suggest, time is all a matter of perspective, not a feature of reality but a result of your missing information about reality. So if your brain hurts when you try to understand time, relax. If you really knew, time might simply disappear.