The Arrow Paradox
Zeno’s arrow paradox appears to show that motion is impossible.
It works by taking a snapshot of an arrow at a point (either in space or in time) in its flight. At that point, and at every other, the arrow is motionless. If there is no point, spatially or temporally, at which the arrow is moving, though, then the arrow is motionless. Contrary to appearances, an arrow in flight cannot move.
If we had a film of the arrow in flight, and broke it down to its individual frames, we would see that in each frame the arrow is simply hovering in the air. It is only when you put all the frames together that the arrow appears to move. In each frame, i.e. at each point, the arrow is motionless.
This is true irrespective of whether we think in terms of time or space.
Motion occurs through space, not at a single point in space. To move, something must get from one point to another, and so at each point considered individually, the arrow is still.
Similarly, motion takes time, it doesn’t occur instantaneously. At any specific point in time, therefore, the arrow cannot be moving.
If at every point and at every moment in its flight the arrow is still, though, then how is it possible for it to move from the bow to its target? If the arrow is made of wood at every point in its flight, then it must be wooden; it can’t be plastic. If it is sharp at every point in its flight, then it must be sharp, not blunt. Similarly, if the arrow is motionless at every point in its flight, then it must be still, not moving.
Contrary to appearances, then, arrows cannot move towards targets. In fact, similar reasoning applies to any other alleged case of motion, so it seems that movement in general is impossible.
Posted: Thursday, September 11, 2008 6:30 PM by Alan Boyle
Peter McCready / Special to msnbc.com
|Click for high-def slide show:
360-degree HD View photos let
you zoom through the Large
The world’s biggest atom-smasher is a smash hit on the Web: It’s only been one day since the Large Hadron Collider’s startup, but the device has already generated an explosion of cool stuff online, including black humor about black holes.
We’re offering a selection of photographer Peter McCready’s 360-degree, zoomable panoramas of the collider’s hot spots as part of our special report on the $10 billion project – but if the HD View plug-in doesn’t work out, you can still take a Flash-based tour of the LHC on McCready’s own Web site.
McCready, who is a system administrator for Queen’s University in Belfast in Northern Ireland, has been taking 360-degree panoramas for years at the European Space Agency and other high-tech locales. It’s all part of his personal campaign to add some extra gee-whiz to the genre.
“It seemed to be more used for the leisure-hotel industry, and I always thought there should be more to it than that,” he told me.
Under the aegis of the World Wide Panorama project, McCready went to Geneva in 2005 and was permitted to take his first set of all-around pictures of the ATLAS experiment. Since then, he has documented all the main experiments with the enthusiastic support of the LHC’s science teams. He just finished up his most recent visit, and the latest set of 10 panoramas should be available on his Web site in four to six weeks.
“It was a massive privilege to visit parts of the experiment that members of the public never get to see,” McCready said.
Here are some more big bangs on the Web (and on TV):
- British physics student Tim Head takes a different approach to chronicling the collider project. Here’s his time-lapse video that shows the assembly of the ATLAS detector from the ground up, accompanied by the music of Ravel’s “Bolero.” Five years of work are condensed into five minutes of must-see Web TV.
- In case you missed seeing Wednesday’s startup in real time (around 4 a.m. ET), here’s a video replay, as well as an extra link to the Large Hadron Rap video that made such a splash last week. You’ll also find ample views of the first hits recorded by the LHC’s Compact Muon Detector and the ATLAS detector.
- Are you still trying to understand what the Large Hadron Collider is all about? Check out the online tutorials from Particle Detectives and the Particle Adventure. Britain’s Science and Technology Facilities Council has a 15-part video series that covers the basics of particle physics as well as the role that the LHC will play. The BBC offers a guide to the machine that rivals our own.
- So what happens to all the terabytes of data that the LHC will generate? This Flash interactive from CERN’s Grid Cafe traces the process, step by step. A decade from now, the Grid may be as big a part of everyday life as the Web is today.
- The History Channel brought “The Next Big Bang” to cable television this week, and in case you missed it, the show will be rebroadcast next week. Another documentary about the subatomic race, “The Atom Smashers,” will air in November on PBS.
- Newsweek provides some expert commentary on the LHC from Nobel-winning physicist Leon Lederman, author of “The God Particle,” and from a flock of physicists including Stephen Hawking.
- Speaking of Hawking, reports that the world-famous British scientist bet $100 that the Higgs boson would not be found at the LHC has sparked some sharp words this week from Peter Higgs, the physicist after whom the long-predicted but never-detected particle was named. That’s not surprising: Hawking has been trash-talking the Higgs boson for more than a decade. But it did give The Register an excuse for working the phrase “Boffinry Bitchslap Brouhaha” into its headline. Priceless …
- And about those black holes: My colleague over at the Clicked blog, Will Femia, is already linking to tongue-in-cheek Web sites that keep you up to date on the LHC’s black-hole status. Bad Astronomy’s Phil Plait puts it another way. The LHC hasn’t gotten to the point of starting collisions, but despite what the doomsayers say, all the evidence shows that the world won’t be sucked into a collider black hole. We’ll have more about that in Friday’s concluding installment of the “Big Bang Machine” series.
Wednesday’s startup was “just the beginning of the story,” said Eric Prebys, the head of the USLHC accelerator research program at Fermilab in Illinois.
Since then, scientists have been shooting proton beams around the collider’s 17-mile-round (27-mile-round) ring hundreds of times, even though today is an official holiday in Geneva. From now on, testing will continue seven days a week, night and day, Prebys told me.
He said those tests will fine-tune the beams going in opposite directions and more than double their energies from the startup level of 450 billion electron volts to around 1 trillion electron volts – which is about the maximum energy achievable by Fermilab’s Tevatron, the world’s current record-holding atom-smasher.
Within a few weeks, the two beams will be brought into collision. That milestone may come in time for the next big celebration on CERN’s schedule: an Oct. 21 gala, attended by heads of state, that will mark the LHC’s formal inauguration.
For updates about the home team, keep tabs on the USLHC blogs and the Symmetry Breaking blog. And for a teen perspective on the LHC’s “First Beam” events as seen from Fermilab, check out the QuarkNet blog and this YouTube video.
Source: MSNBC Science & Technology
By Daily Mail Reporter
Last updated at 4:20 PM on 10th September 2008
They are the toughest animals on the planet – and now scientists have discovered that they can even survive in space.
The tiny creatures, known as tardigrades or water bears, are certainly strange-looking with their eight chubby legs, little claws and probing heads.
Some experts have compared their shape with jelly babies or moles but tardigrades they should not be judged by their ‘cute’ appearance. They are virtually indestructible – they will not die even if they are boiled, frozen, squeezed under pressure or desiccated.
Tardigrades or ‘water bears’ are the toughest creatures on the planet
In fact, they can be completely dried out for years – and then spring back to life as if nothing had happened.
Now researchers have revealed that tardigrades – which usually measure no more than a millimetre in length and live in moss – have withstood the airless extremes of space.
Amazingly, after ten days, some of them did. They became the first animals to survive exposure in space without protection.
The experiment, supported by the European Space Agency, was headed by Dr Ingemar Jonsson, of the University of Kristianstad, Sweden.
‘Our principal finding is that the space vacuum, which entails extreme dehydration, and cosmic radiation were not a problem for water bears,’ he said. But admitted that exactly how they survived ‘remains a mystery.’
The water bears were kept in a chamber on board the FOTON-M3 spacecraft as it orbited 270km above the Earth 270km.
A slide was opened to expose them to the vacuum and the cold. Some were also subjected to the Sun’s UV rays which are 1,000 times stronger in space than on Earth and, incredibly, survived for the return trip. They continued to breed successfully.
Dr Jonsson and his colleagues in Stockholm, Stuttgart, and Cologne published the results of the space study in the journal Current Biology.
He said, ‘The ultraviolet radiation in space is harmful to water bears, although a few individuals can survive even that.’
He believes that even if they suffered DNA damage, the little water bears could somehow repair it. The next challenge is to try to understand the creatures’ ‘exceptional tolerance’ to extreme conditions, he said. It could help scientists learn how to treat cancer.
‘All knowledge involving the repair of genetic damage is central to the field of medicine,’ Dr Jonsson said.
‘One problem with radiation therapy in treating cancer today is that healthy cells are also harmed. If we can document and show that there are special molecules involved in DNA repair in multicellular animals like tardigrades, we might be able to further the development of radiation therapy,’ he added.
German scientist Dr Ralph Schill, who also worked on the project, said, ‘I hoped they would make it but I could hardly have expected this result – you can’t simulate some of the space conditions in the lab’.
Water bears exist in nearly all ecosystems of the world. What makes them unique is that they can survive repeated dehydration and can lose nearly all the water they have in their bodies.
When dehydrated, they enter into a dormant state in which the body contracts and metabolism ceases. In this death-like dormant state, water bears manage to maintain the structures in their cells until water is available to ‘reactivate’ them.
In 1998, Japanese scientists subjected the creatures to pressures up to 6,000 greater than our atmosphere. They lived. In tests, they have also survived X-rays and being frozen to just above absolute zero – that’s minus 273.15C, the coldest temperature possible.
‘No animal has survived open space before,’ says developmental biologist Bob Goldstein of the University of North Carolina.
‘The finding that animals survived rehydration after days in open space – and then produced viable embryos as well – is really remarkable.’
The process makes water bead on any surface
Almost any surface or fabric can be made waterproof but remain breathable thanks to a former military technology.
The process was originally developed to ensure soldiers’ clothing remained impermeable to chemical weapons.
Shoe maker Hi-Tec has signed a deal with the developers of the process to use the technology to waterproof many of its shoes.
The first commercially available shoes treated with the process were shown off in London this week.
The technology was funded by the Ministry of Defence and developed at its Defence Science and Technology Laboratory for making military clothing resistant to nerve agents.
The process – dubbed ion-mask by its inventors – works using a chemical based on the element fluorine. In a closed chamber, the chemical is vaporised and attaches, molecule by molecule, to all the fibres in a fabric.
The chemical makes the surface “hydrophobic” or water-repelling, so that instead of water spreading out it forms droplets on the surface.
The chemical coating covers just the fibres, rather than forming a “skin” across the whole surface, as with currently available waterproofing treatments. That means the spaces between fibres remain open and the fabric is still breathable.
“The normal way in which you’d make a shoe waterproof is put a membrane inside the shoe; Gore-Tex is a well-known example,” says Ian Robins, business development director of P2i, the company marketing the process.
“That’s effectively putting a plastic bag inside the shoe. No water gets inside your shoe, but at the same time that reduces the breathability both in terms of sweat and of heat escaping.”
Treated materials stay cleaner too
Shoe fabric made with the ion-mask process was tested for breathability in an air-flow test, outperforming commercial waterproof fabrics such as Gore-Tex by more than a factor of 100, P2i claims.
The shoes were also subjected to flexing and wear tests, maintaining their breathable waterproof properties even after 100,000 flexes.
The fabrics are also inherently stain-resistant and easier to clean, says P2i
Dr Robins says coating a pair of shoes using the ion-mask process requires just a tenth of a gram of the fluorine compound, and costs in the region of a few dollars – significantly less than the cost of integrating membranes like Gore-Tex into a pair of shoes.
The process can easily be applied to any garments or any material, and Dr Robins suggests that it might also become the basis for a separate after-purchase service business, like dry cleaning.
It can also be used to waterproof outdoor gear. High Street outdoor equipment retailer Millets, owned by Black’s Leisure Group, will be stocking the men’s Hi-Tec ion-mask shoes in 75 stores.
“This could change waterproof footwear as we know it,” says Michelle Swan, a senior footwear buyer at Black’s.
She said the company would keep an eye on the “revolutionary” technology and perhaps use it in other areas of its business.
Good news for potheads making their annual trek to Black Rock, Nev. this week to celebrate Burning Man: A new study says that marijuana appears to fight infections. According to research published in the Journal of Natural Products, the five most common cannabinoid compounds in weed—tetrahydrocannabinol (THC), cannabidiol, cannabigerol, cannabinol and cannabichromene—can kill antibiotic-resistant bacteria. Think MRSA (methicillin-resistant Staphylococcus aureus), which claimed more lives than AIDS in 2007 or, more recently, extensively drug-resistant mycobacterium tuberculosis (XDR-TB.)
Researchers were unable to pinpoint exactly how the ingredients interact with bacterial targets. They called for rigorous clinical trials to determine the safety and effectiveness of cannabinoids as topical antiseptics and as antibacterial agents. Researchers stressed that certain strains of marijuana have high concentrations of nonpsychotropic cannabinoids (specifically CBD and CBG) and that these will be the focus of study for consumer use.* (Sorry to disappoint.)
Washington, August 26: Researchers at the Yerkes National Primate Research Center, Emory University, US, have shown by experiments that monkeys have the feeling of empathy, and they enjoy sharing things with others.
Empathy in seeing the pleasure of another’s fortune is thought to be the impetus for sharing, a trait this study shows transcends primate species.
For the experiment, Frans de Waal, director of the Living Links Center at the Yerkes Research Center, and Kristi Leimgruber, research specialist, led a team of researchers who exchanged tokens for food with eight adult female capuchin monkeys.
Each capuchin was paired with a relative, an unrelated familiar female from her own social group or a stranger (a female from a different group).
The capuchins were then given the choice of two tokens: the selfish option, which rewarded that capuchin alone with an apple slice; or the pro-social option, which rewarded both capuchins with an apple slice.
The monkeys predominantly selected the pro-social token when paired with a relative or familiar individual, but not when paired with a stranger.
According to de Waal, “The fact the capuchins predominantly selected the prosocial option must mean seeing another monkey receive food is satisfying or rewarding for them.”
“We believe prosocial behavior is empathy based. Empathy increases in both humans and animals with social closeness, and in our study, closer partners made more prosocial choices. They seem to care for the welfare of those they know,” he added.
de Waal and his research team will next attempt to determine whether giving is self-rewarding to capuchins because they can eat together or if the monkeys simply like to see the other monkey enjoying food. (ANI)