Senin, 24 November 2014

Zapping video: dinosaurs and robots samurai family

Zapping video: dinosaurs and robots samurai family

In this eighth volume of our inimitable zappings, robots fighting sword ... We discover, in slow motion, dancing strange non-Newtonian fluids and the mysterious song of the comet 67P. A funny ambulance drone shows how it could save lives. And that's not all ... a very busy schedule for this volume rich in science and surprises.

A rich travel science and sights awaits you in this new volume of zapping. Our journey begins with the discovery of robots samurai, then follow a stop in a garden full of amazing carnivorous plants. We continue towards the ice , to meet a robot penguin for their observation. After a short stint in space with Rosetta and its comet, the drones will go doctors save lives. Finally, we will rub us the dinosaurs and other exciting topics to explore in this episode.

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The subjects of zapping this week

Samurai robots with amazing accuracy
Carnivorous plants grow timelapse
A robot to pass unnoticed among the penguins
Dancing in slow motion of a non-Newtonian fluid
The sound of the comet 67P / Churyumov-Gerasimenko
A drone ambulance to treat heart attacks
Dallol in Ethiopia, one of the most hostile areas of the globe
A show with lifelike dinosaurs

Interview: What is dark energy?

Interview: What is dark energy?

The universe is expanding. Taking into account the gravity, the expansion will slow and yet it seems to accelerate over time. This could be due to a strange force: dark energy. Jean-Pierre Luminet, a renowned astrophysicist explains Futura-Sciences that covers this strange notion.

According to general relativity, energy has mass, so she gravitates. The gravitation is attractive, it should slow down the expansion of the universe. However, observation indicates that the expansion is accelerating over time, which seems contradictory. To explain this phenomenon, one can imagine scenarios resulting from quantum theory predicts the existence of negative pressure energy fields. If one fills the space of this form of energy, it will expand rather than contract.

Another simple solution exists: the cosmological constant. It is a term that appears in the equations of general relativity proposed in 1917 by Einstein, taken up later by Georges LemaƮtre, the true father of the Big Bang. LemaƮtre was the first to have argued that the cosmological constant could be interpreted as an energy density after the quantum vacuum and therefore have repellent effects. All this has finally been shown experimentally there fifteen years.

Other theories are they considered?

In some models, you can switch between the dark energy . One of the major assumptions used constantly in cosmology is that the distribution of matter and large-scale energy is very homogeneous and isotropic. However, when reducing the scale we see that the universe is clearly structured. It is very complicated to calculate exact cosmological solutions assuming inhomogeneities. Perhaps the simplistic assumption of a homogeneous universe could give the illusion of a faster expansion which, in fact, does not exist. The question therefore remains completely open.

In short: the H5N8 bird flu in Europe

In short: the H5N8 bird flu in Europe

Known in Asia, the H5N8 strain was discovered in poultry in Germany, the Netherlands and the UK. Highly virulent for birds, it is not dangerous to humans because the virus is not transmitted to humans.

For three years, China, Korea and Japan suffer epidemics of flu bird in poultry, due to a variant of the virus H5N8 said. It is therefore not the H5N1 virus appeared in 2003 that caused 400 deaths or H7N9 , in charge since 2013 of more than a hundred deaths, especially in China, according to WHO figures.

The H5N8 virus, it is very dangerous for birds but harmless to humans. However Scientists monitor it because it is not impossible that a mutation renders dangerous for us. Cases of poultry infections have been reported in November in Europe in factory farms ducks, turkeys and chickens.

The bird flu virus  have traveled with birds migratory , whose droppings have contaminated these farms. These H5 rampant in birds and there are others as the FAO reported in September, a H5N6 strain in China and, more recently and still in this country, an H5N3 virus.

Relive its key moments

The adventure is not over yet.

Futura-Sciences faithful followed the landing November 12, 2014 on our special page , where the live event is still available.

Mission flagship of the European Space Agency's Rosetta must first install a probe in orbit around a comet and put a lander there. Decided in 1993, it was launched on 3 March 2004 and reached 67P / Churyumov-Gerasimenko in August 2014 and it has filed the Philae lander November 12, 2014.

Futura-Sciences has followed this saga. Relive its key moments by following these links:

January 2003: launch delay and lens change. It will not be Comet Wirtanen.
September 2003: the choice of 67P / Churyumov-Gerasimenko and our complete file on the Rosetta mission.
March 2004: the launch of Rosetta .
February 2010: the overview of the Steins asteroid.
July 2010: the overview of the asteroid Lutetia.
January 2014: The wake Rosetta.
April 2014: The first images of 67P / Churyumov-Gerasimenko.
August 2014: Rosetta orbit (almost) around his comet.
September 2014: The close-up images of the comet.
October 15: the final choice of landing site of Philae.
November 5, 2014: The landing site is called Agilkia.

An already excellent scientific return

An already excellent scientific return

One question remains: when Philae will he wake up? It is very difficult to answer due to the fact that we do not know its location or its position relative to the sun. This problem is further added that "it is not enough that the battery charged so that it wakes up" . Indeed, it should warm up some vital parts, the battery will not operate until it is cold. Then they must contact Rosetta will send him work orders. Create a virtuous cycle in which the battery is charging and operates the instruments will not be easy.

As for science, whatever the future of Philae , "we can say that the scientific return is about 80% of what was expected" . The two rebounds, especially the first, "was an opportunity to do the unexpected science ' ! and perform actions that were not provided. Thus, during the first bounce, it was possible to analyze the dust of Philae and magnetometer ROMAP recorded the famous magnetic field of the comet, "a mystery". Indeed it undergoes a periodic variation of twenty seconds that nobody can explain.

On the ground, the priority was to run at least once 10 instruments, totaling 18 sensors . The hammer MUPUS, "used to determine the hardness of the soil and its density as a function of temperature " and the drill worked well. The latter is deployed to 50 centimeters and transferred into the furnace of the instrument COSAC sample he had managed to get on the end. However, the spectrum appears to contain little information, so that we do not know if there was really something to analyze.

The panorama transmitted by Philae

Despite the presence of Rosetta above the comet, we still do not know where exactly landed Philae. "There is considerable uncertainty about its position. " We assume that is in a depression Site B, "but even that, it is not certain" . Rosetta could locate the next few days. We do not know how it arose and in what position he is. Initially, "it was thought that one of the three legs of the landing gear was in the air " , but it seems that it also posed on a rock. That is, it is wedged between two rocks, so that "it will not be easy to remove or modify its position" . Therefore, it is not docked but not stuck because ground controllers were able to rotate the 35 ° "in order to increase the area of solar panels could be sunny, but it is known how much this will help to recharge the battery".

The concern of scientists is to recharge the battery of Philae. Indeed, unlike the website Agilkia , "which offered a great rate of sunshine to recharge, nearly 10 hours a day" , where Philae landed only offers one thirty sunshine. In itself, this situation is not catastrophic, but it will significantly extend its duty cycle. In every other day as planned, it can be best used once a month or every two months. The very good news is that Philae will not die hot as planned. Indeed, as the comet approaches the Sun "like everyone has been optimized to get maximum photon , Philae was heated so hard he had to succumb " . But in the shade between two walls, "Philae could even resist after passing perihelion in August 2015 " . In addition, seasonal effects in the right direction. Philae will go from what appears a winter in a summer period, so that the number of hours per day the sun will rise.

The panorama transmitted by Philae, consisting of several shots, showing two of his feet.  The design of the robot has been added. First observation: it is dark.  The position of Philae, moreover, is not optimal. Yet he did most of his work

Philae is wedged between two rocks and has no foot in the air

However, this has worked very well and we had a little forgotten is the damper, installed on "the main axis of Philae, which is rotated around its landing gear" . In contact with the ground, sank 4 centimeters, ensuring its damping function. These are 4 inches below the expected value, "which seems to show that the surface was actually soft" .

This image was acquired by the Rolis descent camera Philae before it hits the ground, from a distance of 3 km.  It shows the original landing site of Philae (bottom) and it is assumed that he landed somewhere near the top of the image on the tip of the comet.

Philae is wedged between two rocks and has no foot in the air

The surface itself has softened the blow, since "we landed at one meter per second and that we bounced to 38 centimeters per second" . Philae has lost almost two-thirds of its speed. The second bounce, it landed 38 centimeters per second and restarts at 3 cm / s, "which means that we have lost more than ten times the speed" ! The second rebound was therefore extremely soft and lasted only 7 minutes.

The wheel inertia, too, worked very well. Its role was to stabilize the main axis of Philae during the descent to the comet so that it does not rotate in space. "For when Philae was dropped, he was in an attitude such as landing gear of the plane is parallel to the surface at touch". This wheel has stopped at the first contact with the ground but as, by definition, has a great inertia, "she put a long time to stop spinning" . She has continued to stabilize Philae during all or part of the parable of one hour and fifty minutes, and contributed to what he keeps a good position.