There have long been rumors, leaks, and statements about the NSA "breaking" crypto that is widely believed to be unbreakable, and over the years, there's been mounting evidence that in many cases, they can do just that. Now, Alex Halderman and Nadia Heninger, along with a dozen eminent cryptographers have presented a paper at the ACM Conference on Computer and Communications Security (a paper that won the ACM's prize for best paper at the conference) that advances a plausible theory as to what's going on. In some ways, it's very simple -- but it's also very, very dangerous, for all of us. (more…)
What if the Earth were made entirely of protons, and the Moon were made entirely of electrons?
This is, by far, the most destructive What-If scenario to date.
You might imagine an electron Moon orbiting a proton Earth, sort of like a gigantic hydrogen atom. On one level, it makes a kind of sense; after all, electrons orbit protons, and moons orbit planets. In fact, a planetary model of the atom was briefly popular (although it turned out not to be very useful for understanding atoms.This model was (mostly) obsolete by the 1920s, but lived on in an elaborate foam-and-pipe-cleaner diorama I made in 6th grade science class.)
If you put two electrons together, they try to fly apart. Electrons are negatively charged, and the force of repulsion from this charge is about 20 orders of magnitude stronger than the force of gravity pulling them together.
If you put 1052 electrons together—to build a Moon—they push each other apart really hard. In fact, they push each other apart so hard, each electron would be shoved away with an unbelievable amount of energy.
It turns out that, for the proton Earth and electron Moon in Noah's scenario, the planetary model is even more wrong than usual. The Moon wouldn't orbit the Earth because they'd barely have a chance to influence each other;I interpreted the question to mean that the Moon was replaced with a sphere of electrons the size and mass of the Moon, and ditto for the Earth. There are other interpretations, but practically speaking the end result is the same. the forces trying to blow each one apart would be far more powerful than any attractive force between the two.
If we ignore general relativity for a moment—we'll come back to it—we can calculate that the energy from these electrons all pushing on each other would be enough to accelerate all of them outward at near the speed of light.But not past it; we're ignoring general relativity, but not special relativity. Accelerating particles to those speeds isn't unusual; a desktop particle accelerator can accelerate electrons to a reasonable fraction of the speed of light. But the electrons in Noah's Moon would each be carrying much, much more energy than those in a normal accelerator—orders of magnitude more than the Planck energy, which is itself many orders of magnitude larger than the energies we can reach in our largest accelerators. In other words, Noah's question takes us pretty far outside normal physics, into the highly theoretical realm of things like quantum gravity and string theory.
So I contacted Dr. Cindy Keeler, a string theorist with the Niels Bohr Institute. I explained Noah's scenario, and she was kind enough to offer some thoughts.
Dr. Keeler agreed that we shouldn't rely on any calculations that involve putting that much energy in each electron, since it's so far beyond what we're able to test in our accelerators. "I don't trust anything with energy per particle over the Planck scale. The most energy we've really observed is in cosmic rays; more than LHC by circa 106, I think, but still not close to the Planck energy. Being a string theorist, I'm tempted to say something stringy would happen—but the truth is we just don't know."
Luckily, that's not the end of the story. Remember how we're ignoring general relativity? Well, this is one of the very, very rare situations where bringing in general relativity makes a problem easier to solve.
There's a huge amount of potential energy in this scenario—the energy that we imagined would blast all these electrons apart. That energy warps space and time just like mass does.If we let the energy blast the electrons apart at near the speed of light, we'd see that energy actually take the form of mass, as the electrons gained mass relativistically. That is, until something stringy happened. The amount of energy in our electron Moon, it turns out, is about equal to the total mass and energy of the entire visible universe.
An entire universe worth of mass-energy—concentrated into the space of our (relatively small) Moon—would warp space-time so strongly that it would overpower even the repulsion of those 1052 electrons.
Dr. Keeler's diagnosis: "Yup, black hole." But this is no an ordinary black hole; it's a black hole with a lot of electric charge.The proton Earth, which would also be part of this black hole, would reduce the charge, but since an Earth-mass of protons has much less charge than a Moon-mass of electrons, it doesn't affect the result much. And for that, you need a different set of equations—rather than the standard Schwarzschild equations, you need the Reissner–Nordström ones.
In a sense, the Reissner-Nordström equations compare the outward force of the charge to the inward pull of gravity. If the outward push from the charge is large enough, it's possible the event horizon surrounding the black hole can disappear completely. That would leave behind an infinitely-dense object from which light can escape—a naked singularity.
Once you have a naked singularity, physics starts breaking down in very big ways. Quantum mechanics and general relativity give absurd answers, and they're not even the same absurd answers. Some people have argued that the laws of physics don't allow that kind of situation to arise. As Dr. Keeler put it, "Nobody likes a naked singularity."
In the case of an electron Moon, the energy from all those electrons pushing on each other is so large that the gravitational pull wins, and our singularity would form a normal black hole. At least, "normal" in some sense; it would be a black hole as massive as the observable universe.A black hole with the mass of the observable universe would have a radius of 13.8 billion light-years, and the universe is 13.8 billion years old, which has led some people to say "the Universe is a black hole!" (It's not.)
Would this black hole cause the universe to collapse? Hard to say. The answer depends on what the deal with dark energy is, and nobody knows what the deal with dark energy is.
But for now, at least, nearby galaxies would be safe. Since the gravitational influence of the black hole can only expand outward at the speed of light, much of the universe around us would remain blissfully unaware of our ridiculous electron experiment.
Today, The Lancet released the results of a large field trial of a vaccine against Ebola, and the results are more than promising. Within the limitations of the study, the vaccine appears to be 100 percent effective. The results were so good that the trial itself has been stopped, and the vaccine is now being used to control the spread of the disease.
The vaccine is made by the pharmaceutical giant Merck, which licensed it from the Public Health Agency of Canada. It was developed through what has become a fairly standard approach. A harmless virus (vesicular stomatitis virus, or VSV) was engineered so that it also carried the gene for Ebola's major surface protein, simply called glycoprotein. When people receive the vaccination, a harmless infection follows, which triggers an immune response. This response targets not only VSV but the Ebola protein as well. Ideally, once the infection is eliminated, the immune system is able to recognize both VSV and Ebola.
The trial, performed in southern Guinea, ran from April through July 20th of this year (the analysis, paper writing, and peer review must have proceeded at a staggering pace). It used what is called a "ring" design: once an infected individual was identified, a ring of potentially exposed individuals around them was identified. These individuals lived with the infected one, had contact with them after symptoms appeared, or came in contact with their clothes, bedding, or bodily fluids.
Airbus, the European aerospace giant, has unveiled Adeline: its answer to SpaceX's reusable space launch ambitions. Adeline, which stands for Advanced Expendable Launcher with Innovative engine Economy, uses a rather novel solution to get the first stage engines back in one piece: it has wings and propellers that allow the engines to follow a ballistic trajectory, and then fly like an airplane back to a runway.
All current space launch systems—SpaceX's Falcon 9, Airbus' Ariane 5, Russia's Soyuz, etc.—are expendable. During every single rocket launch, the rocket engines and fuel tanks fall back to Earth, usually into the ocean, never to be used again. Rocket engines are not cheap: Orbital Sciences paid around $1 billion (£600 million) to Roscosmos for 20 RD-180 rocket engines.
This is why companies like SpaceX, and now Airbus, are developing technologies that can bring the rocket engines back to the launchpad, so that they can be reused. SpaceX, which is currently leading the charge in this area, says that it wants to reuse rocket engines and fuel tanks within "single-digit hours" of their return. Depending on who you talk to, and the configuration of the rocket, current space launch prices are somewhere around $250-500 million; with reusable components, SpaceX wants to get that price down below $100 million.
Hovertext: Can we make bio-history a thing? Can we? Pleaaaaase?
Last week, Audi announced that it had filled the tank of one of its vehicles with a synthetic diesel fuel made with a high-temperature process that starts with only water and carbon dioxide. While there's a substantial energy input involved in generating the fuel, the company expects that excess renewable energy will eventually be able to supply that energy cheaply.
The diesel was produced through a process called high-temperature electrolysis, in which steam is heated before electricity is used to split the water vapor into hydrogen and oxygen. The high temperatures make this process more efficient and, as Audi notes, the waste heat can be used for other purposes, further boosting the efficiency. The hydrogen can then be combined with carbon dioxide in a process that produces liquid hydrocarbons (these reactions require high temperatures and pressures as well).
The current production facility (partly supported by Germany's Federal Ministry of Education and Research) uses CO2 supplied by a biogas facility, supplemented by a carbon capture facility that pulls the gas from the atmosphere.
Do you think you could ride a bicycle that steers backwards...aka it turns left when you turn right and vice versa? It sounds easy but years of normal bike riding experience makes it almost impossible. Destin Sandlin of Smarter Everyday taught himself how to ride the backwards-steering bike; it took months. Then he tried riding a normal bicycle again...
Loved this video...great stuff. (via ★interesting)Tags: cycling Destin Sandlin science video
Hovertext: The early human gets to keep its job!
A new study examined the galaxy cluster Abell 3827 and found indications that dark matter could be self-interacting. If confirmed, this would mark a significant step forward in the ongoing quest to understand the substance that helps structure the Universe.
The team used the MUSE instrument on the Very Large Telescope (VLT) along with images from the Hubble Space Telescope to map out the cluster. Because large masses such as galaxies and galaxy clusters bend the paths of light, they act as lenses, a process called (surprise!) gravitational lensing. The team made use of the complex web of lensing effects throughout the cluster to map out the dark matter there. The presence of strong gravitational lensing is fortunate for the study, as the dark matter would be invisible without it.
Every galaxy sits within a roughly spherical blob, called a halo, of dark matter. That halo makes up most of the galaxy’s mass. In normal situations this configuration is stable, but when multiple galaxies interact with each other, a process called tidal stripping can take place, in which gravity from one galaxy pulls in material from another. This can separate the dark matter from the stars in the galaxy.
SpaceX's trial-and-error process of learning to land one of its Falcon main stages continued this week. After successfully sending a Dragon capsule toward a rendezvous with the International Space Station, the Falcon reversed course, fired its thrusters, and made its way back into the atmosphere over the Atlantic. After a controlled plunge through the air, it attempted to land on a barge named "Just Read the Instructions." This time, conditions enabled the company to have had an aircraft in the area to film the results.
The video above shows the Falcon dropping at a rather healthy clip until it's quite close to the barge. At that point, the rocket's electronics appear to try to adjust its location; the craft tips while firing its main engines at a much higher level. This appears to be enough to set it down on the barge, but now tilting in the opposite direction. Thrusters at the top of the rocket attempt to correct the tilt but can't; it slowly falls over until it explodes while nearly horizontal.
SpaceX originally posted video footage of the crash landing, but it was taken down and marked private on YouTube on Wednesday afternoon.
The ability to walk upright is a defining characteristic of humans, one that emerged through a long evolutionary history. It's not just a matter of the right bones; our muscular, skeletal, and neural systems have evolved to enable our coordinated movements. The nerves allow us to develop a gait that is optimized to minimize the amount of energy necessary by modulating aspects of our movement such as our step length or arm motions.
Even with all that optimization, walking can be tiring; in fact, people expend more energy walking than any other daily activity. As we age, walking often becomes even more difficult. For decades researchers have explored ways to mitigate the energy cost associated with walking—studies that are typically aimed at helping those who are weaker or disabled.
Recently, scientists and engineers started to look at this issue from a new perspective; they questioned whether the human gait is as efficient as it can be. This interdisciplinary research team developed a device that behaves as an unpowered exoskeleton.