Science

https://archive.li/URhbv

The famous Alcubierre warp drive, introduced in 1994, has long been considered unphysical because it requires enormous amounts of theoretical negative mass or energy density to function . The authors of this study, Bobrick and Martire, suggest that this negative energy problem may not be a fundamental rule for all warp drives, but rather a specific flaw in Alcubierre's original design.

The researchers identify key artificial constraints in the Alcubierre model that mathematically force the need for negative energy. The Alcubierre model assumes the warp bubble has no gravitational effect on the spacetime outside of it, effectively "truncating" the gravitational field. The authors show that this assumption is a likely reason it requires negative energy . Furthermore, Alcubierre designed his drive so a passenger's clock ticks at the same rate as a stationary observer far away . This means the passenger's time is actually accelerated compared to an observer moving alongside the drive, another feature that requires negative energy .

By removing these artificial constraints, the authors developed a new, general model for a warp drive that can be constructed using purely positive energy, or regular matter. This new, physical warp drive is, however, strictly subluminal, meaning it can only travel slower than the speed of light. It is essentially a massive, hollow, spherically symmetric shell of ordinary matter. Unlike the Alcubierre drive, it would have a normal gravitational field outside of it, just like a planet. A passenger inside this shell would be in "flat spacetime," experiencing no gravity due to the Shell Theorem, a principle where the gravitational pull from all parts of the shell perfectly cancels out in the interior. The "warp" effect comes from its enormous mass, which causes time to run slower for the passenger compared to an outside observer. The mass requirements are vast; the paper calculates that an Earth-mass shell compressed to a 10-meter radius would only slow time by a tiny 0.04%.

This paper also clarifies a major misconception about how warp drives work. The original Alcubierre paper suggested the drive's velocity could just be changed as a function of time, but the new study points out that this violates the conservation of energy . The authors stress that a warp drive is an object, specifically a "shell of regular or exotic material moving inertially". Because it is a massive object, it is not a propulsion system itself. It cannot magically accelerate. To move or change velocity, it would require an external form of propulsion, such as a "propellant exhaust system" (like rockets) attached to it.

While this new positive-energy solution is limited to subluminal speeds, the paper reinforces that faster-than-light travel still appears to require negative energy. The authors also note that even for the unphysical Alcubierre drive, the most energy-efficient shape would be a flattened disc, not a sphere. This research is significant because it moves the warp drive concept from a purely unphysical fantasy to an extremely difficult but not theoretically impossible engineering challenge, suggesting a path to construct such spacetimes based on the laws of physics as we know them

The strongest predictor of whether someone believed in COVID-19-related misinformation and risks related to the vaccine was whether they viewed COVID-19 prevention efforts in terms of symbolic strength and weakness. In other words, this group focused on whether an action would make them appear to fend off or “give in” to untoward influence.

[…]

Our findings highlight the limits of countering misinformation directly, because for some people, literal truth is not the point.

In 1939, upon arriving late to his statistics course at the University of California, Berkeley, George Dantzig — a first-year graduate student — copied two problems off the blackboard, thinking they were a homework assignment. He found the homework “harder to do than usual,” he would later recount, and apologized to the professor for taking some extra days to complete it. A few weeks later, his professor told him that he had solved two famous open problems in statistics. Dantzig’s work would provide the basis for his doctoral dissertation and, decades later, inspiration for the film Good Will Hunting.

Dantzig received his doctorate in 1946, just after World War II, and he soon became a mathematical adviser to the newly formed U.S. Air Force. As with all modern wars, World War II’s outcome depended on the prudent allocation of limited resources. But unlike previous wars, this conflict was truly global in scale, and it was won in large part through sheer industrial might. The U.S. could simply produce more tanks, aircraft carriers and bombers than its enemies. Knowing this, the military was intensely interested in optimization problems — that is, how to strategically allocate limited resources in situations that could involve hundreds or thousands of variables.

Jupiter's core is a fuzzy core, not a solid core. It has a bizarre magnetic field and the NASA probe that was there or near there in 2017 confirmed that it has a core (as opposed to the theory that it has no core at all). But it's not solid (as was another possible scientific hypothesis). The discovery by the Juno spacecraft was ultimately an unexpected one and the spacecraft was able to help scientists dismiss or debunk several theories regarding the planet. Large regions of Jupiter are non-convective. And in addition, Saturn may have a fuzzy core too.

Just summarizing what I got from the video.

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“So several times a year we’re taking these potshots at people on the Earth and fortunately so far missing. So far we’ve been very lucky, but it won’t last.”

Deorbiting Starlink satellites may not pose a risk to people, but Dr McDowell said they may still prove problematic.

Scientists are still trying to understand what impact this rate of deorbits might have on the Earth’s atmosphere.

The Australian National University (ANU) operates a quantum random number generator (QRNG) that produces true random numbers by measuring quantum fluctuations of vacuum[^1]. The system generates random bits at 5.7 Gbits/s and makes them freely available through both a web interface and API[^5].

Unlike traditional pseudorandom number generators that rely on mathematical algorithms and seeds, ANU's QRNG creates genuine randomness by detecting quantum phenomena - specifically the electromagnetic field fluctuations that occur in a vacuum due to zero-point energy[^1].

The service offers multiple ways to access the random numbers:

• Direct web interface for visualization and downloads
• JSON API for programmatic access
• Pre-generated random number files up to 5GB in size
• Integration libraries for various programming languages including Python, R, Java, and .NET[^5]

The QRNG has practical applications in:

• Generating cryptographic keys
• Randomized clinical trials
• Computer game simulations
• Password generation
• Weather prediction modeling[^5]

The technical implementation is documented in peer-reviewed physics journals, with the quantum random number generation process detailed in Applied Physics Letters and Physical Review Applied[^1].

[^1]: ANU QRNG – Quantum random numbers [^5]: Frequently asked questions – ANU QRNG

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