Mathematics | Theoretical Physics

Anonymous asked: If energy is conserved and cannot be created or destroyed how can heat and energy dissipate over time?

heat is a form of energy - kinetic energy. when say energy is dissipated over time what is meant is that is is distrubuted from hot to cold evenly inside an isolated system, so energy isnt being created or destroyed - its being spread out over time, while the total energy of the system remains constant

MIT researchers can listen to your conversation by watching your potato chip bag

Imagine someone listening in to your private conversation by filming the bag of chips sitting on the other side of the room. Oddly specific, I know, but researchers at MIT did just that: They’ve created an algorithm that can reconstruct sound (and even intelligible speech) with the tiny vibrations it causes on video.

When sound hits an object, it makes distinct vibrations. “There’s this very subtle signal that’s telling you what the sound passing through is,” said Abe Davis, a graduate student in electrical engineering and computer science at MIT and first author on the paper. But the movement is tiny – sometimes as small as thousandths of a pixel on video. It’s only when all of these signals are averaged, Davis said, that you can extract sound that makes sense. By observing the entire object, you can filter out the noise.

This particular study grew out of an earlier experiment at MIT, led by Michael Rubinstein, now a postdoctoral researcher at Microsoft Research New England. In 2012, Rubinstein amplified tiny variations in video to detect things like the skin color change caused by the pumping of blood. Studying the vibrations caused by sound was a logical next step. But getting intelligible speech out of the analysis was surprising, Davis said.

The results are certainly impressive (and a little scary). In one example shown in a compilation video, a bag of chips is filmed from 15 feet away, through sound-proof glass. The reconstructed audio of someone reciting “Mary Had a Little Lamb” in the same room as the chips isn’t crystal clear. But the words being said are possible to decipher.

In most cases, a high-speed camera is necessary to accomplish the feat. Still, at 2,000 to 6,000 frames per second, the camera used by the researchers is nothing compared to the best available on the market, which can surpass 100,000 frames per second. And the researchers found that even cheaper cameras could be used.

“It’s surprisingly possible to take advantage of a bug called rolling shutter,” Davis said. “Usually, it creates these artifacts in the image that people don’t like.” When cameras use rolling shutter to capture an image, they don’t capture one single point in time. Instead, the camera scans across the frame in one direction, picking up each row at a slightly different moment.

By doing so, the camera happens to encode information at a much higher rate than its actual frame rate. For the researchers, that meant being able to analyze vibrations that should have happened too quickly for capture on film. “It kind of turns a two-dimensional low-speed camera into a one-dimensional high-speed camera,” Davis explained. “As a result, we can recover sounds happening at frequencies several times higher than the frame rate of the camera, which is remarkable when you consider that it’s just a complete accident of the way we make them.”

There are definitely limitations to the technology, Davis said, and it may not make for better sound reconstruction than other methods already in use. “Big brother won’t be able to hear anything that anyone ever says all of a sudden,” Davis said. “But it is possible that you could use this to discover sound in situations where you couldn’t before. It’s just adding one more tool for those forensic applications.”

Davis and his colleagues care more about applications in scientific research. “This is a new dimension to how you can image objects,” he said. “It tells you something about how they respond physically to pressure, but instead of poking and prodding at them, all you need is to play sound at them.”

[source]

Physicists propose Superabsorption of light beyond the limits of classical physics.

In a well-known quantum effect called superradiance, atoms can emit light at an enhanced rate compared to what is possible in classical situations. This high emission rate arises from the way that the atoms interact with the surrounding electromagnetic field. Logically, structures that superradiate must also absorb light at a higher rate than normal, but so far the superabsorption of light has not been observed.
Now in a new paper published in Nature Communications, physicists Kieran Higgins, et al., have theoretically shown that superabsorption can be demonstrated using quantum engineering techniques. Structures capable of superabsorption could have applications including solar energy harvesting, novel quantum camera pixels, and wireless light-based power transmission.
"If you had a ring comprising 40 atoms, this would absorb light 10x faster than any classical approach," Higgins, at Oxford University, told Phys.org. "The key thing in this work is that it’s a fundamentally different way of absorbing light. So if you want to design the most efficient possible absorber and you have a certain number of atoms, this is a new and better way to do it using quantum physics. The atoms behave as if there’s more of them than there actually are, which is the really cool thing."
As the physicists explain, superabsorption is the reciprocal of superradiance. Superradiance was first introduced 60 years ago by the physicist Robert Dicke, and since then has found a variety of applications, including a new class of laser. Physically, superradiance occurs when a system of excited atoms decays and moves down a ladder of states called the “Dicke” or “bright” states. As a result, light can be emitted at an enhanced rate that is proportional to the square of the number of atoms.
In natural systems, light emission dominates over light absorption, which is why superabsorption has not yet been observed. But in the new paper, the scientists have shown that atoms in close proximity and with a suitable geometrical arrangement can interact with each other in such a way as to exhibit superabsorption.

^ A comparison of absorption: Independent atoms (red line) absorb excitons linearly, while a proposed superabsorption scheme (green line) could absorb excitons superlinearly (ideally, N2). The yellow and blue lines represent superabsorption when accounting for costs in different ways.
The key to achieving superabsorption is to use quantum engineering techniques to ensure that most state transitions take place within a specific frequency (which the scientists call the “good” frequency, in contrast with the “bad” frequencies that should be avoided). Photons can then be trapped so they are not emitted back out. Although the system would likely deviate from the “good” frequency over time, there are a few reinitialization schemes that would periodically monitor and correct the system’s frequency.

[source]

Physicists propose Superabsorption of light beyond the limits of classical physics.

In a well-known quantum effect called superradiance, atoms can emit light at an enhanced rate compared to what is possible in classical situations. This high emission rate arises from the way that the atoms interact with the surrounding electromagnetic field. Logically, structures that superradiate must also absorb light at a higher rate than normal, but so far the superabsorption of light has not been observed.

Now in a new paper published in Nature Communications, physicists Kieran Higgins, et al., have theoretically shown that superabsorption can be demonstrated using quantum engineering techniques. Structures capable of superabsorption could have applications including solar energy harvesting, novel quantum camera pixels, and wireless light-based power transmission.

"If you had a ring comprising 40 atoms, this would absorb light 10x faster than any classical approach," Higgins, at Oxford University, told Phys.org. "The key thing in this work is that it’s a fundamentally different way of absorbing light. So if you want to design the most efficient possible absorber and you have a certain number of atoms, this is a new and better way to do it using quantum physics. The atoms behave as if there’s more of them than there actually are, which is the really cool thing."

As the physicists explain, superabsorption is the reciprocal of superradiance. Superradiance was first introduced 60 years ago by the physicist Robert Dicke, and since then has found a variety of applications, including a new class of laser. Physically, superradiance occurs when a system of excited atoms decays and moves down a ladder of states called the “Dicke” or “bright” states. As a result, light can be emitted at an enhanced rate that is proportional to the square of the number of atoms.

In natural systems, light emission dominates over light absorption, which is why superabsorption has not yet been observed. But in the new paper, the scientists have shown that atoms in close proximity and with a suitable geometrical arrangement can interact with each other in such a way as to exhibit superabsorption.

^ A comparison of absorption: Independent atoms (red line) absorb excitons linearly, while a proposed superabsorption scheme (green line) could absorb excitons superlinearly (ideally, N2). The yellow and blue lines represent superabsorption when accounting for costs in different ways.

The key to achieving superabsorption is to use quantum engineering techniques to ensure that most state transitions take place within a specific frequency (which the scientists call the “good” frequency, in contrast with the “bad” frequencies that should be avoided). Photons can then be trapped so they are not emitted back out. Although the system would likely deviate from the “good” frequency over time, there are a few reinitialization schemes that would periodically monitor and correct the system’s frequency.

[source]

trigonometry-is-my-bitch:

A demonstration of the mathematical principles of the original Forth Bridge in Scotland performed at Imperial College in 1887. The central ‘weight’ is Kaichi Watanabe, one of the first Japanese engineers to study in the UK, while Sir John Fowler and Benjamin Baker provide the supports.
Photograph: Imperial College

trigonometry-is-my-bitch:

A demonstration of the mathematical principles of the original Forth Bridge in Scotland performed at Imperial College in 1887. The central ‘weight’ is Kaichi Watanabe, one of the first Japanese engineers to study in the UK, while Sir John Fowler and Benjamin Baker provide the supports.

Photograph: Imperial College

scientastical:

trigonometry-is-my-bitch:

A Flame being extinguished by Electricity.

Whoa What? How/why does this happen, can someone explain?

scientastical
here you go :) - “carbon particles generated in the flame are key for its response to electric fields. carbon particles can easily become charged. The charged particles respond to the electric field, affecting the stability of flames.”
[source]

scientastical:

trigonometry-is-my-bitch:

A Flame being extinguished by Electricity.

Whoa What? How/why does this happen, can someone explain?

scientastical

here you go :) - “carbon particles generated in the flame are key for its response to electric fields. carbon particles can easily become charged. The charged particles respond to the electric field, affecting the stability of flames.”

[source]

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