Daily Archives: June 13, 2020

It's easy to take time's arrow for granted - but the gears of physics actually work just as smoothly in reverse. Maybe that time machine is possible after all?

An experiment from 2019 shows just how much wiggle room we can expect when it comes to distinguishing the past from the future, at least on a quantum scale. It might not allow us to relive the 1960s, but it could help us better understand why not.

Researchers from Russia and the US teamed up to find a way to break, or at least bend, one of physics' most fundamental laws of energy.

The second law of thermodynamics is less a hard rule and more of a guiding principle for the Universe. It says hot things get colder over time as energy transforms and spreads out from areas where it's most intense.

It's a principle that explains why your coffee won't stay hot in a cold room, why it's easier to scramble an egg than unscramble it, and why nobody will ever let you patent a perpetual motion machine.

It's also the closest we can get to a rule that tells us why we can remember what we had for dinner last night, but have no memory of next Christmas.

"That law is closely related to the notion of the arrow of time that posits the one-way direction of time from the past to the future," said quantum physicist Gordey Lesovik from the Moscow Institute of Physics and Technology.

Virtually every other rule in physics can be flipped and still make sense. For example, you could zoom in on a game of pool, and a single collision between any two balls won't look weird if you happened to see it in reverse.

On the other hand, if you watched balls roll out of pockets and reform the starting pyramid, it would be a sobering experience. That's the second law at work for you.

On the macro scale of omelettes and games of pool, we shouldn't expect a lot of give in the laws of thermodynamics. But as we focus in on the tiny gears of reality - in this case, solitary electrons - loopholes appear.

Electrons aren't like tiny billiard balls, they're more akin to information that occupies a space. Their details are defined by something called the Schrdinger equation, which represents the possibilities of an electron's characteristics as a wave of chance.

If this is a bit confusing, let's go back to imagining a game of pool, but this time the lights are off. You start with the information a cue ball in your hand, and then send it rolling across the table.

The Schrdinger equation tells you that ball is somewhere on the pool table moving around at a certain speed. In quantum terms, the ball is everywhere at a bunch of speeds some just more likely than others.

You can stick your hand out and grab it to pinpoint its location, but now you're not sure of how fast it was going. You could also gently brush your finger against it and confidently know its velocity, but where it went... who knows?

There's one other trick you could use, though. A split second after you send that ball rolling, you can be fairly sure it's still near your hand moving at a high rate.

In one sense, the Schrdinger equation predicts the same thing for quantum particles. Over time, the possibilities of a particle's positions and velocities expands.

"However, Schrdinger's equation is reversible," said materials scientist Valerii Vinokur from the Argonne National Laboratory in the US.

"Mathematically, it means that under a certain transformation called complex conjugation, the equation will describe a 'smeared' electron localising back into a small region of space over the same time period."

It's as if your cue ball was no longer spreading out in a wave of infinite possible positions across the dark table, but rewinding back into your hand.

In theory, there's nothing stopping it from occurring spontaneously. You'd need to stare at 10 billion electron-sized pool tables every second and the lifetime of our Universe to see it happen once, though.

Rather than patiently wait around and watch funding trickle away, the team used the undetermined states of particles in a quantum computer as their pool ball, and some clever manipulation of the computer as their 'time machine'.

Each of these states, or qubits, was arranged into a simple state which corresponded to a hand holding the ball. Once the quantum computer was set into action, these states rolled out into a range of possibilities.

By tweaking certain conditions in the computer's setup, those possibilities were confined in a way that effectively rewound the Schrdinger equation deliberately.

To test this, the team launched the set-up again, as if kicking a pool table and watching the scattered balls rearrange into the initial pyramid shape. In about 85 percent of trials based on just two qubits, this is exactly what happened.

On a practical level, the algorithms they used to manipulate the Schrdinger equation into rewinding in this way could help improve the accuracy of quantum computers.

It's not the first time this team has given the second law of thermodynamics a good shake. A couple of years ago they entangled some particles and managed to heat and cool them in such a way they effectively behaved like a perpetual motion machine.

Finding ways to push the limits of such physical laws on the quantum scale just might help us better understand why the Universe 'flows' like it does.

This research was published in Scientific Reports.

A version of this article was first published in March 2019.

Continued here:

Physicists Have Reversed Time on The Smallest Scale Using a Quantum Computer - ScienceAlert

Richard Feynman was one of the greatest educators of the twentieth century. He was also a Nobel Prize-winning physicist known for his unique approaches to communicating complex topics in simple terms without skipping important details. Feynman was a child prodigy in math who worked on the Manhattan Project in his early twenties, won the Nobel Prize for his work in quantum mechanics, and was the most well-known and highly sought-after professor of physics at Caltech. Albert Einstein attended Feynmans first talk as a graduate student. Bill Gates was so influenced by Feynmans skill as an educator that Gates called him the greatest teacher [hed] ever had.

Feynman was perhaps best known for his ability to assimilate explain complex concepts, especially in the undergraduate classes he taught. Feynman explained the key to this ability was his differentiation of two kinds of knowledge. He said, You can know the name of that bird in all the languages of the world, but when youre finished, youll know absolutely nothing whatever about the bird. Youll only know about humans in different places, and what they call the bird I learned very early the difference between knowing the name of something and knowing something.

This is where Feynmans concepts can be applied to EMS education. At the foundational level of Blooms Taxonomy, students have to memorize names and terms in order for higher levels of learning to occur. On the second level students may learn basic facts about anatomy and physiology, but in order for them to apply this information on a real emergency call, this information has to have meaning for them. This is the performance gap that Feynman had identified. There is a difference between knowing the name of a thing (memorization) and knowing a thing (understanding).

Students often focus on their immediate need, which is to know the name of a thing to pass an exam. It is critical that educators prompt students to make connections between knowing the name of something and knowing how they will apply their knowledge about it to provide effective patient care. For example, a student may know the fact that the coronary arteries connect at the base of the aorta. They may even know that the coronary arteries perfuse during diastole. But can they think critically about the relevance of this? How can they apply this information to improve patient care? Rather than lecturing students on facts to memorize, a good educator will help students understand that because the coronary arteries only fill during diastole, this means that during CPR, while chest compressions (systole) eject blood to the body, really effective chest recoil (diastole) is required to perfuse the coronary arteries.

Feynman went further, explaining how good educators can become great educators in four simple steps.

1. Choose Your Topic

This may be better thought of as choose your objective. Feynman emphasized that educators need to be focused for each lesson and clear on exactly what they want the students to learn. Therefore, choosing a topic of airway is not only too broad, it doesnt define what you want a student to be able to do. A clear objective is the key to preparing to teach, setting expectations for students, getting co-educators on the same page, and setting up fair and effective testing.

2. Teach It to a Child

Feynman didnt mean that you had to literally teach the topic to a child. He explained that educators need to consider teaching as if they want a curious five-year-old to use this knowledge. The goal is not to dumb-down the information. The goal is to distill what you communicate into the essential concepts. Again, focus on how the student can apply the information. This forces you, the educator, to test both your complete understanding of the concepts you want students to apply, as well as your communication skills.

Feynman emphasized the importance of writing down those key concepts in the way you would explain it to the curious five-year-old. This forces an educator to do more than feel they could explain a subject well because they know a subject well. Writing it down exposes knowledge and communication gaps and forces the educator to make important decisions about exactly what to leave out, exactly what to teach, and exactly how to teach it. In the words of Albert Einstein, If you cant explain it simply, you don't understand it well enough.

3. Review and Fill In

Step 2 will almost surely expose opportunities for educators to improve their lesson. Maybe they will notice an important gap in their understanding of the subject. Maybe theyll realize the way theyd planned on running the education relied on students understanding of a topic that hadnt yet been thoroughly covered. Or perhaps the original lesson conveyed more knowledge with little focus on how students should apply the knowledge to meet the desired objectives.

4. Organize and Simplify

With the educators knowledge and communication gaps identified and filled in with a laser-focus on the objectives, it is time to make a final pass at the lesson plan (even if the lesson plan is simply educator notes on the back of an envelope). The Feynman technique focuses on step two: being able to teach to a child. The risk of step threeis that the educator will add too much back to the lesson. This final step is to organize the lesson so that it makes sense, focusing on the fundamentals the students will need to perform the objectives. If the students have questions, this is where the educators deeper knowledge and subject matter expertise will shine, but this is not time to roll out the war stories or show off how much more the educator knows than the student. This step is exactly what it says on the label: organize and simplify.

Using this simple technique, Richard Feynman was able to teach the most complex concepts in quantum mechanics to students in undergraduate physics classes. The key for us, as EMS educators, is to know a topic well enough to explain it simply, and to do so in a way that our students learn not just the name of a thing, but how to use it to improve their patient care.

See original here:

Duckworth on Education: The Feynman Technique - EMSWorld

A Sussex physicist has had a scientific breakthrough during lockdown.

A researcher from the quantum physics and technologies department at the University of Sussex has created the state of fifth form matter from her computer at home during lockdown.

Dr Amruta Gadge has successfully created a Bose-Einstein Condensate (BEC) a state of matter where atoms cooled to extreme temperatures clump together and act like one single object. This is thought to be the first time that a BEC has been created in remote conditions, which were made unavoidable due to the coronavirus pandemic.

Despite the closure of university research facilities, Dr Gadge was able to use her computer at home in her living room to control lasers and radio waves that would create the BEC. This development by Sussexs Quantum Systems & Devices research group will have applications in magnetic field research, as well as in medicine, Dr Gadge told The Argus.

This feat marks a step in the path towards operating quantum technology remotely, which could be extremely useful for accessing difficult environments, such as underground or in space.

Dr Gadge and the rest of the team celebrated the achievement in true lockdown style via a Zoom call.

Professer of experimental physics at Sussex University, Peter Krger, told The Argus, We are all extremely excited that we can continue to conduct our experiments remotely during lockdown, and any possible future lockdowns.

See original here:

Sussex Uni physicist creates the fifth state of matter whilst working from home - The Tab

By 1931, Kurt Gdel had proven his second incompleteness theorem, which states that a formal logical system cannot prove itself consistent. This theorem throws cold water on the ultimate ability to prove theories of everything, which have become fashionable in theoretical physics. It implies that any scientific theory is incomplete.

Galileo Galilei went beyond the limitations of pure logic and argued that any physical theory claiming to describe reality must also make predictions that stand up to the scrutiny of experiments. He found experimentally, for example, that heavy objects do not accelerate faster than light objects under the influence of gravity, as previously thought. This result laid the foundation for Albert Einsteins later realization that gravity is not a force but the curvature of spacetime that all test objects respond to in the same way.

Galileos dictum, based on humility, established the bedrock of modern physics over the years. But a new culture of physicists appears to challenge its underlying role now. For example, the pioneer of the theory of cosmic inflation, Alan Guth, replied during a panel discussion to my question of whether inflation is falsifiable that this theory cannot be proven false. He argued that it is a mathematical framework, like gauge theories, that must be valid, and the role of experiments is merely to fix its flexible degrees of freedom. In other words, the theory is adjustable enough to fit any experimental data about the universe.

But if so, can inflation be regarded a physical theory that obeys Galileos dictum? How can a theory claim to explain the beginning of the universe if it cannot be proven false by some hypothetical experimental data? By now, we know of alternative origin stories for our universe, suggesting that it may have gone through a bounce from a previously contracting phase before the big bang or that it started from some special initial state associated with string theory. In two papers that I wrote recently with my Harvard colleague, Xingang Chen and collaborators, we identified an experimental test that revealed tentative evidence in the cosmic microwave background and could favor alternative scenarios over the model of inflation. In short, it subjects inflation to Galileos dictum.

This would hardly be the first time a mathematically ingenious theory failed to capture physical reality. After all, the geocentric Ptolemaic theory of epicycles was mathematically appealing and its framework was broad enough to describe the motion of all planets on the sky. But it was eventually disfavored relative to the heliocentric Newtonian theory of gravity because it required a large number of free parameters that had to be finely tuned individually for each planet.

Despite lessons from the history of science, the notion that some physical theories cannot be refuted, and must be intrinsically true based on abstract reasoning, is still gaining popularity. Additional examples include the hypothetical existence of the multiverse, the conjecture that reality is a computer simulation, applications of the AdS/CFT correspondence to the real worldwhich is not embedded in anti de-Sitter (AdS) space but instead in nearly de-Sitter space of a completely different geometry, or Stephen Wolframs new concept of a theory of everything. Following an inspiring colloquium that Wolfram just gave at Harvards Black Hole Initiative, one thought came to my mind: If this theory predicts the lowest mass possible for an elementary particle, we will be able to test it based on astrophysical data.

The real world is under no obligation to follow our blueprints, just because they are mathematically appealing or easier to formulate than some alternative. The best example is quantum mechanics, whose fundamental principles deviated qualitatively from classical physics but were forced upon us through experiments. After quantum theory was formulated, Albert Einstein debated Niels Bohr against its unexpected nonclassical interpretation, arguing in a 1926 Letter to Max Born that In any event, I am convinced that He [God] is not playing dice. Recent experiments have proven Einsteins intuition false.

Human culture is filled with myths. Science aims to correct preconceived theories by emphasizing the key role of experimental verification. The natural tendency of humans to blindly follow popular conjectures should be moderated, since it places blinders on our scientific vision and suppresses progress in understanding reality.

Mathematical beauty is admirable, but in attempting to figure out reality it should be downgraded to second place relative to evidence. Physics is a dialogue with natureaccomplished through experimental testing of our ideas, and not a monologue in which we formulate our theories of everything and rest on our laurels. We must stay humble, keeping in mind Gdels proof that all mathematical systems are logically incomplete and Galileos insight that most of them may have nothing to do with reality.

Originally posted here:

Beware of 'Theories of Everything' - Scientific American