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A century ago this year, a young Swiss physicist, who had already revolutionized physics with discoveries about the relationship between space and time, developed a radical new understanding of gravity.
In 1915, Albert Einstein published his general theory of relativity, which described gravity as a fundamental property of space-time. He came up with a set of equations that relate the curvature of space-time to the energy and momentum of the matter and radiation that are present in a particular region.
Today, 100 years later, Einstein’s theory of gravitation remains a pillar of modern understanding, and has withstood all the tests that scientists could throw at it. But until recently, it wasn’t possible to do experiments to probe the theory under extreme conditions to see whether it breaks down.
Tag Archives | Physics
Ryan Whitwam via ExtremeTech:
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Despite being a well-established tenet of modern physics, the particle-wave duality of light can be a real mind-bender. This approach to understanding the universe was pioneered by scientists like Albert Einstein and Max Planck, eventually leading to quantum mechanics. Researchers have been trying to visualize light in both forms ever since, but haven’t had success until now. A team at the Swiss Federal Institute of Technology in Lausanne (EPFL) claim they’ve devised an experiment to photograph light as both a particle and wave.
Einstein’s eureka moment in the study of light came when he described the photoelectric effect. When UV light hits a metal surface, it results in an emission of electrons. Einstein explained this phenomenon by proposing that light can act as a particle in addition to a wave. We now know these particles as photons, but that term wasn’t coined until later. Subsequent experiments have confirmed the dual property of light, but actually seeing both at once would be something.
Let’s start with a couple propositions:
The Identity of Indiscernibles
Two objects are identical when they share all the same properties.
The Indiscernibility of Identicles:
If two objects share all the same properties then the two objects are identical.
At a glance, they both seem obvious enough that even mentioning them feels like a waste of time. Things get a little more complicated, however, when you consider the “position” of a property, since it’s also agreed upon by all that no two objects can occupy the same space at the same time. If object x and object y truly share all the same properties, including position, then x and y are truly “identical” in that they are the same object. Even this isn’t terribly controversial (although some have argued against it), but when you apply it to real life something odd can occur, as seen in the following example. … Read the rest
Have you ever wondered what is meant by a moment in time? To capture a moment in time we have to combine slices upon slices of infinitesimal imaginary finites. To get to a moment we will remember there has to have once been a now! What, after all, is “NOW” or “real time,” and how long does it last? I’m talking about right now. Well, by the time that you get to the end of this sentence, it will already be in the past. I mean it’s easy to imagine past, or future, but “now” (this moment) lasts how long? Does it last a second? To me it’s like that needle on a record or the laser on a DVD. The record is your life and the needle is where your consciousness of now is at any given time. The rest of the record has either played or it hasn’t, but the needle is constantly moving.… Read the rest
Years ago in Busan, South Korea, I was in bed when my girlfriend, in what I believe to be an attempt to share interests with each other, asked me what exactly someone studies when they study metaphysics. I considered giving her the definition my professor had offered my class years and years ago on the first day of my first metaphysics course — “Metaphysics is the study of being qua being” — but I refrained from doing so because most people quickly lose interest after hearing that sentence spoken aloud. Instead I opted for a metaphysical topic often used early on in any philosophy department’s curriculum, that of Universals and Particulars. “It’s like, um, we know that there are green things,” I explained, “but, like, is green actually a thing?” (I’m usually more eloquent, but we were both fairly stoned at this point.) She responded by bluntly telling me that was the most useless thing she had ever heard of before rolling over and going to sleep.… Read the rest
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Reports of the death of the Big Bang have been greatly exaggerated. Big Bang theory is alive and well. At the same time, our universe may not have a beginning or end.
Are you seeing the stories this week suggesting that the Big Bang didn’t happen? According to astrophysicist Brian Koberlein – a great science communicator at Rochester Institute of Technology with a popular page on G+ – that’s not quite what the new research (published in early February 2015 Physics Letters B, has suggested. The new study isn’t suggesting there was no Big Bang, Koberlein says. It’s suggesting that the Big Bang did not start with a singularity – a point in space-time when matter is infinitely dense, as at the center of a black hole. How can this be? Koberlein explains on his website:
The catch is that by eliminating the singularity, the model predicts that the universe had no beginning.
E=mc2. Einstein’s great equation represents a pinnacle of mathematical purity. But as the evidence piles up which general relativity struggles to account for, is the very elegance of Einstein’s theories preventing scientists from updating them? Is there always beauty in truth, or are aesthetics a distraction from the fundamental mission of science?
Excellent interview on this with Jon Butterworth, a physics professor at University College London and author of Smashing Physics: The Inside Story of the Hunt for the Higgs.
You have said in the past that beauty is found in simplicity, but isn’t it actually the complex nature of the world that inspires awe?
Obviously it’s a subjective point of view but, for me, what inspires awe is the fact that such complexity can arise for some very simple underlying principles. It’s the combination of complexity and simplicity. If the universe was all manifestly simple, that wouldn’t be so impressive.… Read the rest
Jürgen Schmidhuber writes:
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Konrad Zuse (1910-1995; pronounce: “Conrud Tsoosay”) not only built the first programmable computers (1935-1941) and devised the first higher-level programming language (1945), but also was the first to suggest (in 1967) that the entire universe is being computed on a computer, possibly a cellular automaton (CA). He referred to this as “Rechnender Raum” or Computing Space or Computing Cosmos. Many years later similar ideas were also published / popularized / extended by Edward Fredkin (1980s), Jürgen Schmidhuber (1990s – see overview), and more recently Stephen Wolfram (2002) (see comments and Edwin Clark’s review page). Zuse’s first paper on digital physics and CA-based universes was:
Konrad Zuse, Rechnender Raum, Elektronische Datenverarbeitung, vol. 8, pages 336-344, 1967. Download PDF scan.
Zuse is careful: on page 337 he writes that at the moment we do not have full digital models of physics, but that does not prevent him from asking right there: which would be the consequences of a total discretization of all natural laws?
Because so many of you are Robert Anton Wilson fans, I just know you’re going to be excited that scientists are using Schrodinger’s Cat to create a new quantum computer, as reported by PhysOrg:
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Physicists at the University of Sussex have tamed one of the most counterintuitive phenomena of modern science in their quest to develop a new generation of machines capable of revolutionizing the way we can solve many problems in modern science.
The strange and mysterious nature of quantum mechanics is often illustrated by a thought experiment, known as Schrӧdinger’s Cat, in which a cat is theoretically both dead and alive simultaneously.
According to a new study published this week in Physical Review A, Sussex physicists have now managed to create a special type of “Schrӧdinger’s” cat using new technology based on trapped ions (charged atoms) and microwave radiation.
Like the cat, the researchers made these ions exist in two states simultaneously by creating ‘entanglement’, an effect that challenges the very fabric of reality itself.
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Prospects of developing computing and communication technologies based on quantum properties of light and matter may have taken a major step forward thanks to research by City College of New York physicists led by Dr. Vinod Menon.
In a pioneering study, Professor Menon and his team were able to discover half-light, half-matter particles in atomically thin semiconductors (thickness ~ a millionth of a single sheet of paper) consisting of two-dimensional (2D) layer of molybdenum and sulfur atoms arranged similar to graphene. They sandwiched this 2D material in a light trapping structure to realize these composite quantum particles.
“Besides being a fundamental breakthrough, this opens up the possibility of making devices which take the benefits of both light and matter,” said Professor Menon.
For example one can start envisioning logic gates and signal processors that take on best of light and matter. The discovery is also expected to contribute to developing practical platforms for quantum computing.