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Posted on Sunday, September 13, 2020 @ 11:58:39 EDT in SpaceTime
by Southern
Six more fast radio bursts have been discovered coming from the same mystery cosmic source
Repeating FRBs came from same location far beyond the Milky Way where 10 had previously been detected.
Hannah Osborne
Six additional repeating fast radio bursts have been discovered coming the same unknown source in space. The FRBs came from the same region beyond the Milky Way where 10 bursts had previously been detected – and their discovery should give a greater insight into what caused them.
FRBs are radio signals from deep space that last just a few milliseconds. The first FRB was detected in 2001 and since then over a dozen have been found in telescope data. However, these all appeared to be one-off events, with no two bursts coming from the same location. This means follow-up observations were not possible, keeping their source a mystery.
Current theories as to their cause involve a cataclysmic event like a neutron star collapsing into a black hole or a supernova. Another option is they are coming from a young, highly magnetised, extragalactic neutron star.
In March, scientists announced the discovery of the first repeating FRBs. Ten bursts were recorded coming from the same direction as FRB 121102 – a spot in space far beyond the Milky Way.
Their findings, published in the journal Nature, showed the bursts had the same dispersion measurements as the original FRB, indicating the source must have survived whatever event produced the FRB in the first place. As a result, the bursts cannot be being produced by a one-off event.
Bursts were discovered with the Green Bank telescope Jarek Tuszynski / Wikimedia Commons
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Posted on Thursday, September 10, 2020 @ 12:19:14 EDT in SpaceTime
by Southern
So far, they seem to be—but nobody really understands why
Venkat Srinivasan
The European Southern Observatory's Very Large Telescope, in Chile Image: European Southern Observatory/Flickr under Creative Commons License
When Max Born addressed the South Indian Science Association in November 1935, it was a time of great uncertainty in his life. The Nazi Party had already suspended the renowned quantum mechanics physicist's position at the University of Gottingen in 1933. He had been invited to teach at Cambridge, but it was temporary. Then, the Party terminated his tenure at Gottingen in the summer of 1935. Born took up an offer to work with C. V. Raman and his students for six months at the Indian Institute of Science in Bangalore. While there, he found that his family had lost its German citizenship rights. He was stateless and without a permanent home. And then, there was this uncertainty about two numbers.
The scientific world had been coming to terms with two numbers that had emerged after a series of discoveries and theories in the previous four decades. They were unchanging and they had no units. One, the fine structure constant, defined the strength of interactions between fundamental particles and light. It is expressed as 1/137. The other, mu, related the mass of a proton to an electron.
Born was after a unifying theory to relate all the fundamental forces of nature. He also wanted a theory that would explain where these constants came from. Something, he said, to “explain the existence of the heavy, and light elementary particles and their definite mass quotient 1840."
It might seem a little bizarre that Born worried about a couple of constants. The sciences are full of constants—one defines the speed of light, another quantifies the pull of gravity, and so on. We routinely use these numbers, flipping to dog-eared tables in reference books, and coding them into our software without much thought because, well, they are constants. But the weird thing about such constants is that there is no theory to explain their existence. They are universal and they appear to be unchanging. So is the case with the masses of protons and electrons. But time and time again, they are validated through observation and experiment, not theory.
What Born and so many others were after was a unifying theory that would demonstrate that there could only be one unchanging value for a constant. Without this theory, scientists resort to testing limits of a constant. Measuring the constant is a good way to verify that theories using them make sense, that science stands on firm ground. Error from the measurements can be a huge concern. So, instead of validating the masses of protons and electrons, it's useful to measure the ratio of their masses, a number that is free of the burden of units. Read More...
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Posted on Friday, October 16, 2015 @ 23:12:45 EDT in SpaceTime
by Southern
Owen Hemptonon
Photo by: Shutterstock
QUESTION:
“What is the highest known temperature?”
Asked by: Taylor Sullivan
ANSWER:
Every atom in the universe likes heat. They like heat so much that atoms and subatomic particles vibrate and move around when they’re hot. The hotter they are, the faster they move, and the colder they are, the slower they move. In fact, at absolute zero (0 Kelvin, −273°C, or −460°F), all movements from the atoms stop completely. You can’t get colder than that. It’s like trying to go south from the South Pole, or north from the North Pole; not only won’t it happen, it can’t.
The hottest thing that we know of (and have seen) is actually a lot closer than you might think. It’s right here on Earth at the Large Hadron Collider (LHC). When they smash gold particles together, for a split second the temperature reaches 7.2 trillion degrees Fahrenheit! That’s hotter than a supernova explosion.
But Can We Go Hotter?
Theoretically, yes. The first contender for the hottest temperature is the Planck Temperature, which equals 100 million million million million million degrees, or 1032 K. You just can’t put this kind of temperature into perspective. There’s simply no way to wrap your head around this number. Saying that 1032 K is hot is like saying that the universe takes up some space. (The BBC has a good infographic on the hot and cold extremes, but it’s too large for our site)
This is as hot as you can get in normal physics, because once it gets any hotter, conventional physics just doesn’t work. Weird things happen. Gravitational force becomes as strong as the three other natural forces (electromagnetism, and the strong and weak nuclear forces), and they merge together into one unified force. Understanding how this happens is referred to as the “theory of everything”, the holy grail of modern theoretical physics.
Another contestant for the hottest temperature in the universe comes courtesy of string theorists, who say that it is 1030 K, a little cooler than the contestant above. String theorists believe that the most basic things in the universe aren’t particles, but vibrating strings. They have reason to believe that the maximum temperature achievable is just a bit cooler that the Planck temperature.
You may have heard of the existence temperatures lower than absolute zero; however, negative temperatures are not colder than absolute zero. In fact, negative Kelvin temperatures are hotter than infinite temperatures, and can only happen in systems that have an energy ceiling, and usually only discrete (quantised) systems have that. For more information, check out our article, “Is Absolute Zero Absolute?“
The reason they define the temperatures in this way is because of the mathematical niceness in the formulation of statistical thermodynamics. Also, we have had access to negative temperatures since very long ago, just that we have never reached temperatures so hot.
From Quarks to Quasars
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Posted on Friday, October 16, 2015 @ 22:54:10 EDT in SpaceTime
by Southern
As a black hole loses mass and surface area, it begins to radiate energy more rapidly, thereby heating up.
Temperature is a function of the movement of particles and is measured in a variety of scales including fahrenheit and celsius.
Michael Anissimov
There is no agreed-upon value, among physicists, for a maximum possible temperature. Under the current best-guess of a complete theory of physics, it is the Planck temperature, or 1.41679 x 1032 Kelvins. This translates to about 2.538 x 1032° Fahrenheit. Since the current theories of physics are incomplete, however, it is possible that it could be hotter.
The answer that a typical physicist gives to this question will depend on her implicit opinion of the completeness of the current set of physical theories. Temperature is a function of the motion of particles, so if nothing can move faster than the speed of light, then the maximum may be defined as a gas whose atomic constituents are each moving at the speed of light. The problem is that attaining the speed of light in this universe is impossible; light speed is a quantity that may only be approached asymptotically. The more energy that is put into a particle, the closer it gets to moving at light speed, though it never fully reaches it.
At least one scientist has proposed defining the maximum possible temperature as what someone would get if she took all the energy in the universe and put it into accelerating the lightest possible particle she could find as closely as possible to the speed of light. If this is true, then discoveries about elementary particles and the size/density of the universe could be relevant to discovering the correct answer to the question. If the universe is infinite, there may be no formally defined limit.
Even though infinite temperature may be possible, it might be impossible to observe, making it irrelevant. Under Einstein's theory of relativity, an object accelerated close to the speed of light gains a tremendous amount of mass. That is why no amount of energy can suffice to accelerate any object, even an elementary particle, to the speed of light — it becomes infinitely massive at the limit. If a particle is accelerated to a certain velocity near that of light, it gains enough mass to collapse into a black hole, making it impossible for observers to make statements about its velocity.
The Planck temperature is reached in this universe under at least two separate conditions, according to some theories. The first occurred only once, 1 Planck time (10-43 seconds) after the Big Bang. At this time, the universe existed in an almost perfectly ordered state, with near-zero entropy. It may have even been a singularity, a physical object that can be described by only three quantities: mass, angular momentum, and electric charge. The Second Law of Thermodynamics, however, insists that the entropy (disorderliness) of a closed system must always increase. This means that the early universe had only one direction to go — that of higher entropy — and underwent a near-instantaneous breakdown.
The second set of conditions capable of producing the Planck temperature are those occurring at the final moments of a black hole's life. Black holes evaporate slowly due to quantum tunneling by matter adjacent to the black hole's surface. This effect is so slight that a typical black hole would take 1060 years to radiate away all its mass, but smaller black holes, like those with the mass of a small mountain, may take only 1010 years to evaporate. As a black hole loses mass and surface area, it begins to radiate energy more rapidly, thereby heating up, and at the final instant of its existence, radiates away energy so quickly that it momentarily achieves the Planck temperature.
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