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July 6th, 2019, 21:34
Some events only appear to be random because we can't determine all parameters with sufficiently accuracy. Events like throwing dice, coins comes to mind. For practical purposes, they will remain random because we never will be able to achieve the necessary precision. As such, events like these are a bit related to chaos.

But AFAIK there are some events that are genuinely random, and among those are radioactive decay and other quantum physics processes.

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July 6th, 2019, 21:42
In other words, chaos is the lack of precision
- ilm, 2019
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July 6th, 2019, 21:43
Yes, I think quantum theory takes the view that there is something we could consider true randomness, from our point of view (though I don't think it takes a view necessarily on the fundamental nature of randomness, rather that it considers our ability to measure things is probabilistic). If you really want true random number generator, you want to be using quantum processes of some kind. This crops up in cryptography, where flaws in the psuedorandom number generation of computers are a way in which a code might be broken.
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Last edited by Ripper; July 7th, 2019 at 00:59.
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July 13th, 2019, 12:54
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July 14th, 2019, 09:24
Why the universe seems so strange
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July 19th, 2019, 11:11
Permanent liquid magnets have now been created in the lab
Liquid magnets could help soft robots get around, says Remi Dreyfus, a chemical physicist with the French national research agency CNRS, who is currently conducting research at a joint CNRS-Solvay-University of Pennsylvania lab in Bristol, Pa. Rather than rely on inflatable air pouches or electric current to move — which tether robots to wires or tubes — bots injected with liquid magnetic material could be remotely controlled with magnetic fields (SN Online: 9/19/18).

These droplets might also be combined to manufacture new kinds of materials, such as magnetic sponges or stretchy polymers, says Dreyfus, whose commentary on the study appears in the same issue of Science. “I’m sure people will have many ideas” for how to put ultrasoft magnets to work, he says.
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July 19th, 2019, 12:24
Originally Posted by Eye View Post
Permanent liquid magnets have now been created in the lab
It would be interesting to know the strength of the magnetic field of this type of magnet. If strong enough, it could possible find some use in MRI.

pibbur has googled, but didn't find anything about this

EDIT: Probably not usable for MRI. Most MRI-machine uses super-cooled electromagnets, with strength in the 1-3 Tesla range. Permanent magnetic fields are in general too weak for genereal purpose MRI's, or they will be very huge and bulky. So, Liquid MRI seems at the moment not to be feasible.
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Last edited by pibbur who; July 19th, 2019 at 12:36.
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July 19th, 2019, 12:39
The news article is ‘hot’, see the dates:
X. Liu et al. Reconfigurable ferromagnetic liquid droplets. Science. Vol. 365, July 19, 2019, p. 264. doi: 10.1126/science.aaw8719.

R. Dreyfus. An attractive, reshapable material. Science. Vol. 365, July 19, 2019, p. 219. doi: 10.1126/science.aax8979.

So that is perhaps the reason you were not able find anything?
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July 19th, 2019, 13:17
Originally Posted by Eye View Post
The news article is ‘hot’, see the dates:
X. Liu et al. Reconfigurable ferromagnetic liquid droplets. Science. Vol. 365, July 19, 2019, p. 264. doi: 10.1126/science.aaw8719.

R. Dreyfus. An attractive, reshapable material. Science. Vol. 365, July 19, 2019, p. 219. doi: 10.1126/science.aax8979.

So that is perhaps the reason you were not able find anything?
Probably.

BTW, the strongest commerically available permanent magnets are neodymium magnets. Those are available in up to 1.4 Tesla strength. You can get neodynium magnets for 60USD on Amazon, but I hope they are not that strong, as 1.4 Teslas are dangerous. Being trapped between two magnets of that strength can break bones, and there have actually been deaths. And of course, your credit cards will be toast. Definitely not toys.

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July 19th, 2019, 14:05
I have bought a neodymium magnet recently, a small one: 40x15x9 mm. It is 115 g, holds 50 kg, an n40 magnet.
I dropped a pruning shears in my deep pond, and it worked wonderfully.

Magnetic fishing has gotten quite popular in The Netherlands btw. The authorities are not thrilled about it, because people are fishing up stuff from WWII as well, grenades and bombs, that could go off when moved.
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July 19th, 2019, 14:16
A magnetar has a field strength of up to 10^11 Tesla, which (according to Wikipedia) would be lethal at as far as 1000 km distance due to "distorting the electron clouds of the subject's constituent atoms, rendering the chemistry of life impossible." And "At a distance of halfway from Earth to the moon, a magnetar could strip information from the magnetic stripes of all credit cards on Earth."

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August 8th, 2019, 12:12
NEWS RELEASE 7-AUG-2019
Dark matter may be older than the big bang, study suggests
Using a new, simple mathematical framework, the study shows that dark matter may have been produced before the Big Bang during an era known as the cosmic inflation when space was expanding very rapidly. The rapid expansion is believed to lead to copious production of certain types of particles called scalars. So far, only one scalar particle has been discovered, the famous Higgs boson.

"We do not know what dark matter is, but if it has anything to do with any scalar particles, it may be older than the Big Bang. With the proposed mathematical scenario, we don't have to assume new types of interactions between visible and dark matter beyond gravity, which we already know is there," explains Tenkanen.

While the idea that dark matter existed before the Big Bang is not new, other theorists have not been able to come up with calculations that support the idea. The new study shows that researchers have always overlooked the simplest possible mathematical scenario for dark matter's origins, he says.

The new study also suggests a way to test the origin of dark matter by observing the signatures dark matter leaves on the distribution of matter in the universe.

"While this type of dark matter is too elusive to be found in particle experiments, it can reveal its presence in astronomical observations. We will soon learn more about the origin of dark matter when the Euclid satellite is launched in 2022. It's going to be very exciting to see what it will reveal about dark matter and if its findings can be used to peak into the times before the Big Bang."
Source:
https://www.eurekalert.org/pub_relea…-dmm080719.php

Study Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA:
Dark matter (DM) may have its origin in a pre-big-bang epoch, the cosmic inflation. Here, we consider for the first time a broad class of scenarios where a massive free scalar field unavoidably reaches an equilibrium between its classical and quantum dynamics in a characteristic timescale during inflation and sources the DM density. The study gives the abundance and perturbation spectrum of any DM component sourced by the scalar field. We show that this class of scenarios generically predicts enhanced structure formation, allowing one to test models where DM interacts with matter only gravitationally.
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August 8th, 2019, 12:45
Using a new, simple mathematical framework, the study shows that dark matter may have been produced before the Big Bang during an era known as the cosmic inflation when space was expanding very rapidly. The rapid expansion is believed to lead to copious production of certain types of particles called scalars. So far, only one scalar particle has been discovered, the famous Higgs boson.
I'm a bit puzzled by what they're getting at, here. Cosmic inflation is something that occurred immediately after the big bang, AFAIK.
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August 8th, 2019, 12:54
Originally Posted by Ripper View Post
I'm a bit puzzled by what they're getting at, here. Cosmic inflation is something that occurred immediately after the big bang, AFAIK.
Yeah, that seems wrong. Big bang, then inflation….I've never heard of anyone stating it the other way around. I have read about cosmic bounce models which allow information to persist across a big bang/crunch cycle - these have been around for awhile. They seems to go in and out of fashion - a neat way of sidestepping the issue of 'where did it all come from?'.
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August 8th, 2019, 13:32
Yeah, the cyclical models are quite interesting. There's another version where the universe expands forever, and once we get to the point of only massless particles, too far apart to ever interact, then the ideas of scale and time becomes meaningless - that the unimaginably vast could just as well be considered the infinitesimally small. So, the final phase of the fully expanded universe becomes the starting condition for the next "big bang".

EDIT: Link here, if interested.

I tend to think that we have to accept that something "just is". If we insist on the universe being contingent upon a prime mover, we have an infinite regression of "but where did that come from?"
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August 8th, 2019, 14:14
Originally Posted by pibbur who View Post
Wednesday's xkcd belongs here.



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Of course somebody had to come up with this:


pibbur who wishes it was him. Too late now.

PS. Saw a TV program, mostly about food, partially about a telescope in the Antarctic. Seem like they're planning to take a picture of Saggitarius A* (the hole in the centre of the Milky Way). now. Can't wait to see that. DS
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August 8th, 2019, 16:27
That looks like an eye.
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August 15th, 2019, 14:18
New Zealand: Do not eat the sexy pavement lichen.

https://www.theguardian.com/world/20…avement-lichen
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August 16th, 2019, 02:10
Very cool interview with a prominent advocate for fighting aging. Talking about "life extension escape velocity", cryonics and general perspectives of the future.

loading…
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August 16th, 2019, 10:35
Originally Posted by Ripper View Post
New Zealand: Do not eat the sexy pavement lichen.

https://www.theguardian.com/world/20…avement-lichen
Ah, I just have this great idea about cleaning up our urban environment. Soooo…

Did you guys know that old remains of chewing gum stuck to the pavement have properties similar to viagra? It's been proven by research.

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