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Carl Schoonover and Andrew Fink are confused. As neuroscientists, they know that the brain must be flexible but not too flexible. It must rewire itself in the face of new experiences, but must also consistently represent the features of the external world. How? The relatively simple explanation found in neuroscience textbooks is that specific groups of neurons reliably fire when their owner smells a rose, sees a sunset, or hears a bell. These representations—these patterns of neural firing—presumably stay the same from one moment to the next. But as Schoonover, Fink, and others have found, they sometimes don’t. They change—and to a confusing and unexpected extent.

Schoonover, Fink, and their colleagues from Columbia University allowed mice to sniff the same odors over several days and weeks, and recorded the activity of neurons in the rodents’ piriform cortex—a brain region involved in identifying smells. At a given moment, each odor caused a distinctive group of neurons in this region to fire. But as time went on, the makeup of these groups slowly changed. Some neurons stopped responding to the smells; others started. After a month, each group was almost completely different. Put it this way: The neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time.

This is, of course, just one study, of one brain region, in mice. But other scientists have shown that the same phenomenon, called representational drift, occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery. 

(from https://www.theatlantic.com/science/archive/2021/06/the-brain-isnt-supposed-to-change-this-much/619145/)

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Physicists Study How Universes Might Bubble Up and Collide

Charlie Wood, Contributing Writer

Quanta Magazine, January 25, 2021


The researchers realized that while space may have stopped inflating here (in our bubble universe) and there (in other bubbles), quantum effects should continue to inflate most of space, an idea known as eternal inflation.

The difference between bubble universes and their surroundings comes down to the energy of space itself. When space is as empty as possible and can’t possibly lose more energy, it exists in what physicists call a “true” vacuum state. Think of a ball lying on the floor — it can’t fall any further. But systems can also have “false” vacuum states. Imagine a ball in a bowl on a table. The ball can roll around a bit while more or less staying put. But a large enough jolt will land it on the floor — in the true vacuum.

In the cosmological context, space can get similarly stuck in a false vacuum state. A speck of false vacuum will occasionally relax into true vacuum (likely through a random quantum event), and this true vacuum will balloon outward as a swelling bubble, feasting on the false vacuum’s excess energy, in a process called false vacuum decay. It’s this process that may have started our cosmos with a bang. “A vacuum bubble could have been the first event in the history of our universe,” said Hiranya Peiris, a cosmologist at University College London.

But physicists struggle mightily to predict how vacuum bubbles behave. A bubble’s future depends on countless minute details that add up. Bubbles also change rapidly — their walls approach the speed of light as they fly outward — and feature quantum mechanical randomness and waviness. Different assumptions about these processes give conflicting predictions, with no way to tell which ones might resemble reality. It’s as though “you’ve taken a lot of things that are just very hard for physicists to deal with and mushed them all together and said, ‘Go ahead and figure out what’s going on,’” Braden said.

(from https://www.quantamagazine.org/physicists-study-how-our-universe-might-have-bubbled-up-in-the-multiverse-20210125/)

 

 

 

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Dark matter makes up the lion's share of a galaxy's mass, and it's critical to hold a galaxy's stars, gas and dust together. So, when scientists find evidence twice over that a certain galaxy seems to have a tiny fraction of the dark matter it ought to have, astronomers sit up and pay attention.

Astronomers first suspected something was amiss with DF2 as early as 2018, when they peered at the galaxy using a number of different telescopes, including the Hubble Space Telescope. The researchers didn't entirely know what to make of the strange galaxy, so in 2020, they used Hubble to take another, longer look.
4RWNq8gHw4xSZSfMK2BiXY-970-80.png.webp

The Hubble image of the galaxy DF2 highlighting some of the red giant stars astronomers used to pinpoint the distance from Earth to DF2. (Image credit: NASA/ESA/STScI/Zili Shen (Yale)/Pieter van Dokkum (Yale)/Shany Danieli (IAS)/Alyssa Pagan (STScI))

The greater distance confirms the researchers' initial suspicions that there is much less dark matter in the galaxy than expected.

"For almost every galaxy we look at, we say that we can't see most of the mass because it's dark matter," van Dokkum said in the statement. "... But in this case, what you see is what you get... That's it. It’s not just the tip of the iceberg, it's the whole iceberg."

In addition to DF2, the list of known dark-matter-deficient galaxies is only growing. For instance, much closer to DF2 lies another ultra-diffuse galaxy, DF4, which seems to share its neighbor's dearth of dark matter. We aren't sure how this might have happened, partly since we don't really know how ultra-diffuse galaxies form. 

(from https://www.space.com/hubble-studies-galaxy-missing-dark-matter)

 

Edited by Chroma Starlight
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On 10/24/2020 at 9:11 AM, Rolig Loon said:

Well, you did say "...something that you think changes the way you can see, understand, at or experience the world."  Scripters deal with rotations every time we have to open a door or make a vehicle change direction, and this one concept is a key to understanding how they work... 

 

I love the fourth dimension theory!

I came across a fascinating video about it a few years ago.

OMG I cannot believe I found it!

I had to use "scientists explain the 4th dimension theory", to come across it amongst the many about this topic.

This is a film and it's really amazing, beautiful captures, crisp. Just amazing! I think you will love it and it's easy to understand with how she explains it.

 

 

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On 6/13/2021 at 12:15 PM, Chroma Starlight said:

called representational drift, occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery. 

I love how we haven't been able to dissect the integral part of ourselves that controls everything we experience. It might not be meant to be discovered. Enjoy the process as it goes on its way, its "mysterious" pondering ways.

Although it would be fascinating to unlock every chamber in the brain, to know the unknowable, to perhaps find there is more to what we have found thus far.

Wouldn't it be neat to discover that there is indeed a wealth of information that we have yet to unlock, that could bring us to a new awareness about life itself? 

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On 6/3/2021 at 12:42 PM, Chroma Starlight said:

This is a great and innovative approach to understanding a person's mind processes and perhaps how it could unravel the person's condition to create new treatments to aid those who suffer with this debilitating condition.

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1 hour ago, Kytteh Wytchwood said:

I love the fourth dimension theory!

I came across a fascinating video about it a few years ago.

OMG I cannot believe I found it!

I had to use "scientists explain the 4th dimension theory", to come across it amongst the many about this topic.

This is a film and it's really amazing, beautiful captures, crisp. Just amazing! I think you will love it and it's easy to understand with how she explains it.

 

That's snake oil salesman Klee Irwin's "Quantum Woo", Kytteh.

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