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The Universe Is Accelerating…and No One Knows Why
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REFERENCES
How black holes may be responsible for Dark Energy • How BLACK HOLES May be Responsible for DAR…
Is Dark Energy made of particles? • Is Dark ENERGY made of PARTICLES? The Quin…
What is Dark Energy made of? • What is Dark Energy made of? Quintessence?… CHAPTERS 0:00 The 70% mystery 0:58 How Dark Energy was discovered? 4:26 What could be causing Dark Energy? 6:58 Repulsive Gravity? 10:16 What is the energy made of? 11:56 Evolving Dark energy? Quintesssence 14:18 Could Dark Energy be a particle? 16:43 Could Black Holes cause Dark Energy? SUMMARY Dark energy is one of the greatest mysteries in modern physics. It appears to make up nearly 70% of the universe, yet scientists still do not know what it is. Unlike matter, it does not clump together. Unlike radiation, it does not dilute as space expands. Instead, it causes the expansion of the universe to accelerate, pushing galaxies apart faster over time. The discovery of this acceleration came in the late 1990s when astronomers measured distant Type Ia supernovae, which act as reliable “standard candles.” By comparing their brightness and redshift, researchers could determine how fast the universe expanded at different points in cosmic history. Instead of finding that gravity slowed expansion—as expected—they discovered the opposite: the universe was expanding faster and faster. This unexpected result led to the concept of dark energy, the unknown driver behind cosmic acceleration. One possible explanation is that dark energy is a cosmological constant, represented by the Greek letter lambda in Einstein’s equations. In this model, empty space itself contains a constant energy density known as vacuum energy. Quantum mechanics predicts that empty space is not truly empty; quantum fields constantly fluctuate, producing short-lived “virtual particles.” These fluctuations create energy even in a vacuum. Experiments like the Casimir effect provide evidence that vacuum energy is real. However, this explanation has a major problem. When physicists calculate vacuum energy using quantum theory, the predicted value is about 10¹²⁰ times larger than what observations of the universe allow. This enormous mismatch is widely considered the worst prediction in physics. In general relativity, cosmic acceleration can occur if the universe contains energy with negative pressure. In the Friedmann equation, expansion accelerates when pressure is sufficiently negative relative to energy density. Dark energy appears to have exactly this property, effectively producing a form of repulsive gravity that stretches spacetime. Another possibility is that dark energy is not constant but comes from a dynamic field known as quintessence. In quantum theory, fields can have particle-like excitations, meaning dark energy might correspond to extremely weakly interacting particles. If the strength of this field changes over time, the acceleration of the universe could grow stronger. In extreme scenarios, this could eventually lead to a catastrophic future known as the Big Rip, where galaxies, stars, atoms, and even spacetime itself are torn apart. A more speculative idea suggests a connection between supermassive black holes and dark energy. Some recent studies have observed that black holes appear to grow more massive over billions of years than expected from normal matter accretion alone. Researchers have proposed that black holes might somehow be linked to dark energy, though current evidence only shows a correlation and not a confirmed causal explanation. #darkenergy For now, dark energy remains an observed phenomenon with multiple possible explanations. Whether it is a property of empty space, a new field of physics, or something even deeper, it stands as one of the most profound open questions in cosmology.
CHAPTERS
0:00 The 70% mystery
0:58 How Dark Energy was discovered?
4:26 What could be causing Dark Energy?
6:58 Repulsive Gravity?
10:16 What is the energy made of?
11:56 Evolving Dark energy? Quintesssence
14:18 Could Dark Energy be a particle?
16:43 Could Black Holes cause Dark Energy?
SUMMARY
Dark energy is one of the greatest mysteries in modern physics. It appears to make up nearly 70% of the universe, yet scientists still do not know what it is. Unlike matter, it does not clump together. Unlike radiation, it does not dilute as space expands. Instead, it causes the expansion of the universe to accelerate, pushing galaxies apart faster over time.
The discovery of this acceleration came in the late 1990s when astronomers measured distant Type Ia supernovae, which act as reliable “standard candles.” By comparing their brightness and redshift, researchers could determine how fast the universe expanded at different points in cosmic history. Instead of finding that gravity slowed expansion—as expected—they discovered the opposite: the universe was expanding faster and faster. This unexpected result led to the concept of dark energy, the unknown driver behind cosmic acceleration.
One possible explanation is that dark energy is a cosmological constant, represented by the Greek letter lambda in Einstein’s equations. In this model, empty space itself contains a constant energy density known as vacuum energy. Quantum mechanics predicts that empty space is not truly empty; quantum fields constantly fluctuate, producing short-lived “virtual particles.” These fluctuations create energy even in a vacuum. Experiments like the Casimir effect provide evidence that vacuum energy is real.
Magnetic Monopoles & Magmatter — The Strongest Material That Might Exist
Magnetic monopoles are hypothetical particles with a single magnetic charge — north without south. Predicted by grand unified theories, they may be incredibly massive and could bind together into “magmatter,” an ultra-dense material stronger than anything known in nature.
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/ discord Credits: Magnetic Monopoles & Magmatter — The Strongest Material That Might Exist Written, Produced & Narrated by: Isaac Arthur Select imagery/video supplied by Getty Images Chapters 0:00 Intro 4:52 What Magnetic Monopoles Would Do 10:30 Magmatter: Matter Without Atoms 18:48 Nokia 3,310 19:55 What You Could Build — and What It Would Cost.
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Credits:
Magnetic Monopoles & Magmatter — The Strongest Material That Might Exist.
Written, Produced & Narrated by: Isaac Arthur.
Select imagery/video supplied by Getty Images.
Chapters.
0:00 Intro.
4:52 What Magnetic Monopoles Would Do.
10:30 Magmatter: Matter Without Atoms.
18:48 Nokia 3310
19:55 What You Could Build — and What It Would Cost.
Immune molecule long tied to inflammation may benefit the aging brain
Inflammation in the brain is usually seen as harmful in the aging process—it’s thought to contribute to Alzheimer’s and dementia. But a new study in mice suggests that inflammation, led by an immune molecule called STING (stimulator of interferon genes), might have a role in protecting the aging brain. The findings also have implications for new experimental Alzheimer’s drugs that are designed to block STING.
For the study published in Cell Reports, scientists at Tufts University School of Medicine examined brain function, inflammation, and movement in mice genetically engineered to lack STING, compared with normal controls. They found that mice without STING had worse memory and movement problems, mimicking the senility and frailty seen in people with dementia and Alzheimer’s disease.
“Our data suggest that the inflammatory processes that STING supports may actually be necessary for the brain to stay healthy and in balance during old age,” says Shruti Sharma, an assistant professor of immunology at Tufts University School of Medicine and the study’s senior author.
HES1 regulates bone marrow mesenchymal stromal cell function by suppressing NFATc2-mediated inflammation
The bone marrow microenvironment plays a central role in hematopoiesis and hematologic diseases. A new study investigates how HES1 regulates mesenchymal stromal cell function and inflammatory signaling, exploring a novel pathway that may shape hematopoietic homeostasis and disease biology.
The Notch target gene, Hairy and enhancer of split-1 (HES1), encodes a basic helix-loop-helix transcriptional repressor that influences cell proliferation and differentiation in embryogenesis. Our previous studies indicate that HES1 is required for hematopoiesis under stress conditions. However, the role of HES1 in bone marrow (BM) microenvironment remains to be elucidated. By employing a BM niche specific Hes1 knockout mouse model, here we have investigated the role of HES1 in regulating mesenchymal stromal cell (MSC) homeostasis and their hematopoiesis supportive function. We found that while HES1 is not essential in MSC in supporting steady-state hematopoiesis, Hes1fl/fl Prx1Cre mice are hypersensitive to lipopolysaccharide (LPS) challenge. Deletion of Hes1 in the BM reduces MSC frequency and affects MSC self-renewal and proliferation. Hes1-deficient MSC are less functional in supporting hematopoiesis both in vitro and ex vivo. Transcriptome analysis reveals that disruption of Hes1 in the BM stroma alters the expression of genes critical for cellular metabolism and inflammation. Pharmacological blockage of inflammation rescues Hes1-KO MSC phenotype and improves their hematopoiesis supportive function. Mechanistically, we show that HES1 binds to the conserved E boxes in the promoter of NFATc2, a member of the AT-rich interaction domain superfamily of DNA binding protein, to suppress NFATc2-mediated inflammation. Taken together, our study unveils a pivotal role for HES1 in maintaining BM MSC hemostasis and regulating their hematopoiesis supportive function.
Hematopoietic stem cells (HSC), which give rise to all blood cells, are supported by specialized microenvironments, known as niches, within bone marrow (BM) cavities.1,2 These niches are composed of various non-hematopoietic components, including endosteal and sinusoidal endothelial cells, mesenchymal stromal cells (MSC), and osteoblast-lineage cells.3,4 Studies have shown that BM-derived non-hematopoietic stromal cells are capable of supporting long-term hematopoiesis both in vitro and in vivo. Disruptions to these non-hematopoietic cells within the BM niche may negatively impact hematopoiesis. However, the precise mechanism is still poorly understood.
Notch signaling, mediated by a family of highly conserved receptors, plays a critical role in maintaining bone homeostasis, partly through regulating osteoblast differentiation from MSC, whose activation is induced by their specific ligands.5,6
Mirtazapine for Methamphetamine Use Disorder: A Randomized Clinical Trial
In adults with methamphetamine use disorder, mirtazapine reduced methamphetamine use by approximately two more days per month vs placebo, with no unexpected safety concerns.
Main Outcomes and Measures The primary end point was the change in days of methamphetamine use in the past 28 days from baseline to week 12. Secondary end points were depression, insomnia, HIV risk behavior, quality of life, and methamphetamine-negative oral fluid samples.
Results Of 344 participants randomized, 339 participants received the intervention (167 in the placebo group and 172 in the mirtazapine group). Mean (SD) age was 42.0 (8.6) years, 126 participants (37.2%) were female, and participants had used methamphetamine for a median (IQR) of 24 days (17−28) of the past 28 days at baseline. The mean reduction in days of methamphetamine use from baseline to week 12 was greater in the mirtazapine group (7.0 days of 28 days) than in the placebo group (4.8 days of 28 days; mean difference, 2.2 days; 95% CI, −4.2 to −0.2 days; P = .02). More participants in the mirtazapine group reported drowsiness (47% vs 33%) and weight gain (10% vs 3%). Forty participants (23%) discontinued mirtazapine due to adverse events compared to 25 participants (15%) in the placebo group. No significant effects of mirtazapine on secondary end points were found.
Conclusions and Relevance In this parallel-group randomized clinical trial, mirtazapine delivered in routine clinical practice reduced methamphetamine use in adults with methamphetamine use disorder. No unexpected safety concerns delivering mirtazapine in this setting were found; this finding has important clinical implications in the absence of any approved pharmacotherapies for methamphetamine use disorder.
Your brain may be as blind to reality as a grasshopper is to calculus | Michelle Thaller
In the distant future could we redesign the brain for more understanding of the universe.
Become a Big Think member to unlock expert classes, premium print issues, exclusive events and more: https://bigthink.com/membership/?utm_… What if the universe was never designed to be understood? Astronomer Michelle Thaller makes a case that the human brain, despite its complexity, may be as poorly equipped to grasp ultimate reality as a grasshopper is to.
What if the universe was never designed to be understood? Astronomer Michelle Thaller makes a case that the human brain, despite its complexity, may be as poorly equipped to grasp ultimate reality as a grasshopper is to grasp calculus.
About Michelle Thaller:
Michelle Thaller is an astronomer and Assistant Director for Science Communication at NASA’s Goddard Space Flight Center.
The frequency-dependent effects of primary hand motor cortex stimulation on volitional finger movement
[Brain stimulation] Taquet et al.: “The effect of motor cortex stimulation on finger flexion is frequency dependent.”
We conducted a prospective study in human patients undergoing awake craniotomies to examine whether the effects of cortical stimulation in hand primary motor cortex (M1) can be frequency dependent and inhibitory.
In 11 participants undergoing clinically indicated awake craniotomies, we delivered bursts of 1–333 Hz stimulation during a finger-flexion task. Synchronized electrocorticography (ECoG), finger joint kinematics, electromyography (EMG), and video were recorded.
Inability to flex the index finger during subthreshold stimulation was noted in 3 participants at frequencies 250 Hz when the electrodes were in locations that induced extension of the forefinger at higher amplitudes. Other than these trials, all stimulation events either induced muscle contractions or had no measurable effect.