[neilep (OP)]

White Holes

White holes are a fascinating concept in astrophysics. Essentially, they are the opposite of black holes, spewing matter and energy out rather than pulling it in. According to Einstein's theory of general relativity, a white hole would have a negative mass-energy density. If they exist, they would be surrounded by an event horizon, but with a boundary that nothing could enter, rather than escape. Although still purely theoretical, white holes have sparked interesting discussions amongst physicists. Could they be the "other side" of black holes, or the source of gamma-ray bursts? Exploring these ideas has led to a deeper understanding of the fundamental laws of physics and the behaviour of the universe.

However, it's worth noting that white holes may not necessarily require a negative energy density. In the context of the Schwarzschild solution, which describes "Eternal Black Holes", the mass-energy density is actually zero throughout the spacetime manifold. Nevertheless, some solutions to the Einstein Field Equations do feature stable and traversable wormholes that connect black holes to white holes, and these do require negative energy density. Despite this clarification, the idea of white holes remains fascinating, and it's an interesting topic to explore further.

[neilep (OP)]

Xenon


Xenon is a rare and highly unusual noble gas that makes up only about 0.0000087 parts per million (ppm) of the Earth's atmosphere.

What's remarkable about xenon is that it's one of the few elements that can form compounds with other elements, despite being a noble gas. This is due to its unique electron configuration, which allows it to react with other elements under certain conditions.

Interestingly, xenon has a mix of stable and radioactive isotopes. While most natural xenon is stable, a small percentage of its isotopes have incredibly long half-lives, ranging from 2 x 10^21 to 2 x 10^22 years.

Despite its rarity, xenon has several practical applications, including its use in high-intensity lamps, lasers, and even as a general anaesthetic.

[neilep (OP)]

please note, this is an open-to-all thread...if you want to contribute then do so, next letter is Y.

[Halc]

Yaws is an infectious disease which is rarely fatal but can leave an indelible mark (skin and bones), especially on young victims.

It is interesting due to being the second disease targeted for eradication (after smallpox).  This was first attempted in the 50s, and nearly wiped out, not by vaccines, but with an inexpensive antibiotic.  But as cases dropped to near zero, interest was lost and funding dried up, and it has reappeared in multiple locations, especially poor tropical areas.
The takeaway is not to forget the endgame.  They almost had it, and now they need to start over, and then only if they care.

Wiping this out can be done, but not by ignoring it.  Currently, polio is the only disease thus being targeted.

[paul cotter]

Yaws is caused by an organism identical or nearly identical with that of syphilis. Yaws is NOT a venereal disease. There are several other non venereal diseases caused by such organisms- treponema pallidum/pertenue but I have long forgotten them, I think one of them is called "pinta". Very late addition: the other non venereal treponema infection that I could not remember the name of is "bejel".

[alancalverd]

Pinta was named after Columbus' third ship. Santa Maria, Nina and Pinta took devastation and superstition to the Americas and returned with various transmissible diseases.

[neilep (OP)]

Zooplankton: The Tiny, Shimmering Heroes of Our Oceans!

Zooplankton, the tiny, usually microscopic, animals that drift in the water column of our oceans.

These tiny creatures, which include krill, copepods, and jellyfish larvae, play a vital role in the marine ecosystem. They're a crucial food source for many larger animals, from fish and squid to whales and seabirds.

But zooplankton are more than just a meal ticket. They're also incredibly important for the health of our oceans. By grazing on phytoplankton, they help regulate the ocean's nutrient cycles and prevent excessive algal blooms.
 Zooplankton are often bioluminescent, emitting a dazzling display of light when disturbed.

[neilep (OP)]

Hi,

   I'm not sure that white holes HAVE to have a negative energy density either.   They can be just a region on the spacetime diagram for the maximally extended Schwarzschild solution.   This is more often called the solution describing "Eternal Black Holes".

  The Schwarzschild solution is a vacuum solution of the Einstein Field Equations, that is to say there is precisely zero mass-energy density throughout the entire spacetime manifold described.   To be very clear about this, no negative energy density is really required or will be exhibited anywhere in the spacetime described by this solution.

   None-the-less there are some more interesting solutions of the Einstein Field Equations featuring stable and traversable wormholes that link something like a black hole to a white hole, where negative energy density is required.  So I can understand how some articles would lead you to believe a negative energy density is required for any white hole.   It's also more interesting just to leave your statement in there, overzealous attention to accuracy kills interest.  Indeed, it's sufficiently interesting and well written that I move it should be placed as the first entry in the A-Z,  under the title  "A White Hole".   Then we can have an entry for "Black Hole" under the letter B,  "Can you believe this thing about Black Holes" for the letter C.....and I think you can see where there is going....

Best Wishes.

rewritten

[neilep (OP)]

.
Aurorae, also known as the Northern or Southern Lights, are a breath-taking natural phenomenon that occurs when charged particles from the sun interact with the Earth's magnetic field and atmosphere. This collision causes the particles to be redirected towards the poles, exciting the atoms and molecules and causing them to emit light, which appears as a kaleidoscope of colours dancing across the polar skies. The colour of the aurora depends on the energy of the particles and the altitude at which they collide with the atmosphere, with green being the most common colour, and red, blue, and violet also appearing at different altitudes

[neilep (OP)]

The Baffling Behaviour of Ball Lightning

Ball lightning is a rare and poorly understood atmospheric electrical phenomenon that has been reported throughout history. It appears as a glowing, floating sphere of light, usually during thunderstorms.

Witnesses describe ball lightning as ranging in size from a few centimetres to several metres in diameter, with some reports suggesting it can move slowly or rapidly, even bouncing off surfaces.

Despite extensive research, scientists have yet to explain the exact cause of ball lightning. Theories range from unusual electrical discharges to chemiluminescent reactions, but none have been proven conclusively.

The mystery surrounding ball lightning has captivated scientists and the public alike, inspiring ongoing research and investigation.

[paul cotter]

It has been said that there are as many theories on the subject of ball lightning as there are researchers into this phenomenon. It is a real phenomenon.

[neilep (OP)]

 Cryptobiosis is a near-miraculous state where life practically pauses ? an organism shuts down its metabolism to almost zero, surviving in extreme conditions that would kill nearly anything else.
Some tiny creatures, like tardigrades (aka ?water bears?), can survive being boiled, frozen, irradiated, dehydrated, and even exposed to the vacuum of space ? all thanks to cryptobiosis. In this state, they can dry out completely, roll into a tiny ball called a tun, and lie dormant for decades, possibly even centuries.
Then, with just a drop of water, they wake up ? as if nothing happened. It?s like biological time travel.
Scientists are studying cryptobiosis to unlock secrets for long-term space travel, organ preservation, and even suspended animation in humans. The idea of "pausing" life, then restarting it, isn't just science fiction ? it's already happening in nature!

[neilep (OP)]

Dark Matter: The Invisible Majority of the Universe
Dark matter is a mysterious form of matter that does not emit, absorb, or reflect light, making it completely invisible to current telescopes. Although we cannot see it directly, scientists know it exists because of its gravitational effects on visible matter, such as stars and galaxies. Dark matter is thought to make up about 27% of the universe?s total mass-energy content, vastly outweighing the ordinary matter we are familiar with.
Understanding dark matter is one of the biggest challenges in modern cosmology and particle physics. Researchers are exploring various candidates for dark matter particles, including WIMPs (Weakly Interacting Massive Particles) and axions, but so far, it remains elusive. Unravelling the nature of dark matter could unlock fundamental secrets about the structure, origin, and fate of the cosmos.

[neilep (OP)]

Epigenetics: How Environment Influences Our Genes

Epigenetics is a rapidly growing field of science that explores how behaviours and environmental factors can cause changes in the way our genes work?without altering the DNA sequence itself. Unlike genetic changes, which are permanent, epigenetic changes are reversible and can be influenced by factors such as diet, stress, exposure to toxins, and lifestyle choices.

One of the most studied epigenetic mechanisms involves the addition of chemical tags, such as methyl groups, to DNA or the proteins around which DNA is wrapped. These tags can turn genes on or off, affecting everything from development and ageing to susceptibility to diseases like cancer and diabetes.

What makes epigenetics especially fascinating is its role in inheritance. Some epigenetic markers can be passed from one generation to the next, meaning a parent?s experiences?such as famine or trauma?may impact their offspring?s health.

[Halc]

Fermi Paradox

The Fermi paradox, named after Enrico Fermi, contradicts the lack of evidence of extraterrestrial civilization with the seeming high probability of it.

The argument goes roughly like this:
There's lots of stars, a good percentage with viable planets for life.
Some of that life must have evolved intelligence, interstellar travel, etc and must have populated the galaxy.
Where are they?

Taking apart the paradox requires debunking one of several assumptions made.

Maybe Earth is really unique and those conditions simply don't occur as frequently as Fermi calculated.

The argument assumes that technology is sustainable, but this is questionable since resources are limited and technology falls permanently once they are exhausted.

Maybe they're out there but are good at hiding it.  The ones that are not soon get eliminated.

[Halc]

Ghost flower

The Ghost Flower, Ghost Plant, or Indian Pipe, is one of few plants that lacks chlorophyll and thus does not photosynthesize, so it has no need of leaves.  It has one flower that looks like a snowdrop stuck onto a white stem.

It is considered an epiparasite, meaning it is a parasite of a parasite.  Fungi below the surface feed on live roots of plants, and the ghost flower is a parasite of that fungus, deriving all its nutrition from that fungus.

Why am I bringing this up?  Took a walk with my daughter who spots this sort of thing.

ghostFlower.jpg (84.44 kB . 540x575 - viewed 349 times)
Shot taken on our walk, July 5.

[paul cotter]

In this part of the world we have the broomrapes(what a dubious name!) which also lack chlorophyll but may or may not have the same metabolism as the ghost plant.

[neilep (OP)]

Hydrology is the branch of science that studies water on Earth?how it moves, where it is found, and how it interacts with the environment. Hydrologists examine the water cycle, including processes like evaporation, precipitation, and runoff, to understand how water shapes landscapes and supports life. This field is crucial for managing water resources, predicting floods and droughts, and addressing environmental challenges such as climate change and pollution. By understanding hydrology, scientists can help ensure clean and reliable water supplies for people, agriculture, and ecosystems.

[neilep (OP)]

Invisibility is scientifically possible ? at least on a small scale.
Researchers have developed ?invisibility cloaks? using metamaterials ? specially engineered substances that can bend light around an object. These materials manipulate electromagnetic waves to make objects effectively invisible to certain wavelengths, like microwaves or infrared.
While full human-scale invisibility isn?t here yet, invisibility at microscopic or specific light frequencies is already a reality in labs!

[neilep (OP)]

Jellyfish Anatomy

Jellyfish are characterised by:

1. Umbrella-shaped Bell: Their distinctive body shape, which provides buoyancy and movement.
2. Stinging Tentacles: Jellyfish use these tentacles to capture prey and defend against predators.
3. Bioluminescence: Many jellyfish species have the ability to produce light, which helps them communicate, attract prey, or evade predators.

Jellyfish Life Cycle

Jellyfish undergo a complex life cycle, which includes:

1. Polyp Stage: Jellyfish begin as polyps, attached to a surface, feeding on small prey.
2. Medusa Stage: As they mature, polyps transform into medusae, the free-swimming, bell-shaped form we commonly associate with jellyfish.
3. Reproduction: Jellyfish reproduce through a process called transdifferentiation, where they can transform their adult form back into the polyp stage.

Jellyfish in the Ocean

Jellyfish play a vital role in the marine ecosystem:

1. Food Source: Jellyfish serve as a food source for various marine animals, from sea turtles to fish.
2. Nutrient Cycling: Jellyfish help cycle nutrients through the ocean, contributing to the health of marine ecosystems.

Fun Facts about Jellyfish

- Jellyfish have been to space! In 1991, NASA sent jellyfish to space to study their behaviour in zero gravity.
- Jellyfish have no brain, but they can still navigate and respond to stimuli.
- The largest jellyfish species, the lion's mane jellyfish, can have a bell up to 7 feet wide!