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Physics, Astronomy & Cosmology / Re: What is a black hole made of?

« on: Today at 03:56:17 »

What is a black hole formed from?

Most of the black holes formed today come from the collapse of the core of a star.
- The temperature of a star is so high that electrons are separated from the nucleus of an atom, forming a plasma
- Since electrons & nuclei are "sub-atomic", you could say that black holes are formed from sub-atomic particles.
- As the core of the star collapses, many of the protons and electrons are converted to neutrons (a sub-atomic particle), releasing a burst of neutrinos (which mostly escape). I vaguely recall that around 90% of the energy released in a supernova is in the form of neutrinos.

There is some speculation from cosmologists that, during the early stages of the Big Bang, some black holes may have formed even before protons, electrons and neutrons were  formed. Atoms can't exist at these extreme energy levels, so you might call these "pre-atomic" particles(?)
- Cosmologists think that some of these relic black holes may still exist today

black holes might be viewed not as objects at all but  as extreme spacetime  curvature

Once a black hole has formed, the extreme curvature of spacetime effectively pinches off the singularity from the view of those outside the event horizon.
- At this stage, the only thing you know about the black hole is its mass, spin, and electrical charge.
- At this point, it really doesn't matter what the black hole formed from, because that is not detectable from outside.

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Physics, Astronomy & Cosmology / Re: Why is the Barycenter Equation expressed in terms of mass?

« on: Today at 03:30:58 »

Why is the Barycenter Equation expressed in terms of mass?

Because it literally means "the center of mass"...
- I guess if you wanted to be pedantic, it might be debatable whether the "bary-" part is talking about mass or weight...
- but since the ancient Greeks breathed air and lived within a couple of kilometers of sea level, it doesn't make too much of a difference
- unless you were trying to detect an adulterated gold crown!

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Geek Speak / Re: Going from android to Iphone

« on: Yesterday at 10:07:38 »

I had a recent changeover problem between laptops.
- Microsoft teams refused to say I was active on the new laptop
- Because I was still signed in on the old laptop (even though it was powered down)

It seems that Microsoft Teams can cope with someone having both a laptop and a smartphone
- But someone with two laptops is unthinkable!

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COVID-19 / Re: How could we say if omicron variants are intrinsically less pathogenic?

« on: Yesterday at 10:04:16 »

The newer Omicron variants are reportedly more infectious, and able to reinfect some people who have previously had Omicron.
- That is leading to increasing death rates in many countries
- But the previous Omicron infection should provide some protection against severe disease.

Mask usage is dropping due to lack of public health messages and public exhaustion, so this doesn't help.

The most likely way we will get some useful more data is to:
- infect lab animals (bearing in mind that lab animals are not an exact analogue of a human)
- infect human cell cultures (bearing in mind that a cell culture is not an exact analogue of a whole human)

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Physiology & Medicine / Re: Why where the native Americans so vulnerable to disease?

« on: 26/06/2022 11:47:41 »

are ebola survivors not immune?

Ebola is quite a vicious virus, killing about half of those infected.
- If you don't overcome the virus, it kills quite rapidly
- So it becomes a race between your immune system generating effective antibodies - or the virus killing you first
- Like COVID, Ebola has genes that inhibit the body's innate immune system, allowing it to take over more quickly
- Ebola directly attacks macrophages (white blood cells), which form part of the immune system
- Before a vaccine was available, they used recovered patients to nurse the sick - they didn't need such fancy protective equipment
- They also tried antibody transfusions from recovered patients, to keep the virus under control until the patient could generate their own antibodies.

These days, ring vaccination is used on anyone who may have come into contact with an ebola patient.
- This is difficult to administer, since there is an ongoing uncivil war in the area...
See:  https://en.wikipedia.org/wiki/Ebola

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Technology / Re: Are solar panels worthwhile?

« on: 26/06/2022 11:33:05 »

The cost of natural gas in the eastern states of Australia is tied to the international price.
- The smarter government in Western Australia decreed that all gas exporters had to reserve 15% of production for local use, at a price related to the cost of production, so they are not suffering like the Eastern states.

So gas prices have spiked in the Eastern states:
- Since peak-hour generation is provided by gas turbines, they are bidding higher prices to stay profitable
- Several coal-fired power stations were down for maintenance, when a couple of others broke down, significantly cutting supply (this is how Enron became so profitable!)
- So the energy regulator shut down the spot market for electricity, capped the wholesale price, and told the gas generators to start producing (reimbursement to be worked out later...)
- Some of the coal generators are now back on line, and the electricity market is operating again. Blackouts narrowly averted.

Apparently one contributor to the problem has been the Green party; looking for excess purity, they refused to fund gas-fired generators to be backup supply.
- I thought most people realized that gas is going to be an important bridging power source as we reduce coal consumption, but we still need to meet peak-hour demand.
 - The gas turbine generators are installed by businesses to keep data centers and industry running when there are blackouts. IMHO, it makes sense to use them for peak demand whenever renewables+storage is insufficient.

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Physics, Astronomy & Cosmology / Re: Is the inverse square law only approximately correct in general relativity?

« on: 25/06/2022 10:08:47 »

The reasoning about Event Horizons is almost backward.

I was not thinking about a horizon at a fixed distance.
- After all, the size of our observable universe is not at a fixed distance - it expands at the speed of c.
- But space can expand faster than c, so (in principle) there are distant galaxies that people on Earth could see today, but
 which will not be visible in 10 billion years, because the expansion of space has carried them outside our visible universe.
- If you posit some particle that travelled at c/10 (and didn't slow down), there would be regions of our visible universe that could never detect these particles, because the space in between is/will be expanding faster than c/10.

Usual disclaimer: Ignoring intergalactic medium, electrostatic forces, magnetic fields, etc which will change the velocity and/or direction of real beta particles.

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Physiology & Medicine / Re: Why where the native Americans so vulnerable to disease?

« on: 25/06/2022 09:58:46 »

(disease) spread through carriers who where immune

I think there are 2 different ideas mixed up there:
- People who are immune have overcome the disease, and will not spread the disease
- Carriers are people who have not overcome the disease, but in lingers on in a chronic condition. They can certainly spread the disease.

For example,  the adult sailors who initially explored a new land did not carry smallpox, because it was endemic in Europe, and they were all immune.
- However, later settlers took babies (who were not immune), and smallpox could circulate on a ship among the non-immune children, carrying smallpox to new countries.
- This caused a problem when doctors wanted to carry a milder version of smallpox to the Americas, for use in "variolation" (a precursor to vaccination). So they drafted young orphans who had never suffered smallpox, and transferred smallpox from one to the next, in a chain stretching across the Atlantic.
- Later, bottles of dried smallpox blister were carried to North America, and used to infect blankets, which were given to the native Americans. One soldier who had seen this done in North America later came to the new colony in Australia - followed by an outbreak of smallpox among Australian aborigines.

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Just Chat! / Re: Erectile Dysfunction And Its Solution

« on: 25/06/2022 09:33:42 »

Still the best and funniest advert on TV, though.

Those of us not in the UK haven't seen this ad - can you provide a link into Youtube?

I can't get away from it

If it keeps following you on the internet, it may have entered your advertising profile...

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Physics, Astronomy & Cosmology / Re: Is the inverse square law only approximately correct in general relativity?

« on: 24/06/2022 22:52:52 »

Suppose it was something else like Beta particles being emitted isotropically by the source.

If we assume that the particles are traveling at (say) c/10, then there will be an event horizon beyond which these particles will not pass, because space will be expanding faster than c/10 by the time they got there.
- This event horizon will be much smaller than the event horizon for light (which defines the limits of our observable universe).

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Physiology & Medicine / Re: Why where the native Americans so vulnerable to disease?

« on: 24/06/2022 22:47:36 »

I say again why did the Americas not spread diseases to Europe, were they disease free?

I think it is partly due to which group had the ocean-going ships.
- Europeans had the ships, and crossed the ocean from Europe to the Americas. They took various European endemic diseases with them (to which they were immune), and deposited them in a land which had no immunity.
- If Pre-Columbian Americans had crossed the Atlantic to Europe, carrying their endemic diseases, they may have managed to spread American diseases in Europe (if they weren't sunk by cannons first).

In fact, Columbus did take some Caribbean native back to Europe, but he would have taken the good-looking ones, not the sick and diseased.
- And they would have been quarantined and checked by doctors before they were paraded before the King of Spain.

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New Theories / Re: What is the real meaning of the most-distant-quasar/galaxy?

« on: 24/06/2022 09:17:17 »

3. Bulge (0 - 1KPC) - Why in the bulge each star orbits at different direction and orbital plane?
Why the Dark matter can't force the stars in the bulge to orbit in a disc?
4. Bar (1KPC to 3KPC) - How the dark matter could form the unique structure of the Bar?

Today I heard some projections on what might happen when the Milky Way Galaxy merges with Andromeda to form "Milkomeda".

They suggested that the result will be an elliptical galaxy, with stars taking many random paths.
- ie a bulge larger than our current galaxy
- and no bar
- I am sure that the university/supercomputer-level simulations would have taken into account some hypothetical distribution of Dark Matter in the original galaxies and the merged galaxy

Maybe it is time to go down to the bar and have a glass of dark matter.

13

Just Chat! / Re: Erectile Dysfunction And Its Solution

« on: 24/06/2022 09:09:19 »

COVID can attack the lining of blood vessels, and this can cause dysfunction in many organs....

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Geek Speak / Re: Why different computers/devices may show different times (at seconds precision)?

« on: 24/06/2022 04:13:16 »

The legal time in Darwin (which I am planning to visit next week) is not exactly UTC+9.
- It's UTC+9.5

Adelaide is also UTC+9.5
- In 6 months time, it will be UTC+10.5
- This is not due to continental drift; 6 months ago it was also UTC+10.5

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Just Chat! / Re: Test of the Poll system

« on: 22/06/2022 23:44:38 »

I do now...

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Just Chat! / Re: would it be a good idea to truncate endless pointless arguments?

« on: 22/06/2022 23:43:54 »

The moderators do lock a thread if:
- It keeps going over the same old ground
- It degenerates into name-calling

The moderators can also merge a new thread into an old thread, if it is just repeating the same stuff
- Or split a topic into two threads, if it has diverged into two unrelated topics

The moderators can also suspend participants (temporarily or permanently) if they ignore a warning.

While insults are easy to spot, deciding when to lock a thread requires some judgement: Does it seem to be making some progress, perhaps by branching into closely related relevant areas?

repeated again and again and this goes page after page

You will find this most often in the "New Theories" section.
- Maybe just read the initial proposition (if its not too long), and the most recent comments on it before deciding to read the lot!

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Physiology & Medicine / Re: Why where the native Americans so vulnerable to disease?

« on: 22/06/2022 23:34:41 »

Measles has a nasty side-effect, even if you survive it: It resets your immune system.
So the adult population would have "forgot" all the immunities they developed as children against local diseases.

It is likely that many of the native American adults would have then succumbed to native American diseases.

18

Physiology & Medicine / Re: What is protein priming?

« on: 22/06/2022 08:47:11 »

Are you looking for a general answer, or are you talking about the 2-step process by which the COVID virus enters a cell?
https://proteopedia.org/wiki/index.php/SARS-CoV-2_spike_protein_priming_by_furin

Actually, it is the first step that provides children with some protection from COVID, as pre-pubescent children have very little of this priming protein.

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Physics, Astronomy & Cosmology / Re: Formation of our solar system, the Nova, Nebula, dust and disc formation?

« on: 21/06/2022 03:37:53 »

super nova: gold, also everything heavier than iron, true?

That was once the popular theory.
- It's now considered that various supernova events can create perhaps 25% of heavy elements.
- But today it is felt that the majority of heavy elements are created in neutron star collisions
- a neutron star colliding with another neutron star
- or a neutron star disrupted by a black hole
See the periodic table at: https://en.wikipedia.org/wiki/Nucleosynthesis#History

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Geek Speak / Re: Why different computers/devices may show different times (at seconds precision)?

« on: 21/06/2022 03:26:28 »

Often your Internet Service Provider (ISP) will have an NTP server, whose time is set accurately across high-speed links.
- You can run NTP protocol to the ISP's NTP server. Most of the variation will occur in your connection to your ISP, which runs at the lowest speed on the path.

NTP has various tricks like:
- Measuring the time delay both ways (as mentioned by BC) and taking an average. Unfortunately, most internet access networks are not symmetrical, so the average might have an error of a few ms.
- Sending multiple messages both ways, and using the one(s) that experience the lowest delays
- Repeat this process multiple times per day. The results at 4am are likely to be more accurate than 8pm (fewer NETFLIX streams at 4am...).

There is another anomaly that affects computers occasionally: Leap Seconds
- A number of security protocols rely on accurate timestamps (to discourage replay attacks), and a leap second can make it look like a timestamp is out of date
- NTP includes advance warning of a leap second, but Leap Seconds occur so infrequently that most programmers ignore it
- To avoid this problem, Google decided to spread the leap second over 24 hours (a "leap smear"), instead of being concentrated in 1 second. That meant that Google Time was up to 0.5 seconds different from every other computer. It may have helped Google, but it probably confused some computers talking to Google!
https://developers.google.com/time/smear