1

Physics, Astronomy & Cosmology / Re: What is non-returning twin paradox?

« on: 17/09/2023 16:14:56 »

This is a slightly modified twin paradox to distinguish the effects of relative speeds and acceleration.

In a different inertial reference frame (one in which both stars are moving at -0.4c), this is pretty much exactly the twin paradox, with twin A being stationary the entire time, and twin B going out and back, albeit at 0.4c only outbound, and faster on the return.

OK, so this is trivially computed in the Earth frame. The resolution for any exercise in special relativity is to simply choose a frame (we'll pick Earth since Earth time was specified), all you need to do is compute the dilation factor due to the speed relative to that frame. This is computed (in natural units) with

λ = 1/√(1-v²)

Twin A started a journey to Alpha Centauri 4 light years away in a space ship moving at 0.4c  is expected to arrive 10 years later, according to earth observer.

OK, so in Earth frame, λ=1.091 so 10 / 1.091 = 9 years 2 months elapsed time for twin A.

Twin B stayed home to improve the space ship, so he can go to Alpha Centauri 5 years later at 0.8 c.

0.8c yields a λ of 1.667 so 5 years at home and 3 during the trip, so 8 total.  Not so hard, right? You can do this yourself without asking each and every time.

Classical physics calculation predicts that they'll arrive at Alpha Centauri simultaneously.

Classical in what sense?  Classical physics refers to non-quantum physics. I think you mean Newtonian physics, not classical.  Yes, every theory (including Newtonian) says they get there simultaneously. This is an objective fact, true in any reference frame.

How old are they when they meet up at Alpha Centauri?

As computed above, 9y2m and 8y respectively.

2

General Science / Re: Just how does a metal detector work?

« on: 08/09/2023 12:50:19 »

surely there must be something to do with magnetism that helped it find metal

It has to do with electrical permeability which is related to magnetism. Magnetism would only find ferrous materials, so not say copper, but a metal detector is quite good at finding copper objects.

The idea is that it puts out an EM field which energizes (sets up eddy currents in) anything that allows the internal formation of magnetic lines of force (stainless steel being very bad at this). Then it shuts off and detects ('listens') for the currents created in the objects below. So the object needs to be able to pass electrical current, and it's mostly only metals that do this.

That surely any pirates would be very frustrated by the people who have made metal detectors and by us for finding their treasures so easily!

A decent pirate would bury his treasure a little further than the range of most detectors, and they put it where people tend not to look for it. Metal detectors are great for coins and jewelry dropped in public places like parks and beaches where the grass and sand quickly hide small dropped objects.

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Just Chat! / Re: Is the universe real?

« on: 06/09/2023 15:59:38 »

Recently I learned, through a conversation with Halc, that quantum theory says that one of the following statements must be false: (A) there can be no retrocausality and (B) counterfactual definiteness exists.

More specifically, the principle of locality and principle of counterfactual definiteness (CFD) cannot both be true *.

which is why we need science.

I don't see the two statements as mutually exclusive.

Funny, since it was science (not mere philosophy) that demonstrated the mutual exclusivity of the two principles.

The idea that either of these is false seems incomprehensible to me, on an INTUITIVE level.

I was raised as a Christian and educated in a parochial school which taught me that the teachings of science and mathematics do not contradict the teachings of the Church. But then (around my 20's) the Church decided this was no longer true and one was not allowed to pay attention to the man behind the curtain (Oz reference if you don't get that). I was forced to choose, and that turned out to be pretty simple. I removed one premise that I held (the divine origin of the scripture) and so many pieces fell into place with startling ease.
Clearly it was a good thing to question one's beliefs, and so I learned to identify as many as I could (those intuitions you talk about) and question each of them, learned how to not rationalize, but rather to be rational. That part is not easy.
So began my journey into philosophy, but it turned out that all the pre-20th century philosophers were working on assumptions that science has since cast extreme doubt.  To find the answers I was seeking, I needed to learn the relevant science, not enough to pass a grad-level course, but enough to know the implications. I came to TNS fairly ignorant of relativity and QM, but I learned, and I changed my views as I learned more.

I don't buy into these "simulation" ideas which in my opinion are just science fiction gone crazy.

Most people don't ever think it through, as evidence by the fact that there are two very different versions of it that are nevertheless treated the same. I agree and don't buy into the various versions either.

Buddhism states that reality is an illusion- is it that too far off the mark?

That's a philosophical stance. I don't know exactly what they mean by that statement, so I'm not much qualified to comment further. For instance, how do they define 'reality' and 'illusion'?



* There's a loophole in superdeterminism under which both principles hold, but which is way off the weird end of the scale, and is not listed as a valid interpretation since it suggests that no science can be performed at all.

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New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 05/09/2023 21:48:27 »

I'm not suggesting that time is an illusion

I actually never understood those arguing that time is an illusion. I mean, a physical clock measures it, and a physical device cannot measure something that doesn't exist. So to suggest that time isn't real has to also include the clock not being real, and then you not being real. That's a less popular stance, valid, probably just a refusal to apply the term 'real' to anything.

instead, time has always been passing, and everything that has happened, or is happening, or will happen, takes place somewhere in the infinite and eternal time continuum. That continuum has just one direction, and that is forward in time.

That's an intuitive philosophical stance known as presentism. Most people are presentists, especially those unfamiliar with the term, but it does contradict Einstein's theories, contradicting the most basic premises.  If you deny that all local inertial frames are equally valid, and you deny the constant speed of light, you end up with a totally different theory that came along about a century after Einstein's papers. In this theory, the universe is 3D, not 4D. It is contained by eternal passing time just like you say. There is no big bang, only a (single) big bounce. There are no black holes,. Those things are artifacts only of Einstein's theory.
Look up I. Schmelzer if you're interested, but the theory is more complicated than general relativity, so it isn't an easy read. But it supports the presentism that so many people seem to want.

But also, the time continuum is characterized by a concept called "places".

I think that would be the space continuum, not the time continuum.

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New Theories / Re: Dark Motion. Is it the answer to the Dark Matter and Dark energy problem

« on: 04/09/2023 22:42:21 »

Nasty remarks like that only serve to demean he who delivers them.

Momentus has earned a 10 day vacation for that remark, before which this topic will be closed, so no more posts here from him.
There will be a more careful watch on posts in other topics.

He is not open to anything that challenges his great discovery, as he sees it.

Totally agree that logic, mathematics, and reason fall on deaf ears with this guy. He is here for the conflict, not to learn anything.
I suspect the ban will be permanent before too long.

Thanks to both of you for your efforts, which are noticed by the non-participating reader if not the OP.

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Just Chat! / Re: I'm due to be crowned!

« on: 04/09/2023 01:03:46 »

I'm due to be crowned!

Coming from my father, those words were a threat. "One of these days I'm going to crown you!".

Also, despite the coronation, you'll also always be a hero to me.  You have my thanks that you made the milestone the way one should, not spewing a thousand posts of crap, a feat far more easily achieved as evidenced by some that manage not to get banned on the way there.

You are all invited to the subsequent bash, as soon as the formalities are completed.

I might decline as my wife seems to disapprove of events involving overt debauchery.

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New Theories / Re: Dark Motion. Is it the answer to the Dark Matter and Dark energy problem

« on: 01/09/2023 16:36:38 »

That's quite a handgun!  I'd expect that speed only from a rifle.  Irrelevant. We'll work with those numbers.

The bullet in the breech is obviously travelling at 100km/h and I now pull the trigger and the bullet flies off at 700m/s. The bullet continues it's travel in the direction of the train at 100km/h but now has a speed of 2520km/h.

Exactly, so the force on the bullet cannot always have been perpendicular to its motion.

The force is applied over say 100 usec (a 10th of a msec) which would yield ~700 m/sec over the length of a handgun barrel. We'll assume for simplicity that the force is constant for those 100 usec and zero before and after.

At time 0 the force becomes nonzero, and applied perpendicular to the bullet's initial 28 m/sec motion. After 0.1 usec (a thousanth of the total acceleration time), the bullet has accelerated 0.7 m/sec to the side. Total speed is 28.009 m/sec, which is pretty much the same speed as before because the force is mostly being applied perpendicular to the motion.

But now the bullet is already moving at 0.7 m/sec to the side and any continued force in that direction is now partially behind it, not perpendicular. The speed relative to the tracks begins to climb significantly.

After 10 usec (10th of the time under acceleration, 1/100th of the distance down the barrel, the bullet is now moving at 70 m/sec left and 28 m/sec forward which is 75.4 m/sec total, and now the trajectory is already mostly to the side, so about 0.9 of the force (sin(70 deg))being applied to the bullet contributes to increasing its speed. So the vast majority of the acceleration is pretty much directly in line with the motion of the bullet, not perpendicular with it. Only at first (a nanosecond or so) is the force perpendicular.

Since the direction of the bullet motion changes and the force direction doesn't, the force does not remain perpendicular.
With orbits, as the trajectory changes direction, the force does in lockstep, so it is perpendicular at all times.

It's all the same with the balls, with about 100 usec of acceleration time, perpendicular only at first and not the rest of the time.

8

New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 31/08/2023 19:56:31 »

it is during entropy that everything happens

What does the phrase 'during entropy' even mean?
That's like saying 'during momentum', like they describe a period of time.

The entropy of Earth has more or less been constant over the last billion years, and an awful lot of interesting stuff has happened during that period, so I'm not so sure if the interesting stuff happens when entropy is changing, but you also didn't say 'when entropy was changing'.

1)  the entropy I am referring to is taking place in a finite space that is surrounded by the infinite greater universe

Earth say ...
Again, entropy isn't a process that takes place. It's a value that can be measured, that can change.
 

In line with a premise that all space has always existed, any space that happens to be associated with, i.e. within the vacinity of the aftermath of a big bang event, has a higher energy density than the average density of the greater universe

High enough localized mass density (very little mass is required) that the matter would all exist within its own Schwarzschild radius, meaning it is a big collapse with no outward 'explosion' so to speak. It would result in an instant black hole with a event horizon radius far greater than the radius of our observable universe.

Just saying. That's what necessarily happens if you bang new matter into a small region of existing space. One can be in denial of gravity of course, but then why does it hurt when I fall down?

9

Physics, Astronomy & Cosmology / Re: Quantum Entanglement and Interstellar Communication.

« on: 29/08/2023 16:01:26 »

Don't think so, Alan, but I am not good enough( not good at all!

No, you very much are good enough, and you are correct here.

Now force your particle into an up state:  you therefore know mine is down, and I can measure it.

This is very much wrong. Entanglement does not mean that 'what is done to one particle affects the other'. Yes, a message could be sent if that were true, but it isn't. Spooky action at a distance (as it is called) has never been demonstrated. If it was, all the local interpretations that forbid it would have been falsified.

Spin entanglement says (in short) that if you measure both things in the same way, the results will be correlated.  If you force one of the particle spins, that is the same as declining to take one of the two measurements, leaving nothing to compare.

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New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 21/08/2023 00:22:53 »

We know time passes, but the beginning of time is not easily established. Was there a beginning, or has time been passing eternally?

...
Obviously, All the above imagined images would have Different Time slots.
(egg-t1, crack-t2, served-t3)

Yes, true even if time isn't something that passes. Those three states still have different time slots.

If the Egg is a Fundamentally essential object, without which, no still images can be imagined.

Have no idea what you might be suggesting with this one. An egg hardly seems fundamental, and an image is not an egg, and we have plenty of images of things (unicorn is traditional) that seem not to exist.

Can We then conclude, Without the Egg, Time does not Exist.

That's like saying without the unicorn, time doesn't exist. Time can exist just fine without an egg.
Time can exist without motion, but it's harder. The paint fades over time. That's evidence of time without utilizing the motion of anything.

How do We really measure Time?

Typically by counting regular events. That works, flow or no flow. There is no way to detect flow, so one cannot measure time by any empirical detection of flow.

How do We measure Entropy without the Existence of molecules, atoms, electrons, protons, quarks etc etc?

There would be no 'we' to measure it without that stuff. Entropy isn't especially a particularly meaningful thing without matter or radiation to measure.

Hope some of this helps.

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New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 13/08/2023 01:14:08 »

From Zero's link: Alan Guth.

Just to clarify, the quote does not appear anywhere on the Negative energy wiki page liked by Zero, but it does appear on the blurb for Alan Guth's book, which is one of the references on that wiki page.

Theory of known American theoretical physicist Alan Harvey Guth of the inflationary universe modifies the scientific Big Bang theory, describing the origin of all space, time, matter, and energy, 13.7 billion years ago, from the violent expansion of a singular point of extremely high density and temperature.

Don't know who wrote this blurb, but it is wrong, and I don't think Guth would have worded it that way. The universe was never a singular point since you can linearly (older model) or exponentially (inflation theory) expand one all you want and it will remain a point.

Yes, Guth was one of the major contributors to inflation theory, a significant change and improvement to the big bang model.
This universe is not in conflict with say the Cyclic model of Penrose, which stacks one conformal universe atop the next in infinite series. So in that sense, it does not refer to any one 'the beginning' since there are always more before and after.

If I interpret this correctly, it means that this diagram

can be stacked one atop another, but I might be wrong about that.

12

Just Chat! / Re: Is "new theories" getting worse?

« on: 11/08/2023 13:52:06 »

On a tangentially related note, is Gilyermo a bot?

Spam bot, banned. The point of the post storm was apparently to bury the (writer help) spam in a post in the paroxetine topic.

Always suspicious of a new user, especially one that puts out multiple (useless) posts like that, all at once. The last 7 posts were 30 seconds apart. No human can do that unless all the pages were pre-composed and all you needed to do was change windows and hit the post button.

13

Physiology & Medicine / Re: The Reason For Head Hair.

« on: 06/08/2023 21:06:25 »

Every human being seems to have head hair, or at least be born with it. What purpose does it serve?

Cooling and sunburn protection is a fair guess. Back when such things were evolving we were semi-aquatic, losing hair most other places for swimming/wading, but keeping it on the part that sticks out of the water.
Why does it grow to unlimited length?  Very few species have unchecked hair growth. A cat for instance always has nicely uniform thickness of fur. Human head/beard hair is not fur since it grown unchecked, unlike groin and armpit hair.

Or like many things in human evolution, do we have it because we thought it was attractive at one point?

That's getting it backwards. One evolves to be attracted to a fit mate. A good head of hair spells health over those missing it. A strong beard spells masculinity. I don't think the beard much serves to cool and such since there's hardly any surface blood flow at the chin.

Why does the male lion grow a mane?  If it was heat, the females would need it too. I think the lions need it for combat protection.

To keep your head warm.

If warmth was wanted, we'd not have lost the hair everywhere else. Humans mostly evolved in very warm climates. Those migrating further to colder climates started getting some of it back, but lacked the time to complete the task.
So you put hair in the paces you want kept cool, nappy hair especially which stays wet longer.

Global Warming will turn future Humans..
Bald?

Humans are not currently being eliminated due to excessive hair, even in the warmest places. But take away our grip on technology and humans on warm beaches may well reverse the current trend.

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New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 02/08/2023 18:11:02 »

any chance you could expand on the statement that "the universe is not classical"

In a classical universe, there is no retro-causality (effect before cause) and that objects exist even in the absence of measurment (the moon is there even if never measured).
Bell's theorem proved that at least one of those two principles (locality, counterfactual definiteness, respectively) must be false. No valid quantum interpretation supports both. The universe cannot be classical since it cannot obey both principles.

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New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 01/08/2023 16:32:06 »

What we can observe and/or detect could certainly be a finite expanding universe from a singular event

One observes/detects events and objects, not the universe itself,  So while the universe is still infinite in extent, the contents of it (the parts that exist relative to say our local galaxy cluster) is a very finite list. The rest is counterfactuals.

Positing the existence/state of things that have not been measured gets you classical physics, and it has been demonstrated (proved even) that the universe is not classical.

16

New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 12/07/2023 04:36:55 »

I get that. I define "universe" as all that is, all matter, energy, everything, all connected in the sense that everything occupies one contiguous, infinite space.

Suppose there exists a 5 dimensional being. That can't exist in 3 dimensional space, infinite or not. If it's all connected, then 'universe' is confined only to things with a location in that one space, and not all the existing stuff that isn't in that space.  So the statement seems somewhat self-contradictory.

I don't know. Negative energy? Any examples?

Gravitational energy (PE) is negative. An object that is infinitely distant from all mass (or an object in a massless universe) has zero PE.  Any mass nearby contributes it a more negative potential than that.

17

New Theories / Re: If there was one Big Bang event, why not multiple big bangs?

« on: 07/07/2023 21:01:52 »

there being just one universe, and only one

Well I suppose that depends on your definition of 'universe' and of 'there being' as well. I mean, I take an relational empirical approach, which is even more unusual than most of the stuff you propose. So I define 'there being' relative to X as anything measured by X. That means 'the universe' (all that is measured by X' is quite finite in both space and time. Some star like our own, but in a galaxy 7 BLY away? It doesn't exist to me since I cannot measure it. It isn't in my universe.

You can define this more conventionally, like ('everything that exists'). A thing either has this property or not, so there can be only one set of all things that have this existence property and another set of the things that don't. The universe is the former set. There can by definition be only one of those, and it would even be logically inconsistent to talk about a different universe, since if it existed, it would be part of the one universe by definition. Your post seems to indicate your holding this more conventional definition. The distant star exists even though no light from it has ever reached here yet.

Would it then be safe to say that the infinite universe is full of an infinite amount of matter

Pretty safe, but it doesn't follow. A universe that is infinite but only has 'stuff; locally in one place would have a finite amount of material, and thus most of the infinite space would be dead empty. Some some additional postulate of say homogeneity would get the infinite matter to logically follow.

and [an infinite amount of] energy

That presumes more stuff as well, in particular that the mean energy density of the universe is positive. Since there is very much negative energy out there, maybe the negative energy outdoes the positive stuff. It also doesn't seem to be conserved in a cosmological frame, so the energy is always going both up and down. Dark energy for instance is always going up, but light energy and kinetic energy and such always go down over time. This may not be true in a model like you describe since the cosmological frame is an expanding one with finite time since the beginning. You don't really have a mathematical model that would be needed in order to answer the question of whether your universe has infinite energy or not.

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Physics, Astronomy & Cosmology / Re: Why do kettles make a whoooarr sound?

« on: 06/07/2023 15:06:21 »

  It seems that most people think it's the water that is the main source of the vibrations, probably due to water vapour bubbles being created at the bottom and condensing back into liquid higher up.   Could be.   There's a big change in volume moving from gas to liquid so there may be some rapid local pressure changes when a bit of steam condenses.   Those might travel like pressure waves through the water (either to the surface of the water or to the body of the kettle which will then also locally vibrate).

Thought about it some more.  The bottom of the kettle acts as sort of a drum, amplifying action happening there and transferring  the vibration to the air.
So I place my bets on the creation of the bubbles from liquid state as it touches hot metal. The condensation just isn't going to do anything dramatic and will result in an inaudible fizz at best.

So the liquid sort of explodes into gas. That's the noise. Towards the end there is no liquid at the bottom and it all boils before reaching the metal. Hence less noise at the end.

And yes, if you boil water in a pan, you get the same noise, and it sort of goes away if you stir, only to return moments later when you stop. I think one can stir the water fast enough (at least when it's still pretty cool) that the water touching the very hot (well over boiling temp) metal still hasn't a chance to conduct enough heat away to boil instantly.

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Physics, Astronomy & Cosmology / Re: Why do kettles make a whoooarr sound?

« on: 06/07/2023 06:46:01 »

I have an electric stove and the sound is quite loud. It momentarily increases in intensity if you move the kettle say a cm or so to the side, exposing new 'colder' kettle-bottom to the hot portions of the burner.  But the sound comes from a gas setup as well.  It calms down to being quite quiet just before the boil sets in. My kettle has a fairly defective whistle and one needs to keep an ear out for the quite before the storm, so I've become more attuned to it.

OK, so I do think it is either noise from boiling right at the bottom. The gas makes it a very short distance before condensing back into liquid. But this can't be all since it would continue to make the noise once the boil is reached, and it kind of doesn't. Water at a full boil doesn't make a whole lot of noise at all. So maybe its the condensation going on (the bubbles ending) that makes the noise. That stops happening at the end and it just goes into a rolling boil.

20

New Theories / Re: How the Solar energy is created?

« on: 29/06/2023 18:14:49 »

"This process, known as a PP (proton-proton) chain reaction, emits an enormous amount of energy.

The PP reaction is part of the fusion process. It doesn't make any helium, but it makes one deuterium nucleus out of two protons. The fustion reactors on Earth for instance don't do this, and they mine the ocean for already-existing deuterium and tritium and do only the easy part: Merging two deuterium nuclei into a helium nucleus.

PP is prevalent in smaller stars, but the CNO cycle (a catalytic reaction) is more prevalent in larger ones.

"getting two identical elements to combine is actually very hard.
Because they have the same positive charge, they naturally repel each other."

Well that's true of any nuclei, identical or not.

"The waste produced by nuclear fusion is less radioactive and decays much more quickly."

I think they mean 'more quickly than the waste of fission'.

1. How the Sun could increase its internal temp to that ten million Celsius in order to start the fusion process?

Anything under pressure is going to rise in temperature

How the internal pressure in the sun due to gravity can gain so high temp?

Compression causes higher temps. Here's a typical article going on about it, but most of them concern squeezing of air and not so much stellar processes. There is an incredible amount of energy released by all the mass of a star falling so deep into a major gravity well. It would fall further, but the ignition of the star creates a counter-pressure that staves off further collapse for as long as the reaction can be maintained.
https://www.tec-science.com/thermodynamics/thermodynamic-processes-in-closed-systems/why-does-pressure-and-temperature-increase-during-the-compression-of-a-gas/

Do we have any way to measure that internal temp?

Models. No way to directly measure it. We only see the surface and can measure energy output, mass, magnetic fields, etc.

2. How do we know that in its core, the sun fuses about 620 million metric tons of hydrogen every second?

Energy output can be directly measured. E=mc2 does the rest.

Can we really measure that quantity or is it just based on some mathematical assumption?

All measurement is based on mathematical assumptions, so same thing.

So somehow there must be some radioactive radiation due to fusion activity. Do we really see any radioactive radiation from the Sun?

The waste products tend to stay and decay right in the sun. I imagine there are trace amounts in the solar wind and such. One such product is positrons, and those very much don't lost long enough to reach the surface. They don't decay, but they find electrons and annihilate them.

4. If Fusion activity was real, why it can't run out of control and bomb the entire Sun

The temperature of the sun prevents the density of the fuel from reaching explosive levels. That changes when the fuel runs low and the temperature can no longer maintain enough pressure to hold the star material at its current radius. Then collapse occurs, and the gravitational energy released from that collapse ignites the next layer of fuel (helium say) and that does explode.

6. It is stated: The energy, heat, and light from the sun flow away in the form of electromagnetic radiation (EMR).

Much of which is visible light, yes. We directly observe that, yes, even EMR in other frequencies.

7. So why we can't agree that the Solar energy is created ONLY by its EM energy?

It isn't created by EM energy at all. EM energy is the product, not the fuel.

8 Why this EM energy can't be created by external tidal forces on the Sun without any need for the Fusion activity idea?

There are almost no tidal forces on the sun. There's nothing large and close enough to produce them.

9. Why do we insist to add the idea of that invisible Fusion activity?

Because there's the only other source of energy would be that of falling material, and that is nowhere near enough to maintain the energy level for billions of years. A week maybe is it. This question seems to sound like fusion denialism.