exchemist

32 minutes ago, Genady said:

This is a pair of bar magnets one of which has been demagnetized. How to find out which is it without any other tools or materials?

42 minutes ago, swansont said:

These “informative” posts (and their cousins, the ‘thank you, that’s interesting’ posts) are often precursors to spam; the account is just waiting for their post count to be higher (unlocking some features or just hoping to to be the new account on the block) before posting spam links.

We know the tactics, and will ban if there are actual rules violations.

Hmm, interesting. I had come to suspect as much but it's nice to see it confirmed.

Sometimes I will respond to a post I am a bit suspicious of, on the basis of giving the benefit of the doubt and, in the process, trying to gain evidence one way or the other.  Quite often, the reaction, or lack of it, does indeed lead me to a more decisive view on the nature of the poster. It's a bit of a dilemma, though. One shouldn't react to obvious spam but there is a bit of a grey area when this type of "sleeper bot" behaviour may be occurring. (In the present case I was hoping for an amused or indignant reply, averring that the poster is real and not a bot.)   

1 hour ago, AbstractDreamer said:

I have no model to develop.  I'm only asking questions that we've had for over 100 years since establishing the accepted model.   

There's a giant elephant in the room saying "Spacetime is a single manifold".

There's another giant elephant in the room saying "Space is different from time because we have conditions in flat spacetime where only space expands and time does not dilute".

There is a clear contradiction here.

 

Well obviously there can't be, or cosmic expansion would have been blown up as be a failed model, long since. So it's a question of what you don't understand, rather than a contradiction in the model. But it looks as if you are in dialogue with the right people, so I'll get back to being an interested spectator. 

3 hours ago, AbstractDreamer said:

Yes the relationship between frequency and wavelength automatic.  But wavelength is a measure of space, which we allow to expand as described by the FLRW metric, and frequency is a measure of time... which apparently cant expand (specifically in the case of cosmological redshift and not in the case of dilation).  Why?  Spacetime is a continuum.  Why, in the case of interpreting cosmological redshift, is it not a continuum?

If there are no viable alternatives, then it is the only viable interpretation.  Which is rather surprising considering there is no evidence for space expansion other than cosmological redshift observations.   We observe cosmological wavelengths redshifted in 1912, we theorise space can expand, we develop a model (FLRW) to match redshift observations based on that in 1922.  We can use the model to match subsequent observations based on the same assumptions.  But we cannot then go and claim the model and the mathematics proves space expands.

In analogy:  Newton observed an apple fall, he theorised gravity as a force, he developed models and maths to match his "falling" observations.  We can use the model to match subsequent observations and make predictions rather accurately in most circumstances.  But you cannot use Netwon's law to claim gravity is a force.

Why is that?  Why must there be no time dilation?  What is it about cosmological redshift observations that says space expands but time does not dilute?  If relative motion can dilate time, why should non-relative motion not?  Why are we applying "classical reasoning" to cosmological redshift observations?

Please note I was careful NOT to say there are no viable alternative models. I said it seems there are currently no serious alternatives. 

But if wavelength alters and frequency does not, then surely the speed must change. Do you want to develop a model in which c has changed over time, or something?

I'm just a chemist, not a GR specialist. I've never worked with tensors.  @Mordred seems to be one, however. If you are bothered that space and time are treated differently from the viewpoint of expansion you will have to listen to him.  

57 minutes ago, Eise said:

I guess it is ChatGPT...

I did wonder. The fact that the text is highlighted with a blue background indicates it has been copy-pasted from somewhere. And the poster's one previous post is similarly a little lecture that nobody had really asked for. But one can jump at shadows these days.  

20 minutes ago, davidoliver said:

Indeed, the online world can be filled with various types of users and phenomena that can sometimes lead to tangents and distractions. Let's briefly explore the terms you mentioned:

1. Bots: Bots, short for robots, are software programs designed to perform automated tasks. In the context of the internet, bots can serve various purposes. Some bots are helpful, such as search engine crawlers that index web pages for search results. However, there are also malicious bots, such as spam bots, which can flood platforms with unwanted messages. Social media platforms may also have bots that automate actions like posting, liking, or following accounts.

2. Trolls: Trolls are individuals who intentionally provoke or disrupt online discussions by posting inflammatory or off-topic comments with the aim of eliciting strong reactions from others. They often thrive on creating discord and chaos, rather than engaging in constructive dialogue. Trolling can occur on social media, forums, comment sections, and other online platforms.

3. Socks or sock puppets: Sock puppets are fake accounts or personas created by individuals to deceive others online. The term comes from the idea of controlling a puppet with a hand inside a sock. Sock puppets are typically used to manipulate discussions, support one's own arguments, or create the illusion of a larger following. They may be employed to spread misinformation, sway public opinion, or engage in other deceptive practices.

That's funny, you sound just like a bot. 😁

3 hours ago, chef said:

Greetings!

 

I have a few questions toward my better understanding of one molecule of H2O (water) as follows:

What is the quantitative measurement of one (H2O) molecule of water? .........

Is one molecule of water visible to the naked eye? .........

Anticipating that the measurement of one molecule of water will be smaller than my everyday use of measurements - where does that measurement compare to one eighth of a teaspoon? .........

Do examples of one molecule of water exist in nature or does the smallest natural evidence of water in nature consist of multi-molecules of water? .........

Thank you!

You don't say what quantitative measurement of a molecule you have in mind, so that can't be answered. 

One molecule is not visible to the naked eye. Incidentally, regardless of how good your eyes are, light cannot resolve objects smaller than the wavelength of the light, because it will just diffract round them instead of being reflected. The wavelength of visible light is in the range 380-750nm, whereas a single water molecule is about 0.2nm across.  

Taking one tsp to be 5ml, 1/8 tsp contains approx 2 x 10²² molecules. In words that is twenty thousand  billion billion. 

There is no reason why there should not be single molecules of water floating around in all sorts of places, but we would find it very hard to detect individual molecules as they are so small. So evidence of water, which is what you ask about, generally relies on an aggregation of molecules of some kind.   

2 hours ago, AbstractDreamer said:

Show me where.

It is, but show me where cosmological redshift is interpreted as a decrease in frequency then.

 

Just on this small point, the relationship between speed, c, frequency, ν, and wavelength, λ, is c = νλ. This is true of any wave (light, sound, water etc). So, given that for light c is constant, as observed by us (that being the basic premise from which relativity starts), once you have said its wavelength increases there is no need to say frequency decreases: the relationship is automatic. Everyone knows this, so that's why you don't see it mentioned.  

45 minutes ago, AbstractDreamer said:

I'm not even really asking to justify the FLRW metric.  It is perfectly justified - given its assumptions and premised.

I'm asking to justify why space expansion is the only interpretation of cosmological redshift.

You've said for me to suggest a different interpretation and then explicitly repeated it.  Stop derailing my thread please.

I'm not sure anyone would claim that it is the only interpretation. In science one never formally closes the door to other hypotheses. Surely the claim of science is that it is the leading interpretation, to the extent that there are currently no serious alternatives? 

I have read about the "tired light" hypothesis for example. This was tried by some people for a while but soon blew up, as it implied predictions that were not borne out by observation.https://en.wikipedia.org/wiki/Tired_light 

So the reason @Genady is asking you to put forward an alternative is that there are no viable alternatives that anyone knows about, at least not at the moment.  

1 hour ago, shaileshsharma said:

can anyone help me with the organic chemistry exam Next Month Or I Was Suggested to Take the Coaching or Tutoring Classes. While Researching I found This Tutor Suggestions - (links deleted)  

Thanks in advance for Your Valuable Suggestions!

What do you mean by help? I suppose we might be able to help you with items in your revision topics that you find difficult. Obviously nobody is going to help you cheat in the exam itself.  

34 minutes ago, Brainee said:

What is calculus?

Google it and revert with questions if necessary. There’s no point us reinventing the wheel for you by reciting basic information that is widely available. 

54 minutes ago, ClaCom said:

The procedural position of an autonomous photon in a particle with quantum entanglement of the nucleus, adjusted for light error, will be approximated by dividing space into atomic intervals, and then compiling a procedural matrix of photon positions, which is a matrix with mixed elements. Each photon has the opportunity to act in different positions of the process, forming some sequences and patterns, while the quantification process occurs according to the rule: the more positions a photon occupies, the more likely it is to be in a certain position. Thus, the procedural position of an autonomous photon in a particle with a quantum entanglement of the nucleus, adjusted for light error, can be determined by analyzing the quantification process.

Word salad. 

5 hours ago, Brainee said:

How do boosted fission bombs have fusion fuel in centre since that is where the initiator is?

They don’t, though, do they? I thought the fusion fuel surrounded the fission fuel that sets it off. 

7 hours ago, Saber said:

Dont disappoint me man  no other continent  is circular like this.......* the small circle is the south geo pole

 

If all the  ice melted  although ........the land  underneath would rebound a lot too.............wouldnt it ?

From the responses it is clear that it is the ice that is in an approximately circular pattern, centred on the pole, which is hardly a surprise. The rock of the underlying continent is not. So nothing to do with rotation, just the amount of warmth from the sun, which obviously is at a minimum at the pole.

2 hours ago, Saber said:

Does the shape  of Antarctica    (  being  round shaped )

And its position that the center of that circular shape is approximately on the pole Does have anything to do with the  rotational  forces of the planet ? 

 

Thanx ..........

I don’t believe so. In the geological past, Antarctica or parts of it were at equatorial latitudes : https://discoveringantarctica.org.uk/oceans-atmosphere-landscape/ice-land-and-sea/tectonic-history-into-the-deep-freeze/

6 minutes ago, mistermack said:

What I do is write the post, hilight the bit you want to hide, and then click the eye, and it will just hide the bit you highlighted. 

Thanks I’ve got it now, after some fat finger trouble with my ipad.

3 hours ago, Genady said:

What fraction of the bottle is full?

26 minutes ago, Genady said:

  Reveal hidden contents

Click the "eye" icon and then write here.

Like this?

Just now, exchemist said:

Like this?

2 minutes ago, exchemist said:

Like this?

  Reveal hidden contents

Apparently not. How about this?

 

Aha, got it. Thanks.

14 minutes ago, Genady said:

  Hide contents

  Yes, but what is a ratio between the two?

 

How do you hide responses? 

9 hours ago, swansont said:

 

  Hide contents

1 mile/15 mph = 1/15 of an hour (4 min)

2 miles/30 mph is also 1/15 of an hour.

The return trip must take no time, thus the speed would have to be infinite

 

Yup, ditto. I recall these problems can be a bit counterintuitive, from trying to work the effect of the current in the Thames on a round trip in a sculling boat.  One sculls by the bank against the stream, where it is less strong, and in the centre when going with the stream. (I think I came to the conclusion that the fastest time for a round trip is in still water, since you always lose more time going against the current than you gain when going with it.)  

1 hour ago, MigL said:

You're right CharonY, I didn't read the original paper.
What struck me as odd ( and L Krauss ) was the fact that a scientific rebuttal wasn't allowed, because the original paper was deemed 'non-scientific'.
So why was it printed in a scientific journal ?

I only bring up the teacher/student example to demonstrate that sometimes hierarchical structures are necessary.
Like going to war with an army without hierarchy, and everyone is equal ?|
Or you can tell a judge he's out of order at your trial ?

The uniquely bonkers feature of the paper, it seems to me,  is the apparent equating of any form of hierarchy with “whiteness”. 

10 hours ago, genio said:

I find it hard to believe that an animal flapping their arms would develop wings or feathers and for what purpose to being with. There has to be a supernatural energy or energies behind these intelligent designs or the universe could be a consistent intelligent design in itself.

Evolution doesn't have a direction because the energy from the Sun and the planets is/are always different.

Why don't you make a bit of an effort to inform yourself, then? There is masses of publicly available information on the evolution of flight.  

1 hour ago, John Cuthber said:

I bet "transition metal" is a better phrase.
 

Yes I was wondering about that, but decided it would be better not to lead the witness. 😉 

28 minutes ago, shaileshsharma said:

I'm searching for a natural compound or a class of mixtures normally present in waterways (lakes, oceans) which could possibly tie progress metals. Up until this point I had the option to track down just humic acids for instance. Any idea on another compound?

What is a "progress metal"? Perhaps you are using a translator and it has not chosen a good term. 

40 minutes ago, MigL said:

Hey !  I'm a white male capitalist ( with a soft socialist underbelly ).
I think I treat my fellow humans decently and with respect.
And I don't even have a dog ...

Last I checked, W Buffet and B Gates were both white male capitalists, and each of them has donated more money to various charities than all of SFn's members combined incomes.
( although Bill did treat his wife badly )

Generalizations about people often come back to bite you in the ass.

Yeah but I bet you are guilty of leading a discussion with a marker pen and whiteboard at some point in your life, you evil white supremacist. I know I have, on numerous occasions, mea culpa.  

Just now, Genady said:

This is an important reason. But it is somewhat reduced here, because about half of the electricity on the island is already produced by wind, and they plan to keep installing more turbines.

 

Yes, it would be fun.

I was forgetting you were on an island. If you are - or soon will be - getting predominantly green electricity already, then there may be little environmental advantage. In fact there could be a net disadvantage, due to the manufacture and transport of the panels.