1

Geology, Palaeontology & Archaeology / Re: What kind of rock is this?

« on: 04/05/2021 18:14:42 »

Hi Desafina. Welcome to TNS.

I’m surprised that none of our resident geologists has responded; so, for the time being, perhaps a word or two from an ancient, one time amateur would, at least let you know that you are not being ignored. 

It looks like a ferrous concretion; possibly limonite and/or goethite. Not sure what the central part is, but it will have been the catalyst around which the ferrous layers were deposited.

Don't give up on TNS, it's a much better forum than your initial experience might suggest. 

Stay safe, Bill.

2

Geology, Palaeontology & Archaeology / Re: What is this round-shaped pebble with a conical end?

« on: 08/11/2020 11:41:26 »

I would guess at Echinocorys Sp. but it's a long time since I dabbled in that sort of thing.

3

Physics, Astronomy & Cosmology / Re: How Did Time Come Into Existence ?

« on: 28/07/2020 21:16:57 »

There is no pre-exist,

If this says that everything is eternal, I would not argue with that.  I just wonder if it would leave Neilep feeling he had a woolly answer to the OP; but I'll not bleat about that.

4

Physics, Astronomy & Cosmology / Re: How Did Time Come Into Existence ?

« on: 26/07/2020 14:15:57 »

Time is what separates sequential events. If there are no sequential events, the concept of time is meaningless.

Agreed.  Would you consider it correct to interpret this as implying that time has no independent existence?

If there were no events before the BB, time did not pre-exist the events that occurred thereafter.

This leaves a major question unanswered.  If there were no events and on time before the BB, how could the BB have happened?

5

Physics, Astronomy & Cosmology / Re: How Did Time Come Into Existence ?

« on: 25/07/2020 21:15:37 »

This is a philosophical topic and probably belongs in Just-Chat rather than physics.

Can’t agree with that.  Philosophy might attempt to explain why we are here.  (good luck with that). 
This addresses the question as to how we can be here. Wouldn’t that be fundamental to scientific thought?

As far as I know, it isn't wrong to discuss time on the other side of the big bang event,

In fact, if time cannot be created, it becomes a necessity, if one wants to question our origin.

… since it is not necessarily ordered there, the word 'before' or the tense 'would have had to' may not be applicable.

For time to have been created, to come into existence, there would have to be a time when there wasn't time, which is self-contradictory

So, something, including time (?) must always have “existed”, and is, therefore, eternal.  In which case, 'before' and 'would have had to' cannot be applicable, unless eternity is a length of time.  That’s where it gets interesting.

6

Geology, Palaeontology & Archaeology / Re: Do these rocks contain gold?

« on: 22/06/2020 15:43:15 »

Hi Tree_adventurer 02. Welcome to TNS. 

I'm no expert, either; just an erstwhile amateur.  My initial impression would not be hopeful as far as gold is concerned, but some more details about the specimens, and where you found them, might give our experts a better chance of making an assessment.   

7

Physics, Astronomy & Cosmology / Re: An expanding flat universe?

« on: 14/06/2020 19:45:11 »

The trumpet shape has been around for a while.  Eg.  https://www.independent.co.uk/news/science/the-universe-is-not-round-say-scientists-it-is-shaped-like-a-trumpet-560046.html. 

I have always assumed it was a “mathematical” model, intended as an aid to understand; rather than something that was meant to be taken too literally. 
No one will be surprised that I have grave reservations about the physical demonstration of:-
 
“The thin end would be infinitely long - but so narrow that it would have a finite volume.”

8

Physics, Astronomy & Cosmology / Re: Are there half visible galaxies?

« on: 31/03/2020 17:10:26 »

  But that doesn't mean that , if there's someone exactly a mile away, I can only see the tip of their nose and their toes.

I interpreted Jeffrey’s “shouldn't we be able to see only half a galaxy at the boundary of the visible universe?” as meaning something like: If he boundary of the visible universe coincided with the centre line of a galaxy, would this mean that, in principle, only half of the galaxy would be visible, if we had the ability to see it. 

I suspect that, at that distance, any galaxy would appear so small that the point is moot; but Jeffrey’s question still stands.

9

Physics, Astronomy & Cosmology / Re: Can Atoms Touch Each Other?

« on: 18/12/2019 18:11:40 »

https://wtamu.edu/~cbaird/sq/2013/04/16/do-atoms-ever-actually-touch-each-other/

Note that the everday concept of touch (i.e the hard boundaries of two objects exist at the same location) makes no sense at the atomic level because atoms don't have hard boundaries. Atoms are not really solid spheres. They are fuzzy quantum probability clouds filled with electrons spread out into waving cloud-like shapes called "orbitals".

So, they’re really quite “sheepy” at heart.

10

General Science / Re: Science Photo of the Week

« on: 14/12/2019 18:32:30 »

https://www.simplemost.com/woman-finds-lavender-like-spiny-flower-mantis-bug/

Pseudocreobotra wahlbergii.

11

Chemistry / Re: Why Do Some Sinks Have Brown Stains ?

« on: 14/12/2019 18:09:56 »

No degree in sinkology, I'm afraid, but one question that comes to mind is: What is the concentration of CaCo₃ in the water in the area into which this sink ventured?  A thin film of limescale will accentuate any coffee/tea/almost anything stains.  BC will probably give you a better answer; I'm just a hitch-hiker living in a "hard water" area.

12

Physics, Astronomy & Cosmology / Re: What Do You Call A Moon Of A Moon ?

« on: 14/12/2019 17:08:13 »

Looking at your pic, I'm seriously considering contacting (?)SPCA, Animal Protection, or whatever; but is it too late?  Has she gone? Are you expecting her back for "milking time"?

13

Physics, Astronomy & Cosmology / Re: What is this fifth fundamental force I have just read about?

« on: 25/11/2019 17:15:57 »

https://profmattstrassler.com/

This might be a good place to start.

14

Physics, Astronomy & Cosmology / Re: Is light an independent entity, or is it an effect of a larger mechanism ?

« on: 13/10/2019 13:02:22 »

https://www.science20.com/alpha_meme/fundamental_nature_light-75861

Sascha Vongehr has some interesting comments.

15

Physics, Astronomy & Cosmology / Re: Is there an equivalent of absolute zero when it comes to heat?

« on: 19/09/2019 14:35:52 »

Is the concept of an absolute, approachable but unattainable 0 any less ridiculous?

That’s more interesting than it looks, at first glance.  HUP tells us why we can’t reach 0K; is there a similar principle/law that tells us why we can’t reach infinity?  What about HUP?  I suspect, not, but I’m no expert.

"Infinite" is not a number…..

I think this might have something to do with it. 

16

New Theories / Re: Split from "How fundamental is time?"

« on: 14/04/2019 18:14:18 »

My understanding is that, in science, theories are not proven correct. The best one can do is keep trying to prove them wrong. “After a century of trying”, success is singularly lacking, as far as SR and GR are concerned. Einstein made mistakes.  Hans Ohanian filled a book with them.  Don’t read it if you have a glowing opinion of Einstein as a person, which you want to preserve.   

17

Physics, Astronomy & Cosmology / Re: How long does a virtual photon exist ?

« on: 07/04/2019 12:36:43 »

Virtual photons mediate action at a distance and come into play for instance when one magnet or electrically charged body attracts another hence they must have a non zero lifetime else their speed  would be infinite

   
I’ll try an addition to the following, to see what the experts think of that.

A virtual particle mediates an interaction.  Presumably, this interaction occurs in time, but is often described as being “instantaneous”.  This must involve looking at the concept of instantaneous speed.  When the speed of an object is changing constantly, its instantaneous speed is its speed at a particular instant in time.  This “instant” is a dimensionless point on a time-line.  It is part of the scenario of time, but does not include the concept of duration. 

Of course, there’s a complication here. 

Virtual photons mediate action at a distance, as between two magnets.  To do this, they must have a non-zero lifetime or their speed would be infinite.  Their speed is “c”, so it is constant. A shorter lifetime, therefore, equates to a more restricted range of influence.

If the lifetime of a virtual particle is inversely proportional to its energy, it must follow that the higher the energy of the particle, the shorter its effective range of mediation would be, but, even at the highest possible energy, the lifetime would be non-zero.  It might be reasoned that infinite energy would equate to zero lifetime.  Effectively, zero lifetime would equate to non-existence; so even if the “impossibility” of achieving infinite energy were overcome, this idea would be a non-starter.

None of this serves to identify the mediating “influence” as a particle.  It is a vacuum fluctuation, and the Casimir effect demonstrates that these fluctuations must have qualities we would identify as waves.  Wave/particle duality suggests that we should also expect them to behave as particles, in the right circumstances.  This sounds very much like "real" particles; so, are virtual particles actually particles, or not?

The question: “is it a wave or a particle?” is famously difficult to answer, and often leads to the opinion that “it” is neither a wave, nor a particle, but something of which we have no practical knowledge.

It seems that all we can say, at this juncture, is that the Universe is permeated by fields.  These fields are subject to disturbances.  We perceive the disturbances as having wave-like qualities, but we can also consider them as particles.  In some cases, we can assess these particles as showing permanence, as travelling through space and as reacting with one another. These reactions are such that the mathematics describing them is the same as the mathematics that would describe the exchange of a particle.  The mathematics is most easily understood if expressed in terms of this conceptual particle exchange, and the model can be developed from there.  Essentially, this is the process of applying perturbation theory to a quantum field. Thus, the virtual particle becomes a “representation” within this process. 

18

Physics, Astronomy & Cosmology / Re: Approaching An Event Horizon: Falling Observers At Different Distances

« on: 20/03/2019 18:16:25 »

https://www.thenakedscientists.com/forum/index.php?topic=52973.msg444716#msg444716

This might be worth a look.  If I remember rightly, there were some interesting responses, including a detailed one by Pete.

19

Physics, Astronomy & Cosmology / Re: What is an "event" ?

« on: 18/03/2019 21:29:56 »

Chances are, you've all seen this, but just in case.......

https://profmattstrassler.com/articles-and-posts/relativity-space-astronomy-and-cosmology/history-of-the-universe/hot-big-bang/

20

Physics, Astronomy & Cosmology / Re: Does gravity attract masses in space, or does it curve space between them?

« on: 29/01/2019 22:39:35 »

PS - freefallin still  doesn't sound rite 2 mee!
I have been brainwashed since childhud 2 attribute fallin = goin down...
Freely Floating seems just rite, but den again...
Ain't ne1 elses prob, juz mine.

Wolfson tries to divert "hitch-hikers"from the problem.

Richard Wolfson, “Simply Einstein”, uses the term “free-float” rather than free fall; the meaning is the same, but as he is writing for lay people, he considers it aids visualisation in the case of objects that are not obviously “falling”.