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Physics, Astronomy & Cosmology / Re: Could neutrinos pass through a black hole?

« on: 12/02/2022 13:25:54 »

Perhaps a related question - would hypothetical gravitons be absorbed by a black hole?
- If a black hole is (say) 10km across
- And the gravitational waves have a wavelength of (say) 30,000km?

I expect that wavefunction of the gravitons allow you to calculate the probability that a particular graviton is found at a particular point in space
- There is a finite probability that an individual graviton will impact the event horizon of the black hole
- Since there are so many gravitons in a gravitational wave, some of them will impact the event horizon, and be absorbed.

The same argument applies to photons in an electromagnetic wave with a wavelength of 30,000km.

How might we (in theory) detect that a graviton  had interacted with the  actual singularity** of a black hole?

Could the probability of such an occurrence  exceed by very many orders the lifetime of the universe and so be considered impossible?

** are singularities mathematical objects without a physical counterpart?

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Physics, Astronomy & Cosmology / Re: Could neutrinos pass through a black hole?

« on: 12/02/2022 04:01:15 »

Nothing escapes a black hole, which is not a star, nor even a location in coordinate space.

(with usual apologies  in advance for probable misunderstanding) How then can we say that there is expected to be a Black Hole  at the centre of every Galaxy?

Is there not a frame of reference involved in such a description?

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Physics, Astronomy & Cosmology / Re: If space-time can curve near a black hole, can we drag + move it?

« on: 04/02/2022 01:03:46 »

Hi.

   Could someone clarify how these things work?   Whenever the posts start of with  "Donald presented this...."  or   "Donald wrote in to ask this.....",    then   we're never going to get any interactivity with Donald are we?   
   So am I right that if I asked Donald to clarify a few details, then I'd be wasting my time?

    Also when people write a reply, such as Origin has just done,  will Donald ever see it, hear it or care about the reply in the slightest?   To phrase the question another way:   What is the point of replying to these things?   Would Origin have done just as well to shout his last reply down the street on a quiet night?

Best Wishes

That  was very funny
(I am as baffled as you are)

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Just Chat! / Re: Is life built into the fabric of the Universe?

« on: 03/02/2022 22:56:27 »

" Is life built into the fabric of the Universe?"
Well it's not built outside of the fabric of the universe, is it?

That is a 10 point penalty for over literalism.
;-)

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Just Chat! / Re: Is life built into the fabric of the Universe?

« on: 02/02/2022 23:54:51 »

The entire universe seems to have been an accident. You can invent any kind of universe you like, including one where nothing changes so nothing can evolve. However if it is finite it must have a beginning and an end, so it must contain some element that initiates change. We therefore have to define a universe of infinite temporal and physical extent for life not to evolve.

Oh,I am finding  that confusing  to follow.We know life did evolve .So are you saying  that  we must define  a universe of finite temporal and physical  extent  to fit that observed outcome ( the outcome of life actually having evolved)?

Are you saying that the  observed existence  of life  in the universe  presupposes  a finite  universe?

Again ,quoting you ,@alancalverd

"The entire universe seems to have been an accident"...

You are referring to its " beginning " or its continuous/continued  evolution?

In either case are you perhaps suggesting  that what we might see as physical  laws or rules are simply convenient habits?

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Just Chat! / Is life built into the fabric of the Universe?

« on: 02/02/2022 15:11:01 »

Is/was life an accident  or an accident waiting  to happen?

Can we conceive of any universe (one with different "initial" conditions)  that would not ,at some stage evolve into a stage for life ,no matter how primitive?

Are there any theories that convincingly posit a universe of finite extent(both time and space) where it might be possible for life never to have evolved?

Or is this finite extent precondition  unconvincing?

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Physics, Astronomy & Cosmology / Re: How long does a gravitational wave last?

« on: 24/11/2021 02:34:26 »

Do they travel as as expanding sphere?

Gravitational waves travel in all directions at light speed, so yes in that sense. A given wave isn't spherically symmetric (rings as you put it) any more than a propeller in the air creates spherical waves. It creates more like spirals, strong in the orbital plane and weakest along the axis of rotation.

If so ,is the total  energy  level  on each concentric ring of the sphere the same no matter the distance from the source measurements are made?

There are not concentric rings, and the energy is most concentrated in the orbital plane. If you had an instrument capable of measuring Earth's gravitational waves, it would be stronger out by Neptune's orbit compared to the same distance but along the rotation axis of our solar system.

Thanks,I  think I understand that now.

Still, I am still  wondering if we can still say  that these very asymmetric  "rings" carry away their  energy without  any loss of power at all  as they encounter obstacles in their path.

So would a neutron star or another black hole absorb their energy?

Or indeed just any  object of any appreciable mass?

Or does the gravitational wave go through these objects as if they were not there?

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Physics, Astronomy & Cosmology / Re: How long does a gravitational wave last?

« on: 23/11/2021 17:43:37 »

LIGO has a frequency range to which it is sensitive, about 10 hz to 10k hz, no so different from the range of sound detectable by people. So if the massive objects orbit slower than a 5th of a second, LIGO isn't going to pick it up. Near the merger, the frequency rises very rapidly, resulting the characteristic 'chirp', after which the signal is no longer detectable.
It apparently takes under a second for an orbit to drop from a 5th of a second down to at least the photon-sphere, after which the wave signal fades away.


The waves do 'last forever' in the sense that they keep traveling past Earth out forever, always getting weaker by distance per the inverse square law.

Do they travel as as expanding sphere?

If so ,is the total  energy  level  on each concentric ring of the sphere the same no matter the distance from the source measurements are made?

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Physics, Astronomy & Cosmology / Re: A particle in 2 places at once?

« on: 09/11/2021 15:04:23 »

You could look at it this way. Assume that the 'strict' Copenhagen interpretation is correct. You need to look before the moon will exist. What that state though is that the moon must 'know' where to 'exist' each time you search for it. It would either make you the whole universe, or make that moon 'sentient' in some mean

That would mean the whole universe's existence  depended on a particular sentient observer's perception. (solipsism?)

That is a reductio  ad absurdissimum.

It is the other way round,of course.

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Physics, Astronomy & Cosmology / Re: A particle in 2 places at once?

« on: 06/11/2021 03:10:01 »

This seems to be a classic assumption, and while intuitive, it's wrong. It is in superposition of 0 and 1 until measured, at which point it collapses to one state or the other, as described by an interpretation with collapse. Other interpretations deny collapse, in which case the observer simply becomes entangled with the cat.

OK so this presumably applies to any quantum object,?

For the purposes of us making any determination about it we have to take every probability  regarding its properties and take those probabilities(why are there more than one I don't know) and fix them to actually represent the object.

When that object interacts with its environment  the probabilities are rearranged instantly (?) and there is s new object based on a new set (again why so many superpositioned  probabilities?) of probabilities

Is that anywhere close?

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Physics, Astronomy & Cosmology / Re: A particle in 2 places at once?

« on: 05/11/2021 22:34:28 »

You seem to me to be be saying or implying that ,if measurements were finer and more efficient that the position and the momentum of a particle could be determined separately and not as a pair that are joined at the  hip

Quite the opposite. If you know the position of a particle to infinitesimal precision, you have no information as to its momentum. People look different when they are running compared with standing still, but if you photograph a car with a very short flash, you can't tell whether it is moving forwards, backwards, or stationary Cameras have advanced to the point that you can now get "propellor disc blur" software so that photos of classic aircraft in flight look different from stationary models, but a true "snapshot" gives you no clue as to its speed.

So far, so intuitive. But intuition breaks down if you know that an electron is absolutely stationary, Heisenberg says in that case, you can have no idea where it is!

Oh,it kind of "blinks" out of the realm of information when it is  stationary wrt the observer?

Or does it "fadeout" rather  the more relatively stationary it becomes?

And I suppose that applies to any object ,and not especially to an electron....

There is no principle involved , is there such  that at the quantum level it is impossible for any two objects to be  completely at rest wrt each other?

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Physics, Astronomy & Cosmology / Re: A particle in 2 places at once?

« on: 05/11/2021 00:45:22 »

If I look down onto a football field and see a player, I can tell where his position is on the field and from his momentum I can see which direction he is going. If I look at the position of a particle in a 'field' why is it not possible to see which direction it is going due to its momentum?

Different example to add to what @Halc is saying:
Let’s say your friend is coming to visit you, gives a call as he’s leaving. You know it takes about half an hour, so after 15min he should be half way, but you don’t know. Your model has to include some randomness because of traffic, roadworks etc.
It’s similar with quantum objects, we can model them and we can predict where they probably are, but unless we measure we can’t be sure, and because we can’t see them directly there are problems with the measurements. As @Halc says a measurement can disturb the position of the particle unless we can confine it. There are ways of detecting the electric field of atoms so that researchers can build up some pretty amazing images of the structures and atomic bonds and take measurements from these, however the boundaries of the atoms are fuzzy due to the nature of the electron field.
(Some overlap with @alancalverd I see).

You seem to me to be be saying or implying that ,if measurements were finer and more efficient that the position and the momentum of a particle could be determined separately and not as a pair that are joined at the  hip


Suppose there was  a new particle  discovered  that was millions of times smaller than the electron and it was able to be manipulated  would this  allow us the disentangle the electron's momentum from its position or are these two properties simply two sides of the same coin?

Is there forever and intrinsically a limit to how close an approximation  there can be to a separation  of these two descriptions?

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Physics, Astronomy & Cosmology / Re: A particle in 2 places at once?

« on: 03/11/2021 23:29:38 »

A particle, by definition , can only be in one place at any instant. Problem is that the more accurately you know where it is, the less accurately you know how fast it is travelling or where it will be next. That's simple continuum physics leading to Heisenberg's indeterminacy principle.

Is that an "existential **" situation(I mean ,is that just the way things behave) ?

...or is it a question of a limit of the powers of perception?

I am going to "guess" it is the former and not the latter as I have unconsciously assumed until now.

** bad choice of word,but I want to contrast the ways things actually work with the way we perceive them to do.

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Physics, Astronomy & Cosmology / Anyone listen to Brian Cox's Universe on BBC4 ?

« on: 29/10/2021 13:16:57 »

Specifically where he seems to claim that the first stars were formed at the intersections of the filaments of Dark Matter.

Is this accepted and established science?

Apart from that I was quite impressed by his description of DM.Quite matter of fact  and no theatrics,in fact as if it was pretty well understood apart from not being observed with em radiation

Of course Dark Energy ,which hasn't  come up yet in his new series is a different kettle  of fish  and rather more startling imo.

Out of secondary interest I was going to post this on one of the other forums I post in ,scienceforums.net but one of the mods there  from San Diego,I think had a public run in with Brian Cox some years ago and it might have been a red flag to a bull
https://www.scienceforums.net/topic/64562-a-quick-glance-at-brian-cox-is-full-of-it/page/2/#comments

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 22/10/2021 12:31:18 »

Well could you have it so that some of the universe did fall back on itself

That's one way to describe a black hole. All very crunchy.

Wasn't expecting that. Do the models of the BH and any possible Big Crunch differ in other respects?

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 21/10/2021 22:59:58 »

Does the big bang theory cause a problem for the infinitely expanding universe theory? Our universe is currently expanding and my understanding is that a reduction of that expansion would bring us to the big bang. But wouldn't that mean that the reduction would also have to be infinite?

(think my head just expanded   )

Well could you have it so that some of the universe did fall back on itself but some was just too far distant and "out of reach" so that it  continued its expansion "to infinity and beyond"   ?

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 21/10/2021 00:35:36 »

I think the question deserves inverting - often a good starting point for an investigation.

If the universe is finite, either it has a boundary, or we can define a vector r with its origin here and its endpoint outside the universe. So what is outside that boundary?  Why can't we define a vector with magnitude 2r?

Reminds me of the ending to The Truman Show where the intrepid hero comes to the end of the world and discovers it is made of  billboard paper.

Also reminds me of the crock of gold at the end of the rainbow

I feel  I can live with an infite  universe , but I wouldn't bet the house on it :-)

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 18/10/2021 21:33:23 »

I'm obviously talking about something being identical to within a particular volume

But isolated systems don't exist.

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 18/10/2021 21:21:29 »

@Kryptid I see it the other way round.For there to be an identical system to another it has to have identical connections to its environment.

Taken to the extreme that would mean that system A would be a part of an identical universe (including its past ,since the universe is dynamic)  to that of system B.

So system A =system B

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 18/10/2021 13:47:58 »

But can we begin to tentatively assume that the observable universe may well  be part of an (dynamic) infinite structure?

Rather than hedging our bets as it were,can we just let it sink in to our "world view" that this ,or something very similar can be the starting block  that all our other ideas and theories have to accord with?

A bit like Einstein and the invariance of the speed of light.Just accept it and build around it.

It makes me wonder where the energy "came from" to keep "all this" going.

Is it related to asymmetry?