1

Physics, Astronomy & Cosmology / Re: Can time emerge?

« on: 12/06/2018 19:06:19 »

If you want to take this further then it might be instructive to browse the following article. Where ER=EPR.
https://www.sciencenews.org/blog/context/new-einstein-equation-wormholes-quantum-gravity

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Physics, Astronomy & Cosmology / Re: Can time emerge?

« on: 12/06/2018 12:28:10 »

Wheeler deWitt and the emergence of time.
https://medium.com/the-physics-arxiv-blog/quantum-experiment-shows-how-time-emerges-from-entanglement-d5d3dc850933
An interesting read and not that long.

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Physics, Astronomy & Cosmology / Re: Would your eyeballs really freeze up when exposed to space?

« on: 29/04/2018 19:49:26 »

The fact that the pressure is low and the eyeball is quite strong.

I'm trying to interpret that in a way that gives me information about the possibly explosive fate of the eyeball.  Are you saying that the eyeball is strong enough to withstand internal pressure if exposed to a situation of zero pressure?

When trying to see whether a barrier will collapse "due to pressure," one must consider the pressure on both sides of said barrier. For instance, 20 atmospheres is a lot of pressure, but if both sides are under 20 atmospheres, there is no net pressure pushing the barrier one way or the other.

In the case of an eyeball in space, we can take the pressure of space to be 0 (it is ever so lightly greater than that, but it doesn't matter for this level of calculation), and we can take the pressure from the water to be the vapor pressure of water. At body temp (37 °C) the vapor pressure of pure water is 47.1 mmHg (0.062 atm, so not much), and the vapor pressure of the fluid in your eye will be lightly less (maybe 5% lower?) than that because it is not pure water (and the impurities are mostly proteins and salts, which are not volatile).

So if we assume a pressure of 45 mmHg, which is about 0.6 N/cm², this wouldn't be comfortable, but I don't think it would burst your eye.

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Geology, Palaeontology & Archaeology / Re: Was the 12th dynasty of Egypt ruling at the time of the exodus ?

« on: 29/04/2018 15:58:58 »

The Bible story about the Exodus is constructed of different historical events from different periods, but there is some historical backround. Hyksos played an important role in that event. They had ruled Egypt (Kemi at that time) several centuries earlier and when they had left, people who had supported them and other Apirus or Habirus (falsely labeled as "Israelites"), mainly followers of the Old Kingdom tradition, had been surpressed in Egypt.

The Sea People who were so called Habirus as well, supported Hyksos (related tribally to the Old Kingdom elite) who had settled in Levant, and some rebellious circles in Egypt. Many of The Sea People troops were captured and enslaved to quarries when they had attacked Egypt. All these people were Habirus, whose Sumerian based name has been wrongly transformed as "Hebrew". They were not ancestors of modern Hebrews, but Sumerian- Aryan people (Y- haplogroup R1a), descendants of the priestly and kingly elite of Sumeria and Ancient Egypt. Hyksos (originally Haka-Kasvut) were their tribal brothers.

After Seti II died, his wife Meryamaan Twasarat (Biblical Mirjam) took power with her lover vizier Bay (Aria/ Kuru), who became know as Aaron.  There was a destruction in Egypt during their rule. Rebellious people destroyed temples and looted everywhere, demanding a religious and cultural change in Egypt. Pharaoh Amenmose (originally Sama Moni/Muna), who had co-ruled with Seti II, was part of the team and he became known as "Moses" in future.

This team asked Levantian Hyksos to help them. It is estimated that about 150 000- 200 000 Hyksos came to help with the rebellious who had now liberated also the enslaved Sea People Habirus from quarries. However, they lost at the end and had to leave Egypt with ex- prisoners, leprous, Habirus, Hyksos etc. Part of them directed to Levant, and part of them invaded Greece and finally established a Hellenic high culture there.

I would like to underline, that "Moses" or Amenmose (Sama-Moni/Muna) was tightly related to Hyksos and he even used a Hykso title "Haka-Wasat", which is falsely translated as "Heka- Waset" by ignorant egyptologists.

Hyksos or originally Haka-Kasvut weren´t Asiatic or Semitic, but Aryan Habiru people who had left Egypt during and at the end of the Old Kingdom to establish mines and metal cultures. Arkaim was one of these sites established by Kemi-Egyptian Aryans and they became known as "Hyksos". The problem is that egyptologists have no idea about the language used by Aryans. Their names are systematically wrongly translated.

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Physics, Astronomy & Cosmology / Re: What is a tensor?

« on: 18/04/2018 18:09:24 »

@geordief @Bill S
Just been searching net, try this, easily digested

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Physics, Astronomy & Cosmology / Re: What is a tensor?

« on: 17/04/2018 15:37:42 »

@PmbPhy and @jeffreyH understand tensors and will give you very sound answers with no waffle, but as @Bill S says, perhaps you need to step back a bit.

So ,if in any medium (or apparently also even in a vacuum) any point is associated with more than one force , these forces can be represented by vectors and they are called tensors when they all originate and combine at this one point....

Let’s start by forgetting medium, vacuum, forces, and combining at one point.
Vector is a simple tensor rank 1. Examples can be a force+direction or speed+direction.
Tensors aren’t limited to these values because a tensor is just an array of numerical values that can be used to describe the state or properties of a material or point in space.
Let’s take a simple example of stress. Stress, like pressure is defined as force per unit area and a material can support different forces applied in different directions. Imagine a cube of material with forces acting on it in three dimensions, the stresses on the cube can be obtained and stress state can be represented by 9 components - 3 for each face, force component and 2 components for the area of the face. Hence a second rank tensor.
Stress, strain, thermal conductivity, magnetic susceptibility and electrical permittivity are all second rank tensors, piezoelectricity is described by a third rank tensor, elasticity of single crystals is described by fourth rank tensor.
So very useful, particularly when you add the transformations and operations that @PmbPhy  and @jeffreyH mention.

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Physics, Astronomy & Cosmology / Re: What have I missed regarding This Einstein thought experiment?

« on: 19/03/2018 23:24:12 »

Which bit is incorrect?  All of it?

The bit about how he thought about it is. As Pete says, and I’ll quote Einstien “I should observe such a beam of light as an electromagnetic field at rest.” In other words, the wave would seem stationary, but this was not possible according to Maxwell’s equations, which describe the motion and oscillation of electromagnetic fields.
So he either believed Maxwell was correct or the wave was stationary. He chose Maxwell for the same reason we do, the maths is correct and consistent with experiments of Faraday, Gauss etc.

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Physics, Astronomy & Cosmology / Re: Can we thank Stephen Hawking enough?

« on: 14/03/2018 17:29:14 »

To be honest with you it's the man I'm thinking of and his family.

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Physics, Astronomy & Cosmology / Re: How would we calculate the time left to contact with an EH?

« on: 14/03/2018 10:11:30 »

Are you saying that assertions such as: "To an outside observer any object approaching the Schwarzschild radius appears to take an infinite time to penetrate the event horizon", are incorrect, because the object would vanish before, in the observer's RF, it reached the EH?

Yes.

I hope I don't murder the maths too much, but:
- Let's take Kryptid's calculation of the escape velocity of a black hole at a certain radius: v_e = √((2GM)/r)
- If we are looking at a space probe falling "from infinity", it's velocity at radius r from the center of the black hole will equal the escape velocity given by this equation.
- Plug in the measured mass of the Cygnus X-1 black hole of 14.8 solar masses
- The event horizon is at a radius of r_s=43.6km

For an observer seeing the space probe fall away from him towards the black hole, there would be considerable relativistic doppler redshift, even without gravitational time dilation.
https://en.wikipedia.org/wiki/Relativistic_Doppler_effect#Motion_along_the_line_of_sight

But let's ignore Doppler shift, and put the observer at right angles to the infalling probe, so there is very little Doppler shift.
So now the main source of frequency change is due to gravitational time dilation. This frequency ratio is sqrt(1-r_s/r)

If the distant observer looks at the speed of the infalling space probe, and does a linear extrapolation of the time to impact with the event horizon:
D: Distance to event horizon, in meters
v/c: Velocity, as a fraction of the speed of light
T: Extrapolated time to impact event horizon (in seconds)
TD: Gravitational Time Dilation ratio = ratio of emitted frequency of light to frequency as seen by the distant observer


D(m)     v/c    T(s)   TD
10000   0.902   4E-05   0.432
 1000   0.989   3E-06   0.150
  100   0.999   3E-07   0.048
   10   1.000-   3E-08   0.015
    1   1.000-   3E-09   0.005


If the infalling space probe had a bright beacon on it,
- at 10km its frequency would be halved, and you would predict impact in about 40μs.
- at 100m, it's frequency would be reduced by a factor of 20, and you would expect impact in 0.3μs.
- at 1m, it's frequency would be reduced by a factor of 200, the received power would be reduced by a factor of 200, and you would expect impact in 3ns

You could extend the visibility for a nanosecond or two by using an X-ray beacon, or even setting off a gamma-ray burst with an atomic bomb.

I am sure there is some factor I have missed, but I think the general conclusion is valid - a remote observer would see the space probe approaching the event horizon at a relativistic speed, and around the expected time of impact, the frequency of the beacon would be reduced to undetectability within a very short time (effectively zero frequency and zero emitted power), so it would look as if the space probe had crashed into the black hole and disappeared
See: https://en.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere

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Physics, Astronomy & Cosmology / Re: Is there anything more south than the south pole?

« on: 06/03/2018 07:30:12 »

Valid as this might be mathematically, it involves imaginary time.   Is there a fundamental concept of imaginary time in physics?

As you know imaginary numbers were very much misnamed when discovered, but they do have a physical significance in many situations. In the case of imaginary time there is no physical significance needed, as used by Hawkins, it is a mathematical work around by changing the metric to a Euclidian space which is far easier to handle. If you want to imagine what has been done, it is like rotating the time axis 90 so it is still orthogonal to the 3 space dimensions but now has the same sign (using East Coast convention). It’s known as a Wick rotation if you want to look up details.

I fail to see how drawing an analogy between the two-dimensional surface of the Earth and three-dimensional spacetime solves the problem of something emerging from nothing.

Hawkins was interested in a slightly different issue which is whether the start of time for our universe is from a point eg like a singularity or from a smoother surface - a boundary. A Euclidian space can be modelled as if it is surface of the earth (but you have to imagine that surface is 3 space dimensions) and if you imagine the start of time as the S Pole (in some lectures he uses N Pole) with time axis pointing to N Pole and 2 of the 3 space dimensions at rt angles , then the expansion from the s pole moves up the surface of the earth as a series of time-slice circles (but in 3D). The point about starting from the s Pole is that it is a smooth curve (boundary) rather than a sharp discontinuity like the point of a cone.
Hope that makes some sense.

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Chemistry / Re: What is the chemical equation when SO2 is added to wine?

« on: 01/03/2018 19:59:50 »

What I wrote as two stages can be considered to be just one reaction
SO₂ + H₂O ⇌ HSO⁻₃ + H⁺     

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Physics, Astronomy & Cosmology / Re: What is spacetime made of?

« on: 01/03/2018 19:54:02 »

Well Planck's constant has a well defined value as a quantum mechanical action. If either space or time were quantised it would have to be in Planck units. We have the Planck length and Planck time that could fit the bill. Does it make sense to consider motion to be defined in multiples of these units? Well the speed of light is defined as 1 Planck length over 1 Planck time. So your quanta has to be less than that. Otherwise everything has to move at the speed of light. Therefore the quanta, if they exist, are impossible to measure.

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Physics, Astronomy & Cosmology / Re: Is the radioactive decay dice experiment inaccurate?

« on: 01/03/2018 14:13:53 »

It's a fair demonstration of the meaning of half-life and exponential decay, provided that you begin with enough dice and don't look too closely at the results. With all digital simulations, there is an element of coarseness due to "discretisation error" that can in the worst cases lead to instability and a failure to converge at all. The nuclear decay dice game will always converge but the difference between model and reality, or even repeat model runs,  can be quite striking because the reality, though inherently discrete, usually involves zillions of nuclei.

For a classroom demonstration, any number more than about 300 dice will give a convincing demonstration of both randomness (give each kid 10 - 20 dice to begin with , and look at the range of individual scores after the first throw) and exponential decay with a half-life of one throw (if you discard 4/5/6) or three throws if you just discard 6s.

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Physics, Astronomy & Cosmology / Re: Why do clouds go red at sunset? Why not green, or some other colour?

« on: 28/02/2018 16:57:36 »

I just think my reply in this post started off on the wrong foot, please understand how that could be possible.

That's understandable, but it is a common confusion which we've seen before.

Well, I mentioned "lead" because back in the 80's it was reported there was a type of brown-red haze owing to the lead in fuel at the time, back in the day. Thought I'd throw that one in.

Excellent, context is always useful.
Although lead oxide is red I’m not sure that the tetraethyllead used in fuel produces a particulate which would reflect red, perhaps @chiralSPO  could help here. I suspect that the haze is from other pollutants and lead is an indirect cause. As you know particulates are removed from car exhaust by the catalytic converter, unfortunately lead deposits stop the catalyst working so they can’t be used in cars using leaded fuel, hence greater pollution.

if you've ever travelled to the Australian outback, Northern Territory, Uluru to be specific, and there's a wind blowing kicking up the red dust, you're going to have a spectacular sunset.

Most of the particles involved in red sunset/sunrise are aerosols, that is solid or liquid particles small enough not to settle out rapidly. As @chiralSPO said, If the particle is small compared with the wavelengths of light, it will scatter short wavelengths - blues and violets - more than long wavelengths, such as red. Many man-made aerosols are small enough to do this so they enhance to the sunsets of Los Angeles and other polluted cities.
Natural aerosols come from forest fires, mineral dust kicked up by sandstorms, sea spray and volcanic eruptions, etc. Volcanoes can inject sulfuric acid droplets into the atmosphere and burning fossil fuels releases sulfur dioxide gas into the air, which then turns into sulfuric acid aerosols.
If air pollution is very bad the sky is so saturated that you don't even see the sun clearly and the sunset can appear bright but washed out. This is because aerosols that are close in size or larger than the wavelengths of visible light tend to scatter all colours indiscriminately, increasing the overall brightness of the sky but reducing the colour contrast.
Another big factor in a spectacular sunset is a projection screen. Just like your Pink Floyd eg you need something to project onto, clouds are good so is dust.
However, you don’t want blanket cloud. Here in the northern hemisphere weather systems come to the uk from the west. The leading edge of a warm front has stratus (blanket) cloud which doesn't allow the sun through, when the warm sector has passed the cloud break into cumulus (fluffy piles) which act as a nice projection screen. This is why “red sky at night” works, because the bad weather has passed, high pressure (which tends to trap particles) is on the way and it’s likely to be at least 24hrs before another front is on its way, or if it is on the way it will block the clear path of the sun.

does that equally translate to sunrise, and if not why not?

Yes, the scattering of light works just the same for sunrise. The only difference is the good weather eg high pressure has moved east, so possibility of poor weather is increased.

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Physics, Astronomy & Cosmology / Re: Is general relativity deterministic?

« on: 14/01/2018 12:47:11 »

Alan appears to have addressed this; which just leaves me needing to clarify:-  Is the distinction between indeterminacy and uncertainty that uncertainty is something inherent to the system, while indeterminacy arises from external factors? 

Other way round! I can state my weight is 110 kg with an uncertainty of 1 kg depending on clothing, time of day, etc. Likewise I can state my speed is x/y with an uncertainty depending on how I measured x and y, and I can truncate the calculation of e/π to any level of uncertainty I choose, but 0/0 is inherently indeterminate.

To take Jeffrey's example,I can set up a collimator to select photons coming from a radioactive source, with any degree of traje3ctory precision I choose, subject to the uncertainties of measurement and machining, but the time between the arrival of successive photons is inherently unpredictable because it is subject to the indeterminacy of the decay process.

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Physics, Astronomy & Cosmology / Re: Can anything be "still" in space?

« on: 30/12/2017 09:32:10 »

Let's say we have a position P in spacetime that we know with absolute certainty is stationary with respect to the rest of the universe. We travel past P for one light second and mark another absolute position to show how far light travels for us in 1 second. Other travellers do the same. Their marks are all at different distances to ours since their velocities differed as they passed point P. Since quantum mechanics shows position to be a continuum, these points form an infinite series. Thus we see an infinite amount of variation in the perceived speed of light. The traveller who is stationary at point P would see an instantaneous speed for light. Since he has not moved. However, in relativity it is not possible to tell you are moving or not in an inertial frame of reference. So it can easily be seen that relativity breaks down if we can define a fixed background.

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Physics, Astronomy & Cosmology / Re: Is the big bang theory a hoax?

« on: 28/12/2017 13:33:56 »

Before making any pronouncements maybe those unenlightened individuals should know something.
http://www.science20.com/train_thought/blog/entropy_not_disorder-75081
Read right through. Even the notes at the end. This all stems from the classical view of thermodynamics. It was Boltzmann who applied the idea of disorder to entropy in the context of molecular interactions. Happy learning.

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Physics, Astronomy & Cosmology / Re: Where does the energy come from?

« on: 20/12/2017 22:24:45 »

Do you mean radiation from the object, or radiation from the environment onto the object?

If the object is emitting EM radiation then it must be losing energy, but it doesn't necessarily follow that the velocity must change. A red hot cannonball flying through space has a combination of kinetic, potential (gravitational), and thermal energy. The kinetic and potential energies will match Newtonian models very well, and the cooling of the cannon ball will have no significant effect on the trajectory, even if it represents a significant change in total energy of the projectile. (a 10 kg iron ball moving at 100 m/s has a kinetic energy of 50 kJ, and if it cooled from 600 °C to 200 °C that would require radiation of about 1800 kJ of energy. Where did it come from? Thermal energy (which one could argue is a type of kinetic energy, but it is internal energy).)

Radiation from the environment can be used to slow particles down (https://en.wikipedia.org/wiki/Doppler_cooling), but I don't know how effective that would be on macroscopic objects. EM radiation can also be used to speed things up (https://en.wikipedia.org/wiki/Laser_ablation or https://en.wikipedia.org/wiki/Solar_sail)

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Physics, Astronomy & Cosmology / Re: Is 'time' fundamental?

« on: 28/11/2017 21:31:32 »

Let's look at the original question.

Things happen, and the universe changes. If there is a detectable difference between "before and "after" then the concept of time has meaning, and if there are consistent differences between different systems, its meaning must be universal. If we count sunrises and the grass gets a bit taller as the count increases, there is a common dimension for astronomy and horticulture, which we call time.

At the quantum level I think a lot of confusion is caused by the word "uncertainty", which colloquially implies some involvement of an observer or arbiter. A better translation is "indeterminacy", which doesn't. It's the difference between guessing the position of a raindrop (uncertainty) and knowing you are in fog. Wave mechanics is simply a mathematical model that helps us predict how the universe evolves: it doesn't imply that electrons are waves any more than your income tax code implies that you are a number on paper, but both can be used to predict the probable evolution of something in time.

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Physics, Astronomy & Cosmology / Re: Is it possible to define infinity?

« on: 24/11/2017 22:04:39 »

I’ve been pulling together some more of the content of this thread, there’s some really interesting stuff here.   

 My next task will be to try to integrate the relevant bits into my own, pre-existing, notes.

Therein lies a range of questions:

1.  The whole thing could come to about 8,000 words.  Given that the number of people reading a post is inversely proportional to its length; would anyone read it?   Is it worth posting? 

2.  Where to post?  I thought new theories, but Bohm, Barbour and probably others were there way ahead of me.  So, not new, and probably not a theory in the strict sense.  So, where?

3.  How would I post it?  “Bite-sized” chunks might seem best, but I think the whole will be such that splitting it up would lead to repetition and increased thread drift.

Anyway, it still needs some work, so in the meantime; suggestions welcome.  Be brutal!

Save it as a pdf file and attach it.