1

Physics, Astronomy & Cosmology / Re: LIGO represents an mirror displacement of what?

« on: Yesterday at 12:11:59 »

Empirical evidence suggests "smaller than a breadbox".

My inclination is to say that an electron probably has the same density as a proton or neutron

The proton radius is about 10^-15m
the electron mass is about 1000 times less, so, if the density is that same, that's about a 10 times smaller radius.
10^-16 metres.
Collision measurements give results that say less than 10^-18 metres.

My strong inclination is to say that you are wrong, but that's only based on experimental observation, while you have an inclination on your side.

It's all beside the point since the OP is talking cobblers.

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Physics, Astronomy & Cosmology / Re: LIGO represents an mirror displacement of what?

« on: Yesterday at 11:41:31 »

Wikipedia says

According to modern understanding, the electron is a point particle with a point charge and no spatial extent.

which I suppose is rather stretching the meaning of "understanding".

My inclination is to say that an electron probably has the same density as a proton or neutron, so its radius is probably calculable if not directly measurable.

We can also set a lower limit to its radius from the knowledge that you can't bind two electrons together by gravity, so the maximum gravitational attraction  Gm_e²/d²  must be less than the electrostatic repulsion q_e²/4πε₀d² where d is the diameter of an electron, with mass m_e and charge q_e.

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Physics, Astronomy & Cosmology / Re: LIGO represents an mirror displacement of what?

« on: Yesterday at 09:50:07 »

A problem arises if you consider an electron to be a point charge with no radius: having a measurable mass, it would have infinite density. This would give it an infinite gravitational potential. There are quite enough black holes in the universe without postulating several more inside every atom.

Just one more example of the inappropriateness of  classical modelling in a quantum universe.

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

« on: 13/03/2019 23:48:09 »

No. An EM wave is information

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Physics, Astronomy & Cosmology / Re: Do we go round in circles?

« on: 10/03/2019 12:43:34 »

Before even attempting to go any further, I should check, and possibly improve, my understanding of the mathematical concept of infinity.  Hopefully I will post my thoughts soon.

That path leads to insanity, as many mathematicians have shown!

However most physicists and engineers seem to die with their brains relatively intact, having decided that infinity is a tool determined by context and either means  "Limit_x→0 {A/x}" where A is pretty well anything (physics) or "too big or far away to make any practical difference" (engineering).

Your departure would diminish the challenge and value of these boards! Trying to explain something I think I understand to someone who thinks he doesn't, really gives the grey matter a good workout, and reading the opinions of experts in fields I haven't even thought of is just as much fun. 

Just as Eddington said "the student of physics must become accustomed to having his common sense violated five tims before breakfast", so anyone paddling in the shoals of science must be prepared for some fairly robust exchanges with the whales that explore the deep waters.   

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Chemistry / Re: Why would you burn coal, then turn the carbon dioxide back into "coal"?

« on: 07/03/2019 21:12:53 »

As far as I can tell evan_au's objection stands.

It doesn't really matter what is done with the "coal." I have worked on a few carbon sequestration projects myself--it really only works out if (a) the energy being used to capture and convert the CO₂ is 100% carbon free, and (b) if the product has value. There may be use in products from electrocatalytically reduced CO₂, but if you think of the carbon footprint required to generate the raw materials to build a CO₂-reducing plant on the scale needed to have any effect on the atmospheric composition, it is unlikely to pay for itself (in terms of net CO₂) before it breaks!

Photosynthetic organisms already capture and convert CO₂ far faster than we could hope to do it (in the next few decades, at least). Just look at the slope of the jags on the Keeling curve compared to the slope of the overall trend:

maunaloa_2004.gif (23.92 kB . 540x404 - viewed 526 times)
We just need to focus on not burning the fossil fuels in the first place, and allowing the photoautotrophs to do the work (ie preventing deforestation, promoting reforestation, and promoting healthy oceans). As long as we can allow the downward parts of the jags to extend a little bit, and the upward parts of the hags to be a little less intense, we can return to a reasonable equilibrium pretty quickly.

There might be a tiny little nudge we can do technologically to speed the process along, but focusing money and attention on these sorts of "band-aid fixes" merely diverts it from the "severed jugular" that the actual problem is.

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Physics, Astronomy & Cosmology / Re: What field gives rise to the Van Der Waals forces?

« on: 17/02/2019 18:41:09 »

Since forces can be associated with fields I am wondering what this one is.

The electric field. Is caused by both intermolecular attraction and electron cloud repulsion. Best to look it up in a chemistry text for a solid description.

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Physics, Astronomy & Cosmology / Re: Can two protons differ in mass?

« on: 18/01/2019 00:13:03 »

Indeterminacy would apply equally to the mass of both particles, because the concomitant of indeterminacy is indistinguishability.

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Physics, Astronomy & Cosmology / Re: Has there always been a constant number of photons?

« on: 29/12/2018 17:57:08 »

Does the circumference of a circle with infinite radius equal a straight line?

No. See Cantor on multiple infinities.

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Physics, Astronomy & Cosmology / Re: Is there a detectable direction in which the universe is expanding?

« on: 20/12/2018 10:42:52 »

The Solar System (and our local galaxy cluster) seems to have a measurable motion with respect to the Cosmic Background Radiation. The CMBR seems to be slightly red-shifted in one direction, and slightly blue-shifted in the opposite direction.

Whether this represents random motion of our galaxy, a local gravitational concentration or a random temperature variation in the CMBR is not known for certain.

See: https://en.wikipedia.org/wiki/Cosmic_microwave_background#CMBR_dipole_anisotropy

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Physics, Astronomy & Cosmology / Re: What does the term 'time' relate to in time dilation?

« on: 16/12/2018 22:25:37 »

Experience teaches that trying to forge any kind of link between this sort of mathematical concept and the “real world” leads nowhere. 

Far from it. A rigorous treatment of infintesimals leads to differential calculus, whence we get the whole world of classical physics, mesoscopic engineering and just about everything that distinguishes enlightened men from priests, politicians, philosophers and all the other human dross we scientists scrape off our shoes.

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Physics, Astronomy & Cosmology / Re: Would particles orbit a falling body?

« on: 17/11/2018 19:47:12 »

No, at that close to the Earth, even a steel marble would be within the Roche limit.   Tidal forces generated by the Earth would exceed the gravitational attraction of the marble. For a steel marble you would have to be at least 708 km above the surface for this to not to be the case. 

For objects to orbit the marble, they would have to be within the marble's Hill sphere. A 0.5 cm radius steel marble would have to be ~1689 km above the surface of the Earth in order for its Hill sphere radius to be larger than it own radius, so this is the closest it could be to the Earth and hold anything in orbit around itself.

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Physics, Astronomy & Cosmology / Re: What is needed to create new atoms in the Universe?

« on: 05/11/2018 08:16:56 »

the accretion disc temperature of the SMBH was 10 ^9 , and the temperature of a star's core is 10^6....
 A star at 10^6 is fusing hydrogen into helium. At a higher temperature (an accretion disk) would be fusing the heavier elements

I'm afraid not, because there is more to it than just temperature.

The Lawson Criterion describes three parameters that must be satisfied to get fusion going: density, confinement time, and plasma temperature.
- Density: The density at the center of the Sun is around 150 g/cm³, about 30 times denser than iron. An accretion disk is effectively in free fall, so it is not confined to such extreme densities
- Confinement Time: The Hydrogen from the Sun has been crushed in there for billions of years. Matter in the accretion disk around a black hole might reach maximum pressures for perhaps days or hours before being swallowed by the black hole or spat out in a polar jet.

The Lawson Criterion was applied originally to Hydrogen fusion, but the requirements for density, confinement time, and plasma temperature are even more extreme for fusion of heavier elements.
- There is an additional criterion: Raw materials. Since the universe has more hydrogen than anything else, accretion disks will probably also be dominated by hydrogen. There may not be enough of anything else to fuse much of it.

See: https://en.wikipedia.org/wiki/Lawson_criterion

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Physics, Astronomy & Cosmology / Re: How did scientists measure the mass of the Earth and other planets?

« on: 14/10/2018 09:37:33 »

from: alancalverd on 12/10/2018 09:49:23Using F = GmM/r2 you can calculate the force on a falling object of mass m in terms of M, the mass of the earth, and G, which we assume to be a universal constant.

That doesn’t work.  We’re trying to compute at least a rough G and M here.  We don’t know either of them yet.  We do know force F is 9.8 newtons for a 1KG mass.  We can assume we know r.  We therefore know the product of G and M, but not either separately.

We don't "know" F = 9.8 N/kg. We define the newton as1 kg.m.s^-2, and have a measured value of g = F/m

We don't "assume" r: it is a measured value - see below.

As I said, Cavendish (1797) measured G directly. 

Maskeleyne estimated the density of the planet from an experiment in 1774 at Schiehallion, measuring the deflection of a plumb bob on two sides of the mountain. In fact, that was a measure of G rather than ρ_earth since the assumption that the mountain was homogeneous was more defensible. Newton had considered the possibility but rejected the experiment as too difficult.

As F = ma, we can measure the acceleration of a falling object or the period of a pendulum to get a value for F/m

F=ma works (F 9.8 = 1 (mass) * 9.8 m/sec acceleration), but that doesn’t yield either mass of Earth M nor G, which are the two things we’re trying to determine here.
The pendulum thing is a function of acceleration (9., not of the mass of Earth.  Put a pendulum in a rocket accelerating at that rate and it will have the same period as here on Earth.  It tells you nothing about the mass of the Earth under you.

You have missed the point. If we know F/m we know GM/r², and we have known r since 200 BC (Eratosthenes), so all that was required for an accurate estimate of M was Cavendish's determination of G. The reason for using a pendulum  is that we know the period T = 2π√(Lm/F) for small oscillations, which is a simpler experiment than measuring the acceleration of an object in free fall.

The most amazing fact in all this, hundreds of years and thousands of experiments later,  is that the gravitational masses of all bodies are identical to their inertial masses. Why?

Interestingly, Hipparchus estimated the radius of the moon's orbit around 130 BC, though his assumptions regarding the earth's orbit of the sun were somewhat wild.

15

Physics, Astronomy & Cosmology / Re: What's a black hole made of?

« on: 13/10/2018 01:17:54 »

The illuminous region around the BH's gravitational field represents it's external boundary

There is a region called the "photon sphere", which is outside the event horizon (at 50% greater radius). If you emitted a flash of light here, you would see a series of light echoes as photons from the flash repeatedly orbit the black hole.

Light emitted within the photon sphere eventually finds its way into the black hole.
By itself, the photon sphere does not emit any light, so you could not call this region "luminous".
However, matter in an accretion disk around a rotating black hole is subject to severe shear forces, which does emit a lot of light (including infra-red at the outer parts, and X-Rays at the inner edge).
See: https://en.wikipedia.org/wiki/Photon_sphere

The illuminous region around the BH's gravitational field represents ... is a reflection of the incoming light striking a mass.

If there is no infalling matter (eg from a closely-orbiting companion star) then there is no mass between the photosphere and the event horizon (...if you ignore the hypothetical, microscopically thin, microwave-shifted skin of star matter that fell into the event horizon when the black hole first formed).
For a black hole that is not actively consuming matter, there is no luminous region around it.

This reflection is similar to what occurs on a star, The cooler substrata below the star's surface creates a barrier that the hotter corona reflect off of. During a coronal () we see the cooler substrata mass.

I am not sure what "coronal" event you are talking about - maybe a Coronal Mass Ejection, or the Corona that is visible during an eclipse by the Moon?
But in any case, the density of the corona is so low, and the corona's total light output is so low that it is only visible from Earth's surface during a total solar eclipse. (Space telescopes can see it at other times using a coronagraph - but they don't need to battle Earth's atmosphere...)

Apart from solar eclipses, all that we see of the Sun is the lower layers of the Sun's atmosphere - the photosphere (not to be confused with the photon sphere around black holes!). We don't need to wait for some special coronal event to see it. The photosphere is not solid, and it tends to absorb light rather than reflect it.

The photosphere has almost a black body spectrum of around 5500C, overlain with fine emission and absorption lines from elements in the Sun. It does not reflect the spectrum of the corona (which has a temperature in the millions C).
See: https://en.wikipedia.org/wiki/Photosphere

16

Physics, Astronomy & Cosmology / Re: What's a black hole made of?

« on: 07/10/2018 22:29:18 »

(A Black Hole) cannot be made of normal matter.  That part is wrong.  Normal matter of that mass cannot support its own weight, and breaks down even before the black hole forms.

I think it is just a matter of grammatical tense here.
- We see mechanisms that form black holes from normal matter when a star implodes and/or explodes.
- However, once this matter approaches the singularity, normal matter should be torn apart - it's not clear what the components would be (eg would they be outside the Standard Model?)
- And once it reaches the singularity, normal matter should be mashed together - it's not clear what the result would be
- But really, we can't say much about what happens inside the event horizon of a black hole

Is a BH empty? If it rotates, the answer needs to be no.

We expect that most black holes will form with the angular momentum of their parent star, accretion disk or galaxy.
It is theoretically possible for a black hole to have near-zero angular momentum:
- If there was a merger of two black holes with opposite and equal angular momentum.
- Or transiently, if the black hole was tearing off the atmosphere of a nearby star which was orbiting in the opposite direction to the direction of black hole rotation.
- But I expect that most black holes would have considerable angular momentum

The black hole, is a singularity, it is comprised of unattached subatomic particles

A black hole singularity in general relativity is where all of the particles end up at a single point; all paths entering the event horizon end up at the singularity.

Some theories of Quantum Gravity may allow some quantum fuzziness about the "single point".

But Quantum Gravity is not yet sufficiently mature to assert that "it must be composed of subatomic particles that are not congealed in a structure".

a chiralty gravitational effect

Gravitational waves are polarized.

Once 3 gravitational wave observatories were online, it was possible to detect the polarization of gravitational waves.

The first one was: https://en.wikipedia.org/wiki/GW170814

But I don't understand  "a chiralty gravitational effect".

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Physics, Astronomy & Cosmology / Re: Can the vacuum be affected by gravity?

« on: 23/09/2018 05:04:15 »

Yes. Recall Hawking Radiation.

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Physics, Astronomy & Cosmology / Re: Does gravity have an infinite range?

« on: 21/09/2018 12:12:38 »

Some random thoughts: The Big Bang theory suggests a period of Cosmic Inflation, where for a moment, space expanded faster than the speed of light.

Gravity travels at the speed of light (in a vacuum). So for the moment before Cosmic Inflation, all matter was in the gravitational field of all other matter. This situation did not hold after Cosmic Inflation, nor does it hold for parts of the universe that are now beyond our Visible Universe.

So I suggest that:
- All of the universe once felt the gravitational pull of the rest of the universe, back at the Big Bang
- This was possible because the universe was not infinite, right after the Big Bang
- The effects of gravitational events that occur today (like colliding black holes) will propagate outwards at the speed of light, but will never reach the edge of the universe, as that is a receding boundary. So in this sense, the effects of gravity will have an infinite range in the infinite future (but also an infinitely small effect)...

Caveats:
- I really don't understand unification of the 4 forces in the early stages of the Big Bang.
- I really don't understand how quantization of gravity will affect this

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Geology, Palaeontology & Archaeology / Re: To what extent can Biblical accounts of Noah's flood be believed?

« on: 20/09/2018 12:48:55 »

None of the stories in the old testament are to be taken as fact. My understanding is that when they were first written (over the course of multiple centuries, by different groups of people http://www.ancient-hebrew.org/articles_authors.html ), no one expected the stories to be taken literally (in fact the bible contradicts itself multiple times--allowing for much more complex analysis by the scholars--and contradicts physical possibility many times as well). Instead the stories are meant to be fables, and only in the centuries after the new testament did it become mainstream to believe that it actually happened exactly as it was written. (possibly due to the philosophical influences of christian and muslim schools of thought.)

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Physics, Astronomy & Cosmology / Re: What do strange quarks do?

« on: 13/09/2018 11:54:33 »

the neutron lifetime puzzle

I wondered why I kept seeing different figures for neutron lifetime.

Not the 9 second difference between beam and bottle experiments.

But the larger difference between half-life and mean lifetime...