I once tried to include myself in a discussion topic that went under the label of "what is time?" in which many individuals entered with various perspectives either championing the non-existence of time with respect to change (including me) and others who took rather standard interpretations of relativity (special or general) to describe what they mean. I felt that given some of the resources or knowledge i've attained perhaps the discussion could actually go somewhere or be somewhat more productive.

Over the course of those four years I had realized that philosophy had already been discussing this with already predefined terminology which greatly simplified the discussion so it was easier to see the distinctions being made. Those who were proponents of material/physical change being above time/space (perhaps even making it non-existent or its structures mere abstractions) go under the label of spacetime relationism. Those who are proponents of the distinction of change to time or the existence of time without change (check out the original Sydney Shoemaker thought experiment) went under the label of substantivalists. A good resource for this discussion can be found here and I also thought the John Earman book "world enough and space-time" outlines the discussion surrounding the philosophical interpretational difficulty of general relativity.

I'll also note that in the context of special relativity while there is an interpretation of the theory popularized by Minkowski (I believe) and a Lorentz-ether perspective these are both substantivalist interpretations. Ignoring the vagueness surrounding the concept of the ether, the Minkowski interpretations basically amounts to saying that the symmetries we see dynamically come from our one-way interaction with a real existent spacetime that contains said symmetries inherently. The other perspective basically distinguishes between the symmetries inherent in the spacetime itself (in this case i've seen people go with Galilean or Newtonian spacetime) while the transformations dynamically of forces/fields follows special relativistic equations. Basically Loretz-ether theory here could be that newton was only partially wrong about spacetime but especially incorrect about his dynamics. I'm mentioning this because when people try to emphasize change over time they seem to either be under the impression or think they are required to assert that there is some unique simultaneity relation when in reality while you could build one up (a global time in certain solutions of general relativity) it's not required to hold relationism.

Further, I know this includes philosophy (didn't know exactly where to put it), however, this discussion is fairly close in line with modern forms of physics investigations. Including forms of quantum gravity such as LQG, string theory, or other recent perspectives on quantum mechanics such as relational quantum mechanics.

So. . . what is time then? What are thoughts given this context?

Sincerely, college freshman going on sophomore year

]]>In theory we should be able to decompose any scenario (history of the Universe?) into ensemble of Feynman diagrams, apply CPT symmetry to all of them, getting CPT analogue of entire scenario (?)

There are many QM-based experiments which kind of use time symmetry (?), for example (slides with links) :

Wheeler experiment, delayed choice quantum eraser (DCQE), “asking photons where they have been”, “photonic quantum routers”, Shor algorithm as more sophisticated DCQE.

However, this symmetry is quite nonintuitive, very difficult to really accept – mainly due to irreversibly, thermodynamical counterarguments (are there other reasons?)

Can e.g. this conflict with 2nd law of thermodynamics be resolved by just saying that symmetry of fundamental theories can be broken on the level of solution, like throwing a rock into symmetric lake surface?

Are all processes reversible? (e.g. wavefunction collapse, measurement)

So is our world time/CPT symmetric?

What does it mean?

Personally I interpret it that we live in 4D spacetime, (Einstein's) block universe/eternalism: only travel through some solution (history of the universe) already found in time/CPT symmetric way, like the least action principle or Feynman path/diagram ensemble - is it the proper way to understand this symmetry?

Are there other ways to interpret it?

Anyways, to the topic at hand. One of my family members has run down a rabbit hole of conspiracy theories and pseudoscience and does not believe gravity exists. His evidence for such an outlandish claim is a blog by a user called Zetetic Zen. Which states, "gravity is incoherent dielectric centripetal acceleration towards a null-point of counter-spatial inertia. Essentially a hybrid field modality and byproduct of electromagnetism".

I know these statements are BS, and are not grounded in reality and observation. Although I was hoping for more of a scientific answer of why this doesn't make any sense. For some background I'm not too informed on EM and Dielectricity and just how it relates. Their article is incredibly dense and throws tons of terms everywhere and I don't understand it at all. I have no idea to even start on this, and hope that one of you might be able to assist me.

I'm not sure if I'm allowed to link articles but here it is below:

https://zeteticzen.wordpress.com/2017/06/15/gravity-does-not-exist-the-lorentz-contraction-conundrum/

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Here's a question, and my doubt is at the end of the question. I have been struggling with this doubt for quite long and have been receiving mixed opinions.

A cell of emf 12 v supplies a current of 400 mA to an appliance. After some time the current reduces to 320 mA and the appliance stops working. Find the resistance of the appliance, the terminal voltage of the battery when the appliance stops working, and the internal resistance of the cell.

In my book, the answer to this ques is given as follows:

1. Given, emf = 12 volt, I = 0.4 A

Therefore Resistance of the appliance R = emf/ I = 12/0.4 = 30 ohm

2. Given , I' = 0.32 A

Terminal voltage of battery V = I'R = 0.32*30 = 9.6 volt

3. From emf= V - v,

v ( voltage drop) = emf-V= 12-9.6= 2.4 volt

From v= I'r,

r = v/I'= 2.4/0.32= 7.5 ohm ( internal resistance)

My doubt is, in the 1st part, why isn't R= resistance of the appliance + internal resistance? Why is the internal resistance of the cell ignored in part 1?

A block of 8 kg slides upward through a ramp (without friction) until it goes to rest. ¿What would be the maximum height achieved if the block had an initial velocity is 12 m/s ?

I´ve tried to solve it in different ways (Newton´s Second Law, Kinematics equations, etc) but I always get stuck. I´ve arrived to the conclusion that the problem is missing key information about the angle that the ramp forms with respect to the horizontal. Help!

Actually it should be "Transparent Matter"!

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However, pressure is also proportional to the weight of the air above a given surface. So if the surface area of Earth remains the same, would that not mean the average pressure has to remain the same? Would therefore the volume of the atmosphere contract? (I would assume thermal expansion of liquid/solid interior of the Earth is at a less drastic rate.)

Conversely, real-life climate change is known to increase average global temperatures, which I would presume increases the total volume of the atmosphere. However, it's also known to be more pronounced at the poles than the tropics (I often see this pointed out but I haven't come across anything pointing out why) so would that mean the shape of the atmosphere as well?

This also got me thinking; for the ideal gas law; or some hypothetical differential equivalent thereof; to work at every point in space, that would mean there has to be more volume per unit space where the temperature's higher. Doesn't this suggest the present shape of the atmosphere is actually different than the shape of the Earth? That it would bulge more at the equator than the Earth does, and shrink more at the poles than the Earth does? If climate change expands the atmosphere more rapidly at the poles than the tropics, will this create an atmospheric shape more similar to that of the Earth? (Ie. Larger but more "to scale" than before?)

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Imagine a simple system of two small charged particles (not elementary particles) separated some distance apart.

- we define that the potential energy of this system is U0.

- we compute that the energy stored in the electric field is: E0

(note: we computed E0 by integrating the energy density formula for the electric field over the whole space. No need to consider our particles as point charges - say they contain uniformly distributed finite amount of charge in a small finite volume.)

We slowly separate the two charged particles some distance farther apart. To do this, we invested some work W.

What is now the potential energy U1 of the system? Is it: U1=U0+W?

What is now the field energy E1? Does it equal to E1=E0+W?

What is the change of the total energy of the system - does it equal to W?

My opinion: Yes, the U1=U0+W; yes, the E1=E0+W; and yes, the total energy change equals W. Therefore the change in potential energy and the change in field energy represent the same thing. We should consider either potential energy or the field energy when we compute energy balance. We cannot consider both energy changes as we would be doing double-counting error (in our example, we might compute that the energy difference is 2W instead of W).

Let's be stubborn and try the opposite anyway.... let's suppose that potential energy and field energy are two separate things. In this case we could claim:

U1=U0+x*W

E1=E0+(1-x)*W

(where x is a number between 0 and 1) Using these claims the energy will still balance (the energy change is x*W+(1-x)*W=W), but the question would be what is the factor x? Is it x=0.5? Why?

So, can we safely say that the change in the potential energy and the change in field energy represent one the same thing? Are there exceptions?

]]>After reading about Zeeman effect, I understand that electrons bound in an atom might shift their energies when placed in magnetic field. I ask if this energy shift is also associated with some change in the shape of their orbitals? (I guess, this is equivalent to asking if the probability density function changes).

I would expect that orbitals that have some angular momentum (and magnetic moment) do change their shape. I read that atoms near a magnetar star could look needle-shaped... But I don't see how would an orbital with zero angular momentum (and zero magnetic moment) change its shape?

On the other hand, if no change in orbital shape (probability density) can be associated with electron energy shift in magnetic field, how do then electrons 'shift' their energies (do they speed-up, become heavier or what)?

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I would like to share with you a crewed interstellar spacecraft which I have designed and called Solar One.

It employs a combination of 3 propulsion methods: nuclear fusion, beam-powered propulsion , and photon propulsion.

Basically, several compact fusion reactors power a laser system that propels a huge light sail.

Physicist Robert Forward already proposed in 1983 to use a 26-TW laser system to propel a 100-km light sail, a fresnel lens to focus the beam of the laser, and decelerate the spacecraft with a secondary light sail.

I propose something a bit different, which is to use to use for example a 60 TW-laser to propel a 5-km light sail that would deploy from the spacecraft after the acceleration stage, use parabolic mirrors that gradually change their orientation in order to focus the laser beam, and finally use a photon rocket to decelerate the spacecraft.

In theory, it could be possible to achieve 25% the speed of light, reaching the closest potentially habitable exoplanet in less than 20 years.

There are of course many challenges, like building high-energy continuous-wave lasers, reducing the weight of the nuclear fusion reactors (and of course achieving effective nuclear fusion first), and minimizing the effects of zero gravity during such a long trip.

**What do you guys suggest to overcome these challenges?**

You can find a short video that summarizes all in youtube by searching for The Exoplanets Channel.

]]>Many people think that Chaos Theory is about disorder and randomness. However, it is not literally about disorder in science. It is stranger than you might think.

Then what exactly is Chaos Theory? Let's find out the real meaning of chaos and chaos theory in science.

The word "chaos" means disorder. However, the scientific chaos theory is not about disorder as we use it in our daily lives. The Chaos Theory is about statistical disorder, which has nothing to do with the disorder of your room. It is similar to non-determinism in Quantum Mechanics.

Statistical disorder is about predictability of (the future of) a system. When a system is easily predictable and can be predicted in a straightforward way, then the system is statistically ordered. When a system is less predictable, then it is scientifically more chaotic, no matter how ordered the objects are in it.

After development of Newtonian Physics, scientists thought that if we knew the initial conditions of any system, then we could predict what will happen to that system in any other given time. This was a common belief among many scientists. For example, the solar system is a statistically (almost) ordered system, since when an initial condition is known, we can predict the system in a different time, like we can predict all the solar and lunar eclipses. We can predict the position of any planet or satellite in the solar system in any other given time.

Things changed dramatically with the emergence of Quantum Mechanics. Because it turned out that Quantum Mechanical events are non-deterministic. Especially when we make an observation or take a measurement, the Quantum state collapses non-deterministically. Great scientists like Einstein and even Schrodinger argued against QM. It took some time until we accepted that in Quantum world, things can go very weird and behave without any predictability. Then Quantum Mechanical events were separated from Classical Mechanical events. It was then thought that Quantum Mechanical systems are non-deterministic, or chaotic, and Classical Mechanical events were completely deterministic.

This was the new common belief until Edward Norton Lorenz found out that the atmosphere and the weather were chaotic systems. He was a meteorologist scientist who found out that the weather is an unpredictable system beyond a particular period of time. The famous "Butterfly Effect" was indirectly named by his work. So, Chaos Theory was the second serious shock, after Quantum Mechanics, on the opinion of a deterministic universe even in Classical Mechanical events. Further analyses and simulations showed that even our Solar System is not completely predictable when long periods of times are considered.

Shortly, Chaos Theory is actually about how predictable a system is. A less predictable system is more chaotic.

**What do you think?**

**Is our universe deterministic/predictable as a whole, or chaotic, or a combination of both?**

Many thanks for your help.

]]>I have this understanding of the nature of SpaceTime, and I'm just wondering if this is already common knowledge.

My understanding is this:

Space and time are dualities of each other, so they will be opposite in every way. In their relationship, space is the multiplicity, that which is observable, and time is the singularity, the absence of observation.

Now, The evenly balanced view of this duality would be that only one truly "exists". But since were are of an odd(3) number dimension, the observation of existence is an odd, uneven, asymmetrical balance; therefore that which wouldn't exist, does, just indirectly.

We are of the multiplicity, therefore our observation of singularities can only be through the lack of observation of the multiplicity.

Since, time is the singularity, I understand that it does not pass by, travel, change, or do anything except for a single thing; exist. And it only does so for reference. Space, is the only thing that passes by, travels, changes, etc... It's the one that does two or more things. So, any kind of observation of "time", is actually an absence of observing space. And this sense of "time passing" is due to the oscillation of observation and absence; that wave pattern life loves.

With this understanding, the relativity of SpaceTime makes sense to me, since its more so just Space(Time). Time "contracts", as you increase speed because the observation of Space is less (more blurs and skips) than when moving slower, and always in reference to a universal and unchanging Time.

So, thats a basic explanation, hopefully it makes sense. I'm excited to known if this is new or not and I'll explain more, if there are questions.

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When a ball is thrown upward it becomes at rest at maximum height, at this it is not in equilibrium although it is at rest. It is not at equilibrium because force of gravity is acting on it? Still I cannot find good explanation from exam point of view.I also cannot find the figure/diagram.

If a magnet is spun, moved, shaken while surrounded by a coil, the coil will generate a voltage that would flow as current if the coil has a closed circuit.

If a magnet is moved inside mercury, the currents would be 'tridimensional', in the body of the conductive liquid, probably emphasized in a plane/direction depending on the plane of the magnet motion. Do I have it right to this point ?

If the magnet moving inside the conductive mercury is a conductor itself, and in intimate contact with the currents flowing in the mercury, will the current share paths in and out of the fluid ?

If the magnet moving in conductive fluid is covered with an insulating paint/coat of glass, rubber, whatever; will the electric currents be confined only to the fluid ?

]]>A closed system has a set Mi of possible microstates between which it randomly changes. The set Mi of all possible microstates is partitioned into macrostates, resulting in a partition Ma of Mi. The members of Ma are pairwise disjoint subsets of Mi, and their union is Mi. The entropy S(ma) of a macrostate ma in Ma is the logarithm of the probability P(ma) of ma happening, which is in turn the sum Sum_{mi ∊ ma}p(mi) of the probabilities p(mi) of all microstates mi in ma. The entropy s_{Ma}(mi) of a microstate mi with respect to Ma is the probability of the macrostate in Ma to which mi belongs. The current entropy s_{Ma} of the system with reprect to Ma is the entropy of the microstate in which the system is currently in with respect to Ma.

The Second Law of Thermodynamics simply states that a closed system is more likely to pass from a less probable state into a more probable one than from a more probable state into a less probable one. Thus, it is merely a stochastical truism.

By thermal fluctuations, the fluctuation theorem, and the Poincaré recurrence theorem, and generally by basic stochastical laws, the system will someday go back to a low-entropy state. However, also by basic stochastical considerations, the time during which the system has a high entropy and is thus boring and hostile to life and information processing is vastly greater than the time during which it has a low entropy and is thus interesting and friendly to info-processing and life. Thus, there are vast time swathes during which the system is dull and boring, interspersed by tiny whiles during which it is interesting. Or so it might seem...

Now, what caught my eye is that the entropy we ascribe to a microstate depends on which partition Ma of Mi into macrostates we choose. Physicists usually choose Ma in terms of thermodynamic properties like pressure, temperature and volume. Let’s call this partition of macrostates “Ma_thermo”. However, who says that Ma_thermo is the most natural partition of Mi into macrostates?

For example, I can also define macrostates in terms of, say, how well the particles in the system spell out runes. Let’s call this partition Ma_rune. Now, the system-entropy s_{Ma_thermo} with respect to Ma_thermo can be very different from the system-entropy s_{Ma_rune} with respect to Ma_rune. For example, a microstate in which all the particles spell out tiny Fehu-runes ‘ᚠ’ probably has a high thermodynamic entropy but a low rune entropy.

What’s very interesting is that at any point in time t, we can choose a partition Ma_t of Mi into macrostates such that the entropy s_{Ma_t}(mi_t) of the system at t w.r.t. Ma_t is very low. Doesn’t that mean the following?:

At any time-point t, the entropy s_{Ma_t} of the system is low with respect to some partition Ma_t of Mi into macrostates. Therefore, information processing and life at time t work according to the measure s_{Ma_t} of entropy induced by Ma_t. The system entropy s_{Ma_t}rises as time goes on until info-processing and life based on the Ma_t measure of entropy can no longer work. However, at that later time t’, there will be another partition Ma_t’ of Mi into macrostates such that the system entropy is low w.r.t. Ma_t’. Therefore, at t’, info-processing and life based on the measure s_{Ma_t’} of entropy will be possible at t’. It follows that information processing and life are always possible, it’s just that different forms thereof happen at different times. Why, then, do we regard thermodynamic entropy as a particularly natural measure of entropy? Simply because we happen to live in a time during which thermodynamic entropy is low, so the life that works in our time, including us, is based on the thermodynamic measure of entopy.

Some minor adjusments might have to be made. For instance, it may be the case that a useful partition of Mi into macrostates has to meet certain criteria, e.g. that the macrostates have some measure of neighborhood and closeness to each other such that the system can pass directly from one macrostate only to the same macrostate or a neighboring one. However, won’t there still be many more measures of entropy equally natural as thermodynamic entropy?

Also, once complex structures have been established, these structures will depend on the entropy measure which gave rise to them even if the current optimal entropy measure is a little different.

Together, these adjusments would lead to the following picture:

During each time interval [t1, t2], there is a natural measure of entropy s1 with respect to which the system’s entropy is low at t1. During [t1, t2] – at least during its early part – life and info-processing based on s1 are therefore possible. During the next interval [t2, t3], s1 is very high, but another shape of entropy s2 is very low at t2. Therefore, during [t2, t3] (at least in the beginning), info-processing and life based on s1 are no longer possible, but info-processing and life based on s2 works just fine. During each time interval, the intelligent life that exists then regards as natural the entropy measure which is low in that interval. For example, at a time during which thermodynamic entropy is low, intelligent lifes (including humans) regard thermodynamic entropy as THE entropy, and at a time during which rune entropy is low, intelligent life (likely very different from humans) regards rune entropy as THE entropy.

Therefore my question: Doesn’t all that mean that entropy is low and that info-processing and life in general are possible for a much greater fraction of time than thought before?

]]>First off, hope you're all doing well. I was wondering what is the weight of all the particles in the Earth's atmosphere?

]]>It's difficult to find good intuition about these experiments from only static pictures - the first time I had occasion to see videos was on recent congress on emergent quantum mechanics where Couder had the opening lecture and most of speakers were excited about these experiments. Fortunately I've recently found youtube video of these experiments:

The main qualitative difference with physics is that while Couder uses external clock, particles should rather have internal one - such understanding of wave-particle duality was started by de Broglie in his doctoral thesis:

that with particle's energy: E = mc^2

comes some internal periodic process: E = hf

It is reminded in very interesting Hestenes paper, in which there is also described recent experimental confirmation of this effect (called e.g. zitterbewegung): http://fqxi.org/data/essay-contest-files/Hestenes_Electron_time_essa.pdf

Such internal periodic motion creates periodic wave-like perturbations of surrounding field - giving localized entity also wave nature ... localized constructions of the field are called soltions, so it suggests to search for particles solitons models, which often have such internal periodic motion, like breathers.

What do you think about these experiments? About such understanding of wave-particle duality?

Have particles both natures simultaneously, or maybe only one of them at the time?

In such case when and how it is switched? What about Afshar experiment?

]]>I wanted to discuss time travel in this thread. Suppose that in 2020, you travel back to 1970. You have traveled to 1970 fifty years after it has passed, so you are in a time that is 50 years after 1970. Suppose that in 2020 you travel to 2070. In that case, in an about an instant, 50 years has passed.

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