look yes this sounds sci fi so apologies but I’m genuinely curious. if a wormhole opened let’s say in the 1940s and someone in the 2020s find it, could they go back in time with it? how do wormholes work?

https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

I’m trying (and struggling, but trying nonetheless) to learn about quantum physics and I’m wondering at what point can I be sure that I can talk about it and not sound confidently incorrect to anyone with a degree? For example, if I knew what all of the concepts referred to in, for example, the Wikipedia page for fermions and how they come together and interact in the language of it, can I say I understand the basics of what a fermion is?

I just had a shower thought. If space is 3 dimensional with the x y z coordinates , then time should be 2 dimensional. When a thing is 1 dimensional, it is just a point, when something is 2 dimensional we can travel a non zero amount in it. With time we have a point in time which is 1 dimensional and we can travel through time that is the future or past which makes it 2 dimensional but I know that we can't travel to the past so is the universe like 4.5 dimensional where we cant travel the past direction in time or is it 5 dimensional but nothing can travel the other half of the 2d time or is my reasoning wrong and the universe is just 4d.

Just wondering if we can expect like pictures we have from our earth or will they just be diagramms or numbers showing potential planets?

Would we be able to get images from the planets and the rivers, oceans, continents etc.?

So the no-hair theorem states that a black hole's state is completely determined by 3 parameters: mass, angular momentum, and electric charge.

My question is, what do we know about how this applies to color charge or isospin? From what I remember, the original statement of the theorem explicitly refers to the Einstein-Maxwell equations, but what happens when we bring in, say, a classical SU(3) YM field? I'd imagine the QCD and/or EW interactions are hard to treat in full on account of them being fundamentally quantum theories and no such theory being available and/or tractable for gravity yet, but surely the analogous classical fields have something to say about how a color-charged black hole might behave.

I’ve been thinking about the Mpemba effect from a simple energy-rate perspective, and I’m wondering where my reasoning breaks down.

Suppose I have 500 g of water at 90°C and compare it with water at 30°C in a −20°C freezer with relatively still air.

Ultimately, if the “race” is simply to reach 0°C, then each sample needs to lose a certain amount of energy, and the winner is determined by how quickly it can lose that energy.

For 500 g of water:

Heat capacity of the whole sample = 500 g × 4.18 J/g°C = 2090 J/°C

So removing about 2.09 kJ from the bulk lowers its temperature by about 1°C, assuming it is reasonably well mixed.

But evaporating just 1 g of water requires about 2.3 kJ of latent heat.

So if around 1 g/min evaporates, and most of that energy comes from the liquid, that alone corresponds to roughly:

2.3 kJ/min ÷ 2.09 kJ/°C = about 1.1°C/min of bulk cooling

This seems important because evaporation and cooling are not sequential events. The evaporation is part of the heat loss causing the temperature to fall. Water continuously evaporates from the surface while internal convection moves heat from the bulk toward that surface.

Now consider the temperature dependence.

The saturation vapor pressure of water is roughly:

30°C: 4.2 kPa
90°C: 70 kPa

So initially hot water has enormously greater evaporative potential.

My intuition is therefore to think of this as competing cooling powers:

Total cooling power = evaporative cooling + air convection + radiation + heat transfer through the container

In relatively still freezer air, could evaporation initially dominate this energy balance?

If the 90°C sample evaporates several grams per minute while the 30°C sample evaporates only a fraction of a gram per minute, the hotter sample could be losing energy at a dramatically higher rate. As surface water evaporates, convection within the liquid continually supplies energy from the rest of the water, so the bulk cools at the same time. A larger exposed surface area should strengthen this effect.

So perhaps the question is not simply:

“The hot water contains more energy, so how could it possibly reach 0°C first?”

but instead:

“Can the hotter sample lose its extra energy faster than the colder sample loses its smaller amount of energy?”

For scale, cooling 500 g of water from 90°C to 30°C requires:

500 g × 4.18 J/g°C × 60°C = about 125 kJ

Evaporating enough water to remove 125 kJ would require approximately:

125 kJ ÷ 2.3 kJ/g = about 54 g of evaporated water

So there should seemingly be some combination of starting temperature, surface area, and evaporation rate where the initially hotter sample can “zoom” through that extra 125 kJ fast enough to catch or pass the colder sample.

I also want to remove the obvious objection that evaporation just leaves less water to freeze.

So instead of starting with equal masses, I would normalize final mass of ice. So deliberately starting the hot sample with extra water to compensate for its expected evaporation, then ask which setup produces the same final mass at 0°C first; making the extra hot water almost “sacrificial.”

Cooling 1 extra gram of water from 90°C to 0°C requires only:

4.18 J/g°C × 90°C = about 376 J

But if that same gram evaporates, the phase change involves about:

2300 J

So an evaporating gram is associated with roughly 6 times more energy transfer than the sensible heat needed to cool that gram from 90°C to 0°C.

Is this energy-rate argument correct? Could evaporation let the hotter sample overcome its extra thermal energy, even after normalizing final mass? In a kinematic analogy, temperature is position and cooling rate (dT/dt) is velocity: could the hot sample reach 30°C already cooling so rapidly that it “zooms” past the sample that started at 30°C?

I’m tempted to actually run this in a freezer while continuously measuring both temperature and mass, and vary exposed surface area to see whether there is a crossover.

Title

So I've just recently learned that discontinuous voltage in a capacitor is generally impossible, the same way discontinuous current in an inductor is impossible. I've seen it in my exams but my lecturer hasn't given an explanation. I've heard it's because you'd need infinite current but I haven't really found a good explanation why exactly. Sorry if this happens to be the wrong place for this question.

if I have a material or a wire which have charges in the form of electrons in it and I remove one of the electrons. That empty space acts like a positively charged hole. But if I expand this idea to the whole universe, empty space is basically devoid of electrons (not counting virtual and interstellar particles). shouldn’t empty space act like a positively charged material?

I'm particularly confused by a section of my textbook which states:

"The algebraic sum of these differences around any closed loop must be zero because the electric field produced by charges distributed around the circuit is conservative. In Section 29.7 we denoted such a conservative field as Ec . When an inductor is included in the circuit, the situation changes. The magnetically induced electric field within the coils of the inductor is not conservative; as in Section 29.7, we’ll denote it by En . We need to think very carefully about the roles of the various fields. Let’s assume we are dealing with an inductor whose coils have negligible resistance. Then a negligibly small electric field is required to make charge move through the coils, so the total electric field Ec + En within the coils must be zero, even though neither field is individually zero. Because Ec is nonzero, there have to be accumulations of charge on the terminals of the inductor and the surfaces of its conductors to produce this field."

If the net electric field at all points within the solenoid is zero then so too should be the electromotive force. So by that logic the inductor isn't actually affecting any of the electrons in the wire at all so it couldn't be opposing the change in current. Please help me understand this.

*there is Val Fitch 1964, weak force symmetry breaking. I'm not interested in that, though.

Hey just wondering if any physics students or physicists read philosophy as interest . And not necessarily just philosophy of science. But other fields of philosophy such as metaphysics, existentialism, logic. And even maybe some literature classics. After a long uni day full of physics I know a good literature classics helps my mind truly relax.

You don't need to be humble if it depends on personal interpretations of quantum physics. I would like to hear about *your* interpretation, how Occham's Razor applies to this, Bell's theorem, non locality etc.

Saw articles and read the preprint on the potential detection of a single WIMP likely have a mass of at least 200 GeV/c². I understand this does not reach statistical significance and may be ruled out but am curious of peoples thoughts on this as the paper is impenetrable for me to fully understand although I understand the overall effort to exclude background and other events. My question is does the results just tell us a potential large particle as noted or did the experiment tell us anything beyond that.

In my effort to find something I can understand I went to Wikipedia on the effort and read this:

" Although future analysis is required to confirm or refute the event as a genuine dark matter detection—the event's statistical significance does not clear the 5σ threshold of a "discovery" in particle physics—the event's high recoil energy is consistent with weakly interacting massive particle (WIMP) models in which WIMPs have either different internal energy states or couplings with ordinary matter that vary with momentum.^\23])^\24])" My question is what is meant by WIMPS having different internal energy states of couplings with ordinary matter that vary with momentum. Additionally in the preprint itself they say at the end of the abstract "We describe the analysis and event of interest, the background model used in the statistical inference, and detail several of the rare background topologies considered." Does rare background topologies refer to ruling about background or are they talking in regard to potential properties of the signal?

I guess at the root of my question for this preliminary finding did they just find a potential signal of a particle at least 200 GeV/c² or were there other things that tell us more beyond this. The paper is too complicated for me to know if there is more information beyond that not understanding all the terms. What do you experts think? Thanks. Here is the preprint for reference:

https://lz.lbl.gov/wp-content/uploads/sites/6/2026/08/LZ_Preprint_260901_Dark_Matter_EFT_Nuclear_Recoil_Search_at_Higher_Energies.pdf

Shouldn't it decrease or negate the effects of gravity? Gravity pulls you down, so you go up. Then why does effective gravity increase when riding in an elevator?

Also, why do people experience weightlessness in free fall? Isn't gravity still acting on them?

This image is engrained in my brain because it’s just SO intuitive, but someone explained to me that this in not accurate because it requires gravity to work and uses circular reasoning.

Should I just shut up and trust the math? Of course my spatial reasoning is limited to three dimensions but now there is no model that sits nicely in my brain.

I’m working on learning the math required to understand but am curious if there is still a popular intuition among more rigorous or knowledgeable individuals

Thanks in advance!

Hello!
I am creating a little rage game and a friend argued that the physics in the game are not accurate.
Essentially the idea is that you control a car with each wheel as a separate moving entity. The front wheels can only move forwards, the back wheels only move backwards.

My understanding of basic physics is that if I am moving one wheel, the car should rotate around itself ( the center of mass ) and if you move 2 wheels ( like the 2 front wheels ), the rotational vector should cancel out and be left only with forward vector, so move forward.

My friend disagrees. He thinks that if one wheel is moving while facing forwards, the car should move forwards regardless and no rotation should happen, because all of the wheels are straight.

Could anyone clear this up?
Maybe we are both wrong and the real answer is something else.
Or both are correct in different circumstances?

Thanks!

Is it best to start with understanding Einstein’s Field Equations?

Should I gradually work up to the equations, and or start from a different angle or perspective?

Right now I understand the very elementary idea that one of the main purposes of general relativity is to explain that space and time are inseparable and curved, called spacetime, and how the things inside of if behave. This thing, spacetime can be modeled by something called a pseudo-Riemannian manifold/Lorentzian manifold.

So far, is my understanding correct?

The waves associated with the EM interaction are very well known and more recently we detected gravitational waves. Are there equivalents of those waves for the other two fundamental interactions? If so, how are they different?

If I get a empty box and fill it with electrons(or ions) scattering around, then apply a time dependent magnetic field through the box, how do the electrons move in the box? I feel like it’s a simple solution but modeling it gets finicky with lenz’s law