# Tag Info

2

I'd like to perhaps a slightly different viewpoint to your question and maybe turn it around a little. Probability is hard. Very hard. Defining the foundations of probability and statistics so that they are altogether sound and rigorous is actually a work in progress. It definitely is not complete. On the other hand Quantum mechanics is easy. Very easy! I'm ...

0

It doesn't make sense that satellites cannot detect radiation on the ground. They can detect visible light which is far less penetrating than gamma radiation from a decaying radioisotope. Remember, we are talking about MASSIVE amounts of radioactive isotopes in the atmosphere. They have fingerprints, I'm confident, which can be detected from space. Also, ...

0

You can also use PLotly, a collaborative, web-based graphing platform with APIs in Python, R, MATLAB, Julia, and Perl. You you can find the code to make these examples in their documentation. .

2

Let me try to give you a kitchen-table explanation. I can't help you with statistics vis-a-vis quantum mechanics, but probability is very basic. The underlying "real stuff" in quantum mechanics are numbers that, when squared, produce probabilities of seeing things. Typically, these numbers are complex, but they don't always have to be. These numbers are ...

3

I'm going to explain roughly what the Born Rule, following Stan Liou's comment. One of the Postulates of Quantum Mechanics relates a mathematical quantity, the wave function (or state $\psi$ of a Hilbert space, $\mathcal{H}$) to a measurable entity, the probability of a given event to happen. The idea goes like this: if you want to measure a quantity ...

1

What science tries to do is paint as complete and consistent of picture in the language of mathematics as possible. This in practice means figuring out how pieces fit together rather than tackling questions like why is there a puzzle to begin with.

1

anna v wrote in her answer: The only answer to "why" is this "because", data says so. I'd like to provide another example. Consider the question "How does matter move through space". In trying to answer this, Aristotelian arguments could satisfy someone of the answer. Prodding further, Aristotelian arguments don't hold up and we need to use Newtonian ...

2

Physics is concerned with abstract, mathematical models that describe the behaviour of particles, space, time etc and that are tested with observations and experiments. If a model is in agreement with experiments, under certain conditions and up to a certain accuracy, then it is accepted (for situations where those conditions hold). But a theory remains an ...

1

Here are my two cents of the euro: Physics is a science that has a large body of observations, and a limited number of mathematical models/theories that aim to organize and explain those observations and , very important, get validated by predicting the behavior of new observations. Mathematical theories start with axioms and some tools that develop ...

3

"Why" is the fundamental scientific question, the question regarding cause and effect. "How" already implies that certain things cause others, and sometimes it seems that cause and effect are not that easy to distinguish. You can't do any science without "why". Take, for example, the question: "How does CO2 contribute to climate change?" This is a ...

5

No, I do not regret getting my (forthcoming) PhD. I do sometimes regret changing subject areas from my MS to my PhD (MS is on theoretical condensed matter, PhD is on computational astrophysics) but only because it's added 2 or 3 years to my academic career. I have never had anyone ask me any of those questions, but Likely not going to happen in our ...

6

I agree with the others that physics is fundamentally a "hard science" which is (or should be) concerned exclusively with physical, empirical facts, but I have to disagree with the assertion that "How?" is a scientific question while "Why?" is not. Moreover, philosophy is central to scientific research despite not being itself the end goal. This discussion ...

6

In English, asking 'why' is a request for an explanation of, reasons for, or purpose of something. Physics does provide explanations and some types of reasons, but doesn't concern itself will questions of purpose at all, at least not in any teleological sense. So physics answers some types of why questions but not others, because in English usage 'why' is ...

4

"Why" is the question for philosophers. "How" is the question for physicists. The task of a physical scientist is to find a model that adequately describes "how" nature behaves. When more than one model fits, see Occam's Razor. The question of "why" nature is described by one model or another is best left to the philosopher and, be aware, that path leads ...

13

English is pretty imprecise and asking questions of the form "Why does ..." feels natural even when "How does ..." would suffice. "Why" has philosophical overtones because it goes beyond just "How". Physics is a science and the scientific method is tried-and-true method for gaining knowledge about how things work. I'd suggest that in any place you have a ...

0

Yes, a particle can have potential energy in one dimension as potential energy depends upon the configuration of the body. We can have configuration in one dimension as in hook's law and hence potential energy.

2

Sure, a particle can have potential energy in one dimension. Just look at Hooke's Law or the gravitational force. Both of those are conservative forces in one dimension ($x$ and $r$, respectively) that have a corresponding potential energy. In higher dimensions, nothing has to change, but it is possible to have potential energies which depend on the value ...

3

All our sophisticated mathematical tools - Derivatives and Integrals, Fourier Transforms, Groups and Representations, Riemann Tensors, Kähler manifolds, etc. are merely descriptive techniques. What exists is what exists, independent of how we try to describe it. New mathematical ideas often help us see known phenomena more clearly, or deal with the ...

7

this is a broad, complex, somewhat tricky question with many angles that an entire survey or book could be written on but unfortunately it seems one hasnt yet. heres a "grab bag" of some deep parallels noticed over the years that such a book might cover & "research leads" for further inquiry. Modelling and simulation. as computing capability has ...

3

The link between Computer Science and Physics can be very subtle sometimes. For example, consider this article: http://arxiv.org/abs/1010.0128 The point is the following. Consider a quantum algorithm in order to solve an NP-complete problem (i.e.: a hard problem, which is conjectured not to be solvable in polynomial time). Now, consider a classical ...

5

There are numerous examples of people using genetic algorithms, for example, to optimize some output where an actual solution of the equation would be otherwise impossible. Information entropy, which is a generic computing concept, has some hold on statistical physics. But I cannot think of a case I have seen where a concept from cutting edge computer ...

0

For electric circuits, CircuitLab is a nice online editor and simulator. There are some restrictions to what you can do without an account or with a free account - I can't remember the details - but you can use print-screen to get nice pictures out of it. I like it because it is really at the level of simplicity I need: if I'm explaining a basic ...

1

Gerard 't Hooft certainly thinks so. What if you are older, and you are not at all looking forward to join those noisy crowds of young students ? It should be possible, these days, to collect all knowledge you need from the internet. [...] This way, the costs of becoming a theoretical physicist should not exceed much the price of a computer with ...

0

If you do not yet master calculus, I recommend the book Zeldovich Ya.B., Yaglom I.M.: Higher Math for Beginners, Mir 1988 which is great. Then, you need to understand 1) ordinary differential equations of 1st and 2nd order and have some idea about 2) many-variable calculus and 3) linear operators and matrices. If you want to understand Hamilton's ...

0

In the UK, Lagrangian mechanics would normally be taught to first or second year undergraduate students who have a solid understanding of Newtonian dynamics and calculus with multiple variables. For an idea of the kind of texts you might need you could look at university syllabuses such as: University of Manchester: ...

-1

I think it's useful to think about space-time as being like a foam ball. The point of unifying space and time comes from relativity. Consider that when lengths contract, times also dilate. This is a bit like squishing our foam ball in the middle, causing it to bulge at the top and bottom. In other words, the bending of space-time is fundamentally a ...

3

Here's a useful link. For me, it's helpful to think there are clocks and rulers. The clock I have is the only one I have to measure time, and the ruler I have is the only one I have to measure distance, but you can think of space as being spanned by a big lattice of rulers, and if some of them get shortened or lengthened relative to others, there's no way ...

8

According to Wikipedia: In particle physics, the history of quantum field theory starts with its creation by Paul Dirac, when he attempted to quantize the electromagnetic field in the late 1920s. [My emphasis.] And according to Wikipedia's entry on Dirac: He was the first to develop quantum field theory, which underlies all theoretical work on ...

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QFT was formulated over many decades, from the 20's to the 70's, by many people from the USA, Europe and the USSR, amongst others. Although QFT is an active research topic, QFT was demonstrated to be consistent by 't Hooft in the 70's. Whilst particular achievements and developments are attributable to specific individuals, QFT was the result of innumerable ...

1

Basically, the universe has a speed limit. No object can ever exceed the speed of light. Now imagine you decide to prove Einstein wrong by building a train capable of nearly reaching the speed of light, and then shooting a bullet forward in that train, so that the bullet will break the speed of light. In order to preserve this speed limit, time for you and ...

1

Both approaches are equally correct in this case. $F = mv^2/R$ is just a consequence of the law for rotational motion, which says $\tau = I\alpha$ (Torque = Moment of Inertia * Angular acceleration). The former formula may be used in case the objects in consideration are point masses. But the latter, more general version of the formula is applicable for ...

1

There will always be solutions that can't be analytical. For example, any model of more than two bodies without any special constraints, cannot be solved analytically. From the gravitational interactions between three planets to three particles interacting (electromagnetically or otherwise) in quantum theory. To have mathematically analytical solutions, ...

7

No. There is nothing wrong with perturbation theory, or with theories with known, restricted accuracy. The point of theory is to explain the results of observation from as simple an initial theoretical standpoint as possible. Therefore: Since experiment always has a finite uncertainty, one can only ask that theory match the experimental value within its ...

4

The whole volume XVII of the Proceedings of the Cambridge Philosophical Society is available on the Internet Archive at the url https://archive.org/details/proceedingsofcam1718191316camb It is p.43 as marked in the text and p.60 in the document. It is available in pdf, ePub, Kindle, Daisy and DjVu formats, as well as a dedicated (very nice) online ...

3

Muons are single-particle excitations (states) of the $e-\mu-\tau$ quantum field, except that these states don't have definite values of energy (they are in a superposition of states that have definite energy). Because states with different energies change at different rates, this superposition changes with time. After some time has elapsed, the ...

1

What I think you're trying to get at is the vaccum energy. Weight is always associated with a force, so on earth we feel the force of gravity on our body and we call that our weight. Now Einstein showed us that there is an equivalence between mass and energy. What we know from Quantum Field Theory is that there is some underlying amount of energy just ...

3

OK, I watched the video. It consists of two parts. The first part talks about General relativity and the introduction of a cosmological constant, which from the argument should not exist in completely empty space. He then goes to the Quantum Field Theory vacuum which has the continuous creation and annihilation of all possible fields of virtual particles ...

4

My suggestion, don't waste your time on it. Only from this Not only does the helical particle wave concept explain all the characteristics of light, etc., by means of a single model, but it allows one to calculate the exact position, velocity and spin of any relativistic particle without the need for such dubious concepts as: Einstein's time ...

0

Yes, he did. There's a press release at UCSB that acknowledges it as his second win: http://www.ia.ucsb.edu/pa/display.aspx?pkey=3161 The reason for this is, presumably, that the committee is considering giving him the bigger "2014 Fundamental Physics Prize." In essence, the Physics Frontiers prize is a nomination for that. (This is based on the ...

1

We do exercise a force on Earth. Let's say that the force in question is F. When F acts on you it provides an acceleration of F/m (where m is your mass) and when the same force F acts on the earth it provides an acceleration of F/M (where M is the mass of the Earth). As M >>>>>> m, the acceleration provide does not create some perceptive change in the ...

4

Let's say you got fatter and fatter until you were the same mass as the earth, and, at the same time, the earth got smaller and smaller until it was only as massive as you were to start with. Now after this has happened, you must agree that you are now exerting a gravitational force on the earth (since you and the earth have now effectively switched roles, ...

5

There is no significance in the choice between upper- and lower-case $\psi$ (or $\Psi$) to denote a system's wavefunction. The two are used interchangeably and it is the author's discretion to use either symbol. (On the other hand, of course, one shouldn't use the two symbols interchangeably within the same text; if both are used they would refer to ...

1

You're looking for experimental particle physics on a big detector at a national lab: There's no end to the custom electronics and embedded systems associated with the data acquisition, Computer science is definitely required (analysis of big data sets), and Plenty of really interesting fundamental physics. If you are still at the university go talk ...

0

I love Alonzo Church, but not for his contributions to Physics. The connection between algorithms and the real physical world can never be more than approximate. Noise is essential to the concept of probability, and probability is now essential to Physics via Quantum Mechanics. But Wiener saw this even classically, so I will go classical. No finite ...

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