Expansion Definition and 1000 Threads

I can't understand how both the material and the scale's expansion are being taken into account at the respective temperatures. Please explain the concept in detail.

I am enrolled in a plumbing program with Stratford Career Institute. In the chapter in my plumbing textbook about Water Heaters, the textbook authors assert that hot water in a water heater rises to the top of a water heater. The authors assert that cold water sinks to the bottom of a water...

The universe started off as a point and has been expanding for 13.7 billion years. Since this is a finite amount of time, how can the universe be infinite?

I grew up in a time when we thought the universe was finite in size - even if unbounded. I am now hearing (from some right here on PF) that scientists think maybe the universe is infinite in extent. But if the Big Bang bubble was once a finite size and expanded (smaller than an atom, big as a...

Mentor note: Moved from a technical math section, so missing the template. TL;DR Summary: I'm trying to solve the differential equations (D^2 -4D + 3 )y = 2xexp(3x) + 3exp(x)Cos2x On this page , I've solve particular integral by 2 ways, 1st is above the line in which ( see 7th equality from...

I've already got "Personal Speculation Warning" and I had a private conversation with @Nugatory, who told me, that I have to publish it in an appropriate peer-reviewed journal before it can be posted for discussion here. I replied with a question, if he is willing to believe, that...

I could imagine the multipole expansion of a point charge not at the origin intuitively only up to the dipole moment but not higher my thought goes as follows : imagine u have only a point charge + q at r0 this is equivalent to have also in addition to it +q and -q at the origin which result in...

The broadening of the light curves of distant supernovae is considered the most important argument in favor of the Big Bang theory and the Doppler effect. As I read, the authors of all studies of this kind are unanimous in the fact that the curves broaden with increasing redshift, and that this...

I am reading Griffiths chapter 3.4.3 on origin of coordinates in multipole expansion (can be found online here https://peppyhare.github.io/r/notes/griffiths/ch3-4/) And I got stuck at this: For the figure 3.22: the dipole moment $p = qd\hat{y}$ and has a corresponding dipole term in the...

According to Hubble's law, galaxies are moving away from Earth at a speed proportional to their distance. In other words, the further away they are, the faster they move away from the Earth. The speed of galaxies is determined by their redshift. Based on this law, some scientists have come to...

$$\delta W_{rev}=-PdV\tag{3}$$ and so $$(dU)_{rev}=TdS-PdV\tag{4}$$ For an irreversible, closed system we have $$(dU)_{irrev}=\delta Q_{irrev}+\delta W_{irrev}\tag{5}$$ My question is about the following statement Sure, internal energy is a state function. I still don't understand...

In the following expansion how to find the coefficients ##\alpha## and ##\beta##? $$|S, S_z\rangle = \alpha |S+1/2, S_z+1/2\rangle \otimes |1/2,-1/2\rangle + \beta |S+1/2, S_z-1/2\rangle \otimes |1/2,+1/2\rangle$$

I do not know if this is the place to post this. I am not a great physicist. Actually, I was an Electronic/Electrical Technician before I retired. I learned that the vacuum of space is filled with matter/antimatter particles popping out of nothing and destroying themselves almost instantly. My...

The cosmological redshift is generally assumed to be due to space expansion. But if spacetime is locally flat Minkowskian then surely photon wavelength should not change?

The first equation states that every wavefunction can be written as a sum of wavefunctions of definite momentum, with A_p being defined as the coefficients in the expansion such that when you take the |wavefunction|^2 it equals 1 - fine. We then multiply by the wavefunction conjugate and...

If neon is stored at 40 psi . 65 degrees fahrenheit. How do i calculate the psi in a closed system when the container is heated.

I had a question today as a part of my studies which was 1) If space is ever expanding what is the pressure on the creating space (universe) upon creation and 2) at what rate might you assume the quantum field is also being created and is it being affected by this pressure of creation. This is...

Is it theoretically possible for the expansion of the universe to red-shift the energy of a photon all the way to zero? If so, what happens to the photon? Or does the photon's energy only approach zero as an asymptote?

I don't understand the discovery of "accelerating expansion" in 1998 (hence the postulate of dark energy, etc..), because Hubble's old law already described exponentially accelerating expansion in 1929, right?

Hi I'm a medical doctor, this is just a hobby my uncle got me interested in as a kid. If the universe is acceleration and galaxies are moving further apart, we assume the universe as a whole is expanding as a result. It's also projected to my understanding that eventually the universe will...

I have two concentric thick cylinders in close tolerance (currently 50 micron gap), with a thin layer of glue between them. Internal cylinder is made from steel and external cylinder is made from ceramic (so the thermal expansion coefficient is not the same) The assembly is headed form inside...

##(1+x)^n=1+C_1x+C_2x^2+C_3x^3...+C_nx^n## Let ##x=1##, hence ##2^n=1+C_1+C_2+C_3...+C_n## which is equal to the sum of the coefficients. I originally thought the sum of the coefficients would be ##2^n-1## since the very first term ##1## is just a number and has no variable. But apparently...

Orodruin said in another thread that "the spacetime of a spatially flat universe generally has curvature". Is the expansion (or contraction) of a spatially flat universe the manifestation of the curvature of its spacetime? If so, does the expansion correspond to a positive or negative curvature?

I am trying to find some sources about time dimension expansion during spacetime expansion. Why do We assume that only spacial dimensions expand? I only found a lot of weird arguments. Btw, temporal dimension expansion does not mean that second was shorter in the past. Similarly to spacial...

Sorry for my questions as an amateur interested in physics: If light changes its frequency during a long time of travel in space (vacuum?) for all observers (redshift) and therefore its energy decreases (E=hf), what "entity" absorbs this energy? I suppose the answer will be that the wavelength...

Can the expansion/creation of space in the universe affect the speed of light over long distances? (dividing the space traveled (including expanded space) by the travel time). If the Hubble constant is valid throughout the universe, it follows that from a certain Megaparsec of distance, galaxies...

Ref: Principles of Physical Cosmology by P.J.E. Peoples, Princeton Univ. Press This question is likely fully answered somewhere, but I cant find it. Hubble obtained (1926) the mean mass density of the Universe as 10^-31 g/c.c. The gravitational stability equation gives (McCrea, Milne (1934))...

Just wanted to know if I was barking up the wrong bush or not with my working out if anyone could help?

How can space expand when space is not a physical thing? I’ve heard some say that is not expanding but rather it is getting less dense, which to me implies the same thing.

To be clear, I'm looking for the speed at which points in space were moving apart from one another in the universe as it existed 370000 years after the big bang, not the Hubble parameter (expansion rate) derived from our current distance within our current time. Thanks in advance!

Here's as far as I've gotten in the research (please correct any errors I'm making). The stages of high density had included these periods: • light at high energy was in a cycle of forming into matter, forming back into light, and so on • until things cooled enough for nucleons to form •...

$$\int \text{d}^4 q \, \frac{1}{(q^2 + m^2)\left(1+\frac{q^2}{\Lambda^2}\right)^2} =2 \pi^2\left(\frac{\Lambda^2}{2}-m^2 \log \frac{\Lambda}{m} \right) + o(\Lambda^0)$$ How to get this result? The notation ##o(\Lambda^0)## means all terms constant in Lambda, which we ignore because we are...

I read this old thread: https://www.physicsforums.com/threads/what-happens-to-time-as-space-is-expanding.1001016/ And I am confused by the responses. When I consider time dimension expansion, I perceive it the same way as space dimension expansion. The expansion doesn't change the unit size...

I believe in the Big Bang but I struggle with something. If the Big Bang happened and universe is expanding there has to be something (or really nothing) there for the universe to be expanding into. Any thoughts?

Hello, assuming to keep an aluminum alloy motorcycle frame not in use, still, will the daily temperature variations cause thermal fatigue due to the continuous expansions and retractions or is the force developed by a few degrees of variations not sufficient to create microstructural dislocations?

Necessary condition for a curve to provide a weak extremum. Let ##x(t)## be the extremum curve. Let ##x=x(t,u) = x(t) + u\eta(t)## be the curve with variation in the neighbourhood of ##(\varepsilon,\varepsilon')##. Let $$I(u) = \int^b_aL(t,x(t,u),\dot{x}(t,u))dt = \int^b_aL(t,x(t) +...

The GR predictions for the universe's size are those of fig.a. Whereas the Hubble expansion is exponential, fig.b. How are the two reconciled?

I suspect it will help if you know about my background: I did some linear algebra in university but never used it and am now in my mid 60s. I am interested in understanding the mathematics of quantum physics. I have read a number of layman's texts on quantum mechanics, but they all gloss over...

For this problem, The solution is, I understand their logic for their equation, but when I was trying to solve this problem, I came up with a different expression: ##\Delta A = \Delta L_x\Delta L_y## ##\Delta L_x =\Delta L_y = \Delta L## since this is a square. ##\Delta A = \Delta L^2##...

I the lambda-CDM model, is the expansion of spacetime uniform around all of spacetime, is there a smooth transition between expanding parts of spacetime (the voids) and non-expanding parts of spacetime, or is there a sharp distinction between expanding and non-expanding parts of spacetime. Is...

Wikipedia states the following in their article about the expansion of the universe: If the cosmological principle was discovered to be false in our universe, i.e. our universe was discovered to be inhomogeneous or anisotropic or both on very large scales and the FLRW metric does not hold for...

[FONT=arial]Observational evidence for cosmological coupling of black holes and its implications for an astrophysical source of dark energy [FONT=arial] Comments?

What is the meaning of the expansion at first order in ##\delta_2## and ##\delta_3## at the second step in the last line? These quantities are not "small" - on the contrary, the entire point is to then take the ##\epsilon \to 0## limit and the counterterms blow up

Using the adiabatic process formula, I've calculated the change in volume for a volume of gas with an initial pressure of 10 psig expanding to 0 psig. The initial volume is 100 cubic inches and the expanded volume is 144.9. This is a difference of 44.9. The total work done ends up being about...

Can you please explain this series f(x+\alpha)=\sum^{\infty}_{n=0}\frac{\alpha^n}{n!}\frac{d^nf}{dx^n} I am confused. Around which point is this Taylor series?

when you do a multipole expansion of the vector potential you get a monopole, dipole, quadrupole and so on terms. The monopole term for a current loop is μI/4πr*∫dl’ which goes to 0 as the integral is over a closed loop. I am kinda confused on that as evaulating the integral gives the arc length...

Greetings everyone. I learned that the distance between molecules in liquid increases while the temperature increases. Hence, its density is decreased. The process is thermal expansion. At the same time, the collision between molecules would be more frequent when the temperature increases...

Everywhere on the net, there is no image that the expansion has a departing point, through an expansion in spherical form... Why is that?

I proceeded in the usual manner in which we take ##dU = 0## in the case of free expansion because there is no heat transfer in the box, as well as no work is done. We can write, taking ## U ## as the function of ##V## and ##T##, $$ dU(V,T) = \left( \dfrac{\partial U}{\partial V} \right)_T ~...

For a freely expanding ideal gas(irreversible transformation), the change in entropy is the same as in a reversible transformation with the same initial and final states. I don't quite understand why this is true, since Clausius' theorm only has this corrolary when the two transformations are...