Questions tagged [scales]

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Does the minimum connection time of ocean surface currents depend on the patch scale?

The Nature paper "The timescales of global surface-ocean connectivity" attempts to model "minimum connectivity times (Min-T), or distances based on the fastest times that particles can ...
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What is the difference between scale invariance and scale free?

A question several years ago asked, "What is the difference between scale invariance and self-similarity. It appears that a new term has become popular in recent years, which is "scale ...
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Energy density at a given scale in terms of the Energy Spectrum

Background: Let us have a turbulent fluid with a random velocity field $\mathbf{u}(\mathbf{x})$. The volume averaged kinetic energy density $\mathscr{E}_K$ can be expressed as $$\mathscr{E}_K=\frac{1}{...
Sayan Mandal's user avatar
7 votes
3 answers
1k views

How can we determine the energy scale of a physics theory?

It is very common in physics, when we refer to the most diverse theories, on the most diverse length scales, we also refer to their energy scale. It is through the energy scale that we classify a ...
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Calculating an anisotropic or component Taylor microscale

The Taylor microscale in isotropic turbulence is given by: $$\lambda = \sqrt{ 15 \frac{\nu \ v'^2}{\epsilon} }$$ where v' is the root mean square of the velocity fluctuations. In general, for ...
rdemyan's user avatar
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Scale dependent dimensionality

Many theories of quantum gravity features the so called "dimensional reduction" (e.g. Asymptotic Safety, Causal Dynamical Triangulations, Euclidean Dynamical Triangulations, Loop Quantum ...
Kregnach's user avatar
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About the formula of the Taylor microscale

I am running simulations of a non-isotropic turbulent flow and I need to compute the Taylor microscale. The formula one can find in the book Turbulent flows (Stephen B. Pope) is : $\lambda = \sqrt{10} ...
StrangeGorov's user avatar
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1 answer
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Weight on a scale

imagine that you're at the baggage weigh in point at an airport. your luggage is on the scale and you try to cheat the price by pivoting your heel on the ground and toe beneath one end of the suitcase ...
Ryan-O's user avatar
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2 answers
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Simple dynamics im really confused

So my question is a little dumb: if an object on a scale has a weight that points downwards and the scale exerts normal force on the object upwards, cancelling the forces acted on the object then what ...
noosah's user avatar
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Characteristic time scale in floquet system?

In Floquet formalism, we have quasi-energy spectrum instead of energy spectrum. However, if we have a driving force with a low frequency, we shall be able to use adiabatic approximation and regard the ...
Taveren Sa's user avatar
1 vote
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Present value of the cosmological scale factor, important or arbitrary?

I'm now confused about a subject that I thought was very clear to me, until recently. So I need to sort this clearly once and for all. Consider the standard FLRW cosmology in classical general ...
Cham's user avatar
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How does the eddy velocity scale with its time scale?

According to Kolmogorov's energy casacade model, if we have a flow with inertial velocity scale $\mathcal{V}$, inertial length scale $\mathcal{L}$ then we can calculate the eddy velocity of an eddy ...
Thomas Wagenaar's user avatar
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171 views

Scale bars (SEM-Zeiss)

I am using ImageJ to measure distances in an SEM image. The scale bar I'm using looks like this What is the correct distance represented by the scale bar? Is it line 1 or 2?
Aleksejus Pacalovas's user avatar
2 votes
2 answers
5k views

Bath-Scales weight or mass?

I read that bath scales measure body weight and not mass which means they measure m*g and not m. If I got a reading of 50 kg, does that mean that my mass is nearly 5? Units of m*g aren't kg so why ...
dan's user avatar
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1 answer
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What it means for something to be twice as hot?

Can the statement "the sun is $1000$ times hotter than the Earth" make sense without a scale system. I often hear such statements but does it only make sense when using a system with $0$ as ...
Ruochan Liu's user avatar
2 votes
0 answers
93 views

Formula to get scales of the two components (radial and perpendicular) of Baryonic Acoustic Oscillations (BAO)

In an astrophysics context about BAO (Baryonic Acoustic Oscillation), it is written on the following paper BAO paper : "BAO are much smaller in amplitude than the CMB acoustic peaks, and are ...
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5 votes
2 answers
302 views

Power law behaviour at phase transition point & presence of fluctuations of all length scales

In physics, exponentials such as $\exp(-r/\xi) $ typically come with a natural length scale $\xi$ while power laws such as $\sim 1/r^n$ don't have a definite length scale (at least not readily ...
SRS's user avatar
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Continuum assumption: validity & motivation

I still can't grasp why the so-called continuum assumption can be taken as reasonable under the proper conditions. Let's consider the space-time microscopic distribution of a generic tensor field. If ...
Federico Toso's user avatar
1 vote
1 answer
640 views

Why do hot-wire instruments have a non-linear scale?

Hot-wire instruments are used to measure rms voltage or rms current in AC circuits. The construction of a hot-wire instrument is shown in the following diagram: Image source: Hitzdrahtmesswerk (Hot ...
Vishnu's user avatar
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1 answer
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If space expands, why does a liter of water stay a liter? [duplicate]

From observing the universe, we know that space expands. I see what that means on cosmic scales. But what does it mean on smaller scales? If I have a graduated beaker of 2 liter, and 1 liter of ...
Volker Siegel's user avatar
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1 answer
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How can I verify the relation $m\omega^2 = |\textrm{constant}|$ using logarithmic plot? [closed]

We have demonstrated the uniform circular motion in the lab. Centripetal force and the radius are constant while the mass of the object increased 5 times thus 5 different angular velocities were ...
Ç.Eti's user avatar
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3 answers
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Why is the Kelvin scale formed using the triple point of water rather than the freezing point?

I am trying to learn some thermodynamics by watching the lecture series on YouTube by MIT. In the second lecture, from 9:00 to 9:45, the lecturer talks about why the freezing point of water as defined ...
Vishal Jain's user avatar
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7 votes
3 answers
118 views

How unique is the length scale picked out by intelligent life? [closed]

Our human bodies pick out a length scale (let’s say 1m). How unique is this scale and why did it arise? In other words, how much smaller could humans, or multicellular lifeforms in general, be while ...
Michael Angelo's user avatar
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2 answers
133 views

What is the admissible range of sizes or scales for double slit experiments?

Sometimes, the slits are in the range of nanometers, but I often bump into comments saying you can try this at home with lasers and polarized glass. Recently, I even found clearly macroscopic pictures ...
Michelange Baudoux's user avatar
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2 answers
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What is the distrubition of the forces on the hand-scale

In the picture above, I am applying 32 33 Newtons of force if I am not wrong. But, what is the forces on my both hands? Do they share it equally? Thanks.
muyustan's user avatar
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3 answers
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Why does a scale measure the normal force and not the weight of an object?

I don't understand the reason scales measure the normal force instead of the weight.
austingae's user avatar
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0 answers
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is there any experimental method for measurement of thickness at atomic scale?

is there any experimental method for measurement of thickness at atomic scale? there are some methods for measurement of thickness even at nano scales such as AFM,TEM but my question is about atomic ...
hoda's user avatar
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2 votes
2 answers
78 views

Weighing machine, kg vs. N

When I stand on a weighing machine and it shows me the number 75 , is it my mass in Kg or the Normal Force due to gravity in N
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3 votes
1 answer
146 views

What does Earth feel like when squeezed?

he average density is about 4g/cm^3 so if the earth was in the size of an orange, it would feel like a rather heavy ball. The crust is relatively thin, and the earth is said to be solid land masses ...
Per Alexandersson's user avatar
1 vote
0 answers
150 views

How scale invariance is broken in nature?

By definition a system will exhibit scale invariance at low energies if it has an IR fixed point. I am having some doubts on how to interpret this fact in terms of quantum field theory and to ...
AoZora's user avatar
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1 answer
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Cosmological densities when universe was/will be a different size

Supposing a spatially flat, matter-dominated universe, the expression for the Hubble parameter is: $$ H^{2}=H_{0}^{2}\left(\frac{\Omega_{m}}{a^{3}}+\Omega_{\Lambda}\right) $$ The previous equation ...
Kandrax's user avatar
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1 vote
3 answers
201 views

Where is the line between Quantum and Relativity?

Its often said QM is for the very small and GR for the very large. This brings to mind that there should be some limit at which one starts to apply and the other stops. Now I know there are more ...
christo183's user avatar
1 vote
1 answer
2k views

Specific heat of water in unit J/kg °F

We know that specific heat of water is 4186 J/kg °C This is the amount of heat per unit mass required to raise/change the temperature by one degree Celsius. We also know that ∆°C = 5/9 °∆F = ∆K (...
user600016's user avatar
0 votes
3 answers
58 views

If mass produces gravity, and gravity curves the part of space, then why you say, that electron has no form\scale? [closed]

Using Einstein's equation we can calculate the space-time curving(but I'm too stupid to do this). Hence, why everybody say that electron has no form\scale (although has spin at the same time)?
user avatar
-3 votes
1 answer
153 views

Theory on how to break the speed of light [closed]

I am 14 years old and I think I have a good grasp on physics but I have a question. Imagine you were to shrink everything in the universe (except for yourself) down to the size of an atom and it was ...
Samuel carson's user avatar
3 votes
1 answer
247 views

Is there a relation between large-scale oscillations and small-scale oscillations?

From Neural oscillation - Wikipedia: Oscillatory activity in the brain is widely observed at different levels of organization and is thought to play a key role in processing neural information. In ...
Ooker's user avatar
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2 answers
190 views

Is there a natural scale associated with polynomials?

This question is related to a previous question asked here. Power laws are scale invariant. They don't have a built-in or characteristic scale associated with them. Exponentials such as $e^{-x/\xi}$ ...
SRS's user avatar
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1 vote
2 answers
130 views

Energy scales and Lorentz Transformations

There are many particle physics processes where the initial particles must have some minimum energy in order to create the final ones. However, since I could just run through the lab really fast in ...
P. C. Spaniel's user avatar
6 votes
3 answers
1k views

Dressing vs. renormalization

In the past, my understanding was always that the processes of dressing a bare quantity (such as mass or charge) and renormalizing these same properties are different things. Dressing, as far as I ...
Janosh's user avatar
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1 vote
1 answer
364 views

Leading order DGLAP evolution

Consider the leading-order (LO) DGLAP ((Dokshitzer–Gribov–Lipatov–Altarelli–Parisi) equation $$x \mu^2 \frac{d xg(x,\mu^2)}{d\mu^2}= \alpha_s \int_x^1 dz P_{gg}(z) \frac{x}{z} g(\frac{x}{z}, \mu^2) + \...
CAF's user avatar
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0 votes
1 answer
3k views

Proof of X-LFP/UFP-LFP=constant for all scales of temperature

I came across this formula to convert from one unit of temperature to another. I could not find any proof for this though. In the formula, 'X' is the temperature value to be converted, 'UFP' is the ...
Rayyan Asif Khan's user avatar
6 votes
1 answer
1k views

Scale invariance at phase transitions

The Wikipedia entry for scale invariance states In statistical mechanics, scale invariance is a feature of phase transitions. The key observation is that near a phase transition or critical ...
Janosh's user avatar
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3 votes
2 answers
1k views

What is the Planck scale magnetic field strength?

Using the constants $\mu_0$ (or $\varepsilon_0$), $c$, $\hbar$, $e$ and $G$, it is possible to define two quantities with units of magnetic field : \begin{align} B_1 &= \sqrt{\frac{\mu_0 c^7}{\...
Cham's user avatar
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2 votes
1 answer
154 views

What would a regular bathroom scale indicate as it's sinking underwater

It seems intuitive that a (waterproofed) spring-based scale placed at the bottom of a lake would indicate the weight of the water column above it. But assume the scale sinks from the surface of the ...
Dan Dascalescu's user avatar
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0 answers
101 views

Balanced forces in scales

We have scales-like mechanism with a spring. Rigidity of the spring $C=10\ \mathrm{kg/cm}$, initial length $L_0=60\ \mathrm{mm}$ and diameter $d=\ \mathrm{10mm}$. Without any weight the scales are in ...
lexicore's user avatar
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1 vote
1 answer
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How can physicists observe events at large scales such as a star birth?

I read recently multiple articles about physicists observing the birth of a star, or a star swallowed by a black hole. However I can't manage to understand how these phenomena are observable at such ...
matt's user avatar
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2 votes
1 answer
19k views

How can a beam balance measure mass?

In Newtonian physics, mass is the amount of matter in an object. So, how can a beam balance measure the amount of matter in an object (which is the mass of the object).
Adik001's user avatar
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-2 votes
6 answers
428 views

Which way will the scale tip? [duplicate]

This problem has bothered me for quite some time and I can't solve it. I have even tried to make a construction, but it sometimes tips to the left and sometimes tips to the right :). When we submerge ...
user3368512's user avatar
5 votes
1 answer
2k views

What is a "scale length", and how do I calculate it for galaxies?

I'm trying to work through, understand, and apply concepts regarding mass models of galaxies. Looking at the Hernquist model, I'm finding the equation $$Φ(r)=−\frac{GM}{r+a},$$ where a is the scale ...
Pulchritude's user avatar
8 votes
2 answers
3k views

Why is the string length around the Planck length?

In string theory, it is assumed that a string is about the size of a Planck length, $$\ell_{string} \sim \ell_{Pl} \simeq 10^{-35}\,\text m.$$ Why that length? Why not for example a hundred times ...
Asmund's user avatar
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