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Questions tagged [scales]

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2
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1answer
102 views

When do you use Quantum Mechanics? [duplicate]

Given a problem, how does one know whether to use quantum mechanics or classical mechanics? Take for example electron scattering from a nucleus. The electrons are given a wavefunction in this case. ...
1
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3answers
138 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 ...
0
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1answer
49 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 (...
0
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3answers
55 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)?
0
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0answers
136 views

Is there a solutions manual for Goldenfeld's 'Lectures on Phase Transitions and the Renormalization Group'?

Is there a solutions manual for Goldenfeld's 'Lectures on Phase Transitions and the Renormalization Group'? I'm teaching myself by working through the exercises in this book. Does anyone know of an ...
-3
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1answer
122 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 ...
3
votes
1answer
156 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 ...
0
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2answers
101 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 $e^{-x/\xi}$ ...
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2answers
70 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 ...
3
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2answers
260 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 ...
1
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1answer
132 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) + \...
0
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1answer
489 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 ...
4
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1answer
259 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 ...
1
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1answer
426 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}{\...
3
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1answer
71 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 ...
0
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0answers
85 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 ...
1
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1answer
63 views

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 ...
-1
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1answer
8k 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).
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6answers
170 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 ...
3
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1answer
520 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 ...
7
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2answers
533 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 ...
0
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1answer
501 views

Critical density as a function of scale factor

I am trying to do some cosmology problems. In an exercise given by my teacher he wrote the following: $$ \Omega_m(a) = \frac{\rho_M(a)}{\rho_{crit}(a)} = \frac{\rho_{M,0}/a^3}{\rho_{crit}(0)(H/H_0)^2}....
0
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1answer
652 views

Why does the scale reading depend on the position of the object on the scale and how to equalize that?

I have a KERN DS 100K0.5 industrial platform scale, range up to 100 kg, resolution 0.5 g, more or less like this: The specifications say reproducibility 0.5 g, linearity 1.5 g. When I stand on the ...
5
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1answer
208 views

Is there any guarantee that there will be only one point on the isotherm curve of a system that has a certain Y coord?

When reading this part of the "heat and thermodynamics" book of Zemansky, is there any guarantee that there will be only ONE intersection of the $Y=Y_1$ and the isotherm line? The alternative of ...
2
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3answers
781 views

Why are high energies equivalent to short distances?

Why are the regimes in high-energy collisions called short distances? Qualitatively I only know that the higher the given energy of the colliding particles "the smaller are the pieces yielded by ...
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0answers
33 views

Possible intermediate scales of baryogenesis?

The conventional beyond Standard Model explanation of baryogenesis is that, within Grand Unified Theories (GUT), there exist some new heavy scalar bosons of mass $M_{\rm GUT}\sim10^{15}$ GeV, which ...
9
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2answers
533 views

Does the scale at which the observations are made, have a role in the physical laws which are obtained? [closed]

I am starting studying quantum mechanics and observed that classical physics ceases to be accurate at the microscopic world (atomic length-scales). Here is my question, cast as a thought experiment ...
5
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1answer
2k views

Why is the apparent weight smaller when you crouch down on a scale?

I am having a problem understanding the concept of the apparent weight change when you crouch down, stand up, and jump on the scale. What is happening that makes the scale change?
5
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2answers
2k views

Maximum reading after dropping a mass onto a scale

If one drops an object onto a scale, the needle will temporarily spike to a high reading. Given a mass $m$ dropped from a height $h$ above a spring scale, is there a good way to approximate what the ...
0
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3answers
275 views

On a scale, why does the heavier object go down?

When you balance a pencil on your finger, I have always wondered, "Why does the heavier part go down, and the lighter, up?"
2
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3answers
222 views

Why are log scales so common?

I am currently reading a very nice book on scales in physics. There is a discussion on the different physical scales which are based on the effect of the corresponding phenomena, the given examples ...
1
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1answer
149 views

Connection between the cosmological constant $\Lambda$ and the cutoff scale $\Lambda$

I'm trying to understand the connection between the $\Lambda$ from cosmology and the $\Lambda$ from QFT. Cosmology: The cosmological constant enters the Einstein equations. In the special case of the ...
32
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1answer
3k views

Are all machines linearly scalable?

For all machines (cars, elevators, computers, etc), when size, power requirements, dimensions are scaled by a constant N, will it work just as is? Will a car with all its parts 10x larger still work ...
76
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7answers
24k views

Which way does the scale tip?

I found the problem described in the attached picture on the internet. In the comment sections there were two opposing solutions. So it made me wonder which of those would be the actual solution. So ...
0
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1answer
544 views

How can I ensure my scale is not affected my surface beneath it

I have person weighing spring scale. I live in Japan where the house has wood floors which deflect significantly under weight. I weighed my self in the bathroom and in the tiled bath area. The ...
2
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0answers
89 views

sensitive scale & resistance of analog current meter

Does the resistance of an analog current meter increase or decrease when it is set to a more sensitive scale (lower range)?
4
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2answers
767 views

Why do we have a TeV scale?

When model building we don't want to introduce any new scales into our theory. We usually try to have new particles at the Higgs (TeV) scale (to solve the hierarchy problem), at the GUT scale, or at ...
5
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2answers
430 views

If Earth was the size of an orange, what consistency would it be? [closed]

I understand that the Earth is composed of a thin crust "floating" over a semi-solid layer of mantle. I was wondering how it would feel at a human scale, say the size of an orange in your hand. Could ...
6
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3answers
12k views

What is the logic behind the Fahrenheit scale?

The Fahrenheit scale is defined by fixed points on the scale. What interests me is the apparent arbitrary chosen numbers in these fix-points. First wikipedia wites from 32 to 212. -and later in the ...
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4answers
9k views

If there were no space between nuclei, how big would the Earth be?

I have some people telling me it would be the size of baseball. I am quite doubtful on this. If this is true, then the gaps must be so incredibly huge that everything should be transparent. I am not a ...
5
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2answers
3k views

Is there scale by size of all discovered particles?

Atom: Neutron: Elementary particles: Is there scale by size of all discovered particles? From neutron and proton to electron and to boson? Compare to each other, like this I have found many ...
10
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2answers
35k views

What does the Reynolds Number of a flow represent physically?

What does the Reynolds Number of a flow represent physically? I am having trouble understanding the meaning and the utility of the Reynolds number for a certain flow, could someone please tell me how ...
4
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1answer
176 views

For how long must a molecule remain stable to be considered “stable”?

In the Star Trek: Voyager episode The Omega Directive, Seven of Nine says that the Borg synthesized a molecule which was "kept [] stable for one trillionth of a nanosecond before it destabilized". ...
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1answer
2k views

Explanation of energy levels in molecules, atoms, nuclei and their relationship

Why are the energy levels of molecules, the atoms that form them and the nuclei inside the atoms considered separately? Or phrased in a different way- what is it that makes their energy levels so ...
5
votes
1answer
591 views

Definition of Fine-Tuning

I've looked in and out the forum, and found no precise definition of the meaning of fine-tuning in physics. QUESTION Is it possible to give a precise definition of fine-tuning? Of course, I guess ...
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2answers
1k views

What is the hierarchy problem?

BACKGROUND So far I understood that the hierarchy problem was the large difference between the gravitational scale, $M_{pl}\sim 10^{18}\; [GeV]$, compared with the electroweak scale, $M_{ew}\sim 10^3\...
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5answers
4k views

Planck mass is about the mass of one eyebrow hair

Unlike most Planck units named after "Planck" such as Planck length, Planck temperature, etc, the Planck mass seems more closed to daily life. It is about $10^{-5}$g, same order of magnitude of one ...
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1answer
2k views

Relationship between hierarchy problem and higgs fine tuning?

I often hear of hierarchy problem being used synonymous with Higgs fine tuning (esp with regards with motivations for SUSY). What exactly is the relationship between the two problems? As I understand ...
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1answer
331 views

Reference for understanding characteristic length and time scales in a system (in particular electronic transport)

I am working on the transport properties of two dimensional electron gas in semiconductor heterostructures and am interested in the characteristic length and time scales of the system like elastic ...
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3answers
262 views

Why is current not 0 in a regular resistor - battery circuit immediately after you closed a circuit?

In regular open circuits with either a capacitor or inductor element, (when capacitor is uncharged) with a battery, when a switch is closed to complete the circuit the current is said to be 0 because ...