# Questions tagged [absolute-units]

Absolute units, or natural units, are a system of units where certain dimensionful constants are set to 1. This often simplifies various formulae.

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### Can fundamental quantities be "unified"?

( Probably a stupid question. But the thought crossed my mind. I'm not a physicist; I'm a mathematician) Is there any way that the fundamental quantities (like length, time ) be "unified" in some ...
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### Derive the conversion factor from SI to Geometric units [closed]

In the geometrized system of units, $G = c = 1$. This directly gives us the definitions for second and kilogram in this system, as $1\:s = c_0\:m$ and $1\:kg = G_0c_0^{-2}\:m$, where I have used the ...
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### Converting units when $c=G=1$

In my homework assignment it is written that to convert from time to length you need to multiply by $c$, and to convert from mass to length you need to multiply by $G/c^2$, however I dont entirely ...
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### Why does natural units technique only works in equations in Physics?

Example where it will not work is $(\frac{A}{B})^m = n$. Set $A=B=1$ and then solve for $m$. And example where it will work is: $(E/c)^2 = p^2+ (mc)^2$. You can drop $c$ and put it back later by ...
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### Are there any system of units where we get the value of all the fundamental constants to be 1?

As far as I know the magnitude of constants depends on our units of measurements, so are there any units of measurements such that all the magnitude of all the fundamental constants is 1?
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### What is the advantage of natural units over SI units?

Why do physics professionals often use various different systems of units instead of SI units. Especially I ask about when constants like $c$ or $\hbar$ are put to 1....what is the advantage of this?
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### System of Units Based on Energy and Time

Is it possible to have a system of units in which Time and Energy as the fundamental quantities and others as derived quantities. Also using only pi,e , avagadro number and planck's constant
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### In particle physics/SM, how to demonstrate that dimension of length is 1/energy?

In particle physics/Standard Model, using $\hbar=1, c=1$, how to demonstrate that dimension of length is 1/energy? More generally, how to find dimension of a given operator, for example the covariant ...
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### Unit of Pressure - $\frac{N}{m^2}$ or $\frac{kg}{cm^2}$

I am came across Pressure being given with unit $\frac{kg}{m^2}$ at a lot of technical papers I am reading. However, as far as I understand, Pressure is defined as $\frac{N}{m^2}$ which is not same ...
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### How to reintroduce $\hbar$ and $c$ into a formula written in natural units? [duplicate]

I am looking for a way to translate formulas written in natural units into either HLU units or SI units. Seeing the Planck constant and the speed of light would help me understand what is going on. ...
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### Undoing problems caused by setting $c = 1$ { or "Undoing $c = 1$" }

In the mathematical derivation of equations for physics, and involving wave propagation in particular, the propagation speed at the start of the derivation is often set to one (c = 1). I am working ...
The speed of light in vacuum is approximated to be $3×10^8\ ms^{-1}.$ But, if we change the units, we can get a different number. For example, it won't be $3×10^8$ if we used $ft\,s^{-1}$ instead of $... 1answer 70 views ### The expression of the fine-structure constant post-May 2019 [closed] Those of us who are engineers were never fond of the common expression from physicists that $$\alpha = \frac{e^2}{\hbar c}$$ implying that the units of the elementary charge are in "$\sqrt{hc}$". ... 2answers 74 views ### Would setting the ideal gas constant to$1$yield an attractive natural temperature scale? [closed] In this recent question, there was a comment 'The "zero point" of Kelvin is natural, but the scale is not'. This led me to wonder whether setting$R = 1$in the ideal gas law would be an attractive ... 3answers 337 views ### How to find the corrsponding expression after working with natural units$\hbar=c=1$? If one does long calculations in natural units how does one find the right expression in let's say SI units in the end? I know that natural units make the calculations easier and also help to show ... 0answers 38 views ### Grasping systems of units Perhaps it's that I've grown up with the SI system of units, but there's something about other unit systems that doesn't sit well with me. For example, Coulomb's law in Gaussian units can be written ... 1answer 2k views ### A question about natural/geometrized units I had a question about the following document- Natural units I understand the conversion factors. But if you look at the tables, they take an SI unit, say 1 kg, convert it into geometrized units, say ... 2answers 170 views ### Factors of$c$when giving masses in natural units? I am starting a course on particle physics, and have been introduced to natural units. I am slightly confused, because we are using 'natural units', and yet masses are stated as, for instance,$139.6\ ...
Good evening, I'm reading the paper Prehawking radiation by William G. Unruh where it says: ...a time scale of order of $m^{3}$ in Planck units, or $10^{53}$ ages of the current universe for a ...