Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 207910

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

5 votes

How to rigorously put back dimensions in equations involving natural units?

It is tricky! Let's see what happens in the example you asked about. The starting point is $$ x^{'} = \dfrac{x-vt}{\sqrt{1-v^2}}. \tag1 $$ From the denominator on the right hand side we deduce that $v …
Andrew Steane's user avatar
24 votes
Accepted

Isn’t natural units prone to mistakes?

You are quite correct that the use of natural units removes a useful method for detecting errors. This is an example of a more general concept in information theory. If you use the minimum number of s …
Andrew Steane's user avatar
8 votes

Is the exact definition of the Planck units important?

I think it's all just order-of-magnitude stuff and factors of $\pi$ etc. are unimportant, but would be happy to be corrected. Having said that, if someone defined a Planck time $t_p$ and then defined …
Andrew Steane's user avatar
2 votes

Why don't we take the universal gravitational constant $G$ to be equal to 1 in $F= \frac{Gm_...

Ok let's try it. Say mass $m_1 = 1000$ kg is at distance $1$ metre from mass $m_2 = 0.5$ kg. How will mass $m_2$ move? With $G=1$ the force on it is $F = m_1 m_2/r^2 = 500$ newtons. So the acceleratio …
Andrew Steane's user avatar
2 votes

Is my friend right about omitting $c^2$ in world famous tiny equation?

Your friend was more wrong than right, as others here have said. I am just adding some thoughts that emerged after long experience with relativity. This becomes a question of practicalities. Basically …
Andrew Steane's user avatar