So I was thinking about the question "What if Boltzmann's constant [tex]k[/tex] were different?" but then I got thinking about the nature of the question. What is the significance of a constant? Can you say one dimensioned constant is more fundamental than the other one? For example, I can imagine someone saying "[tex]c[/tex] is more fundamental than the gas constant [tex]R[/tex]" but does that have any meaning other than a personal liking for the speed of light? "What if I change [tex]k[/tex]?" Is that a well-defined question? Should I specify "If everything else stays the same"? And is that certainly non-contradictory? (For example how do I know if other constants are maybe defined using [tex]k[/tex]?) And it is often said that the real fundamental constants are the dimensionless ones. Why is this? I remember reading a quote that: any change in a dimensioned quantity is unnoticeable if it not accompanied with a change in a dimensionless quantity. If a dimensionless quantity changes, then certainly something measurable changes. Now why is this? And does this make it a more fundamental constant? Also they say one can use natural units in which, for example, [tex]c = 1[/tex]. I really CAN'T understand this: How can it NOT have a unit? If I then say [tex]v = 1/2[/tex], surely that is not correct? Is it not like saying "My bag weighs 2" and then assuming somebody will add the unit kg? For example if [tex]c = 1[/tex], it would be allowed to use the mathematical statement [tex]e^c = 1[/tex], but if I were to use a non-natural unit system, I would not be allowed to do that, because then I'd have a dimensioned exponent... Any other comments about constants are welcome. One last one: is there a fundamental difference in asking "What if [tex]k[/tex] had a different value?" and "What if [tex]k[/tex] could differ in different parts of our universe?" ?