# If the gravitational constant had a different value

• I
• Ranku
Ranku
If the gravitational constant had a different value, say a lower value than the present value, and since the gravitational constant is a part of Planck dimensions, such as Planck mass, Planck length, etc., how would quantum and classical processes be affected? Are there problems which use the Planck dimension, such as Planck mass, which would be better served if the gravitational constant had a different value?

I think you are going to need to be more specific in your question. It sounds a lot like "If things were different would they be different?"

Isn't this the same as the "what if the speed of light were different" thread? Messing with dimensionful fundamental constants turns out to be nothing but a unit change. You need to change a dimensionless constant. I don't know what that constant would be in this case, however.

I think you are going to need to be more specific in your question. It sounds a lot like "If things were different would they be different?"
I was wondering are there any outstanding problems or issues in physics wherein changing the value of a fundamental constant like gravitational constant or a composite constant like Planck mass, might help in resolving the issue or give a more a more accurate fit with observation?

Motore
Ranku said:
I was wondering are there any outstanding problems or issues in physics wherein changing the value of a fundamental constant like gravitational constant or a composite constant like Planck mass, might help in resolving the issue or give a more a more accurate fit with observation?
Gosh, we scientists sure are ignorant yokels, aren't we.

Where do you think the value of G comes from? Observation. How can it better match observation if it were different?

Lordy.

Last edited:
Demystifier and Ranku
Lordy.

Ranku said:
If the gravitational constant had a different value
Asking this question about a constant that is not dimensionless is always problematic, because you can't just change that one constant and keep everything else the same. This usually comes up when people ask what if the speed of light were different; the actual physically meaningful question is what if the fine structure constant were different, since the latter is the dimensionless constant that is relevant for electromagnetism.

In the case of gravity, we don't know of any dimensionless constant that is purely associated with it, which suggests that in fact there is no way to just change the strength of gravity and keep everything else the same. Which means your question would be unanswerable as it stands; we would have to figure out what else would have to change if the gravitational constant changed, and we don't have a good way of answering that question either. We probably will not have a good understanding of this unless and until we develop a theory of quantum gravity.

Ranku
phinds said:
My favourite 'what if' question of all time: What if an observer were to travel alongside a light ray, whereby the observer would no longer be able to tell both of them are moving at all?

berkeman
PeterDonis said:
Asking this question about a constant that is not dimensionless is always problematic, because you can't just change that one constant and keep everything else the same. This usually comes up when people ask what if the speed of light were different; the actual physically meaningful question is what if the fine structure constant were different, since the latter is the dimensionless constant that is relevant for electromagnetism.

In the case of gravity, we don't know of any dimensionless constant that is purely associated with it, which suggests that in fact there is no way to just change the strength of gravity and keep everything else the same. Which means your question would be unanswerable as it stands; we would have to figure out what else would have to change if the gravitational constant changed, and we don't have a good way of answering that question either. We probably will not have a good understanding of this unless and until we develop a theory of quantum gravity.
Thank you for answering a 'stupid question' in a non-stupid way.

Ranku said:
My favourite 'what if' question of all time: What if an observer were to travel alongside a light ray, whereby the observer would no longer be able to tell both of them are moving at all?
Einstein already gave the correct answer to this one: it's impossible. Light must move at ##c## relative to any observer: that's what Maxwell's Equations tell us.

PeterDonis said:
Einstein already gave the correct answer to this one: it's impossible. Light must move at ##c## relative to any observer: that's what Maxwell's Equa
Of course. I mentioned it to make the point to some of the other mentors who are mocking my 'stupid question'.

Ranku said:
some of the other mentors
There is only one mentor participating in this thread, @PeterDonis

Ranku said:
stupid question
The only person who used that phrase was you. This kind of passive-aggressive nonsense tends not to fly here.

FWIW, I don't think it was a stupid question. I do, however, think it was a lazy question.

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