1. ## Astronomy bros

So reading about the gravitational constant, seems like a study in 2015 or so concluded that the gravitational constant doesn’t change. Is this a bit myopic? They used a supernovae to determine the decay of nickel in some kind of spectrum analysis from a distance still within our galaxy? How does this prove a universal constant, particularly when we are in the fringes of a black hole ( which is the center of our galaxy)?

Surely to validate, we’d need measurements outside of the galaxy, in a different galaxy?

2. Originally Posted by Deathguard
So reading about the gravitational constant, seems like a study in 2015 or so concluded that the gravitational constant doesn’t change. Is this a bit myopic? They used a supernovae to determine the decay of nickel in some kind of spectrum analysis from a distance still within our galaxy? How does this prove a universal constant, particularly when we are in the fringes of a black hole ( which is the center of our galaxy)?

Surely to validate, we’d need measurements outside of the galaxy, in a different galaxy?
To help me understand your question, are you suggesting the gravity from our own black hole (of which there are many more in our galaxy than just the one at the center) is interfering with the measurements?

If that is the case, all matter across the universe interacts with all other matter. Even if we observe matter in another galaxy, the extremely large black hole at the center of our galaxy would still have an effect on it.

Or do I just not understand your question?

3. Originally Posted by Ironmanlet
To help me understand your question, are you suggesting the gravity from our own black hole (of which there are many more in our galaxy than just the one at the center) is interfering with the measurements?

If that is the case, all matter across the universe interacts with all other matter. Even if we observe matter in another galaxy, the extremely large black hole at the center of our galaxy would still have an effect on it.

Or do I just not understand your question?
I apologize for the confusion. Yes.

Isn’t it sensical that our perception of the universe would be relative to a series of bodies - including any mass producing significant gravitational distortion like a black hole (where bodies within the spiral are obviously affected)?

4. I assume this is the study in question

https://arxiv.org/abs/1402.1534

Didn't read, but the briefest glance at Figure 1 reveals your statement

"They used a supernovae [sic] to determine the decay of nickel in some kind of spectrum analysis from a distance still within our galaxy?"

....isn't accurate. Many supernovae were used as data points, many very far away from our galaxy (a clue: a redshift > 1 as part of the data).

I also do not follow what this has to do with black holes.

5. get this guy a nobel prize in physics

stick to bench pressing homey

we can fukkin measure all visible structure and see what is and isnt gravitationally bound.

we literally got a fukkin galaxy barreling towards us.

6. Originally Posted by numberguy12
I assume this is the study in question

https://arxiv.org/abs/1402.1534

Didn't read, but the briefest glance at Figure 1 reveals your statement

"They used a supernovae [sic] to determine the decay of nickel in some kind of spectrum analysis from a distance still within our galaxy?"

....isn't accurate. Many supernovae were used as data points, many very far away from our galaxy (a clue: a redshift > 1 as part of the data).

I also do not follow what this has to do with black holes.
Well that prob settles my curiosity then if they did indeed measure outside of the galaxy, at least in part.

How it has to do with black holes: that black holes cause spatial/time distortion - thus measuring things closer to a black hole might require an adjustment in the math?

Mind you, I admit I’m not trained in this, so willingly admit ignorance.

Continuing: If we are influenced from our vantage point on earth by gravitational forces exerted from our black hole in the center of our galaxy - which has enough energy and mass to cause such large spirals - then wouldn’t it be a safe assumption some manner of distortion may skew perspective, even within the spiral, let alone the outside of it?

I’ve heard of red shift before, my understanding is that it’s some spectrum analysis relating to a universal fringe? Could this ever be distorted relative to different locations in the universe though? Or even time appearing different - to what orientation you are looking at?

Hopefully sone can appreciate the open nature (thinking out loud.. in writing form) of my questioning.

7. Originally Posted by AltarOfPlagues
get this guy a nobel prize in physics

stick to bench pressing homey

we can fukkin measure all visible structure and see what is and isnt gravitationally bound.

we literally got a fukkin galaxy barreling towards us.
Lol!

Just curious/skeptical I suppose. Maybe one day I’ll pick up some books on physics & astrophysics.

8. Originally Posted by Deathguard
I’ve heard of red shift before, my understanding is that it’s some spectrum analysis relating to a universal fringe? Could this ever be distorted relative to different locations in the universe though? Or even time appearing different - to what orientation you are looking at?

Hopefully sone can appreciate the open nature (thinking out loud.. in writing form) of my questioning.
i appreciate your question and i take issue with your calling the oft measured studied and re-confirmed gravitational constant "myopic".

gravity is everywhere, it cant distort gravity calculations and observations.

however cosmologists often admit that the laws of physics themselves may be different beyond what we are able to observe - that is to say, beyond the observable universe.

edit - apparently some fringe physicists have used a fluctuating emergent gravity to explain away dark energy, but that was probably their reasoning... erik verlinde

https://en.wikipedia.org/wiki/Entrop...e&#39;s_theory

9. there are more fundamental properties of the universe (cosmic background radiation and mass denisty of the universe) which track w MOND moreso than with a non-constant gravity.

we can observe gravity working like we think it should in all the structure (galaxies) we observe, but weird things start to happen at the edges. it seems better now to call this an edge problem (dark matter) than a gravity problem.

https://en.wikipedia.org/wiki/Dark_matter_halo

10. Whooooooo cares? I set all my constants to 1 anyways.

11. the universe is

5% matter
25% dark matter*
70% dark energy**

*dark matter is essentially observable perturbations in predicted movement of structure. eg spiral galaxies dont spin like they are posed to at the edge. if you model it as if something is there and has gravitational influence, then it works. dark matter is further confirmed by baryon acoustic oscillations. if you break out cosmic microwave background into wavelengths you can study the oscillating collapses of portions of space right after the big bang. the oscillations are damped by dark matter.

*dark energy is the accelerating expansion of the universe

12. Originally Posted by ExiledFromFit
Whooooooo cares? I set all my constants to 1 anyways.

You might care if G was literally 1 m^3/(kg*s^2)* as things around you would drop at 147,000,000,000 m/s^2, your weight would be 15 billion times your weight now at the surface of the earth, everything would be flattened to nothing, and life wouldn't exist. Not to mention the earth would be collapsing in on itself, it would not have its orbit, the sun would be long gone, and the universe as we know it would have collapsed in on itself, in a big Crunch. Just trivial little details I guess.

*:Unless you are playing some kind of game with the units in setting G equal to 1. Sure, G is 1 if we invent a new unit of mass, say a quorg, equal to about 15 billion kg, and our units of G are m^3*quorg^-1*s^-2. Or better yet, use the natural units for G (Planck length^3*plank mass^-1*plank time^-2), and voila.....G is now 1. But I'm sure you didn't mean this.

13. Originally Posted by numberguy12
You might care if G was literally 1 m^3/(kg*s^2)* as things around you would drop at 147,000,000,000 m/s^2, your weight would be 15 billion times your weight now at the surface of the earth, everything would be flattened to nothing, and life wouldn't exist. Not to mention the earth would be collapsing in on itself, it would not have its orbit, the sun would be long gone, and the universe as we know it would have collapsed in on itself, in a big Crunch. Just trivial little details I guess.

*:Unless you are playing some kind of game with the units in setting G equal to 1. Sure, G is 1 if we invent a new unit of mass, say a quorg, equal to about 15 billion kg, and our units of G are m^3*quorg^-1*s^-2. Or better yet, use the natural units for G (Planck length^3*plank mass^-1*plank time^-2), and voila.....G is now 1. But I'm sure you didn't mean this.
Obviously that's what I meant. Just becomes tricky if you don't know anymore in what arbitrary unit system you work in It's only for rough calculations to get the idea behind something.

14. Does it really matter since we'll all be dead soon?

15. Originally Posted by ExiledFromFit
Obviously that's what I meant. Just becomes tricky if you don't know anymore in what arbitrary unit system you work in It's only for rough calculations to get the idea behind something.
Something to consider:

The above is not a problem of merely arbitrarily determining the constant G by selection of units. If it was, there wouldn't be studies like the above that investigate both cosmologically and experimentally whether G changes in time or space. That is, the gist of the problem is whether the strength of the gravitational interaction changes.

For example, it is questioned whether the gravitational coupling constant αG, defined as the gravitational attraction between two electrons (Gme^2/hc), varies. And αG is a dimensionless constant, so there is no just saying...well it's just a matter of units.

The problem above about determining whether G changes is worthy of scientific investigation- so far the evidence seems to point to that it doesn't, and if it did somehow, it would be a very small change.

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