Is gravitational constant unchanging over age of universe?

In summary, there is strong evidence that the gravitational constant has remained relatively constant throughout the history of the universe. While there may be some slight variations, current measurements suggest that it has not changed by more than 2% over the last 13.8 billion years. More recent and precise measurements are ongoing to further constrain the possible changes in the gravitational constant.
  • #1
Gate2wire
do we know for a fact that the gravitational constant has always been the same since the dawn of the universe? I feel like gravitational forces should slowly be decreasing as the universe ages (meaning that assuming mass of Earth doesn't change, we should weigh a bit less in a billion years) ...but I can't find any articles on a changing gravitational constant, proving or disproving.
 
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  • #2
Gate2wire said:
I feel like gravitational forces should slowly be decreasing as the universe ages (meaning that assuming mass of Earth doesn't change, we should weigh a bit less in a billion years)

why do YOU think that ?
 
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  • #3
Gate2wire said:
do we know for a fact that the gravitational constant has always been the same since the dawn of the universe?

No, but we have strong evidence suggesting that it must have been within a very small amount of its current value for most of the last 13.8 billion years or so.

Gate2wire said:
I feel like gravitational forces should slowly be decreasing as the universe ages (meaning that assuming mass of Earth doesn't change, we should weigh a bit less in a billion years) ...but I can't find any articles on a changing gravitational constant, proving or disproving.

I'm sure there's at least a handful of papers out there dealing with this issue, but for the most part our observations of distant parts of the universe (corresponding to very far in the past) inherently place tight constraints on what the gravitational constant can be. Too high or too low and our universe just wouldn't look the way it does today when we view it through our telescopes.

I caution you against coming up with an idea based on how you "feel" something should be unless you are directly working in a specific field on a specific problem, and even then you should be careful. Human intuition is far from reliable.
 
  • #4
Experimental measurements are never exact, so all we can do (in the absence of finding a change) is setting upper limits on the possible changes.

We know it changed by less than 1 part in 10 billion per year within the last 9 billion years: Measurement. In other words, it can't have been completely different billions of years ago.
More recent measurements are more precise, but limited to the last decades: In this time, the constant changed by less than 2 parts in a trillion per year: Measurement. Assuming a constant rate of change, this means the gravitational constant didn't change by more than 2% over the history of the universe. The current APOLLO measurements will improve this upper limit by a factor of about 20, constraining a linear change to less than 0.1% over the history of the universe.
 

FAQ: Is gravitational constant unchanging over age of universe?

1. Is the value of the gravitational constant the same throughout the entire universe?

The value of the gravitational constant, denoted by G, is believed to be constant throughout the entire observable universe. This means that no matter where you are in the universe, the strength of gravity between two objects will be the same. However, there are some theories that suggest the value of G may have been different in the past or may vary in other regions of the universe that we cannot observe.

2. Has the gravitational constant always been the same since the beginning of the universe?

Currently, there is no evidence to suggest that the value of G has changed since the beginning of the universe. In fact, the current understanding is that G is a fundamental constant and has remained constant since the early stages of the universe. However, our understanding of the early universe is still limited, so this is an area of ongoing research.

3. How is the value of the gravitational constant determined?

The value of G was first measured by Henry Cavendish in the late 18th century using a torsion balance experiment. Since then, numerous experiments have been conducted to measure G, with the most recent and precise value being determined by the National Institute for Standards and Technology (NIST) in 2014.

4. Are there any factors that could cause the value of the gravitational constant to change?

While there is currently no evidence to suggest that the value of G changes, there are some theories that propose it could vary in certain scenarios. For example, some theories suggest that in the early stages of the universe, when the energy density was much higher, the value of G may have been different. Additionally, some theories of gravity, such as modified Newtonian dynamics (MOND), propose that the value of G may change in extremely low or high gravitational fields.

5. How does the value of the gravitational constant affect the expansion of the universe?

The value of G is one of the fundamental parameters that determines the rate of expansion of the universe. Along with the density of matter and dark energy, it plays a crucial role in the dynamics of the universe. A slightly different value of G could potentially lead to a vastly different evolution of the universe, making it an important constant to study and understand.

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