Conservation of Energy Question

[m_robertson]

Okay, so as I understand it, matter and energy can't be created nor destroyed, only converted from one form to another. So the question I have is, does that mean the total amount of energy in the universe is always the same? Presumably it is energy that is driving the accelerated expansion of the universe throughout the course time, so am I right in assuming that this energy will never be consumed no matter how long time goes on for?

 

[Nathanael]

Okay, so as I understand it, matter and energy can't be created nor destroyed, only converted from one form to another. So the question I have is, does that mean the total amount of energy in the universe is always the same? Presumably it is energy that is driving the accelerated expansion of the universe throughout the course time, so am I right in assuming that this energy will never be consumed no matter how long time goes on for?

Conservation of energy applies to any closed system.
Now some people seem to have certain understandings of the word "universe" but to me, "universe" is synonymous with "(all of) existence"

So the question I have is, does that mean the total amount of energy in the universe is always the same?

If by "the universe" you mean "existence" then, we can't know that. It may be philosophized, it may be suspected, it may even be theorized, but at the end of the day conservation of energy is derived from various closed systems within a bigger system, so we can't truly know if it applies to "the entire system"
P.S. I am not a scientist, (maybe in 10 years,) so this is not a "scientific" answer. It's simply my perspective of "conservation of energy"
(Various perspectives are good to have, as long as you don't think that I'm trying to say that my answer is the truth.)

 

[Khashishi]

The simple answer is that it is not known if energy is conserved on the universal scale, because it is not easy to define the energy associated with the expansion of space and gravitational energy in general relativity. This is probably because our theories just aren't good enough yet.

Energy is conserved in systems where you can neglect the effects of gravity and space expansion.

 

[m_robertson]

I see, thanks. I had an idea in my head of blowing a ping pong ball across a table with a straw. As I blow the ball I am using up oxygen (energy) which will eventually run out and stop the ball rolling, however in order for the supply of oxygen to remain constant enough to keep the ball in motion the ball must give up some of its mass and reintroduce some of that mass back into my lungs. So eventually the ball will deteriorate yet will continue to roll across the table as it gives up part of its own mass to maintain momentum and will accelerate as its reduced size experiences less and less friction. I have no idea how relevant it is to the discussion, but I saw it as a kind of analogy for the expansion of the universe and is what sparked my queries in the first place, as I wasn't sure how energy was being distributed and how it was being conserved over all as it transforms into mass and vice versa.

 

[PJC01]

Yes, you are correct in your understanding of the conservation of energy. The total amount of energy in the universe is constant and cannot be created or destroyed. This is known as the first law of thermodynamics. Energy can only be converted from one form to another, such as from potential energy to kinetic energy.

In regards to the accelerated expansion of the universe, it is believed that this is driven by a mysterious force called dark energy. While we do not fully understand the nature of dark energy, it is thought to be a form of energy that exists throughout the universe and is responsible for the expansion. So, in a sense, this energy is not being consumed, but rather it is being used to drive the expansion.

However, it is important to note that while the total amount of energy in the universe remains constant, it can still be transferred and distributed in different ways. For example, energy from the sun is constantly being converted and transferred to different forms on Earth, such as solar energy being converted to chemical energy in plants through photosynthesis. So while the total amount of energy remains the same, it can still be utilized and transformed in various ways.

Overall, the conservation of energy is a fundamental principle in physics and plays a crucial role in understanding the workings of the universe.