The first law of thermodynamics - conservation of energy

a reply to: iamthevirus

Is it a theory or did they actually weigh black holes?

a reply to: iamthevirus

There is no dark energy,

Proof ?

a reply to: Gothmog

The (theoretical physicist) are glitching hardcore because we can't get to intergalactic space (the space between the galaxies) to scoop up a bottle of empty space and bring it back to the work bench to figure out what it is.

They're using their math to try to do that...

Experimental physicists are the real-deal, the theoreticians are just talking heads using a tool which if examined closely one discovers has its own set of problems.

The composition of galactic space (the galactic medium) is mostly hydrogen, what they're after resides outside the galaxy.

Don't be rude just try to ignore it and let em do what they do, someone is bound to make an educated guess but how that would be tested in our lifetimes who knows?

originally posted by: Untun
a reply to: iamthevirus

Is it a theory or did they actually weigh black holes?

Mass and energy are the same thing so a bodies energy can be referred to as its mass... specially when dealing with black holes and thermodynamics.

I used the term mass because of the context of comparing two 10lb objects.

Similar how when speaking of electricity you can refer to it as a fluid for visualization purposes.

a reply to: Untun

We can't weigh the sun or stars either but we know their mass by their energy, that's referred to as solar-masses in the general context of physics.

originally posted by: Untun
Hi all, thank you for joining.

I have a question about the first law of thermodynamics. It's rather a simple question.

Am I right stating the first law of thermodynamics states energy cannot be created nor destroyed?

You're missing the "isolated system" part of the definition:

"The law of conservation of energy states that the total energy of any isolated system (for which energy and matter transfer through the system boundary are not possible) is constant; energy can be transformed from one form to another, but can be neither created nor destroyed. "

If so, we know there is energy in the universe, if energy cannot be created, how did energy occur in the first place?

We can't draw a box around the universe to make it an isolated system, so it's hard to make a direct application of the first law. We don't even know if the universe is finite or infinite. If it's infinite it would be hard to draw a box around it to make it an isolated system.

Still there are some interesting hypotheses that propose the net amount of energy in the universe was zero to begin with before the big bang, and is still zero now. Of course we can't do anything but speculate about "before the big bang" but we can measure different types of energy in the universe now, and some types do seem to cancel or offset each other.

Zero-energy universe

The zero-energy universe hypothesis proposes that the total amount of energy in the universe is exactly zero: its amount of positive energy in the form of matter is exactly canceled out by its negative energy in the form of gravity.[1] Some physicists, such as Lawrence Krauss, Stephen Hawking or Alexander Vilenkin, call or called this state "a universe from nothingness", although the zero-energy universe model requires both a matter field with positive energy and a gravitational field with negative energy to exist.[2]

As mentioned in the article above, Lawrence Krauss has proposed total energy before the big bang was zero, and total energy after the big bang is still zero because positive matter energy and negative gravitational energy cancel out. Whether this is actually true, is still a matter of ongoing research:

Experimental proof for the observable universe being a "zero-energy universe" is currently inconclusive.

If we get a better understanding of dark matter, that may help to resolve whether that hypothesis is true. Here is a video where Dr. Krauss explains the idea:

'A Universe From Nothing' by Lawrence Krauss, AAI 2009

Lawrence Krauss gives a talk on our current picture of the universe, how it will end, and how it could have come from nothing.

originally posted by: [post=26635267]Untun] how did energy occur?

Light... from the 5th dimension

originally posted by: iamthevirus

originally posted by: [post=26635267]Untun] how did energy occur?

Light... from the 5th dimension

start here,

5 Dimensional Space

They suggested that electromagnetism resulted from a gravitational field that is “polarized” in the fifth dimension.

Einstein-Maxwell Equations

that QM stuff will rot yur brane...

a reply to: Arbitrageur

Insulated energy does not dissipate? I am saying that correct? What type of energy are they actually talking about? Batteries drain for instance.

I'm having a hard time believing space is infinite, it's like having an unmeasurable endless hamburger. Don't they call it space because it's a thing that can be measured?

a reply to: iamthevirus

Oh, that kind of energy, mass is energy. So when new stars are born for instance this star was something else before because the universe can only create from what is already existing. I think I get the point.

I have an example.

Can someone explain how the first law of thermodynamics applies to burning a log of wood?

Is it weird to ask, because I could be missing a point here.

originally posted by: Untun
I have an example.

Can someone explain how the first law of thermodynamics applies to burning a log of wood?

Is it weird to ask, because I could be missing a point here.

The stored energy of the log and of the “air” are transformed into heat and light energy which then dissaptes out into the world in the form of waves.

originally posted by: Untun
a reply to: Arbitrageur

Insulated energy does not dissipate? I am saying that correct? What type of energy are they actually talking about? Batteries drain for instance.

Follow the definition as closely as possible. Insulation only slows down the transfer of energy, it doesn't stop it, so insulation does not meet the definition "(for which energy and matter transfer through the system boundary are not possible)", in fact the insulation itself could then be part of the system if it's absorbing energy from the system.

The First Law of Thermodynamics

An isolated system exchanges neither energy nor matter with the surroundings. A truly isolated system does not actually exist, however, because energy is always exchanged between a system and its surroundings, although this process may take place very slowly. An insulated thermos containing hot coffee approximates an isolated system, but eventually the coffee cools as heat is transferred to the surroundings. In all cases, the amount of heat lost by a system is equal to the amount of heat gained by its surroundings and vice versa. That is, the total energy of a system plus its surroundings is constant, which must be true if energy is conserved.

Note that the "cold fusion" claims were based on calorimetry experiments, which are difficult to do precisely because isolating the system under study, and accounting for all the variables is diffucult. So in practice, it's very difficult to completely isolate a system and the best we can usually do is approximately isolate it to where flow of energy in or out of the system are hopefully minimal relative to the processes under study inside the system.

In some cases it's good enough for experimental purposes to approximately isolate a system, if studying a fast reaction in a well insulated closed reaction vessel, for example.

I'm having a hard time believing space is infinite, it's like having an unmeasurable endless hamburger.

Look at it this way...there's a conceptual problem if it is infinite, because we can't conceive of infinity very well, but also if it's not infinite, because that raises more questions we don't have the answer to, like "where is the edge?" and "what's beyond the edge?" While we may never know the answer with 100% certainty, measurements of a parameter of the geometry of the universe called "flatness" suggest infinity, but they have some error bars so the measurements could also mean really, really large and not infinite.

How do we know the universe is flat?

We say that the universe is flat, and this means that parallel lines will always remain parallel. 90-degree turns behave as true 90-degree turns, and everything makes sense.

But what are the implications for the entire universe? What does this tell us?

Unfortunately, the biggest thing is what it doesn't tell us. We still don't know if the universe is finite or infinite. If we could measure its curvature, we could know that we're in a finite universe, and get a sense of what its actual true size is, out beyond the observable universe we can measure.

We know that the volume of the universe is at least 100 times more than we can observe. At least.

a reply to: Arbitrageur

I'm like thinking now, ok, they don't know it the universe is infinite but they do know it is flat. Is there a difference to what they refer to as universe and space?

To me, space means everything in the sense that it is all space and solarsystems, you could say all of "creation".

To the OP: you are simplifying.

Thermodynamics states that in a closed system, matter/energy cannot be created or destroyed. Firstly, as has been noted, we do not know the Universe is a closed system. Some mathematics insist that there are dimensions we cannot observe, so our observable Universe can appear to be a closed system while not truly being a closed system.

Secondly, there are many different forms of energy. Imagine a rock hurtling through empty space. It has energy based on its velocity (kinetic energy). If it comes close enough to a planet, it is attracted to that planet by gravity. It therefore has potential energy relative to that planet that will be turned into kinetic energy as it accelerates toward the planet. Therefore, every object in the Universe has potential energy relative to every other object.

Also, there is the question of just how much energy is in space right now. We cannot measure (and thus cannot know) how much absolute energy there is. Energy is measured as a difference between two energetic states. One cannot simply state that a point in space has a certain voltage (electrical potential)... one can state that a point in space has a voltage relative to another point. In other words, it is meaningless to talk about absolute energy.

On Earth, we measure energy relative to know points or as the amount of fluctuation from normal or with time.

Yeah, I know, that all just muddied your question... but if you will do some serious critical thinking on the subject, it should clear the mud up somewhat.

a reply to: Untun

Can someone explain how the first law of thermodynamics applies to burning a log of wood?

That would be a chemical reaction, specifically oxidation.

The wood is made up of molecules, which are themselves atoms bonded together. This is usually covalent bonding, where bonds between atoms can be said to have a specific energy. Before ignition, the wood is stable; it will not combust spontaneously because the energy required to break those covalent bonds is not present. Once energy is introduced (as in the wood is placed into an area which has an abundance of heat energy), some of those covalent bonds will absorb enough energy to break. At that point, the bonds will reform to the lowest available energy level they can. In the case of wood, this is mostly carbon and hydrogen; carbon and oxygen react to form carbon dioxide which has the lowest energy requirement for the covalent bonds. Hydrogen will form water, which has an extremely low covalent bond energy.

As an example, let's look at one carboniferous molecule in the wood. It does not have nearly as low a covalent bonding energy as carbon dioxide, but without additional sufficient energy, the bonds that are there will remain. Once additional energy is inserted into the system, the carbon atom's bonds can become energetic enough to break. That allows the carbon to reform new, lower-energy bonds with oxygen, giving off carbon dioxide. The oxygen bonds require much less energy than the previous carbon bonds, and that difference is given off in the form of heat. The heat produced can now break other carbon bonds, allowing more carbon dioxide to form and releasing more energy. The whole thing becomes a self-sustaining chemical reaction until all the covalent bonds are broken and reform to a lower energy level.

If one were to capture all the resulting chemicals from a log of wood and compare it to the chemical composition of the wood in its original state, one would find that the sum of all the chemical bond energies in the wood, minus the heat energy given off, equals exactly the bond energies in the ash and gases produced. No energy is created; part of the chemical bond energies has simply been changed into heat energy.

TheRedneck

a reply to: TheRedneck

You triggered some insight.

It made me think that even in an open system energy cannot be lost, so, actually, just the idea energy always transforms not matter where it ends up to be.

originally posted by: TheRedneck
To the OP: you are simplifying.

Thermodynamics states that in a closed system, matter/energy cannot be created or destroyed.

I gave the definition above, in which the first law of thermodynamics refers to an isolated system, which sounds similar to, but is not the same as a closed system, in fact the difference is quite important.

The First Law of Thermodynamics

Three kinds of systems are important in chemistry. An open system can exchange both matter and energy with its surroundings. A pot of boiling water is an open system because a burner supplies energy in the form of heat, and matter in the form of water vapor is lost as the water boils. A closed system can exchange energy but not matter with its surroundings. The sealed pouch of a ready-made dinner that is dropped into a pot of boiling water is a closed system because thermal energy is transferred to the system from the boiling water but no matter is exchanged (unless the pouch leaks, in which case it is no longer a closed system). An isolated system exchanges neither energy nor matter with the surroundings.

So the example given of a "closed system" is the "sealed pouch of a ready-made dinner that is dropped into a pot of boiling water", and it absorbs energy from the boiling water without violating the "closed system" definition. So if we are still discussing the first law of thermodynamics subject of the thread, what we really want is an isolated system, not just a closed system. All isolated systems are closed systems, but not all closed systems are isolated systems.

If one were to capture all the resulting chemicals from a log of wood and compare it to the chemical composition of the wood in its original state, one would find that the sum of all the chemical bond energies in the wood, minus the heat energy given off, equals exactly the bond energies in the ash and gases produced. No energy is created; part of the chemical bond energies has simply been changed into heat energy.

Good explanation.

Thx for posting all so far.

a reply to: Untun

I start a physics class on the 29th? Are you in school by any chance?

a reply to: Brotherman

Only at the school of life at the moment.