Physics Help Forum Question on Matter, Energy & The Expanding Universe

 Philosophy of Physics Philosophy of Physics Forum - Philosophical questions about our universe

 Mar 16th 2018, 09:44 AM #1 Junior Member     Join Date: Mar 2018 Location: Santa Cruz, California Posts: 2 Question on Matter, Energy & The Expanding Universe Hi - I'm an English major, not a physicist - never taken a physics class in my life, but I've been wondering about something, and hope for some help. Here it is. Is it fair to say the universe is a fixed system? By that I mean that all the matter that exists in the universe is all there is (that we know of), right? And matter = energy. And matter can neither be created nor destroyed. So how is it that the rate or speed that the universe is expanding is increasing? Wouldn't that require that the net energy of the system is increasing? If matter can neither be created nor destroyed, and matter = energy, and the universe is a fixed system, how can the universe be expanding at an ever increasing rate of speed? Thanks for your help. I just don't understand.
Mar 16th 2018, 11:10 AM   #2
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 Originally Posted by dpschutz Hi - Is it fair to say the universe is a fixed system? By that I mean that all the matter that exists in the universe is all there is (that we know of), right?
We don't actually know this.

Firstly, we know that things aren't randomly appearing and disappearing... apart from a few well known examples (such as supernova explosions), things tend to still be there if we go and look at them again the following year.

Secondly, we know that we can observe objects at increasingly larger distances and, because of the finite speed of light, those objects appear much older. And, if we look back far enough, we reach a point where all we observe is a "wall" of opaque light about 300,000 years after the Big Bang. This is called the Cosmic Microwave Background (CMB) radiation and is believed to be a consequence of matter-radiation decoupling, which was an event in the early Universe. This prevents us probing any further the 'boundary' of the Universe, at least with current observing technology.

So, in current cosmological theories, an assumption that there is no gain/loss of celestial objects across the CMB boundary is often made and it seems to be an okay assumption, but we don't know for sure.

 And matter = energy.
No, matter and energy are different. However, in nuclear reactions (happening in the cores of stars), for example, it is possible to convert between the two. Therefore, an evaluation of the total "contents" of the Universe should include both mass and energy.

 And matter can neither be created nor destroyed.
Mass can be converted to energy and vice versa... However, if you convert mass to an equivalent energy unit using $\displaystyle E=mc^2$, or vice versa using $\displaystyle m = \frac{E}{c^2}$, then you can define the contents of the Universe as the sum of the mass and energy components of that variable. It is that total which must be constant.

 So how is it that the rate or speed that the universe is expanding is increasing?
The observations show that the Universe is accelerating. There is no explanation for why this is the case, but the name given to any energy transfer going to this acceleration is called "dark energy". Generally, if something is considered "dark" in astrophysics, it is unknown.

 Wouldn't that require that the net energy of the system is increasing?
No. Consider a balloon, for example. After blowing up a balloon and tying the knot, the contents of the balloon are fixed and the size of the balloon is constant. However, if you take the balloon to an environment with a lower external pressure, the balloon is free to expand because there is a pressure difference with the external environment. It will accelerate until the pressure difference is equal, and then the rate of expansion is constant. Generally, as the balloon continues to expand, the pressure difference will decrease until it becomes negative and then the balloon will decelerate its expansion. Over time, the size the balloon will oscillate until equilibrium is established, at which point the balloon adopts a new fixed size that was larger than the original one. The actual mechanics of the expansion and the oscillation depend on that pressure difference, the balloon material and how the pressure difference changes as the balloon expands. This stuff can be calculated and the mathematics has been explored fully using thermodynamics and simple harmonic oscillations.

You can think of the Universe as a bit like a balloon that is expanding. We don't know why it is expanding, but in order for it to expand in an accelerating manner, some kind of "pressure difference" must cause it. However, the use of the term "pressure difference" is misleading because we simply don't know what is actually causing it. Therefore, the term "dark energy" is used instead, which is the typical naming scheme for unknown stuff in astronomy and astrophysics.

 Mar 16th 2018, 12:51 PM #3 Junior Member     Join Date: Mar 2018 Location: Santa Cruz, California Posts: 2 Hello benit13 - Thanks very much for your reply. I confess I find "some kind of pressure difference" to be a bit unsatisfying, although I qualify that with repeating that I've never taken a physics class, so what do I know. OK, more random thoughts. Dark Matter. From what I've read, physics predicts 10 dimensions. We experience 3, and the 4th is time. Could it be that "dark matter" is actually just matter that exists in different dimensions, and that all dimensions exert some kind of force on all other dimensions? And I have a completely rediculous unprovable (presently) theory on all this. Personally, I think the universe is infused with life. When the big bang happenned, the raw ingredients of life were distributed throughout the universe. And to quote Jeff Goldbloom, "Life finds a way." Wherever it can find a way, life finds a way. And IMO, life = energy AS David Christian points out in his TED talk "Big History" perhaps it is the case that the 2nd law of thermodynamics is only partially correct. Perhapes things are progressing towards increasing complexity - including life. As the universe gets more populated with life, the net energy of the univers increases. That's what I think. I think dark matter is other-dimensional - and we don't have the tools - yet - to peer into other dimensions, so we are unable to "see" the dark matter. Life exists across all dimensions. Life increases throughout the universe, and life is progressively getting more complex. Greater complexity of life = greater energy in the universe. Totally rediculous. And perhaps just as plausible as "we don't know?"
 Mar 16th 2018, 07:24 PM #4 Senior Member   Join Date: Apr 2017 Posts: 269 I would advise you to keep an open mind , question everything ... there are many holes in the official story ... A benit has pointed out ...."The observations show that the Universe is accelerating. There is no explanation for why this is the case, but the name given to any energy transfer going to this acceleration is called "dark energy". This expansion cannot be explained by current theories , so they just hypothesis "dark energy" ... and this makes established theories work ... no experimental evidence for this dark energy at all ..... Same with dark matter , better observations showed that galaxies should fly apart , not enough mass to hold them together ....No problem dream up "dark matter" and put it in the right places , then everything works ....dark matter cannot be detected or observed in any way , no experimental evidence for its existence ! Don't be intimidated by astrophysics , you just need common sense... Last edited by topsquark; Mar 16th 2018 at 09:32 PM.
 Mar 16th 2018, 09:35 PM #5 Forum Admin     Join Date: Apr 2008 Location: On the dance floor, baby! Posts: 2,238 Talk to any competent Physicist and they will tell you that we don't have any idea of what they are. Dark energy and dark matter are simply terms given to two effects that we can see and measure (to a degree) but have no way to explain. There is no secret that is being kept from us by the establishment here. No more conspiracies, oz. -Dan benit13 likes this. __________________ Do not meddle in the affairs of dragons for you are crunchy and taste good with ketchup. See the forum rules here.
 Mar 17th 2018, 04:01 AM #6 Senior Member     Join Date: Jun 2016 Location: England Posts: 441 Hi DPSchutz The questions you pose are exactly the questions physicists are asking themselves. They have made guesses as to the answers (dark energy, dark mater) but there is very little evidence that these guesses are correct and having looked for evidence very hard for many years, there is perhaps increasing evidence that these guesses are possibly not correct. Don't feel bad that you don't understand, no one does! __________________ ~\o/~
Mar 17th 2018, 08:58 AM   #7
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 Originally Posted by dpschutz Is it fair to say the universe is a fixed system? By that I mean that all the matter that exists in the universe is all there is (that we know of), right?
The universe is in a constant state of change. matter is being created and destroyed all the time. While the total amount of energy is constant it doesn't mean the form its in is constant. In fact cosmologists hold that the total energy of the universe is zero and that's why no violation of energy conservation occurred when/if it was created from nothing. There is a balance of positive energy in the form of kinetic energy and mass-energy with the negative energy from gravitational potential energy. So when gravitational potential energy decreases more and more matter can be created in the form of mass-energy.

 Originally Posted by dpschutz And matter = energy.
No. As explained above they are different things. As far as energy and mass goes there's a lot of misconceptions about it. I recommend this article
https://aapt.scitation.org/doi/10.1119/1.2431183

 Originally Posted by dpschutz And matter can neither be created nor destroyed.
Sure it can. That's how we came to be.

 Originally Posted by dpschutz So how is it that the rate or speed that the universe is expanding is increasing?

 Originally Posted by dpschutz Wouldn't that require that the net energy of the system is increasing?
No.

 Originally Posted by dpschutz Thanks for your help. I just don't understand.
Want to know what I love in this life? I love when people recognize what they don't know and then seek to understand it. Bravo!

I myself know that there's a huge amount of things I don't know, even in physics. If people are sharp then they'll note what I don't respond to and come to realize that its because I'm a bit ignorant on the subject. I just don't advertise that fact all the time but I don't actively hide it.

 Mar 29th 2018, 07:45 PM #8 Junior Member   Join Date: Mar 2018 Location: Xinhui Guangdong Province China Posts: 10 The Appropriate Mathematics to Explain Cosmos(Physics) In my first article Mathematics In the Eyes of God, I think that the mathematics people used to explain cosmos（physics）might somewhat deviate from the real cosmos(physics). Let’s talk about a straight line in cosmos. People have two opinions. First, in an open space, people say a straight line extends faraway in two directions , just go. Second, in a close space, a straight line extends in two directions and meet together at the infinite point at last, the so-called extension line. Which is the real straight line in cosmos? Suppose that it is the second one. Next, let’s see what will happen. In order to represent a point on an extension line, we use homogenous coordinate, (X1,X2). The relation with open space straight line is X=X1/X2, so the speed relation is X’=(X1’X2-X1X2’)/X2²，because X2 is a constant, soX2’=0. then X’=X1’/X2. We get the homogenous coordinate speed relation equation V=V1/X2. Next, let’s see what will happen if we put it into the mass-speed equation in Special Relativity. We arrive at the homogenous coordinate mass-speed equation: Result 1: it is possible thatV1 exceed C. Result2: cosmos is parallel possibly. One X2 value represents a certain cosmos. If X2=1,this is the matter world we are familiar with . Next, try to use it to explain some physics problem. Subject1: the particle – wave duality. If X2=1, it is the matter particle. If X21+X22+……X2n=1, it might be the probability wave. Subject2:if X2＞1, we can explain why photon can move with the speed C and it’s mass does not rise to infinite. Next let’s see the mass-energy equation, it change to be Maybe, it can explain some phenomena in quasar. Why quasar is so bright? Chen Li Qiang March 12, 2018 Xinhui Guangdong province,china

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