Dark Energy Theory

[peterbct]

Starting with the general concept of the "Big Bang" as the origin of our stellar universe, with all its wonders and mysteries, one of the many current questions posed about outer space is that of increasing speed detected in the continuing travel of all of the galaxies further and further from each other and away from their point of origin. The apparent acceleration of the rate of movement is unexplaineed and "dark energy" is felt to cause this phenomena.

My theory in this connection may be seemingly simplistic but is logical in my mind. As the myriad of bodies of matter involved travel outward from their origin they obviously increase the distance from each other and from the source of the big bang. This increased distance would decrease any gravitational effect, or force which would otherwise bring them back together eventually and therefore, with decreased resistance to their flight but with constant momentum, their outward speed would increase.

The so-called dark energy would, accordingly, be simply a decrease in force in opposition to their movement rather than an increase in force which would cause the observed acceleration.


peterbct

 

[BurgerB75]

But, and correct me if I'm wrong, but in order to increase their speed (which has been observed) that would require the addition of energy.

 

[Gravity_Ray]

An interesting idea peterbct and one that could be correct, how will you test this theory of yours?

Your idea does seem to fly in the face of Newton's first law of motion; an object will stay in motion with the same speed and in the same direction unless acted upon by a sum of physical forces.

So you maybe correct if you say that the universe itself is expanding and the objects in it are moving away from each other faster. However, Dark energy is talking about the objects 'in' the universe (If I understand it correctly). This is the cosmological constant, a constant energy density filling space homogeneously.

So (again if I am understanding this correctly), if you look at a Type 1A Supernovae (a standard candle), it suggests the expansion of the Universe and its acceleration. These objects are IN the universe and just relate that the universe is expanding faster. So technically they do have to observe Newton's first law of motion.

 

[ramparts]

Peter, it's great that you're interested in cosmology! It's a really fascinating field. I like that you're thinking critically and coming up with your own ideas, but you have some pretty fundamental misconceptions which should be cleared up.

First of all, a force which attracts something in the direction opposite to its motion acts to slow that thing down - so if you're moving away from me and I'm pulling on you with some force, what that force does is slow down your motion away from me (and possibly start to move you towards me). If I were to start decreasing that force, you would most certainly not speed up! You would just slow down less. There being less of an attractive force doesn't make things speed up - only a repulsive force can make things speed up (assuming they're moving away from the source of the force). This is why your idea wouldn't work.

Also, you have a very, very common misconception about the Big Bang, namely that it was somehow a motion away from a certain point. You call this point the "origin" of the Big Bang. In fact, the Big Bang wasn't an explosion within space, but an explosion of space, if that makes sense. Think about the surface of a balloon - when you blow up the balloon, the surface expands and all the points on it move away from each other, but there's no central point on the surface of the balloon which you'd call the origin of that expansion. The same is true with the expansion of the universe; it's an expansion of space that pulls everything along with it, rather than an intrinsic motion of galaxies.

 

[Couerl]

The balloon analogy satisfies the imagery linked to expansion, but not so much the "bang" itself. Most think of the big bang as a kind of firecracker or giant holy hand grenade going off from a central point, when it is actually easier to visualize it like a pot of water (infinite in dimension already,.. perhaps) which suddenly came to a boil, virtually everywhere and all at once. These are great times and I hope someone will be able to infer what Dark Energy actually represents in the coming decades and I also hope it isn't a great spaghetti monster. :lol:

 

[michaelmozina]

Starting with the general concept of the "Big Bang" as the origin of our stellar universe, with all its wonders and mysteries, one of the many current questions posed about outer space is that of increasing speed detected in the continuing travel of all of the galaxies further and further from each other and away from their point of origin. The apparent acceleration of the rate of movement is unexplaineed and "dark energy" is felt to cause this phenomena.

My theory in this connection may be seemingly simplistic but is logical in my mind. As the myriad of bodies of matter involved travel outward from their origin they obviously increase the distance from each other and from the source of the big bang. This increased distance would decrease any gravitational effect, or force which would otherwise bring them back together eventually and therefore, with decreased resistance to their flight but with constant momentum, their outward speed would increase.

The so-called dark energy would, accordingly, be simply a decrease in force in opposition to their movement rather than an increase in force which would cause the observed acceleration.

Actually an expansion of matter would result not in an increase in the speed of the expansion, but rather it would result in a decrease of *deceleration" over time, and eventually a near constant expansion rate. That expansion process would not cause anything to accelerate faster.

 

[SteveCNC]

You know I have heard the description a lot from many sources about the expansion of the universe and all that but in your description with a balloon putting dots on it and they all move apart as you inflate . The dots you refer to are stationary also so even if an object has no momentum in any direction it would still be moving away from all the other dots . So couldn't the accelerated speed to which other galaxies are accelerating away just be that the expansion is what's actually speeding up not their motion ? or is the expansion rate constant ? I'm pretty sure it hasn't stopped or reversed .

 

[Floridian]

Using Peter's theory.

What if, the force of gravity itself is stretching spacetime, making it seem like it is expanding, thereby increasing the separation between objects. As objects move farther away, gravity spreads out and stretches in all directions, stretching space-time.

I guess the speed increases we see would need to be based on the expansion of space and not the objects direct speed, but can w e tell?

 

[a_lost_packet_]

...The so-called dark energy would, accordingly, be simply a decrease in force in opposition to their movement rather than an increase in force which would cause the observed acceleration...

Look at it this way: If gravity's effect decreases with distance then, as you say, there is less of an attractive force holding things together. BUT, if, in turn, those things begin accelerating then additional force is required.

Construct a hill with a straight, level slope at its apex. Now, with one push, roll a ball up that hill so that it crests the edge and begins to roll on the level plane. When it gets to the top and begins to roll on the level plane, is it going to increase in velocity? If it does, where does that energy come from? A great deal of the initial energy was bled off by the object having to negotiate the steep curve of the hill. Additional energy is required for the ball to gain in momentum once it reaches the level plane, right? It's not going to accelerate by itself even though it has negotiated the hill.

Its movement is no longer impeded yet, it isn't helped along unless some other force is at work making that happen. (On a hypothetical, imaginary plane with corresponding imaginary everything else. )

Don't forget that objects in the Universe that have mass also effect gravity. So, galaxies that are near to each other attract each other as well. Those accelerating galaxies are still attracted to each other. In fact, your keyboard has a gravitic effect on the Andromeda galaxy.. just a very, very, very small one. By pushing down the keys on your keyboard, you're countering the effects of the multitudes of distant planets, solar systems and galaxies. The little spring inside has enough potential energy to counter the effects of Earth's gravity. In fact, if the tiny plastic ridges on the stay for the key were removed, the key would fly off the keyboard in defiance of Earth's gravity. Gravity is very, very weak. But, it's pervasive in that while it decreases with distance according to the inverse square law, it never simply goes away. It's also additive. So, every mass-bearing element in a certain direction will be acting to make you fall in that direction, no matter how far away they are, with effects that vary inversely with the square of their respective distance.. Alternatively, your mass is also acting upon them in the same way as well.

To sum: In order for your idea to explain an observed effect, there must be some other energy at work. Removing or lessening the effects of gravity doesn't impart energy into the system unless there is something "else" we don't know. And, you'd have to explain that as well.

 

[Garson007]

I've always thought that entropy could be the cause, but entropy wouldn't account for the objects accelerating away from each other, only that they are moving away from each other to begin with. I do however entertain the idea that a potential modification to Newtonian physics and gravitational law could explain this effect over that of an unobservable matter.

 

[ramparts]

You know I have heard the description a lot from many sources about the expansion of the universe and all that but in your description with a balloon putting dots on it and they all move apart as you inflate . The dots you refer to are stationary also so even if an object has no momentum in any direction it would still be moving away from all the other dots . So couldn't the accelerated speed to which other galaxies are accelerating away just be that the expansion is what's actually speeding up not their motion ? or is the expansion rate constant ? I'm pretty sure it hasn't stopped or reversed .

Exactly!! The dots on the balloon are stationary. Similarly, galaxies and whatnot can be considered to be stationary in the Universe and they still move apart from each other. They're not moving - the background is*.

So the acceleration is an acceleration of the expansion rate of space. We can define that at any given time (with a number called the Hubble parameter), and we find that it is getting bigger over time.

*Note: of course galaxies do interact with each other and move locally, but even when there's no local movement, there's still expansion. Local movement tends to act against the expansion.

 

[ramparts]

I've always thought that entropy could be the cause, but entropy wouldn't account for the objects accelerating away from each other, only that they are moving away from each other to begin with. I do however entertain the idea that a potential modification to Newtonian physics and gravitational law could explain this effect over that of an unobservable matter.

It's a common notion. Unlike dark matter (where the case is all but shut in favor of matter, over a modification to gravity), dark energy could very well be caused by a modification to Einstein's theory of gravity, and lots of very intelligent people are working on just that. And, most intriguingly, all but a handful of the modified gravity theories (possibly all) are mathematically equivalent to a theory with regular Einstein gravity plus a new matter/energy field. So in this case, the distinction might not be so clear-cut after all.