# Expanding universe

Status
Not open for further replies.
O

#### Olib1990

##### Guest
Hey everyone im new to this forum, i have just been reading "A breifer history of time" and came along a section about the universe expanding. I understand how space-time is explained using a rubber sheet and where you place objects on it, it creates a dip and other objects get dragged in. So when reading about the universe not only expanding but speeding up! I thought perhaps this could be explained in the same way but flipped over...... What if the centre of the universe is at the top of a giant theoretical mountain in space time, and the surrounding universe is "falling" down what you would call a giant mountain and gravity is not strong enough to stop it falling. Then as everything gets further and further down the "mountain" gravity is getting weaker and weaker and thus the objects move faster and faster.

I dont know how possible this is but it seems in no way different to the earth sat in space-time and things falling in, just on a universal scale.

What do you think?

Thanks

F

#### Fallingstar1971

##### Guest
Perhaps "Spacetime" is the "canvass" that the universe was created on.

Personally, I see the Universe as one giant blob evaporating in all directions. What we are seeing twords the edge with acceleration is where the bubbles(galaxies) have broken off and are speeding into whatever is beyond.

Like a boiling pot of water, the bubbles(Galaxies) form twords the heat source(big bang) and through heat, evaporate away from said heat source(big bang) in all directions. The energy provided by the heat is enough to overcome gravity which causes bubbles(galaxies) to break(boil) away.

In a pot of water, the heated gas bubbles to the top seemingly defying gravity. Now I know this has to do with gasses being lighter than water, and heated gases rising through convection, but on a universal scale with no "up" would not these gasses then expand in all directions?

With gravity no longer a factor (except locally, like galactic black hole anchors and so forth) the farther away from the "center" you get, the faster you will go as the gravity force fades on an extra-galactic scale. (In other words, if your on the "edge" and your not INSIDE a galaxy, then gravity is so weak twords the "center" that it doesn't really apply)

In observing this "boiling" affect from the inside, it would appear that all galaxies are moving away.

In observing this "boiling" affect it may appear that space itself is expanding, but now I wonder if space is stable and everything inside it is creating the illusion that it is expanding. If I shrunk you down to the size where you could stand on a molecule of oxygen, then place you just above the burner in a hot air balloon and turned it on, would not the "Universe"(area inside the hot air balloon) inflate? Even though "space" is not expanding, it appears to be, at least to our observer standing on a molecule which is so small compared to the area inside the balloon that our observer would never see the wall of the balloon, to him, the wall would be the edge of his universe, the farthest they could see, with every molecule racing twords the edge, bounce off and "Inflating" the balloon. All the closer molecules would be racing around in all direction, but the farther out you go, the more uniform they are in moving twords the "edge" and inflating the balloon.

But what if there was no "edge"?

The molecules(galaxies) would then race outbound forever. As resistance fades their outgoing speed increases. Once resistance = zero, they are now moving at c. With no "edge" to bounce off of, they hold there energy. None of it is transfered due to impact and they just keep going faster.

I would think that since the CMB has NOT completely faded away, that the universe still retains much heat twords its "center". This energy has not fully dissipated as seen with the CMB. It is this energy, in the form of heat that fuels expansion. Or what appears to be expansion.

Now you may be thinking "With all that heat, would we not fry? Would not everything be cooked?"

Well, everything IS cooked. All natural elements are made in stars. Even you and me. The iron in our blood, the air that we breathe, all cooked up in stars.

All it takes is a fraction of a degree above absolute zero, and now you have movement. Just the smallest fraction of a degree. Now molecules are in motion. The more that move, the more heat. Multiply that on up to bigger structures like stars and planets, and now you have a LOT of heat (compared to absolute zero)

Heat, no matter how little, causes that molecules in the matter that it interacts with to speed up, causing it to expand.

The Universe, no matter how cooled of it is (at this point) is still generating heat, therefore, it is still expanding.

Thats my take on it anyway

Star

O

#### Olib1990

##### Guest
Hmmm.... i get your point, but heat only creates movement on a molecular scale, the only reason we see heat make movement on earth is because it is reacting with the air around and making the surrounding air move, so when the air is heated below a heat source the air below it rises and carries the heat source with it, pretty much how a hot air baloon works. However in space there is no air to react with so i cannot see how heat could cause a galaxy to travel at 1.3 million miles per hour (speed of the milky way).

Its the fact that the expansion is speeding up which is the tough part to work out. The only thing thats logical to me is that there is some kind of mass beyond the observable universe that is pulling everything out, other than that your into the realms of dark energy etc.

Another thing is, if photons have no mass, how can they be effected by gravity, i know its off subject but i wanna know

F

#### Fallingstar1971

##### Guest
Im talking a LOT of heat here......... with next to zero resistance. Newtons Law states that an object put into motion will stay in motion until an outside force slows it down.

With no outside force, these galaxies at the edge of the observable Universe would maintain there velocity since the moment of their creation.

But there IS something outside the observable Universe. Something SO massive it is altering the course of galaxies

http://www.space.com/scienceastronomy/0 ... flows.html

Theres your outside force, and its localized so you can compare this "Dark Flow" area to everything else around it

But on a whole, its moving out in all directions.

Picture this......

I take a heat source, put it in space and surround it by a water shell with no sunlight to heat the shell. If the heat source is deactivated, the water should freeze making a giant iceball. For the purpose of this thought experiment, the ball is stationary and is not moving in relationship to its surroundings.

Now I activate the heat source and increase the temperature until the water begins to boil. If the ball is not moving, then which way will the ice evaporate?

Well, it depends upon how fast I heat the iceball. If I do it slowly enough, gradually enough, it will evaporate in all directions pretty much uniformly.

If I heat it too fast, cracks could form causing steam to jet out along the faults in the ice, this could cause "clumps" of water/ice vapor more concentrated in the areas that lie in the direction of the fault line

Now I am not suggesting that the early Universe was an iceball, Im just using water and ice for the comparison.

If all the matter in the universe were condensed into a single ball, and by nature itself with all that mass something funny would happen at the core. All that mass, all that pressure, something had to give. Something "ignited" and heated the matterball (if you will, perhaps a fusion or antimatter explosion) VERY quickly, causing theses cracks, and evaporated matter would jet out in specific directions along these cracks causing concentrations of matter to condense twords the end of these jets. Moments later with all this faultlines the matterball can no longer contain itself and it explodes sending matter in all directions, but not uniformly. Along the paths of the jets, resting twords the ends, there would be more matter then everywhere else, causing "clumpiness" if you will that later could have sparked galaxy formations. Now that the super SUPER massive matter ball is gone, there is no longer a strong enough gravitational "anchor" to hold the matter that created the newly formed galaxies in place. They continue to rush outward with no resistance (other then their own gravity that is used to "anchor" the stars in the individual galaxies) but no outside resistance. They will continue to travel at whatever speed they were going when they were created, with the objects farthest away moving the fastest. Clumps forming galactic clusters could effect themselves locally with mergers and so forth, but on a whole, the entire cluster is moving away.

Perhaps there was a jet larger then the rest, perhaps this "dark flow" is simply the effect of these galaxies forming too close to this jet and they are being swept along in the wake like someone being pulled into the wake of a boat. The jet has passed, and were are seeing the wake closing behind it.

Or perhaps there is another complete universe close by pulling on ours.

Or perhaps this is where God lives.....(if that is your belief)

There is still SO much about the Universe we dont know or understand. We are only allowed to view a tiny portion of it because on the limitations of light speed. This is the "observable" Universe. Is this ALL there is? Apparently not if the observations of this "dark flow" are correct. There is SO much more to see, SO much more to learn.

These are all just my personal thoughts. Maybe I am right, probably I am wrong. But it does make sense (to me it does anyway)

O

#### Olib1990

##### Guest
Yeah your right about the ice ball as a way of explaining the big bang, but the matter would only have the power of the initial burst, even the furthest galaies are pulled back by gravity, but they are just moving so fast it has no effect, the thing is that these galaxies are speeding up, and so the origional burst from the big bang cannot make it speed up, even if gravity is getting weaker, it would not cause the galaxies to speed up. If you were driving your car in a vacuum with no friction, and you pressed the brale (Gravity) then gently released (gravity getting weaker) you would not speed up, you would just stay the same speed.

We have much more to learn, however what is beyond is probably something people will not know for a long time, since we are always bound by the speed of light, only billions of years of observing will show us what is beyond.

M

#### Mamluk

##### Guest
The notion of an expanding universe has its base on the precept that light travels at a constant speed in specific situations (in a vacuum etc). For the past 100 years or so, physicists have been taught that electromagnetic radiation (including light) travels at the same constant speed ad-infinitum. The generally accepted theories on the nature of the universe and its physical properties are significantly influenced by this precept. In order to keep this precept intact, many theories have had to be devised to cater for the situations where the observed reality diverged from the expected. These may include notions of space-time, dark matter, dark energy, big-bang theory and the expansion (and acceleration of that expansion) of the universe. It is my contention that this precept is not entirely correct. Can I prove it? No is the short answer, but perhaps one day I will be able to do so. I can however forward an argument that supports this claim.

It is my contention that the speed at which electromagnetic radiation travels decreases at a fixed rate. Without external influences, it will do so until it stops. The rate at which the speed decreases is around (surprise, surprise) 72.5 +- 2.5 (km/s)/Mpc – the Hubble Constant. This is the same rate at which the universe is said to be expanding. So which is likely to be more correct? The expanding universe with a constant speed at which electromagnetic radiation travels as accepted by almost all physicists, or a relatively static universe (in terms of expansion/contraction) with a decreasing speed at which electromagnetic radiation travels as proposed here?

If my proposal is correct, then we will never be able to receive any electromagnetic radiation beyond a physical distance. If I am incorrect, then we either can (obviously I wouldn’t be writing this if I already though we already could) or will at some point in the future. So:

Mdt = Mpc * (c / H) / cy

Where:

Mdt = Maximum distance electromagnetic radiation can travel
Mpc = Megaparsec = 3.0857^19 km
c = speed of light = 299,792 km/s
H = Hubble constant = 72.5 km/s/Mpc (in this example)
cy = distance light travels in a year at c = 9,460528^12

Therefore Mdt = 13.5 billion light years. Let us say between 13 and 14 billion light years given the vagaries of the value of the Hubble Constant.

And so, we on earth should never be able to receive any electromagnetic radiation (light, microwave background radiation etc) beyond 14 billion light years away. Strangely enough, this is exactly the outer limit of what we have seen/received to date.

O

#### origin

##### Guest
It is my contention that the speed at which electromagnetic radiation travels decreases at a fixed rate. Without external influences, it will do so until it stops. The rate at which the speed decreases is around (surprise, surprise) 72.5 +- 2.5 (km/s)/Mpc – the Hubble Constant. This is the same rate at which the universe is said to be expanding. So which is likely to be more correct? The expanding universe with a constant speed at which electromagnetic radiation travels as accepted by almost all physicists, or a relatively static universe (in terms of expansion/contraction) with a decreasing speed at which electromagnetic radiation travels as proposed here?

If this were true then the electromagnet radiation that is hitting the earth should be arriving at different velocities, which it is not. The velocity of the light from the sun is the same as the velocity of the light coming from the furthest observable galaxies.

O

#### origin

##### Guest
And so, we on earth should never be able to receive any electromagnetic radiation (light, microwave background radiation etc) beyond 14 billion light years away. Strangely enough, this is exactly the outer limit of what we have seen/received to date.

That is not some strange coincidence that you have discovered. We can not observe galaxies beyond this distance because their recession velocities exceed the speed of light so the light will never reach us. You are using the hubble constant which is about expansion of the universe and recession speeds, so since you are using that constant of course you are going to come up with the same answers for the maximum size of the observable universe. The expansion model makes much more sense because we DO see a redshift in light and we DO NOT see a velocity change in light.

M

#### Mamluk

##### Guest
origin":kog03pkq said:
And so, we on earth should never be able to receive any electromagnetic radiation (light, microwave background radiation etc) beyond 14 billion light years away. Strangely enough, this is exactly the outer limit of what we have seen/received to date.

That is not some strange coincidence that you have discovered. We can not observe galaxies beyond this distance because their recession velocities exceed the speed of light so the light will never reach us. You are using the hubble constant which is about expansion of the universe and recession speeds, so since you are using that constant of course you are going to come up with the same answers for the maximum size of the observable universe. The expansion model makes much more sense because we DO see a redshift in light and we DO NOT see a velocity change in light.

The recession velocities of galaxies etc (assuming an expanding universe at the Hubble constant) would indeed be approaching the speed of light at that distance. This does not however apply to the CMBR. A redshift in light is "interpreted" as a recessional velocity. It could equally be "interpreted" by a reduction in the speed of light. As alluded to above, I would be interested in hearing how a velocity change (or a non-velocity change) in light is measured.

Status
Not open for further replies.

Replies
2
Views
454
Replies
2
Views
600
Replies
8
Views
1K
Replies
1
Views
422
Replies
1
Views
316