Please visit : http://antwrp.gsfc.nasa.gov/apod/astropix.html
Proof for infinite expansion
Just so you know, it is impossible to prove anything when it comes to science. Interesting picture though 
| coolsmile wrote: |
| it is impossible to prove anything when it comes to science. |
Difficult, sometimes impossible, but not always impossible. The fact that ice is actually frozen water is quite well proven.
| muhendisabi wrote: |
| Please visit : http://antwrp.gsfc.nasa.gov/apod/astropix.html |
The link you gave is the "Astronomy Picture of the Day", which leads to a new (and usually quite interesting) picture and explanation each day that you visit it. The picture I assume you are referring to is the one for Dec 17, and the permanent archive link is:
http://antwrp.gsfc.nasa.gov/apod/ap061217.html
The experiment is a test of the presence of dark energy, but I found the article somewhat paradoxical. All energy has mass, according to Einstein, so should attract objects. Yet the article talks about repelling objects, as if it's presence decreased the effective mass of the universe. Perhaps someone else understands their point better.
Beautiful pictures.
I do not believe expansion.
I do not believe expansion.
I however don't understand how the proval of the casimir effect proves that space itself will continue to expand forever?
| Detremmerie wrote: |
| I however don't understand how the proval of the casimir effect proves that space itself will continue to expand forever? |
I can explain if you like ?
Casimir Effect basically shows the presence of 'zero point' energy. So let's start with a description of the actual effect and then go from there.
Casimir Effect Experiment
Essentially experimental procedure is to put two plates very very close together. Really close. So close that they are closer than the wavelength of most energy (and, therefore, matter as well).
Now, Zero point energy is essentially the description of what happens in 'empty' space.
Empty space is actually teeming with pairs of 'virtual' particle-antiparticles. These are constantly coming into existence and then annihilating each other again almost instantly - so fast that they are never detected.
The Casimir effect, however, would predict that as the plates get closer and closer, eventually they will be so close that no energy or matter can exist between them. Energy/matter at this scale, as you may know, is 'quantised' which means it comes in chunks. You cannot have, for example, half a photon. Once this size is reached, the theory predicts, the plates will be still experiencing a force from all the zero point energy around them but no force between them. The effect, obviously, would be to force the plates together because of the difference in...err.. (I'll call it 'pressure').
Do you follow me so far ? Here's the first piecer of news - this has been shown to actually happen in experiment - the plates are sucked together with a definite force, even in the hardest vacuum we can generate.
Now, you will probably be aware that Dark Matter is vexing a lot of people at the moment. We know there is lots of it out there but we don't know what it is.
Well, this is one possible candidate. All the opposite particles flying about the place would certainly make a huge contribution, even though their existence is so infinitesimally brief.
But it gets even better and better if you believe the theory.....
Next, imagine the Universe as a balloon expanding into the 'nothingness' surrounding it.
Obviously the nothingness does not have any of this zero point energy because it has no matter and no space for such matter to exist in. This would seem to predict that the emptiness of space is at a higher 'pressure' than the nothingness it is 'growing' into.
This model might help picture it - this is one of Einstein's models.
* If a piston capping a cylinder of vacuum is pulled out, producing more vacuum, the vacuum within the cylinder then has more energy which must have been supplied by a force pulling on the piston.
* If the vacuum is trying to pull the piston back into the cylinder, it must have a negative pressure, since a positive pressure would tend to push the piston out.
(Source http://www.astro.ucla.edu/)
If you think this through it means that space will be 'attracted' into the nothingness.
Previously iut was conjectured that nothingness could not be t a lower 'pressure' than a hard vacuum so there would be no difference in 'pressure'. This theory suggests theree us a constant force expanding the universe into the nothingness because the universe is full of zero point energy. This difference in 'pressure' is exactly the sort of force that scientists are looking for (called Dark Energy) to explain why the universe is flying apart faster and faster.
Do you still follow me ? If so then you now understand the gist of the introduction to the basics of the theory.
So now we have a potential explanation for dark energy, dark matter and expansion all in one go. Amazing eh ?
The problem is that it doesn't work in theory (yet?).
To find out why you will need to be interested enough to do some more reading and it will be a bit harder than this easy and gentle intro to the subject (if I do say so myself, I think this is a very clear primer on the subject).
Sources to take this further.
Description of the effect itself
Nice Slide show on the subject
Good paper on the topic called Casimir Effect confronts Cosmological Constant
Physicists discussion forum on this subject
Conference papers from a recent convention on the subject
Gravity Research
Enjoy...
| ocalhoun wrote: | ||
Difficult, sometimes impossible, but not always impossible. The fact that ice is actually frozen water is quite well proven. |
That is true, but what I meant is you cannot technically prove anything you cannot measere Very Accurately, most of the time, I see people use realitive terms
You ask someone to explain how something proves the universe is expanding and you get a massive explanation 
a very interesting one too.
Alas tis part of science that things are mostly theorised, though I love it when people say relegion is more valid because its not based on theories they base it on "faith"
a very interesting one too.
Alas tis part of science that things are mostly theorised, though I love it when people say relegion is more valid because its not based on theories
they base it on "faith" Actually the whole of science is based on theory. I bang on about this a lot so apologies to those who already know what I'm about to say....
Scientific method is based on the fact that nothing can be proved for sure (aside from formal statements in logic). One simple illustration would be : The Sun has risen every morning, billions of times without fail therefore it is my theory that the Sun will rise every morning.
The theory is wrong because it is certain that one day the sun will NOT rise.
This problem of proving something is called the problem of Induction and was first highlighted by Hume. Karl Popper proposed the solution that is accepted and used in all modern science. The solution was simply to turn the problem on it's head.
Although no number of observations can ever prove a theory correct, one single observation can prove it incorrect. Therefore instead of trying to prove a theory scientists should try to disprove a theory.
For this reason science never claims that a theory is correct or true or any other such form of words. Some people mistakenly take this to mean that there is uncertainty or doubt about the theory in question. This is not normally the case. The theory of gravity is, for sure, 'only' a theory but few doubt that the theory works and describes our observations. The same is true for most other current theories.
Before a theory is accepted as valid, it is called a hypothesis. A hypothesis needs to be tested by experiment/observation in order to try to refute it. If it survives this process (called peer review) then it can be accepted as theory. All theory, therefore, has already been through a very extensive process designed to prove it false and is, therefore, likely to be valid.
Theory very rarely is 'disproved' in the way some claim. What is much more common is that a new theory will expand an old theory and make it work in situations which were either never considered by the original theory or which the original theory was known to break down. A classic example would be the replacement of Newtonian theories of motion by those of Einstein. It was not that Newton's theories were one day OK and the next day wrong. The fact is that Newton's theories are still used in the majority of situations where calculations about motion are made. Very few scientists need to use Einstein's relativity equations because for most purposes the answers produced by Newtonian physics are perfectly satisfactory and whilst the Einstein equations will produce a more accurate answer the extra accuracy is not needed in most situations.
Regards
Chris
Scientific method is based on the fact that nothing can be proved for sure (aside from formal statements in logic). One simple illustration would be : The Sun has risen every morning, billions of times without fail therefore it is my theory that the Sun will rise every morning.
The theory is wrong because it is certain that one day the sun will NOT rise.
This problem of proving something is called the problem of Induction and was first highlighted by Hume. Karl Popper proposed the solution that is accepted and used in all modern science. The solution was simply to turn the problem on it's head.
Although no number of observations can ever prove a theory correct, one single observation can prove it incorrect. Therefore instead of trying to prove a theory scientists should try to disprove a theory.
For this reason science never claims that a theory is correct or true or any other such form of words. Some people mistakenly take this to mean that there is uncertainty or doubt about the theory in question. This is not normally the case. The theory of gravity is, for sure, 'only' a theory but few doubt that the theory works and describes our observations. The same is true for most other current theories.
Before a theory is accepted as valid, it is called a hypothesis. A hypothesis needs to be tested by experiment/observation in order to try to refute it. If it survives this process (called peer review) then it can be accepted as theory. All theory, therefore, has already been through a very extensive process designed to prove it false and is, therefore, likely to be valid.
Theory very rarely is 'disproved' in the way some claim. What is much more common is that a new theory will expand an old theory and make it work in situations which were either never considered by the original theory or which the original theory was known to break down. A classic example would be the replacement of Newtonian theories of motion by those of Einstein. It was not that Newton's theories were one day OK and the next day wrong. The fact is that Newton's theories are still used in the majority of situations where calculations about motion are made. Very few scientists need to use Einstein's relativity equations because for most purposes the answers produced by Newtonian physics are perfectly satisfactory and whilst the Einstein equations will produce a more accurate answer the extra accuracy is not needed in most situations.
Regards
Chris
| coolsmile wrote: |
| Just so you know, it is impossible to prove anything when it comes to science. Interesting picture though |
Well, now, that just isn't true. It's not only possible, but doable. You take some aksioms (undisputable facts), and using them you prove that something else is valid. Aksioms are logicaly true. To deny them would be to deny the human logic itself. And that would mean that logic is really fictious, and that isn't true.
hmmm.. i dunno...if true then this means we ca almost make hatever we want..this is anew starting base for anything.
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