The Big Bang Theory under threat from quantum graphity breakthrough

[haxartus]

It's kind of confusing indeed. Normal matter and normal energy are the same. Well, i guess matter is just a form of energy. Dark matter and dark energy aren't connected in that way. We know enough about dark matter to say with confidence that it's not matter in a casual sense. It's probably closer to neutrinos or photons, except with mass (apparently, huge mass). Dark energy we know practically nothing about. Only that it causes the expansion. In fact, dark energy isn't even detectible (as far as i know), the only reason it's postulated to exist is because there must be additional energy in the universe to cause that much expansion. So yeah, both are placeholder terms we know practically nothing about, except what they cause.

There is also Dark Flow which might indicate the existence of something outside of the visible Universe, possibly a neighboring Universe.

[Deleted]

I choose to believe what i was programmed to believe.

[Deleted]

I choose to believe what i was programmed to believe.

You don't choose what you believe. You either believe in something or you don't. You weren't programmed by anyone... are you drunk?

[Sackman]

It's kind of confusing indeed. Normal matter and normal energy are the same. Well, i guess matter is just a form of energy. Dark matter and dark energy aren't connected in that way. We know enough about dark matter to say with confidence that it's not matter in a casual sense. It's probably closer to neutrinos or photons, except with mass (apparently, huge mass). Dark energy we know practically nothing about. Only that it causes the expansion. In fact, dark energy isn't even detectible (as far as i know), the only reason it's postulated to exist is because there must be additional energy in the universe to cause that much expansion. So yeah, both are placeholder terms we know practically nothing about, except what they cause.

I haven't read up on my cosmology and physics in a long while but does String Theory not postulate reasons other than dark matter for the expansion?

(I'm asking because you seem to be keeping yourself well informed)

[semaphore]

I haven't read up on my cosmology and physics in a long while but does String Theory not postulate reasons other than dark matter for the expansion?

I think string theory mostly attempts to explain dark matter itself, rather than trying provide an alternative explaination altogether.

[Wikiy]

I haven't read up on my cosmology and physics in a long while but does String Theory not postulate reasons other than dark matter for the expansion?

(I'm asking because you seem to be keeping yourself well informed)

As i said, dark matter takes no part in the expansion of the universe (well, actually, it does, it drives it back by contributing to the ordinary gravity of the universe, which acts opposite to dark energy, if it weren't for dark matter, the expansion would've been a lot faster). It's the dark energy that causes the expansion. As for string theory, i don't think it tries to explain either. All string theory does is try to unite quantum mechanics and general relativity, of which neither has anything to do with dark matter or dark energy.

There is a hypothesis that dark matter is actually only the gravitational effect (which is the only thing that was detected anyway, dark matter itself hasn't been detected) of ordinary matter from other universes which somehow penetrates the "membranes" in between the universe and causes a gravitational effect in this one through higher dimension. String theory, even though it proposes higher dimensions, doesn't propose more universes, as far as i know.

But you shouldn't take my word for it. String theory isn't something i'm very interested in because it's hypothetical, too complicated for me, and plain crazy, so i don't really keep myself well informed regarding string theory.

Edit: Seems that, since gravity and dark matter are classical physics problems, string theory, as a proposed Theory of Everything (which is supposed to unite quantum mechanics and general relativity - classical mechanics) will, somehow, through quanta-mechanical effects, have to explain dark matter and dark energy. But this just makes it even harder on string theory. One more reason to not put too much trust in it, yet.

I'm somewhat fond of Quantum loop gravity for 2 reasons: 1) It says that spacetime isn't just nothing, but is quantized in the same sense as elementary particles are and 2) It changes the Big Bang theory in such a sense that it's actually a Big Bounce; that our universe resulted from a collapse of a previous universe. I know, this opens a question equally big as the one we have now (what was there before the Big Bang): What was there at the start of the cycle? But at least it explains our universe in a way. Here's a bit more about the Big Bounce as a result of loop quantum gravity:

According to some oscillatory universe theorists, the Big Bang was simply the beginning of a period of expansion that followed a period of contraction. In this view, one could talk of a Big Crunch followed by a Big Bang, or more simply, a Big Bounce. This suggests that we could be living at any point in an infinite sequence of universes, or conversely the current universe could be the very first iteration. However, if the condition of the interval phase "between bounces", considered the 'hypothesis of the primeval atom', is taken into full contingency such enumeration may be meaningless because that condition could represent a singularity in time at each instance, if such perpetual return was absolute and undifferentiated.

The main idea behind the quantum theory of a Big Bounce is that, as density approaches infinity, the behavior of the quantum foam changes. All the so-called fundamental physical constants, including the speed of light in a vacuum, were not so constant during the Big Crunch, especially in the interval stretching 10−43 seconds before and after the point of inflection. (One unit of Planck time is about 10−43 seconds.)

If the fundamental physical constants were determined in a quantum-mechanical manner during the Big Crunch, then their apparently inexplicable values in this universe would not be so surprising, it being understood here that a universe is that which exists between a Big Bang and its Big Crunch.

One of the main problems with the Big Bang theory is that at the moment of the Big Bang, there is a singularity of zero volume and infinite energy. This is normally interpreted as the end of the physics as we know it; in this case, of the theory of general relativity. This is why one expects quantum effects to become important and avoid the singularity.

However, research in loop quantum cosmology purported to show that a previously existing universe collapsed, not to the point of singularity, but to a point before that where the quantum effects of gravity become so strongly repulsive that the universe rebounds back out, forming a new branch. Throughout this collapse and bounce, the evolution is unitary.

[Svifnymr]

We know the space is expanding because the image of every galaxy that isn't in our cluster or supercluster is moving away. The same goes if you take the images of 2 different galaxies that aren't in our cluster or supercluster. It's not that we have to know that the galaxies are moving away from each other, we know their images are. Everything is moving away from us, except our cluster and supercluster (the gravity is strong enough to keep things together) but if you also look at any other galaxy, everything's moving away from it. This essentially means the whole universe is its own center, it's another strong pointer as to why the Big Bang Theory is correct, i.e., the universe used to be a point which was its own centre, it held the whole universe "inside" it, and the moment it started expanding, the centre of the whole universe started expanding.

The poster was referencing the distances involved. Closest other solar system is what, 4 light years? So whatever info we get from it's position is four years old and extrapolated from that. As you get further away, the information is even older. So, what if the universe was expanding 1000 years ago, but has since stopped but we haven't noticed because we won't get those measurements any time soon. And of course you must factor in the length of time we've accurately been measuring such things also.

"Over the last 70 years we've noticed that the position of starts from 5000 years ago says they're expanding at an ever accelerating rate!"

[semaphore]

The poster was referencing the distances involved. Closest other solar system is what, 4 light years? So whatever info we get from it's position is four years old and extrapolated from that. As you get further away, the information is even older. So, what if the universe was expanding 1000 years ago, but has since stopped but we haven't noticed because we won't get those measurements any time soon. And of course you must factor in the length of time we've accurately been measuring such things also.

Unless the expansion stopped overnight, we ought to see it slow down instead of speeding up.

[Wikiy]

The poster was referencing the distances involved. Closest other solar system is what, 4 light years? So whatever info we get from it's position is four years old and extrapolated from that. As you get further away, the information is even older. So, what if the universe was expanding 1000 years ago, but has since stopped but we haven't noticed because we won't get those measurements any time soon. And of course you must factor in the length of time we've accurately been measuring such things also.

"Over the last 70 years we've noticed that the position of starts from 5000 years ago says they're expanding at an ever accelerating rate!"

Redshift. If the expansion stopped at some point, then an object 1 billion light years away (which can be measured by other means) wouldn't be proportionally "redder" (proportional to a distance of 1 billion light years) than it is because at some point, the wavelengths of light from that object would have stopped being elongated (and the longer the wavelengths are, the more closer it is to the red color on the EM spectrum).

[Pum]

its not proven yet so you cant say one theory is more correct than another.

---------- Post added 2012-08-21 at 03:50 AM ----------

another question i would like to ask is.
if there was no humans in this universe and no lifeforms at all. does this universe actually exist?
if yes how does it exist when there is no life forms there to acknowlege it.

As interesting as this thread is, I am deeply infuriated by everything this guy is saying.

WHERE IS THE REASON?!

[superstarz]

It was proven that the universe is flat, not that Gravity represents negative energy. And even if this is the case, the expansion of the Universe clearly overcomes gravity, so there is a disbalance somewhere.

could you please tell me how the universe is flat?
how did they find that out without even exploring the edges of the universe.


if the universe is flat. what is at the top of the universe and at the bottom.
because you say it is flat then there should be a top and bottom right?

[Gothicshark]

could you please tell me how the universe is flat?
how did they find that out without even exploring the edges of the universe.


if the universe is flat. what is at the top of the universe and at the bottom.
because you say it is flat then there should be a top and bottom right?

See this video:
http://youtu.be/i4UpvpHNGpM
http://www.ted.com/talks/george_smoo..._universe.html

[Svifnymr]

Redshift. If the expansion stopped at some point, then an object 1 billion light years away (which can be measured by other means) wouldn't be proportionally "redder" (proportional to a distance of 1 billion light years) than it is because at some point, the wavelengths of light from that object would have stopped being elongated (and the longer the wavelengths are, the more closer it is to the red color on the EM spectrum).

Sure, but how long before the change registered from there to here? That's the question he asked, I believe. Assuming any measurable information will not travel to us faster than the speed of light, that information on the object 1 billion light years away will be 1 billion years old. Obviously we're using closer objects for extrapolation as well.

[Wikiy]

Sure, but how long before the change registered from there to here? That's the question he asked, I believe. Assuming any measurable information will not travel to us faster than the speed of light, that information on the object 1 billion light years away will be 1 billion years old. Obviously we're using closer objects for extrapolation as well.

I can't say i really understand you. If there was any change, it'd be registered in an incorrect redshift of the light rays (and light rays wont take any longer to reach us from where they started because the expansion of the universe actually adds to their speed, so they aren't just moving at the speed of light, they're moving at the speed of light plus whatever the speed of expansion is on the line between 2 objects). I don't know, English isn't my first language and i can't say i understand what exactly you're getting at.

[hellboyy]

if you like to refuse scientific theories you should also refuse using electricity, your computer, your phone, live in a modern house, use your plumbing, eat any farmed food, use your car, go to a medical doctor etc, because all these things are based on scientific theories.

[Svifnymr]

I can't say i really understand you. If there was any change, it'd be registered in an incorrect redshift of the light rays (and light rays wont take any longer to reach us from where they started because the expansion of the universe actually adds to their speed, so they aren't just moving at the speed of light, they're moving at the speed of light plus whatever the speed of expansion is on the line between 2 objects). I don't know, English isn't my first language and i can't say i understand what exactly you're getting at.

If something is say, 100 thousand light years away from us when expansion stopped/slowed, how long would it take for us to detect that change from when it occurred? And again, we've been taking fairly accurate measurements of such distances for say, 100 years?

[Adam Jensen]

http://www.ted.com/talks/george_smoo..._universe.html

I have never felt less insignificant before than I did while watching that video lol.

But seriously, that was fascinating.

[semaphore]

If something is say, 100 thousand light years away from us when expansion stopped/slowed, how long would it take for us to detect that change from when it occurred?

100,000 years.

And again, we've been taking fairly accurate measurements of such distances for say, 100 years?

That's not really an issue, though. Why do you think that's a problem?

[Wikiy]

If something is say, 100 thousand light years away from us when expansion stopped/slowed, how long would it take for us to detect that change from when it occurred? And again, we've been taking fairly accurate measurements of such distances for say, 100 years?

It would take 100 000 years, of course. But the expansion of the universe isn't something local. It's a property of space. If it stops at one place, it'll stop everywhere. It would also pretty much mean god exists.

[v2prwsmb45yhuq3wj23vpjk]

It would take 100 000 years, of course. But the expansion of the universe isn't something local. It's a property of space. If it stops at one place, it'll stop everywhere. It would also pretty much mean god exists.

I feel like probability waves are something so extremely puzzling that the expansion of the universe not being universal or stopping, etc. would not indicate that a god exists, rather that our understanding is incomplete.