Nobel Prize for Dark Energy trio

Saul Perlmutter, Brian Schmidt & Adam Riess

Study matter and its motion through spacetime...

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Re: Nobel Prize for Dark Energy trio

#21  Postby newolder » Oct 06, 2011 2:42 pm

Dudely wrote:
newolder wrote:
Dudely wrote:

Are you being facetious? Perhaps preying on an imperfect analogy?

The universe is expanding because for some crazy unknown reason it started expanding at the big bang. Gravity is slowing it down by. . . being gravity. At a certain density the matter in the universe should be enough to let gravity take over and collapse everything back again.

isn't this primitive cyclic model what the prize winning entry disproves by repeated experiment? :ask:


I said "At a certain density the matter in the universe should be enough to let gravity take over and collapse everything back again." I did not say the density IS above that value, or that it ever would be. In fact- as I explain a few sentences later- it isn't.

Then i shudve read further. :oops: Sry.
Precisely because we don't see the expansion slowing down we know this not to be the case. However, we have to add a bunch of crazy unproven variables into the mix to make all our observations jive with one another. This is what dark energy and dark matter is for.

I don't know what u mean by crazy and/or unproven but dark matter accounts for (amongst other things) the rotation speeds of stars in galaxies (neither crazy nor unproven) and Einstein's (not even a mistake) cosmological constant accounts 4 accelerated expansion. :scratch:

If the density was above that critical value a collapse is what would happen. You can do the math yourself if you like- I did, so it cant be that hard :lol:. Of course, now we have to take into account all the dark stuff, but we really don't even know if that's the right answer yet.

Wheeler and/or de Witt published all teh necessary calculations, iirc.
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Re: Nobel Prize for Dark Energy trio

#22  Postby tuco » Oct 06, 2011 3:17 pm

Dudely wrote:
tuco wrote:Facetious? Those are questions one gets when one starts to ask what the nature of space-time is. Nothing, but not that kind of dark energy, sounds good to me as it brings us back on topic - 2 < 0


Ok, excuse me then. It's hard to tell online, especially when you have such a density of sarcasm as on this forum (I would have it no other way)!


You asked me about new matter being created when the universe expands and when I explained that isn't what would happen (and that it is, in fact, impossible), your response was to ask what was in the new space and that you didn't like making matter without energy. . . which is what I had just said wouldn't happen. That's why I thought you were being facetious.

Expanding space-time increase mass in the same way bread rising increases the number of raisins in the dough. It doesn't.


No excuse needed as no offense was taken. I tend to agree I did not like the metaphor used by Mr Riess, at the same time, OP question seemed just as facetious and when we say A we must say B. It if was that self-evident how it works, no Nobel then I guess. The question essentially was: What is the nature of the bread? as the raisins are irrelevant at this point where we talk about expansion on microscopic scale. How about this: Can I influence this expansion? By stretching the bread a little, somehow.
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Re: Nobel Prize for Dark Energy trio

#23  Postby Dudely » Oct 06, 2011 5:37 pm

newolder wrote:
I don't know what u mean by crazy and/or unproven but dark matter accounts for (amongst other things) the rotation speeds of stars in galaxies (neither crazy nor unproven)


Yes. It accounts for it because we made it up to fit what we saw. It's a great idea, and probably correct, but we have exactly zero evidence for it other than it's existence being inferred by the fact that our calculations are off when we look at very large objects. Obviously something is there, we just have absolutely no idea what is going on. It is the prevailing theory, it fits quite well, and I think it's probably going to be validated very soon. But it is crazy, and it is unproven.

newolder wrote:
and Einstein's (not even a mistake) cosmological constant accounts 4 accelerated expansion. :scratch:


Almost correct, but not quite.

Einstein postulated the "cosmological constant" as a way to keep the universe static. Basically Einstein disbelieved in quantum mechanics (the discovery of quantum mechanics ironically came as a direct result of Einstein's theories) and tried for most of his life to come up with a way to pretend that "god does not play dice" which is layman for "Quantum mechanics? LALALA I CAN'T HEAR YOU". He thought discovering the universe's laws was a way of seeing the mind of god and didn't like the idea that, on a fundamental level, no one can know an exact result ahead of time or know the exact speed and location of any particle. Einstein's constant was simply a way to keep the universe static while still allow his general relativity equations to work. It was a needless mutilation of his theory and he came to regret it a great deal. So yes, it was a mistake.

The "Constant" we've come up with now is very similar- it's sort of this layer of energy we can't normally interact with that works throughout the universe to push everything apart. That's what we call dark energy.

So it's simply a humorous coincidence that there happens to be a very similar "constant" that does the same kind of thing as Einstein (but in the other direction, so to speak).

And, just like dark matter, dark energy is completely hypothetical with no direct evidence for its existence. Again, it's the best theory and I personally think it will be validated long before I die of old age. But let's not count our chickens before they hatch.
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Re: Nobel Prize for Dark Energy trio

#24  Postby Dudely » Oct 06, 2011 5:52 pm

tuco wrote: Can I influence this expansion? By stretching the bread a little, somehow.


The best answer I can give is this:

If you figure out a way to do that you've also figured out a way to achieve faster-than-light travel without violating any physical laws.

So no. Maybe we'll figure it out eventually. There are a few theories but it involves the spaceship never being able to leave the expanding bubble and/or getting totally destroyed when it stops moving.
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Re: Nobel Prize for Dark Energy trio

#25  Postby newolder » Oct 07, 2011 7:18 am

Dudely wrote:...But it is crazy, and it is unproven.

Then we disagree on what is crazy and unproven. :thumbup:

newolder wrote:
and Einstein's (not even a mistake) cosmological constant accounts 4 accelerated expansion. :scratch:


Almost correct, but not quite.

Einstein postulated the "cosmological constant" as a way to keep the universe static. Basically Einstein disbelieved in quantum mechanics (the discovery of quantum mechanics ironically came as a direct result of Einstein's theories) and tried for most of his life to come up with a way to pretend that "god does not play dice" which is layman for "Quantum mechanics? LALALA I CAN'T HEAR YOU". He thought discovering the universe's laws was a way of seeing the mind of god and didn't like the idea that, on a fundamental level, no one can know an exact result ahead of time or know the exact speed and location of any particle. Einstein's constant was simply a way to keep the universe static while still allow his general relativity equations to work. It was a needless mutilation of his theory and he came to regret it a great deal. So yes, it was a mistake.

Not even close to correct. Quantum theory had 0 to do with the cosmological constant and, if Einstein had been more watchful/adventurous, he would have been able, using the cc, to predict the accelerated expansion we now observe.
The "Constant" we've come up with now is very similar- it's sort of this layer of energy we can't normally interact with that works throughout the universe to push everything apart. That's what we call dark energy.

So it's simply a humorous coincidence that there happens to be a very similar "constant" that does the same kind of thing as Einstein (but in the other direction, so to speak).

That's just bs. :lol:

And, just like dark matter, dark energy is completely hypothetical with no direct evidence for its existence.

Yeah, riiiight, and the Nobel Committee haz been conned. :lol:
Again, it's the best theory and I personally think it will be validated long before I die of old age. But let's not count our chickens before they hatch.

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Re: Nobel Prize for Dark Energy trio

#26  Postby THWOTH » Oct 07, 2011 7:47 am

From what I can gather nobody in physics really likes dark energy or dark matter because they are so... you know... dark. To me it seems that physics has fashioned a missing piece of the jigsaw puzzle based on the outline of the hole but at present does not have a clue as to what's on the piece - is it an elephant's toe or a mouse's ear?



OK, I'll get my coat....

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Re: Nobel Prize for Dark Energy trio

#27  Postby twistor59 » Oct 07, 2011 8:06 am

For a good account of Einstein's treatment of the cosmological constant, see section II here.

The paper also gives a good summary of its relationship with dark energy.
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Re: Nobel Prize for Dark Energy trio

#28  Postby THWOTH » Oct 07, 2011 8:19 am

Cheers T59 :thumbup:
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Re: Nobel Prize for Dark Energy trio

#29  Postby tuco » Oct 07, 2011 8:51 am

Interpretations of: God does not play dice, vary.

Does God Play Dice? - http://www.hawking.org.uk/index.php/lec ... ectures/64

Of course, later Mr Hawking reconsidered when he claimed that even black holes do not eat information. Well, that is my, layman, understanding of the matter.

---
edit: just hmm side note

[Albert] Einstein's theism, such as it was, was his faith that God does not play dice with the universe -- that there are elegant, eventually discoverable laws, not randomness, at work. Saying "I'm not an atheist," he explained:

"We are in the position of a little child entering a huge library filled with books in many different languages. The child knows someone must have written those books. It does not know how. It does not understand the languages in which they are written. The child dimly suspects a mysterious order in the arrangement of the books but doesn't know what it is."

http://www.washingtonpost.com/wp-dyn/ar ... 5Jan5.html
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Re: Nobel Prize for Dark Energy trio

#30  Postby Dudely » Oct 12, 2011 1:09 pm

newolder wrote:
Dudely wrote:
So it's simply a humorous coincidence that there happens to be a very similar "constant" that does the same kind of thing as Einstein (but in the other direction, so to speak).

That's just bs. :lol:


Why do you say that? Einstein came up with a constant to explain why the universe is static. We've come up with one to explain why it's expanding. While similar, they were conceived for completely different reasons. How is this BS?


As a side note I will admit you were right in stating that I was a bit off with the quantum stuff having anything at all to do with his cosmological constant stuff. I've been reading a lot about Einstein lately and must have gotten confused.
(Side note on my side note: Einstein fucked his cousin, had a kid, and then abandoned it. What a douche bag, eh?)

newolder wrote:

And, just like dark matter, dark energy is completely hypothetical with no direct evidence for its existence.

Yeah, riiiight, and the Nobel Committee haz been conned. :lol:
Again, it's the best theory and I personally think it will be validated long before I die of old age. But let's not count our chickens before they hatch.

:scratch:


I say this with the greatest respect, but I think you need to reconsider the meaning and purpose of the scientific method. Dark matter and dark energy have no direct evidence for their existence. Period. They are a hypothesis and have not even obtained the status of theory. There is nothing at all wrong with saying this. The Nobel prize committee has not been "conned"; no one is pulling the wool over anyone's eyes. Everyone knows there is no evidence for it. The reason they got the prize is because now that physics is so robust any new idea must fit so well in the existing framework that if it's accepted by even a substantial minority of physicists the likelihood that it will be eventually validated by evidence is extremely good. Even if it's wrong it will probably be 90% right.

The value those scientists made was not in coming up with some robust and perfectly validated theory, it was in doing the work in coming up with the explanatory framework in the first place. Dark matter and dark energy fit so well that we're still finding places where it fits with eery accuracy. Lawrence Krauss's did a talk once that included a lot of these. I think he called it "A Universe From Nothing". I can't reccomend it highly enough.

[youtube]http://www.youtube.com/watch?v=7ImvlS8PLIo [/youtube]

In the interest of scientific accuracy and intellectual honesty I must mention the current level of understanding and validation by evidence. If I talked about dark energy and dark matter and didn't mention that it's just a hypothesis I would not feel like I was being honest.
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Re: Nobel Prize for Dark Energy trio

#31  Postby Pulsar » Oct 12, 2011 4:35 pm

I don't know if I've posted it before on this forum, but if anyone wants to know the maths behind the current standard cosmological model and its interpretation, I highly recommend this article:

http://www.mso.anu.edu.au/~charley/papers/DavisLineweaver04.pdf
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Re: Nobel Prize for Dark Energy trio

#32  Postby THWOTH » Oct 12, 2011 11:48 pm

Thanks for the link Pulsar. :thumbup:
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Re: Nobel Prize for Dark Energy trio

#33  Postby surreptitious57 » Oct 13, 2011 12:48 am

One needs to understand a fundamental
truth here and it is this : there will always
be mysteries in science. Man will never unlock
every single secret of the Universe. When finally
what constitutes the three darks - energy, matter,
flow - has been solved, it will only be a matter of time
before something else crops up. So physicists should not
be disheartened at this. After all it would be a rather boring
world if we knew everything. We need to be patient and realise
what we are up against : an expanding Universe which has always
existed even if once it was only composed of energy and not matter
and us, a rather young species with a tiny mammalian brain that thinks
it can unravel all the mysteries of the Cosmos it lives in though it will carry
on long after we have ceased to exist when the Sun implodes five billion years
from now. We are in the library. We know what some of the books say but there is
still so much to learn. We may not have enough time to read them all but must press on
A MIND IS LIKE A PARACHUTE : IT DOES NOT WORK UNLESS IT IS OPEN
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Re: Nobel Prize for Dark Energy trio

#34  Postby Dudely » Oct 13, 2011 5:51 pm

There's a difference between thinking you can unravel the mysteries of the cosmos and hoping you can.

No scientist actually sets out thinking that they can find an answer. He or she merely hope to gain the insight- and possibly recognition- that has come to so many before them. The list goes on seemingly forever: Einstein, Newton, Galileo, Feynman; these are people who gave humanity great knowledge not because they thought they could but simply because they wanted to. And for every celebrated genius there are thousands upon thousands of failures.

So what exactly is wrong with what we're doing?
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Re: Nobel Prize for Dark Energy trio

#35  Postby THWOTH » Oct 13, 2011 5:57 pm

Dudely wrote:[...] So what exactly is wrong with what we're doing?

Nothing. Adding to the sum total of human knowledge has got to be among the noble and virtuous of human endeavours. Using science to figure out how to separate people from their money, or building systems to manage hedge funds, etc, well, that seems rather a waste of healthy brains to me.
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Re: Nobel Prize for Dark Energy trio

#36  Postby surreptitious57 » Oct 14, 2011 4:51 am

Dudely wrote:

So what exactly is wrong with what we're doing ?


I never stated there is anything wrong in what
we are doing. I am all in favour of pushing ourselves
to discover as much as we can about the Universe. I am
just merely suggesting that we need to realise that there are
limitations. Specifically two : time and intelligence. We only have
five billion years left before the Sun implodes and that will be the end
of human civilisation unless we develop advanced space travel and discover
alternative compatible worlds. And we have a limited brain capacity too. We are
after all nothing more than advanced bacteria. So I am all for learning much as we can
Just realise that one day all this will cease to be. Nothing lasts for ever. Everything eventually dies
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Re: Nobel Prize for Dark Energy trio

#37  Postby newolder » Oct 14, 2011 7:41 pm

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Re: Nobel Prize for Dark Energy trio

#38  Postby cavarka9 » Oct 16, 2011 4:43 am

nonsense, there is nothing much to understand here. Einstein's theory predicted a universe which was not static,it either expands or contracts, physicists squirm, now they have to explain why, theoretical physicists get uncertain, so they take a peak at the data experimentalists have to show, they find from the data of the period* and see it as implying a static. Einstein adds a constant which counteracts gravity and lo behold a static universe, no further need to explain the origin of the universe, it always was. Few years later, with more data, it turns out that the universe is indeed expanding. Now, Einstein admits mistake because he realizes that he shouldnt have doubted his equations and fiddled with it. Many years later, the data suggests that the universe seems to be expanding at a higher rate than assumed from hubbles data. Now it is coincidental that the const eintstein used happens to explain the universe we observe today to a good degree. Hence Einstein being the famous Einstein of the e=mc^2 fame could not have made a mistake twice out of ignorance of the data of the universe, no he couldnt because he was all knowing, he infact made a prediction!.
The question which remains is whether the constant helps to model things as they are right from the beginning or does it model it accurately only at this instant of the universe. I will bet that the constant must have changed and will change because the constant must come from another factor which we havent considered, this must be true because all factors must eventually be a part of the universe, we dont know what the mechanism is and hence heuristically represent it by a constant. Because its addition was unprincipled to begin with.It was added to confirm to the wrong data earlier and removed in accordance to the improvement in data in between and finally brought in confirm to the data as it stands today.
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