Dark Flow

[5810Singer]

I haven't heard of this phenomenon before today, here's some wiki:

http://en.wikipedia.org/wiki/Dark_flow




There is a documentary about it on BBC2 at 21:00 GMT tonight, it'll be on BBC iPlayer after that I should imagine.

Can any of you physicists share your knowledge on this topic?

 

[Prolescum]

Sounds good, will watch.

 

[Master_Ghost_Knight]

I have don't know to much of the topic, however looking at the wiki descriptions some contradictions becomes quite aparent, being the most visible of which the fact that we are observing the influences of elements outside our observable universe, which is a direct contradiction of what being outside our observable universe means.

 

[aeroeng314]

the most visible of which the fact that we are observing the influences of elements outside our observable universe

It doesn't actually say that, though.

it would in a certain sense be outside our visible universe; however, it would still be in our past light cone.

I don't see a problem with that statement.

 

[5810Singer]

I have don't know to much of the topic, however looking at the wiki descriptions some contradictions becomes quite aparent, being the most visible of which the fact that we are observing the influences of elements outside our observable universe, which is a direct contradiction of what being outside our observable universe means.

If something outside the visible universe influences something within the visible universe how does that contradict "what being outside our observable universe means?"

The phenomenon creating the effect is unobservable, but the objects/phenomena being effected are observable....where's the contradiction?




BTW,.....the documentary was shit,....they waffled for 50mins and then spent 10mins on the advertised subject, and didn't even manage that 10mins very well.

 

[Squawk]

Did anyone else watch it? I did, and it annoyed the crap out of me. How many times did they have to show that damn baloon inflating and then bursting, or show that fucking explosion?

That program would have lost nothing at all condensed into 10 mins.

 

[5810Singer]

Did anyone else watch it? I did, and it annoyed the crap out of me. How many times did they have to show that damn baloon inflating and then bursting, or show that fucking explosion?

That program would have lost nothing at all condensed into 10 mins.

Yea, see above.

If there's any mileage in "dark flow", then the BBC will make a proper documentary at some point,....if "dark flow" dies a death then.....I guess they didn't waste too much time on a fruitless topic.

But 50mins of wobbly balloons, and slow-mo gun-powder explosions,......it was the scientific equivalent of the Teletubbies..... :roll: :facepalm:

 

[Master_Ghost_Knight]

If something outside the visible universe influences something within the visible universe how does that contradict "what being outside our observable universe means?"

The phenomenon creating the effect is unobservable, but the objects/phenomena being effected are observable....where's the contradiction?

Something being outside of our visible universe means that anything traveling at the speed of light from it twards us would never reach us due to the inflation of space. Sense literaly nothing travels faster then the speed of light and that's including gravity or any other phenomena that produces any influence what so ever, then the problem is that you got lost on the rellay of the effect from point A to B then C completly forgething that this is still a path from A to C.
In other words, for something outside our visible universe to affect something else, it would have transfer information at luminal or subluminal speeds too whatever destination might be, and then relay information (probable photons) that must also travel to us from whatever was affected at luminal or subluminal speeds, given that triangular inequalities must also be acounted for this means that the information has reached you at subluminal speed, which means one of 2 things:
1. That the information between whatever was affected to us was delayed along it's path, and thus whatever effects you are observing took place while the causer of the effect was still in the observable universe, even if later has crossed that line. (the same way I can have a picture of my grandman before she died, but that doesn't mean that she went shoping the next morning from the afterlife).
2. Whatever affected what you are observing is still in the observable universe.

You could have picked this up easily by putting it this way, if you can observe the effects of something, then inderectly you can have information about their state and thus you are inderectly observing it.
So observing something in the unobservable universe is nonsense, unless of course there is something wrong with my definitions.

 

[Master_Ghost_Knight]

it would in a certain sense be outside our visible universe; however, it would still be in our past light cone.

I don't see a problem with that statement.

The first sentece, says that the object is outside our light cone, the second says it is inside. Unless they figured out a way to be in both places at the same time that is a contradiction.

 

[Demojen]

<Bill Clinton> I am not here.

 

[nasher168]

Did anyone else watch it? I did, and it annoyed the crap out of me. How many times did they have to show that damn baloon inflating and then bursting, or show that fucking explosion?

That program would have lost nothing at all condensed into 10 mins.

Aye, they could have just explained it basically in layman's terms, then just said "We actually don't have a bloody clue...yet" and left it at that.

 

[aeroeng314]

The first sentece, says that the object is outside our light cone, the second says it is inside.

No, it doesn't say that. It says outside the visible universe, not outside the observable universe. It also says "in a certain sense", which is true, because the cause of this motion isn't visible because its location is prior to the universe becoming transparent, so it isn't visible in that sense.

 

[Demojen]

No, it doesn't say that. It says outside the visible universe, not outside the observable universe. It also says "in a certain sense", which is true, because the cause of this motion isn't visible because its location is prior to the universe becoming transparent, so it isn't visible in that sense.

Observable is visable.

Just because you can't see it, does not make it invisable to everything.
It is rather "short sighted" to assume otherwise.

If memory serves me, to my knowledge the universe is both transparent and opaque and has always been since the big bang. The only moment it could be argued to not been both, is at the point the first dimension existed and the second did not....

We don't know though whether or not the first four dimensions existed independent of one another or were created with one another at the same time.

 

[Master_Ghost_Knight]

No, it doesn't say that. It says outside the visible universe, not outside the observable universe. It also says "in a certain sense", which is true, because the cause of this motion isn't visible because its location is prior to the universe becoming transparent, so it isn't visible in that sense.

Can you please develop the difference between your definition of visible and observable, it might be that we are not talking in the same terms.

 

[Prolescum]

Fortunately, I neglected to watch it. One nil to the prole.

 

[aeroeng314]

By visible I mean visible in the electromagnetic radiation sense. By that, I mean that the cause itself is directly visible by either reflected or emitted EM radiation instead of relying on its interactions with other visible things.

Observable is visable.

Dark matter is not visible, but is observable. So, no, they aren't the same.

If memory serves me, to my knowledge the universe is both transparent and opaque and has always been since the big bang.

Those are two mutually exclusive things. And the universe as a whole cannot be both at the same time in the same space. There was a period of time after the big bang during which the universe (the entire universe) was opaque to EM radiation. This is because the average temperature was still high enough that all matter in the universe was still in an ionized plasma state. After the universal expansion cooled it enough, stable atoms were formed and the universe became transparent to EM radiation. The remnant of this is the Cosmic Microwave Background Radiation. This all happened some 380000 years after the big bang.

It was never both and you're talking nonsense.

 

[Ozymandyus]

Something being outside of our visible universe means that anything traveling at the speed of light from it twards us would never reach us due to the inflation of space. Sense literaly nothing travels faster then the speed of light and that's including gravity or any other phenomena that produces any influence what so ever, then the problem is that you got lost on the rellay of the effect from point A to B then C completly forgething that this is still a path from A to C.
In other words, for something outside our visible universe to affect something else, it would have transfer information at luminal or subluminal speeds too whatever destination might be, and then relay information (probable photons) that must also travel to us from whatever was affected at luminal or subluminal speeds, given that triangular inequalities must also be acounted for this means that the information has reached you at subluminal speed, which means one of 2 things:
1. That the information between whatever was affected to us was delayed along it's path, and thus whatever effects you are observing took place while the causer of the effect was still in the observable universe, even if later has crossed that line. (the same way I can have a picture of my grandman before she died, but that doesn't mean that she went shoping the next morning from the afterlife).
2. Whatever affected what you are observing is still in the observable universe.

You could have picked this up easily by putting it this way, if you can observe the effects of something, then inderectly you can have information about their state and thus you are inderectly observing it.
So observing something in the unobservable universe is nonsense, unless of course there is something wrong with my definitions.

The problem being that because of the expansion of space there are objects that are more distant than the time that the universe has existed allows for. Since the universe is expanding, masses that were close enough to affect each other gravitationally 1 billion years ago can be more than 1 billion lightyears apart. even while travelling at sub-luminal speeds.

 

[Demojen]

Dark matter is not visible, but is observable. So, no, they aren't the same.

By your definition of visable, yes.
By *the* definition of visable, no.

It's nice that you can redefine words to operate on a level that makes you correct, but that doesn't make you correct on any level that matters.
This is why we scrutinize things in science.
"Because I said so" isn't a good enough answer.

Again, you're applying your own exclusive definition of visable, transparent and opaque, but use the words in context you will see I did not mention who or what was observing it and for a very good reason.

I thought for a moment when you elaborated "to EM radiation" you might be conceding to the obvious quagmire creating your own definitions for things illustrates but it seems you only mentioned EM radiation as a placeholder for your brain.

Get off wikipedia and think for yourself.

 

[Ozymandyus]

The word visible most certainly can be used to only mean EM radiation that falls in the visible spectrum. In fact I would reckon it is the most common definition of the word visible...
1. capable of being seen <stars visible to the naked eye> b : situated in the region of the electromagnetic spectrum perceptible to human vision <visible light> ,used of radiation having a wavelength between about 400 nanometers and 700 nanometers

But in any case, that's not really whats being talked about here: This article is about something that is not visible or even directly observable. If I understand it correctly, this phenomenon is inferred by the reactions of other things that ARE observable and neither 'dark flow' nor whatever causes this motion is directly observable or visible in whatever way you are using those words.

Anyway, in my opinion observability and visibility should not be considered the same in this conversation. When trying to be clear and scientific visible should be used in its most specific sense, which is the visible spectrum of light. We can make observations about visible objects, and we can make observations about things that have no visible component at all... observations about what people are thinking for example. Not sure how anyone could claim such a thing is visible, but you can clearly make observations about what people are thinking. , he is not the one redefining words here.

 

[Master_Ghost_Knight]

By visible I mean visible in the electromagnetic radiation sense. By that, I mean that the cause itself is directly visible by either reflected or emitted EM radiation instead of relying on its interactions with other visible things.

Observable is visable.

Dark matter is not visible, but is observable. So, no, they aren't the same.

If memory serves me, to my knowledge the universe is both transparent and opaque and has always been since the big bang.

Those are two mutually exclusive things. And the universe as a whole cannot be both at the same time in the same space. There was a period of time after the big bang during which the universe (the entire universe) was opaque to EM radiation. This is because the average temperature was still high enough that all matter in the universe was still in an ionized plasma state. After the universal expansion cooled it enough, stable atoms were formed and the universe became transparent to EM radiation. The remnant of this is the Cosmic Microwave Background Radiation. This all happened some 380000 years after the big bang.

It was never both and you're talking nonsense.

Fair enough, but the definition of visible universe is a defined radius of what you can potentially see either or not you are able to do so, being that EM radiation travels at the speed of light, the distinction is irrelevant.

However rethinking my case, there is a possibility that someone may mean that object A is estimated to have fall beyound our visible horizon during the time it took for the information to travel, but I doubt that was the case sense I personaly I don't see any merit of defining the region of "visible universe" if not on the time frame of the current vantage point (and as so my position would hold).