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Dark matter scaffolding of universe detected for the first time

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Re: Dark matter scaffolding of universe detected for the first time

#31

Post by jeggers5 »

Tloewald wrote: post #27
mkup wrote: post #26

Earlier quoted context omitted.

(A bit off-topic question to physics expert on HN) I've read that supermassive black hole accretion is the most energy-effective process of mass to energy conversion in the Universe (50% efficiency or so). I'm just curious: Where does all that energy go? Extremely powerful jets of radiation are emitted into the intergalaxy space and then what? Does it just disappear? Isn't this energy responsible for Universe expansi…

Same place sunlight goes.

It would be amazing if somebody could answer this too. If I turn a lamp on and off in a sealed room of mirrors, why doesn't the light just keep bouncing off the walls and illuminate the room?

Re: Dark matter scaffolding of universe detected for the first time

#32

Post by [deleted] »

rwmj wrote: post #28
Xcelerate wrote: post #8

Earlier quoted context omitted.

I said earlier in the post "there's one interaction between ALL of the particles that is missing: gravity", so it was implied. Perhaps I should have made that a little clearer.

I thought the interaction with the Higgs is supposed to create mass?

[deleted]

Re: Dark matter scaffolding of universe detected for the first time

#33

Post by scott_s »

jeggers5 wrote: post #31
Tloewald wrote: post #27

Earlier quoted context omitted.

Same place sunlight goes.

It would be amazing if somebody could answer this too. If I turn a lamp on and off in a sealed room of mirrors, why doesn't the light just keep bouncing off the walls and illuminate the room?

Mirrors are not perfect reflectors; some light will be absorbed.

Re: Dark matter scaffolding of universe detected for the first time

#34

Post by lepton »

jeggers5 wrote: post #31
Tloewald wrote: post #27

Earlier quoted context omitted.

Same place sunlight goes.

It would be amazing if somebody could answer this too. If I turn a lamp on and off in a sealed room of mirrors, why doesn't the light just keep bouncing off the walls and illuminate the room?

The reflection is not perfect; the mirrors absorb some light (and warm up...).

Re: Dark matter scaffolding of universe detected for the first time

#35

Post by scott_s »

kamaal wrote: post #14
tb wrote: post #5

Earlier quoted context omitted.

> Some other particle may interact with nothing we are familiar with -- and thus we could never study it. Is it even "real" then? Philosophically, this is equivalent to the question of whether other universes, which do not interact with ours and therefore we cannot study, exist or are "real". It is not a question that Science can answer.

Oh well, That question really has far reaching implications. Because if we say Science is what we observe and describe as per our interpretations of logic(And the language of logic - 'Math') then our science is really broken. Because what we can observe doesn't often turn out to be true and what is true is not often observed. Because look at it this way. We are now saying Dark Matter doesn't interact anyway with ligh…

We are now saying Dark Matter doesn't interact anyway with light nor something else. Hence observing, detecting or modeling them out through conjectures manufactured through thin air is nothing more than what religion was some centuries ago.

It interacts gravitationally with other matter.

Re: Dark matter scaffolding of universe detected for the first time

#36

Post by codeflo »

jeggers5 wrote: post #31
Tloewald wrote: post #27

Earlier quoted context omitted.

Same place sunlight goes.

It would be amazing if somebody could answer this too. If I turn a lamp on and off in a sealed room of mirrors, why doesn't the light just keep bouncing off the walls and illuminate the room?

Well yes, when the light hits a mirror, a certain percentage (say 95% of the energy) bounces back, which can hit another mirror and so forth. There's no limit, but after a few dozen bounces, the remaining light is virtually undetectable.

Really, the exact same thing happens in a standard white painted room, the two differences being that the mirrors reflect more of the light (so that a dimmer light source will suffice to reach the same level of illumination), and that the reflection is directed instead of diffuse (this only changes the shape of the reflected light, not its amount). Maybe you can explain what's confusing you.

Re: Dark matter scaffolding of universe detected for the first time

#37

Post by kyberias »

InclinedPlane wrote: post #25

So, interestingly enough the leading theory for the identity of the bulk of dark matter is the "weekly interacting massive particle" (or WIMP) the neutralino, and there has been recent evidence from the Fermi gamma-ray telescope that supports the theory that the neutralino is the primary component of dark matter. http://arxiv.org/abs/1201.1003 http://arxiv.org/abs/1205.1045

Since this is Hacker News I have to point out that the "weekly interacting massive particle" could be, for example, my over-weight boss whom I have to meet every monday. ;)

Re: Dark matter scaffolding of universe detected for the first time

#38

Post by Retric »

jeggers5 wrote: post #31
Tloewald wrote: post #27

Earlier quoted context omitted.

Same place sunlight goes.

It would be amazing if somebody could answer this too. If I turn a lamp on and off in a sealed room of mirrors, why doesn't the light just keep bouncing off the walls and illuminate the room?

Some of that energy turns into heat every time the photons hit something, but heat is a mix of kinetic energy and light so you do get a fraction of that light bouncing around indefinitely, it's just not in the visible spectrum.

Think of it like dropping a ball an a hard vs soft surface. In both cases things bounce. Even on a hard floor the ball stops bouncing after a while, and in both cases the ball / floor / air get's get's warmer from the balls energy.

Re: Dark matter scaffolding of universe detected for the first time

#39

Post by syncerr »

lloeki wrote: post #17
syncerr wrote: post #3

It is worth noting that there was no direct detection of dark matter. It comes from a measurement of gravitational lensing, which has been going on for awhile˟˟. Critical response: http://www.scilogs.eu/en/blog/the-dark-matter-crisis/2012-07... Source: http://www.nature.com/nature/journal/v487/n7406/full/nature1... ˟˟ http://physicsworld.com/cws/article/news/2006/aug/25/gravity...

Indeed, it's more like observing a magnetic field by dropping iron dust on a sheet of paper, and gently hit/shake it until the field lines "appear". It makes me wonder why we can't observe dark matter (which seems to emit only pure gravitation, and no light nor electromagnetic radiation). Could it be because there's no actual matter (i.e pure gravitational waves, like the magnet+iron+paper experiment)? Or are they ma…

http://en.wikipedia.org/wiki/Dark_matter#Direct_detection_ex...

Re: Dark matter scaffolding of universe detected for the first time

#40

Post by syncerr »

jeggers5 wrote: post #31
Tloewald wrote: post #27

Earlier quoted context omitted.

Same place sunlight goes.

It would be amazing if somebody could answer this too. If I turn a lamp on and off in a sealed room of mirrors, why doesn't the light just keep bouncing off the walls and illuminate the room?

I assume light collides with atmosphere as well. Only in a perfect vacuum, light would travel forever?
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