NationStates Jolt Archive

Video. (http://universe.nasa.gov/science/darkenergy.html)
What do you think dark energy is? And no, a cosmology degree is not required to post.
Basically:

Cosmological constant = universal, static property of the universe.
Quintessence = variable aspect of the universe.
Modified relativity/gravity = failure of relativity on a large scale.

More technical:
• Cosmological constant (w = -1)
Originally introduced by Albert Einstein, it was later suggested by Yakov Zel'dovich that quantum vacuum energy would produce a constant energy density and pressure. However, theoretical predictions yield a cosmological constant that is 120 orders of magnitude higher than the observational value. Regardless of cosmology, quantum vacuum energy exists. Whether the cosmic contribution is in fact zero, or finely tuned, is one of the outstanding challenges in physics.

• Quintessence (w > -1)
A form of energy with negative pressure that varies with space and time. Quintessence is dynamic, unlike the cosmological constant, and its average energy density and pressure slowly decay with time. This feature might help to explain the tuning and sudden onset of cosmic acceleration. Modelled as a scalar field, quintessence predicts particle-like excitations with a mass of about 10-33 eV (see Caldwell and Steinhardt in further reading).

• Other vacuum energy (w < -1)
Unless we are the victims of a conspiracy of systematic effects, w < -1 is the sign of really exotic physics. In one model, quantum effects of a quintessence-like field lead to modifications of general relativity, while other models suggest that the dark-energy density actually grows with time, possibly causing the universe to end in a catastrophic "big rip". Other novel ideas include an exotic field that causes a cosmological-constant-like acceleration but that varies in space.

• Modification of general relativity
Various attempts have been made to modify Einstein's general theory of relativity, and therefore avoid the need for exotic matter to drive the accelerated expansion. While some are difficult to distinguish from quintessence, many predict violations of the equivalence principle (which is the bedrock of general relativity) or departures from the universal 1/r gravitational potential.

article (http://www.lbl.gov/Science-Articles/Archive/Phys-HST-supernovae-sidebar1.html) wiki (http://en.wikipedia.org/wiki/Dark_energy) another article (http://physicsweb.org/articles/world/17/5/7)

I don't know enough to speculate, astronomy is just a hobby for me. My gut tells me that there's something we're overlooking, and that one day the idea of "dark energy" (or "dark matter", as well) will seem as quaint and outdated as the 19th century notion of "the ether" does today. I have no real logical reason for thinking that, just a gut feeling.

Where's the "insufficient data" option? Really, I don't think anyone knows enough about it to definitively say what it is or isn't. Hopefully we'll figure it out in the next couple decades...I suspect that at some point someone's going to come up with a TOE (theory of everything, along the lines of M-Theory or Loop Quantum Gravity) and find a dark energy term in there somewhere. Maybe. :confused:

Insufficient data, as was previously mentioned.

A grasping attempt to bridge the gaps in our knowledge.

Dark Energy is neither exotic nor particularly spectacular.

Dark energy is energy we can't detect. We theorize it's existence, and due to gaps in certain equations, we know that there is energy floating about out there that we don't have the means to measure, but we can't identify it since we can't detect it, either directly or indirectly.

That's all. No big mystery.

Dark Energy is neither exotic nor particularly spectacular.

Dark energy is energy we can't detect. We theorize it's existence, and due to gaps in certain equations, we know that there is energy floating about out there that we don't have the means to measure, but we can't identify it since we can't detect it, either directly or indirectly.

That's all. No big mystery.

So it's the fudge factor that makes everything come out right? Einstein postulated that first, but you're in good company. I'm a Cosmic Triangle kind of guy, so I'm voting for inflation.

So it's the fudge factor that makes everything come out right? Einstein postulated that first, but you're in good company. I'm a Cosmic Triangle kind of guy, so I'm voting for inflation.

Inflation means something very different in the context of cosmology. Inflation describes the process by which the early universe expanded from submicroscopic size to an astronomical scale in an insanely short timeframe. The theory was developed in the 80s and makes some very accurate predictions about the distribution of matter in the universe. Unless what you're saying is that dark energy is some kind of milder form of the hyper-inflation that occurred then...again, I lack sufficient information. That's the frustrating part about science, there isn't always an answer right away.

I'm pretty sure it's unobservable, almost undetectable stuff that is used to explain how exactly the various cosmological constants are what they are and how the universe developed as it did.

It's the stuff that makes the stuff what it is today.

I'm pretty sure it's unobservable, almost undetectable stuff that is used to explain how exactly the various cosmological constants are what they are and how the universe developed as it did.

It's the stuff that makes the stuff what it is today.

Actually, what is usually referred to as "dark energy" is the very mysterious energy that is making the expansion of the universe accelerate. Matter and dark matter should be slowing the expansion down (gravitationally attracting everything together), but instead the expansion is speeding up. Dark energy is the term that's used to describe whatever is causing that (it seems to be a property of space itself, as it doesn't diminish as the universe spreads out).
[/physics major]

Video. (http://universe.nasa.gov/science/darkenergy.html)
What do you think dark energy is? And no, a cosmology degree is not required to post.
Basically:

Cosmological constant = universal, static property of the universe.
Quintessence = variable aspect of the universe.
Modified relativity/gravity = failure of relativity on a large scale.

More technical:


article (http://www.lbl.gov/Science-Articles/Archive/Phys-HST-supernovae-sidebar1.html) wiki (http://en.wikipedia.org/wiki/Dark_energy) another article (http://physicsweb.org/articles/world/17/5/7)

Personally I think the theories of dark energy and dark matter are utter claptrap. For no real reason.
As an amateur physicist (and mathematician, and historian :D) I know I'm being quite irrational; I base my disbelief on nothing other than the fact that it gets on my nerves and doesn't sound right.
I am, however, a great proponent of the idea of particles with negative mass and energy.

Ilaer

Actually, what is usually referred to as "dark energy" is the very mysterious energy that is making the expansion of the universe accelerate. Matter and dark matter should be slowing the expansion down (gravitationally attracting everything together), but instead the expansion is speeding up. Dark energy is the term that's used to describe whatever is causing that (it seems to be a property of space itself, as it doesn't diminish as the universe spreads out).
[/physics major]

I still prefer my 'space-time is similar to a liquid and thus the universal expansion and the Cosmological Constant are caused by a process remarkably similar to diffusion' theory. :D

Ilaer

Inflation means something very different in the context of cosmology. Inflation describes the process by which the early universe expanded from submicroscopic size to an astronomical scale in an insanely short timeframe. The theory was developed in the 80s and makes some very accurate predictions about the distribution of matter in the universe. Unless what you're saying is that dark energy is some kind of milder form of the hyper-inflation that occurred then...again, I lack sufficient information. That's the frustrating part about science, there isn't always an answer right away.
There is evidence to back up parts of the Cosmic Triangle theory. Background Microwave radiation is strongly suggesting a flat universe. Additionally, a universe that is expanding at an accelerating rate is also evident, when one looks at red shifts and the brightnesses of Type 1a supernovae. I guess you could call the dark energy that exists in this case, quintessence. But it's the "negative pressure" kind that makes the universe expand.

I'm not a cosmologist, I just started reading about this when a friend wanted me to read a paper about background microwave radiation, microwaves being my specialty.

There is evidence to back up parts of the Cosmic Triangle theory. Background Microwave radiation is strongly suggesting a flat universe. Additionally, a universe that is expanding at an accelerating rate is also evident, when one looks at red shifts and the brightnesses of Type 1a supernovae. I guess you could call the dark energy that exists in this case, quintessence. But it's the "negative pressure" kind that makes the universe expand.

I'm not a cosmologist, I just started reading about this when a friend wanted me to read a paper about background microwave radiation, microwaves being my specialty.

Nifty.

And yeah. Dark Energy isn't a gap in knowledge. We are aware based on our observational data that dark energy exists in some form. We just don't know what the hell it actually is.

My bet is on cosmological constant. It's merely the cost of having space.

I like pictures of stars and galaxies and nebulas and such. *nods* What?

I like pictures of stars and galaxies and nebulas and such. *nods* What?

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

Now if you'd seen that looking through a telescope, might not you think you'd seen the fucking eye of GOD?

Nifty.

And yeah. Dark Energy isn't a gap in knowledge. We are aware based on our observational data that dark energy exists in some form. We just don't know what the hell it actually is.

My bet is on cosmological constant. It's merely the cost of having space.
That goes back to Einstein and L-Gs fudge factor. It doesn't help explain the accelerating expansion that has been demonstrated. I don't know that anything has been discredited, though. I'm certainly not going to tell L-G that he's wrong.
I made that mistake with a friend of mine at Georgia Tech. He thought that he had made cold fusion work and I found out that the thermocouples weren't calibrated.

That goes back to Einstein and L-Gs fudge factor. It doesn't help explain the accelerating expansion that has been demonstrated. I don't know that anything has been discredited, though. I'm certainly not going to tell L-G that he's wrong.
I made that mistake with a friend of mine at Georgia Tech. He thought that he had made cold fusion work and I found out that the thermocouples weren't calibrated.

Fucking Ow. That had to suck.

Fucking Ow. That had to suck.
Everyone got over it. There were at least three universities that were trying to duplicate some results from Utah. I think an MIT guy ended up trying to patent some of the processes. I don't know what happened because none of the processes really went anywhere. It wasn't really my research. I was just there "holding the flashlight", so to speak.

Everyone got over it. There were at least three universities that were trying to duplicate some results from Utah. I think an MIT guy ended up trying to patent some of the processes. I don't know what happened because none of the processes really went anywhere. It wasn't really my research. I was just there "holding the flashlight", so to speak.

Aye. We may have run into a similar situation in the atmospheric physics lab I work in. Apparently the image processing algorithm I've been using on IDL hasn't been taking into account warping effects from the imager. We're working to correct it now, but the same algorithm was used in the data produced for a paper published a few years back by my prof and his (then) boss.

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

Now if you'd seen that looking through a telescope, might not you think you'd seen the fucking eye of GOD?
*looks over shoulder*
Uhm, my dear colleague - would you mind taking a look through this here telescope as well? I think we're being watched! :D

That's exactly what I mean, though. I can spend hours upon hours just looking at the heavens.

*looks over shoulder*
Uhm, my dear colleague - would you mind taking a look through this here telescope as well? I think we're being watched! :D

That's exactly what I mean, though. I can spend hours upon hours just looking at the heavens.

My honest advice: If you live in an area of low light pollution, or near a place that has low light pollution, buy a telescope (doesn't have to be a big one) figure out how to use it, and go stargazing.

A few years back I bought a 3.5" Reflector for around $1700. Given that larger models have come out since, you may be able to find a good, cheap, telescope. I'd recommend buying one with a motor, so you don't have to recalibrate it every five minutes.

My honest advice: If you live in an area of low light pollution, or near a place that has low light pollution, buy a telescope (doesn't have to be a big one) figure out how to use it, and go stargazing.

A few years back I bought a 3.5" Reflector for around $1700. Given that larger models have come out since, you may be able to find a good, cheap, telescope. I'd recommend buying one with a motor, so you don't have to recalibrate it every five minutes.

I wish I lived in a low light pollution area...I even have a decent telescope that I got while I was in Ann Arbor, but now I go to school in LA and live in Phoenix...

My honest advice: If you live in an area of low light pollution, or near a place that has low light pollution, buy a telescope (doesn't have to be a big one) figure out how to use it, and go stargazing.
That would be a dream come true!
Although, maybe, I should go check out our university's telescope. (I believe they even have two?) It's not that I haven't been attending this school for a long time.
But it's not really low light pollution around here.
A few years back I bought a 3.5" Reflector for around $1700. Given that larger models have come out since, you may be able to find a good, cheap, telescope. I'd recommend buying one with a motor, so you don't have to recalibrate it every five minutes.
$1700 is totally beyond what I could afford any time soon. Thanks for the advice, I'll keep that in mind when I hit the lottery jackpot. :D

That would be a dream come true!
Although, maybe, I should go check out our university's telescope. (I believe they even have two?) It's not that I haven't been attending this school for a long time.
But it's not really low light pollution around here.

$1700 is totally beyond what I could afford any time soon. Thanks for the advice, I'll keep that in mind when I hit the lottery jackpot. :D

When we were both younger and I was poorer, my daughter and I built an 8" Dobsonian (http://members.aol.com/sfsidewalk/intro.htm)reflector for a couple hundred dollars. It was fun as anything, plus the 'scope worked pretty well.

I wish I lived in a low light pollution area...I even have a decent telescope that I got while I was in Ann Arbor, but now I go to school in LA and live in Phoenix...

LA!!?? Phoenix??!! You probably live less that a half hour's drive from a nice, dark desert in either place, don't you? No haze, no humidity...Wow!

Ugh,

I didn't watch the video, but I really hope this is not one of those "we noticed an anomaly so we are going to make something up" things.

What is dark energy? Nothing. And it's a stupid way to spend your time thinking about it. Just because some jackhole can't get his shit together doesn't mean you should buy into the crap he turns out. (And it is always he).

The thing is, you can't say, I don't know. So people make stupid shit up to avoid saying I don't know. And it always goes back to Einstein's cosmological constant. Because that's right, you are the next fucking Einstein (who frankly I'm iffy about anyway).

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

Now if you'd seen that looking through a telescope, might not you think you'd seen the fucking eye of GOD?

Wow...that is just so magnificent

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

Now if you'd seen that looking through a telescope, might not you think you'd seen the fucking eye of GOD?

No, I wouldn't.

No more than when I eat fresh scallops.

The cosmological constant doesn't even need to be a thing. It was a fudge factor Einstein introduced to overcome gravity in his static universe, because Einstein pre-dated the big bang theory.

As it happens, Einstein's fudge has some usefulness (the accelerating expansion means we need something in addition to inertia), but appealing to Einstein to give the concept validity is foolish because Einstein got it completely wrong.

Ugh,

I didn't watch the video, but I really hope this is not one of those "we noticed an anomaly so we are going to make something up" things.

What is dark energy? Nothing. And it's a stupid way to spend your time thinking about it. Just because some jackhole can't get his shit together doesn't mean you should buy into the crap he turns out. (And it is always he).

The thing is, you can't say, I don't know. So people make stupid shit up to avoid saying I don't know. And it always goes back to Einstein's cosmological constant. Because that's right, you are the next fucking Einstein (who frankly I'm iffy about anyway).

Right. Because one guy looking through a telescope game up with the idea of dark energy.

It wasn't built upon years of research wherein the disproportionate acceleration of the expansion of the universe was discovered, tested, and repeatedly confirmed. It wasn't then proposed and searched for (and is still being searched for and continuing to be verified) by an entire fucking FIELD of physicists.

No, apparently it was just one bumfuck in a lab who pulled it out of his ass. Thank you for that gem of wisdom. :rolleyes: