Dark Energy – the most mysterious matter in the Universe

[pavelcherepan]

"It sounds rather strange that we have no firm idea about what makes up 74% of the universe. It's as though we had explored all the land on the planet Earth and never in all our travels encountered an ocean."

Based on this massage, it's quite clear that there is no evidence for the 74% of the dark energy! .

It isn't that I'm saying what I think I know. I'm saying what Hubble site knows. Or maybe I just didn't fully understand their description.

However, if I did understand correctly this description, do you think that there is a severe error at Hubble site? Do we have to believe that they have no clue about what they are saying?

 

I had a look at Dark Energy section on the Hubble site and there is a slide show that explains briefly of how Dark Energy was discovered and what data it was based on. So we do have evidence that DE exists, we just don't yet know what it is.

[Strange]

Or maybe I just didn't fully understand their description.

 

That seems to be the case. (It seems to be true for almost everything you read.)

 

The evidence:

 

The Nobel Prize in Physics 2011 was divided, one half awarded to Saul Perlmutter, the other half jointly to Brian P. Schmidt and Adam G. Riess "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae".

http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/

 

- We do not know what the cause of that accelerating expansion is.

 

- The name given to this unknown cause is "dark energy".

 

- If modelled as energy it makes up 74% of the total mass-energy of the universe.

 

Is that simple enough for you?

Edited March 9, 2015 by Strange

[swansont]

 

 

 

In our days, all the information is available at the web.

With regards to the 74% of the dark energy:

Please see again the valuable information from Hubblesite:

By: http://hubblesite.or...dark_energy.php

"It sounds rather strange that we have no firm idea about what makes up 74% of the universe. It's as though we had explored all the land on the planet Earth and never in all our travels encountered an ocean."

Based on this massage, it's quite clear that there is no evidence for the 74% of the dark energy! .

It isn't that I'm saying what I think I know. I'm saying what Hubble site knows. Or maybe I just didn't fully understand their description.

 

On the nosey!

 

Put another way: there are two types of people in the world. Those who can extrapolate from incomplete information.

 

We have analyzed what's out there, and only a small part of it is normal matter, i.e. the behavior we have observed requires that something else exist. We don't yet know exactly what those things are, but from what we do know, there are two components which we call dark matter and dark energy.

[David Levy]

 

On the nosey!

 

Put another way: there are two types of people in the world. Those who can extrapolate from incomplete information.

 

We have analyzed what's out there, and only a small part of it is normal matter, i.e. the behavior we have observed requires that something else exist. We don't yet know exactly what those things are, but from what we do know, there are two components which we call dark matter and dark energy.

Sorry, based on the message from Hubble site, it is clear that they didn't find any real sign for Dark energy.

It is stated that they have "no firm idea about what makes up 74% of the universe". It means that they have no idea what makes up the dark energy. Hence, so far they couldn't find any evidence for dark energy!

It is stated: "Dark energy and dark matter, detectable only because of their effect on the visible matter around them, make up most of the universe".

Therefore, there is no direct way to detect dark matter and dark energy.

It is also stated: "It's as though we had explored all the land on the planet Earth and never in all our travels encountered an ocean.".

Therefore, they couldn't find any evidence for dark energy or dark matter after exploring the whole Universe.

Are you sure that this is not the correct message?

Would you kindly explain why do you think that those messages are actually a confirmation for the existence of dark energy?

Edited March 9, 2015 by David Levy

[Strange]

It is stated that they have "no firm idea about what makes up 74% of the universe". It means that they have no idea what makes up the dark energy. Hence, so far they couldn't find any evidence for dark energy!

 

It seems like English is not your first language, so let's try again.

 

You are confusing two different things: knowledge of the existence of dark energy, and knowledge of the nature of dark energy.

 

1. they have no idea what makes up the dark energy Correct. The do not know what it is. Which is why there are many research projects looking at different possible hypotheses.

 

2. Hence, so far they couldn't find any evidence for dark energy! Wrong. There IS evidence for something that has the effects labelled "dark energy". This is the reason that people are trying to understand what it is (see point 1).

 

So, in summary: there IS evidence for dark energy. There is not yet an explanation for what it is.

 

Is that clear?

 

 

Would you kindly explain why do you think that those messages are actually a confirmation for the existence of dark energy?

 

They are not a confirmation of the existence of dark energy; they are about our lack of understanding of what dark energy is.

 

The confirmation of the existence of dark energy is the observations I linked to in post #27.

 

The same issues are relevant to dark matter as well: we know that something exists that has the effects labelled "dark matter" but we do not know (yet) what that the cause is (e.g. wrong theory of gravity, invisible matter, invisible pink unicorns, etc ...)

Edited March 9, 2015 by Strange

[Mordred]

Have you never heard the term indirect evidence? Direct evidence is something you can actually see and measure. Like a rock, take that rock drop it in a cup of water. The level of the water rises. From the change in water level we can indirectly measure the mass of the rock.

 

Dark energy is similar. Through the changes in distance measurements and the ideal gas laws, including thermodynamic laws we can measure dark energy. Indirectly.

[Strange]

It is stated that they have "no firm idea about what makes up 74% of the universe". It means that they have no idea what makes up the dark energy. Hence, so far they couldn't find any evidence for dark energy!

 

It sounds as if you think the process went something like this:

 

Two physicists are sitting in a bar. It is late and they have drunk a lot of beer and whiskey. They are discussing what to pretend they are researching next.

"Hey, what if there was some form of energy we couldn't detect?"

"Cool! You mean an energy equivalent to that 'dark matter' those guys at X University made up?"

"Eggzactly." [belches] "So we call it dark energy, right?"

"Right. But we have to make it sound more important somehow so we can get some time on The Hubble Space Toy"

"Yeah. So they say there is like 5 times more dark matter than normal matter? Well we can beat them at that: we will say there is 5 times more of our dark energy than their crummy dark matter!"

"Brilliant! But what about evidence?

"Evidence? We're not at school now. This is real science. No one cares about evidence."

They order another round of drinks.

[Mordred]

That's where I went wrong!!I didn't drink enough to invent flambetty foam. Bartender!

[David Levy]

 

Have you never heard the term indirect evidence? Direct evidence is something you can actually see and measure. Like a rock, take that rock drop it in a cup of water. The level of the water rises. From the change in water level we can indirectly measure the mass of the rock.

 

Dark energy is similar. Through the changes in distance measurements and the ideal gas laws, including thermodynamic laws we can measure dark energy. Indirectly.

I like this indirect evidence.

Let's use your example about the rock in a cup.

However, instead of water let's use a cup of coffee.

So, if we add a rock the level rises.

If we add a metal the level rises.

If we add sugar, salt or even poo the level rises.

If we set it at the microwave (without adding any ingredient), at critical temperature, the level rises.

So, if you see the cup with level increase of 20%, are you sure that you will know what kind of ingredient had been added?

If you know, then we can trust any indirect evidence.

[Strange]

So, if you see the cup with level increase of 20%, are you sure that you will know what kind of ingredient had been added?

 

Exactly! You've got it.

 

You know something made the level rise (let's call it "dark sugar") but you don't know what is is.

 

Maybe a rock has been added. Maybe it isn't something added, maybe the coffee has expanded. Maybe the cup has shrunk.

 

You know there is something making the level rise and you have a number of hypotheses to explain it.

 

Now you can do some research: send probes into the coffee, measure its temperature and density, try to find a frequency of light that can see through it, etc, etc.

This has turned out to be a really good analogy...

From the change in water level we can indirectly measure the mass of the rock.

 

<cough> Volume of the rock ...

[Mordred]

Lol right volume, too early in the am.

[David Levy]

 

Exactly! You've got it.

 

You know something made the level rise (let's call it "dark sugar") but you don't know what is is.

 

Maybe a rock has been added. Maybe it isn't something added, maybe the coffee has expanded. Maybe the cup has shrunk.

 

You know there is something making the level rise and you have a number of hypotheses to explain it.

This has turned out to be a really good analogy...

<cough> Volume of the rock ...

Perfect!!!

Yes, you have number of hypotheses!!!

It could be dark energy, black energy, dark matter, black matter or something else like dark sugar.

Now you can do some research: send probes into the coffee, measure its temperature and density, try to find a frequency of light that can see through it, etc, etc.

Now, let's do research:

For Probe – Use Hubble telescope.

So, do you see the dark energy – No.

Do you see the black energy – No.

Do you see the dark matter – No.

Do you see the black matter – No.

So, what does it mean?

Is there any chance that it is something else (Dark sugar...)?

Edited March 9, 2015 by David Levy

[Strange]

Just to continue with the analogy: we named our unknown cause for the rise in level "dark sugar" because that is what we expect to be added to coffee (1). When we find the real reason then journalists will continue to call it "dark sugar" for a while even if it turns out not to be sugar. Eventually, it will be given a new name based on what it really is.

 

 

(1) we will ignore, for the moment, the fact that sugar won't make the level rise

Is there any chance that it is something else?

 

Of course. No one knows what it is. It could be something no one has thought of yet.

 

So, do you see the dark energy – No.

 

 

Hubble isn't expecting to "see" dark energy. They are just gathering more data to try and constrain the properties of this unknown thing in order to eliminate some of the hypotheses.

Yes, you have number of hypotheses!!!
It could be dark energy, black energy, dark matter, black matter or something else.

 

None of those are hypotheses. They are just meaningless names.

Edited March 9, 2015 by Strange

[swansont]

 

 

I like this indirect evidence.

Let's use your example about the rock in a cup.

However, instead of water let's use a cup of coffee.

So, if we add a rock the level rises.

If we add a metal the level rises.

If we add sugar, salt or even poo the level rises.

If we set it at the microwave (without adding any ingredient), at critical temperature, the level rises.

So, if you see the cup with level increase of 20%, are you sure that you will know what kind of ingredient had been added?

If you know, then we can trust any indirect evidence.

 

No. That's the whole point you're missing. You know something has been added. But you still have to determine what it is. But your claim is basically that we don't know anything has been added, even though the level rose.

Perfect!!!

Yes, you have number of hypotheses!!!

It could be dark energy, black energy, dark matter, black matter or something else like dark sugar.

No, it couldn't be. If it was dark matter, that wouldn't explain the acceleration of the expansion. Dark matter is required to explain other behavior.

 

I don't know what black energy or black matter is supposed to be. AFAIK there is no evidence that would lead to other types of matter or energy, since we haven't figured out the details of dark energy yet.

 

Now, let's do research:

For Probe – Use Hubble telescope.

So, do you see the dark energy – No.

Do you see the black energy – No.

Do you see the dark matter – No.

Do you see the black matter – No.

So, what does it mean?

Is there any chance that it is something else (Dark sugar...)?

 

Anything the Hubble directly observes will be normal matter, so you can't use it for direct observation. Only how dark energy (or dark matter) ends up affecting normal matter.

[Sensei]

 

Perfect!!!

Yes, you have number of hypotheses!!!

It could be dark energy, black energy, dark matter, black matter or something else like dark sugar.

Now, let's do research:

For Probe – Use Hubble telescope.

So, do you see the dark energy – No.

Do you see the black energy – No.

Do you see the dark matter – No.

Do you see the black matter – No.

So, what does it mean?

Is there any chance that it is something else (Dark sugar...)?

 

Do you see electrons? No.

Do you see protons? No.

Just their interactions.

 

When electron with high kinetic energy passes through medium in Cloud Chamber, we see leaved trace. (You should now ask, how to detect it's electron, not muon-, not pion- etc but it's mainstream physics question)

When electron with high kinetic energy in vacuum tube is hitting something, there is created photon.

When electrons gather on surface, we see how they're repelling each other f.e. electric plume, or in other electrostatic device.

 

If star is spinning in circle around nothing, this nothing is called typically black hole. We detect it by looking at surrounding stars and their behaviors and interactions.

Edited March 9, 2015 by Sensei

[David Levy]

No. That's the whole point you're missing. You know something has been added.

No, I disagree.

We just know for sure that the level had been increased by 20%.

This is the only evidence which we know!

There is no evidence that something had beed added to the cup of coffee.

Please be aware that by a critical temperature, we should get the same effect.

But you still have to determine what it is..

Sure, but so far we have no real capability to determine what is it.

As stated by Mordred - a probe is needed.

Unfortunately, so far we couldn't get real evidence from our Hubble telescope probe.

Therefore, any prediction or hypotheses might be correct or incorrect.

Edited March 9, 2015 by David Levy

[MigL]

I guess David falls into the second category of the two kinds of people in this world, Swansont.

( I really liked that )

 

And Strange, Mordred's rock could have been floating, like an ice 'rock'.

[Strange]

We just know for sure that the level had been increased by 20%.

This is the only evidence which we know!

 

And, for dark energy, the only thing we know is that the rate of expansion is accelerating. (I say "know"; but it is possible that further evidence would show that to be incorrect; hence the use of Hubble to gather more data.)

 

Unfortunately, so far we couldn't get real evidence from our Hubble telescope probe.

Therefore, any prediction or hypotheses might be correct or incorrect.

 

Of course. That is what hypothesis means: not yet confirmed. There are about half a dozen plausible hypotheses to explain dark energy. So far, none of them have further evidence so any or all of them could be wrong. Which is why we call it "dark energy".

[swansont]

No, I disagree.

We just know for sure that the level had been increased by 20%.

This is the only evidence which we know!

There is no evidence that something had beed added to the cup of coffee.

Please be aware that by a critical temperature, we should get the same effect.

 

Um, what's this "critical temperature" of which you speak? Water's expansion coefficient varies with temperature but is always smaller than 0.0007 per degree. There is no way a temperature change can account for a 20% increase in the volume of the liquid. Can't even get close. That's information we have, akin to knowing how baryonic matter works, and how it can only account for a small fraction of what we see.

 

Thus, if we see a 20% increase in volume of our liquid, we know something has been added.

[David Levy]

And, for dark energy, the only thing we know is that the rate of expansion is accelerating.

Yes, that is correct.

(I say "know"; but it is possible that further evidence would show that to be incorrect; hence the use of Hubble to gather more data.)

No, this issue had been confirmed.

The rate of expansion is accelerating. There is no need for further evidence to confirm this issue.

 

There are about half a dozen plausible hypotheses to explain dark energy. ".

Sorry, we do not have to explain the dark energy!!!

The dark energy is needed to explain why the rate of expansion is accelerating.

However, there might be some other explanations for that issue.

Currently, the science estimates that dark energy is the preferable solution for this accelaration.

Unfortunately, so far there is no evidence to confirm the existence of dark energy.

Therefore, there is a chance that dark energy isn't the correct answer for what we see.

So far, none of them have further evidence so any or all of them could be wrong. Which is why we call it "dark energy".

I have got the impression that we call it dark energy becouse we really don't know what is it. If our scientists knew what it is than there is no need for the word dark. They could call it transient gravity", "reversible force" or even "unbalance power".

Therefore, as long as we have no evidence for it, and as long as we have no clue what is it, we will call it dark energy…

 

Um, what's this "critical temperature" of which you speak? Water's expansion coefficient varies with temperature but is always smaller than 0.0007 per degree. There is no way a temperature change can account for a 20% increase in the volume of the liquid. Can't even get close. That's information we have, akin to knowing how baryonic matter works, and how it can only account for a small fraction of what we see.

 

Thus, if we see a 20% increase in volume of our liquid, we know something has been added.

It's coffee.

Did you ever try to set a cup of coffee in the microwave?

If you didn't – please don't try it now.

Unless, you have a free day to clean your microwave…

[Sensei]

 

There is no way a temperature change can account for a 20% increase in the volume of the liquid. Can't even get close.

 

Photos taken 6 March. Showing increase of volume of liquid during distillation after heating near to 100 C. At least 50 mL is in dephlegmator (accidently took photo when there was "explosion")..

Edited March 9, 2015 by Sensei

[Strange]

Sorry, we do not have to explain the dark energy!!!

The dark energy is needed to explain why the rate of expansion is accelerating.

However, there might be some other explanations for that issue.

 

"Dark energy" is not an explanation. It is a place-holder for the explanation. Because we do not know what the explanation is. So when people (e.g. me) say, "we need to explain dark energy" it is shorthand for "we need to explain the cause of the apparent accelerating expansion of the universe as observed by Perlmutter, Schmitt and Riess".

 

One possible explanation (which you dismiss) is that their observations were wrong. Or that the observations are not caused by accelerating expansion. These would all fall under the label "dark energy". As would quantum gravity, quintessence, Chaplygin gas, a cosmological constant, changes to GR on large scales, a whole new theory of gravity and cosmology, magical unicorns and anything else you can think of.

 

I have got the impression that we call it dark energy becouse we really don't know what is it.

Therefore, as long as we have no evidence for it, and as long as we have no clue what is it, we will call it dark energy…

 

Exactly. You've got it. "Dark energy" is a technical way of saying "dunno"

[Mordred]

Just to be clear per volume the energy density of the cosmological constant stays constant. It's the volume that changes. The accelerating expansion is due to the recessive velocity

 

V=Hd Hubbles law states the greater the seperation distance the greater the recessive velocity.

[swansont]

 

It's coffee.

Did you ever try to set a cup of coffee in the microwave?

If you didn't – please don't try it now.

Unless, you have a free day to clean your microwave…

 

I have colleagues who microwave a cup of coffee to warm it up.

 

You appear to be referring to boiling, which does not increase the volume of the liquid. Plus, we can see that it's boiling. The salient point here is that we have evidence that the situation has some interaction taking place. You are claiming that there is no evidence.

 

Photos taken 6 March. Showing increase of volume of liquid during distillation after heating near to 100 C. At least 50 mL is in dephlegmator (accidently took photo when there was "explosion")..

Before.pngAfter.png

 

 

Yep. 50 mL out of 2000 is 2.5%, much less than 20%.

Yes, that is correct.

No, this issue had been confirmed.

The rate of expansion is accelerating. There is no need for further evidence to confirm this issue.

 

 

Wait. Confirmed? With … evidence?

[Sensei]

 

Yep. 50 mL out of 2000 is 2.5%, much less than 20%.

 

You misunderstood.

50+ mL is above in dephlegmator (and not visible on the photo).

So to what is visible on photo (compare difference between levels) there is needed to be added more.

The next time I will do it, I will try to measure how much it's increasing volume more precisely.

But what is on photo (including what is in dephlegmator) looks like 2000 mL -> 2150 mL

I have seen more extreme increases, but have not made photos.

Edited March 9, 2015 by Sensei