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Dark Matter is Invisible, does not emit Energy or Light and it's about 80% of the Universe's mass.

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code1211

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Not if the exercise is to treat science like a religion. Whatever dark matter is, it's not magic. This is where we go wrong a lot. We treat the educated guesses of the educated as no better than the uneducated guesses of the uneducated. All things are not equal.

Asking this forum what dark matter is is less likely to produce a reasonable answer than asking a kindergarten class how babies are made. You're going to get a variety of answers, all misinformed.
And assuming that a particular thing that is entirely mysterious to have only those qualities that are comforting to you and no other qualities seems limiting.

I am not asserting answers.

I am asking questions.

Would the instruction you offer to those in school include the command to never ask questions?
 

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Move this to Science & Technology
I was wondering about that when I picked the place to start the thread.

It seems to cross boundaries, but those boundaries are just conveniences set up t help us prepare for the discussion. To me, baseball and football are very different considerations. To my ex-wife, it's all just SPORTS.

I notice that this little question has generated more than 400 comments.

To me, that's of greater interest than in which forum this is placed.
 

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(from Reply #398):
No.
...As far as I am aware there has only ever been one occaision when a land power has defeated a naval one. That would be Sparta defeating Athens once. It did not last long though. They came back...
Actually, Sparta became a naval power for about the last 10 or so years of the Peloponnesian War. I am not sure to what extent their fleet was manned by Laconians, but it was commanded by the Spartan Lysander, an admiral of genius.

After several years of fighting the Athenian navy to a draw, Lysander caught it beached at a location named Aegospotami and destroyed it. With no fleet Athens could not avoid being besieged and starved into surrender.

Athens was soon able to recover to a some extent, and to rebuild its fleet. However, Sparta remained the dominant Greek power for a generation until it was defeated, on land for the first time in centuries, at Leuctra, not by Athens but by Thebes.
 

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(from Reply #398):

Actually, Sparta became a naval power for about the last 10 or so years of the Peloponnesian War. I am not sure to what extent their fleet was manned by Laconians, but it was commanded by the Spartan Lysander, an admiral of genius.

After several years of fighting the Athenian navy to a draw, Lysander caught it beached at a location named Aegospotami and destroyed it. With no fleet Athens could not avoid being besieged and starved into surrender.

Athens was soon able to recover to a some extent, and to rebuild its fleet. However, Sparta remained the dominant Greek power for a generation until it was defeated, on land for the first time in centuries, at Leuctra, not by Athens but by Thebes.
Your knowledge of the ancient Greeks is better than mine.

Do you know of any other occaision when a land power was able to defeat a naval power?
 

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Do you know of any other occaision when a land power was able to defeat a naval power?
I can't think of many, and you are right to point out the decisive advantages of having a good navy.

During the Marathon campaign Athens apparently had no navy capable of resisting the Persians. Athens decided to change that situation pronto!- about 10 years later it had the strongest navy in Greece, and led the combined Greek fleet to the great victory of Salamis.

Medieval Japan had no navy when it was invaded twice by The Mongols who might have had 1000s of ships. The first invasion was wiped out by a typhoon, but during the second the Mongols landed large forces which were fought on even terms on land by the Japanese. Then a later-arriving typhoon sank the second Mongol fleet, and Japan would not again be threatened with invasion for about 700 years.

The American revolutionaries had no navy but fought the British army to a standstill for three years. It is fair to point out, though, that the final American victory might have been impossible without intervention by France and its fleet.
 

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I can't think of many, and you are right to point out the decisive advantages of having a good navy.

During the Marathon campaign Athens apparently had no navy capable of resisting the Persians. Athens decided to change that situation pronto!- about 10 years later it had the strongest navy in Greece, and led the combined Greek fleet to the great victory of Salamis.

Medieval Japan had no navy when it was invaded twice by The Mongols who might have had 1000s of ships. The first invasion was wiped out by a typhoon, but during the second the Mongols landed large forces which were fought on even terms on land by the Japanese. Then a later-arriving typhoon sank the second Mongol fleet, and Japan would not again be threatened with invasion for about 700 years.

The American revolutionaries had no navy but fought the British army to a standstill for three years. It is fair to point out, though, that the final American victory might have been impossible without intervention by France and its fleet.

Good point perhaps the naval power always wins against a land power is right unless you are talking about internal wars or wars of colonialism/independance. I am thinking of Vietnam and the various moments of the British Empire's withdrawl from the world. Indeed all the colonial powers....
 

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Dark Matter is an interesting thing. It can't be seen and can't be quantified except that it must be there. It acts on things we can see. If it's not there, everything would be different.

Stars orbiting the centers of Galaxies are moving fast enough that they'd be thrown free if there was not a great deal more mass "holding them in" than can be measured in our "physical" universe.

There has to be more mass present, but it is undetectable to us. We cannot see it, cannot feel it, cannot taste it, smell it or hear it. We can only measure its effect on things we can see.

Without jumping to unjustified conclusions, this seems to conform to descriptions of spiritual or mystical events/objects/beings.

Our Physical Universe is just a small fraction of the whole. Dark matter seems to flow through the universe invisibly, but, well, universally. If you are reading this, Dark Matter is currently between you and the screen on which the words appear.

Especially at this time of year when the spiritual and mystical is contemplated, it seems appropriate to understand that most of our reality has been revealed scientifically to be beyond our rational comprehension. Whether you're a devotee of religion or Star Wars, it seems Hamlet was right: "There are more things in Heaven and Earth, Horatio, Than are dreamt of in your philosophy."

It seems reasonable to assume that if Dark Matter can redirect the course of Stars, it's pretty powerful stuff.

Is massively augmented gravity Dark Matter's only purpose? Seems like there are lots of questions just now being considered.

What Is Dark Matter? | Research
The bolded text is wrong...Dark matter is detected...through it's gravitational effect on on the matter we can see by way of electromagnetism...There are four fundamental forces in nature...Everything we can detect is made observable by one or more of those four forces...Absolutely everything. There is nothing "spiritual" about it whatsoever.

Dark matter is similar to black holes in this regard...we can't see them...but we can see the impact they have gravitationally and electromagnetically on their surroundings.
 

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The bolded text is wrong...Dark matter is detected...through it's gravitational effect on on the matter we can see by way of electromagnetism...There are four fundamental forces in nature...Everything we can detect is made observable by one or more of those four forces...Absolutely everything. There is nothing "spiritual" about it whatsoever.

Dark matter is similar to black holes in this regard...we can't see them...but we can see the impact they have gravitationally and electromagnetically on their surroundings.
One of the effects of EFFECT of Dark matter is measurable as Gravity. That is what you said and is what I said before you said it. That's how we know it's there.

IF you can post the exact, proven nature of Dark Matter, I'd be very interested to see the link.

You are free to proceed.
 

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One of the effects of EFFECT of Dark matter is measurable as Gravity. That is what you said and is what I said before you said it. That's how we know it's there.

IF you can post the exact, proven nature of Dark Matter, I'd be very interested to see the link.

You are free to proceed.
You said it is undetected...That's not true...Just because we can't see it doesn't mean we don't detect it. Dark matter interacts with "normal" matter gravitationally. We can't "see" gravitational waves either, but we know they are there because they have been detected and measured at LIGO. Two black holes colliding was the cause of the gravitational waves first detected. We can't see them either, but we know they were involved and what the masses of the two were before and as they merged together.and what the combined mass was after the merger..less than the sum of the two by the way..That information was contained in the gravitational waves every bit as much as pictures and sound are transmitted using electromagnetic waves.

When you use the word "effect", please realize that that's how nature works...We never "see" or detect anything directly...When you look at something you are not seeing it, you are seeing the light emitted or scattered by it. Gravitational waves are just another way of "seeing" something. In this case, dark matter as it warps the fabric of spacetime.
 
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D_NATURED

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And assuming that a particular thing that is entirely mysterious to have only those qualities that are comforting to you and no other qualities seems limiting.

I am not asserting answers.

I am asking questions.

Would the instruction you offer to those in school include the command to never ask questions?
No, my advice to them would be that when they find themselves without answers, they would be lazy to just declare magic to be the answer. That sort of strategy is for those who need ANY answer and don't care if it's the right one.
 

Empirica

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One physicist described dark matter as a fudge factor introduced to balance equations. What it means is that the equations may not be a good representation of what is going on, but so far they haven't been able to come up with anything better.

Don't hang your hat on the existence of dark matter. Cosmology is ripe for a paradigm shift.
All of it is beyond me.

Neil deGrasse Tyson has some thoughts on it:

"Could we be seeing the effects of forces from another dimension?

Are we feeling the ordinary gravity of ordinary matter crossing the membrane of a phantom universe adjacent to ours?

If so, this could be just one of an in nite assortment of uni- verses that comprise the multiverse.

Sounds exotic and unbelievable."

https://www.popsci.com/why-dark-matter-matters#page-2

In other words, he's got no clue.

If it's an us-them proposition, there's more of them than us.
I think I've kinda figured this out from the information provided here by Code1211 and Lowdown....now pay attention!

I'm no rocket surgeon by any stretch; but we've heard of Dark Matter and Dark Energy but what we have here is Dark Gravity.

Now we all know that gravity is a bi-product of matter and the greater the matter's mass the greater the force of its gravity.

And this unexplainable gravity is obviously evidence of a source of matter despite our current inability to detect its physical presence.

Therefore it must be in some unknown form or inaccessible location yet close enough for its gravity to effect force on the matter we can see.

So rather than refer to it as Dark Matter it should be Undetectable Matter and call the force it exerts on our universe Dark Gravity.

So say we all ?
 

grip

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I think I've kinda figured this out from the information provided here by Code1211 and Lowdown....now pay attention!

I'm no rocket surgeon by any stretch; but we've heard of Dark Matter and Dark Energy but what we have here is Dark Gravity.

Now we all know that gravity is a bi-product of matter and the greater the matter's mass the greater the force of its gravity.

And this unexplainable gravity is obviously evidence of a source of matter despite our current inability to detect its physical presence.

Therefore it must be in some unknown form or inaccessible location yet close enough for its gravity to effect force on the matter we can see.

So rather than refer to it as Dark Matter it should be Undetectable Matter and call the force it exerts on our universe Dark Gravity.

So say we all ?

Gravity may not be the source of mass but it's certainly the force that accumulates matter. Gravity though maybe a universal force associated with matter thru space.
 

code1211

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I think I've kinda figured this out from the information provided here by Code1211 and Lowdown....now pay attention!

I'm no rocket surgeon by any stretch; but we've heard of Dark Matter and Dark Energy but what we have here is Dark Gravity.

Now we all know that gravity is a bi-product of matter and the greater the matter's mass the greater the force of its gravity.

And this unexplainable gravity is obviously evidence of a source of matter despite our current inability to detect its physical presence.

Therefore it must be in some unknown form or inaccessible location yet close enough for its gravity to effect force on the matter we can see.

So rather than refer to it as Dark Matter it should be Undetectable Matter and call the force it exerts on our universe Dark Gravity.

So say we all ?
As far as it goes, what you post does not seem to counter what the physicists I hear dumbing down their theories to a level I can grasp seem to be saying. However, I'm just some schlub who is in awe of the possibilities they describe.

Neil de Gras Tyson says there is far more to this than simply "Dark Matter". They call it "Dark", in passing, because they have no clue what it might be and also no clue why they can't SEE it.

Dr. Tyson reading this would very likely be shaking his head wondering how I could have messed up his thinking so completely.

The Dark Matter seems to exist in far greater quantity than the visible matter. In addition, though, there is also Dark Energy that exists, also invisibly, that does not attract, but rather expands the Universe, PUSHING stuff.

Another feature of Dark Matter and Dark Energy is that they seem to exist creating a pattern, forming a framework, that extends across the whole Universe and that seem to dictate where the visible galaxies form.

In view of the quantities and scales they are discussing, our visible Universe is pretty minor. The sheer size of the things in question is mind boggling.

The Visible Universe is like the discarded particles of peels and bones after the picnic was enjoyed. In this analogy, we are the bacteria dining on a too-small-to-see shred of one of those discarded particles. Yummy! ;)
 

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As far as it goes, what you post does not seem to counter what the physicists I hear dumbing down their theories to a level I can grasp seem to be saying. However, I'm just some schlub who is in awe of the possibilities they describe.

Neil de Gras Tyson says there is far more to this than simply "Dark Matter". They call it "Dark", in passing, because they have no clue what it might be and also no clue why they can't SEE it.

Dr. Tyson reading this would very likely be shaking his head wondering how I could have messed up his thinking so completely.

The Dark Matter seems to exist in far greater quantity than the visible matter. In addition, though, there is also Dark Energy that exists, also invisibly, that does not attract, but rather expands the Universe, PUSHING stuff.

Another feature of Dark Matter and Dark Energy is that they seem to exist creating a pattern, forming a framework, that extends across the whole Universe and that seem to dictate where the visible galaxies form.

In view of the quantities and scales they are discussing, our visible Universe is pretty minor. The sheer size of the things in question is mind boggling.

The Visible Universe is like the discarded particles of peels and bones after the picnic was enjoyed. In this analogy, we are the bacteria dining on a too-small-to-see shred of one of those discarded particles. Yummy! ;)
There is a huge distinction between Dark Matter and Dark Energy. We can measure the effects of Dark Matter and produce 3D maps of its location throughout the universe.


The same cannot be said about Dark Energy. In fact, Dark Energy is a relatively new concept that began in 1998. The study used 48 Type Ia supernovae (or so they thought) to calculate the rate of acceleration of the universe in order to refine the Hubble constant.

When they discovered from the data they collected that the universe was accelerating at a much faster rate than expected, they blamed the phenomena on a non-existent force they called Dark Energy.

A few years later we began to discover anomalous Type Ia supernovae. Not only were we discovering super luminous Type Ia supernovae, we were also discovering extremely dim Type Ia supernovae. By 2013 we discovered enough of these extremely dim Type Ia supernovae to create a whole new class of supernovae: Type Iax.

Somewhere between 18% and 48% of all Type Ia supernovae prior to 2013 have been incorrectly classified and should actually be the much dimmer Type Iax supernovae.

Extremely dim Type Ia supernovae would appear to be much further away than they really are, while super luminous Type Ia supernovae will appear much closer than they really are, because in 1998 they applied the exact same absolute magnitude to all Type Ia supernovae and could not tell the difference between the three different types.

Therefore, the most likely explanation of Dark Energy is a mathematical error on our part due to our lack of understanding of Type Ia supernovae.

Sources:
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant - The Astronomical Journal, Volume 116, Number 3, 1998 (open access)
The Exceptionally Luminous Type Ia Supernova 2007if -The Astronomical Journal, Volume 715, Number 2, 2010 (open access)
Type Iax Supernovae: A New Class of Stellar Explosion* -The Astronomical Journal, Volume 767, Number 1, 2013 (open access)
 
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code1211

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There is a huge distinction between Dark Matter and Dark Energy. We can measure the effects of Dark Matter and produce 3D maps of its location throughout the universe.


The same cannot be said about Dark Energy. In fact, Dark Energy is a relatively new concept that began in 1998. The study used 48 Type Ia supernovae (or so they thought) to calculate the rate of acceleration of the universe in order to refine the Hubble constant.

When they discovered from the data they collected that the universe was accelerating at a much faster rate than expected, they blamed the phenomena on a non-existent force they called Dark Energy.

A few years later we began to discover anomalous Type Ia supernovae. Not only were we discovering super luminous Type Ia supernovae, we were also discovering extremely dim Type Ia supernovae. By 2013 we discovered enough of these extremely dim Type Ia supernovae to create a whole new class of supernovae: Type Iax.

Somewhere between 18% and 48% of all Type Ia supernovae prior to 2013 have been incorrectly classified and should actually be the much dimmer Type Iax supernovae.

Extremely dim Type Ia supernovae would appear to be much further away than they really are, while super luminous Type Ia supernovae will appear much closer than they really are, because in 1998 they applied the exact same absolute magnitude to all Type Ia supernovae and could not tell the difference between the three different types.

Therefore, the most likely explanation of Dark Energy is a mathematical error on our part due to our lack of understanding of Type Ia supernovae.

Sources:
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant - The Astronomical Journal, Volume 116, Number 3, 1998 (open access)
The Exceptionally Luminous Type Ia Supernova 2007if -The Astronomical Journal, Volume 715, Number 2, 2010 (open access)
Type Iax Supernovae: A New Class of Stellar Explosion* -The Astronomical Journal, Volume 767, Number 1, 2013 (open access)
You will need to send your ideas to the folks who produce the "sciencey" shows I see on the educational channels.
 

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You will need to send your ideas to the folks who produce the "sciencey" shows I see on the educational channels.
It wouldn't to any good. Even though we can distinguish the difference between Type Ia and Type Iax supernovae, it requires obtaining very specific data which astronomers are not collecting. Specifically, it requires measuring the blue-shift of the SN's ejecta. All Type Ia SN have an ejecta rate in excess of 10,000 kps. While all Type Iax SN have an ejecta rate of less than 8,000 kps. Knowing the speed of the SN ejecta would allow us to distinguish between the two SN, but nobody is collecting this information.

I made the same observation after they completed their most recent Type Ia SN survey back in February:

The Most Recent Observations of Nearby Type Ia Supernovae

Without collecting that data they are risking repeating the same error, and they know it. Apparently they have a great deal invested in Dark Energy and do not want to see it disappear, particularly if they have to admit that Dark Energy only exists because of their lack of understanding.
 

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It wouldn't to any good. Even though we can distinguish the difference between Type Ia and Type Iax supernovae, it requires obtaining very specific data which astronomers are not collecting. Specifically, it requires measuring the blue-shift of the SN's ejecta. All Type Ia SN have an ejecta rate in excess of 10,000 kps. While all Type Iax SN have an ejecta rate of less than 8,000 kps. Knowing the speed of the SN ejecta would allow us to distinguish between the two SN, but nobody is collecting this information.

I made the same observation after they completed their most recent Type Ia SN survey back in February:

The Most Recent Observations of Nearby Type Ia Supernovae

Without collecting that data they are risking repeating the same error, and they know it. Apparently they have a great deal invested in Dark Energy and do not want to see it disappear, particularly if they have to admit that Dark Energy only exists because of their lack of understanding.
If the thoughts in your post were cinder blocks flying in my direction, I would be uninjured. That's how far over my head they are passing. ;)

Liberal Arts degree here. You're casting pearls before swine.

That said, I did try to click on the thing that looked like a link, but it didn't take me anywhere.

Anyway, thank you for trying to penetrate my shield of low science aptitude. It's a tough job and your efforts are appreciated!

The "sciencey" shows that appeal to me are dumbed down to a level similar to the "Dr. Proton" level from "The Big Bang Theory". The only "real" scientists I can understand are the ones that also play a scientist on TV.
 

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If the thoughts in your post were cinder blocks flying in my direction, I would be uninjured. That's how far over my head they are passing. ;)

Liberal Arts degree here. You're casting pearls before swine.

That said, I did try to click on the thing that looked like a link, but it didn't take me anywhere.

Anyway, thank you for trying to penetrate my shield of low science aptitude. It's a tough job and your efforts are appreciated!

The "sciencey" shows that appeal to me are dumbed down to a level similar to the "Dr. Proton" level from "The Big Bang Theory". The only "real" scientists I can understand are the ones that also play a scientist on TV.
The link I provided is to a thread with the same name that I started in the Science & Technology forum: The Most Recent Observations of Nearby Type Ia Supernovae

I point out that the data they collected was incomplete. Without additional information, such as the blue-shift of SN ejecta, we will not be able to distinguish between a Type Ia and Type Iax SN.

It also means that we cannot use the Type Ia SN as our Standard Candle. If we cannot distinguish between a super luminous, a normal, and an extremely dim Type Ia SN, then we cannot pretend to know the absolute magnitude of the SN. If we don't know the absolute magnitude of a SN, then we cannot use it to measure distance.

As I mentioned above, the study that created Dark Energy used 48 Type Ia SN, or so they believed. They assigned all 48 of those SN with an absolute magnitude of -19.46. Then using their apparent magnitude they were able to calculate the distances. The only problem is that not all 48 of those SN had an absolute magnitude of -19.46. Some may have been brighter, but at least 9 and as many as 23 of those 48 SN were well below the absolute magnitude of -19.46. That would have made them appear much further away than they really were.

Knowing the specific type of SN also has a profound effect on not only the existence of Dark Energy, but also the age of the universe, and even the Lambda-CDM model which goes back to the Big Bang and the original cosmological constant. So it has the potential to change a great many significant things in cosmology and astrophysics.
 
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