Is dark matter real?

hockeyguy
hockeyguy
Joined: 29 Aug 05
Posts: 85
Credit: 15,622
RAC: 0
Topic 191404

Is sounds to me like we simply added dark matter to make our equations work, kind of like Einstein's cosmological constant, or his "biggest blunder". What I am asking is is it possible that dark matter is not real, and there are flaws in our equations or in our way of thinking? Is there any actual evidence that dark matter is real, besides the fact that there are anomalies in our understanding of physics? Why havent we found dark matter on or near earth? Can string theory offer any alternate explanations to the anomalies?

And if it is real would it help explain the Pioneer anomaly?

tullio
tullio
Joined: 22 Jan 05
Posts: 1,994
Credit: 31,546,165
RAC: 12,278

Is dark matter real?

Quote:

Is sounds to me like we simply added dark matter to make our equations work, kind of like Einstein's cosmological constant, or his "biggest blunder". What I am asking is is it possible that dark matter is not real, and there are flaws in our equations or in our way of thinking? Is there any actual evidence that dark matter is real, besides the fact that there are anomalies in our understanding of physics? Why havent we found dark matter on or near earth? Can string theory offer any alternate explanations to the anomalies?

And if it is real would it help explain the Pioneer anomaly?


I think that dark energy is even darker than dark matter. Maybe we shall have to build a hierarchy of dark objects, like the hierarchy of infinities conceived by mathematicians.Perhaps all we need is another Newton. Quote by memory:
Nature and nature's laws lay hid in night.
God said Let Newton be! and there was light.
With apologies to Alexander Pope.
Tullio

MarkF
MarkF
Joined: 12 Apr 05
Posts: 393
Credit: 1,516,715
RAC: 0

hockeyguy: RE: Is sounds

hockeyguy:

Quote:
Is sounds to me like we simply added dark matter to make our equations work

You are correct and lacking strong evidence most cosmologist are sticky with the model.

Quote:
Can string theory offer any alternate explanations

Super String Theory has not yet been able to predict much of anything yet. Without hard numbers it is hard say SST can explain anything.

Quote:
And if it is real would it help explain the Pioneer anomaly

If there where similar Voyager 1 and Voyager 2 anomalies then IMHO it would make sense to look to at modifing the theory of gravity. As it stands the behavour all other deep space probes fits within existing theory.

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,020
Credit: 102,128,294
RAC: 165,160

RE: Is sounds to me like we

Quote:

Is sounds to me like we simply added dark matter to make our equations work, kind of like Einstein's cosmological constant, or his "biggest blunder". What I am asking is is it possible that dark matter is not real, and there are flaws in our equations or in our way of thinking? Is there any actual evidence that dark matter is real, besides the fact that there are anomalies in our understanding of physics? Why havent we found dark matter on or near earth? Can string theory offer any alternate explanations to the anomalies?

And if it is real would it help explain the Pioneer anomaly?


Both types of 'dark' have their origins in observations. Both are attempts to bridge theory to reality, which is a healthy activity.
The dark matter idea arose from considering orbital speeds of galaxy constituents around the currently detectable bits. The measured speeds are wrong if we assume the visible matter alone dictates such movements. It has been deduced to be 'cold', meaning that it's kinetic energy is much less than it's rest mass/energy ( or is non-relativistic if you like ). If present, this matter would also have implications on larger scales too ....
The dark energy idea arose from movements on those much larger scales. Some supernovae studies ( Type 1a ) have been interpreted to indicate that the universe is expanding ( first derivative of scale here ) faster now than it was some time past. Prior theory did not expect that. This acceleration ( second derivative ) can be explained if a 'pressure' term is bunged into the equations of general relativity that are proposed to govern the universe's evolution.
I liken the situation to the null Michelson-Morley result for the ( non ) existence of the ether, in that resolution will involve throwing out something fairly sacred! Both dark's have a forest of assumptions in their propositions. Maybe a big tree needs to be felled.
If you can skim over the denser/mathematical points you will get a good feel for this stuff here. Go to the ones by Rocky Kolb ( at the bottom, Friday August 5 ), who is the only cosmologist whom I can understand much at all. He does humorous and informative overviews of the state of play here.
Cheers, Mike.

( edit ) The second of his lectures here is the easier one.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

snarkophilus
snarkophilus
Joined: 25 Feb 05
Posts: 1
Credit: 76,335
RAC: 0

There is a very interesting

There is a very interesting discussion (almost a tutorial) of the observational evidence for dark matter going on at the Bad Astronomy/Universe Today bulletin board.

http://www.bautforum.com/showthread.php?t=42223

It's a multi-part series, but it's been very illuminating for me thus far.

[B@H] Ray
[B@H] Ray
Joined: 4 Jun 05
Posts: 621
Credit: 49,583
RAC: 0

So when will we have a

So when will we have a program to search for dark matter and dark energy?

Oh yes forgot they have to be able to detect it first, so no program.


Try the Pizza@Home project, good crunching.

Nereid
Nereid
Joined: 9 Feb 05
Posts: 79
Credit: 925,034
RAC: 0

There are already several

There are already several programmes underway, searching for Dark Matter, right here on Earth.

For example, [url="http://www.astro.columbia.edu/~lxe/XENON/"]XENON[/url] and [url="http://www.mpi-hd.mpg.de/non_acc/dm.html"]HDMS[/url].

IIRC, one of the analyses done by the [url="http://www.esa.int/esaMI/Integral/SEMY146Y3EE_0.html"]INTEGRAL SPI team[/url] concerned possible signatures of decays of some kinds of SUSY DM.

And let's not forget [url="http://wwwmacho.mcmaster.ca/"]MACHO[/url], which is a programme explicitly designed to search for one kind of DM (yes, you guessed it, MACHOs - massive compact halo objects).

tullio
tullio
Joined: 22 Jan 05
Posts: 1,994
Credit: 31,546,165
RAC: 12,278

RE: There are already

Message 38287 in response to message 38286

Quote:

There are already several programmes underway, searching for Dark Matter, right here on Earth.

For example, [url="http://www.astro.columbia.edu/~lxe/XENON/"]XENON[/url] and [url="http://www.mpi-hd.mpg.de/non_acc/dm.html"]HDMS[/url].

IIRC, one of the analyses done by the [url="http://www.esa.int/esaMI/Integral/SEMY146Y3EE_0.html"]INTEGRAL SPI team[/url] concerned possible signatures of decays of some kinds of SUSY DM.

And let's not forget [url="http://wwwmacho.mcmaster.ca/"]MACHO[/url], which is a programme explicitly designed to search for one kind of DM (yes, you guessed it, MACHOs - massive compact halo objects).


Cannot see any of these links. It says "http unknown.
Tullio

Odysseus
Odysseus
Joined: 17 Dec 05
Posts: 372
Credit: 8,981,861
RAC: 4,329

RE: RE: There are already

Message 38288 in response to message 38287

Quote:
Quote:

There are already several programmes underway, searching for Dark Matter, right here on Earth.
For example, [url=http://www.astro.columbia.edu/~lxe/XENON/"]XENON[/url] and HDMS.

IIRC, one of the analyses done by the INTEGRAL SPI team concerned possible signatures of decays of some kinds of SUSY DM.

And let's not forget MACHO, which is a programme explicitly designed to search for one kind of DM (yes, you guessed it, MACHOs - massive compact halo objects).


Cannot see any of these links. It says "http unknown.


Superfluous quotation marks in the links: an extra "http://" is being prepended. If my edits to the versions quoted above still don't work, just delete the excess from your browser's address field.

Nereid
Nereid
Joined: 9 Feb 05
Posts: 79
Credit: 925,034
RAC: 0

RE: There are already

Message 38289 in response to message 38286

Quote:

There are already several programmes underway, searching for Dark Matter, right here on Earth.

For example, XENON and HDMS.

IIRC, one of the analyses done by the INTEGRAL SPI team concerned possible signatures of decays of some kinds of SUSY DM.

And let's not forget MACHO, which is a programme explicitly designed to search for one kind of DM (yes, you guessed it, MACHOs - massive compact halo objects).

Apologies - I didn't read the BBCode tags syntax carefully enough (instead I used one that applies on a different BB that I frequent).

I've fixed them, tested them, and they work now.

(where's the Oops smilie?)

Stan Pleban
Stan Pleban
Joined: 2 Dec 05
Posts: 73
Credit: 4,628,450
RAC: 0

here's another article on

here's another article on searching for dark matter

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.