Dark Matter Mapped

[XFool]

Mysterious dark matter mapped in finest detail yet

BBC News

It's being described as the most detailed ever map of the influence of dark matter through cosmic history.

"A telescope in Chile has traced the distribution of this mysterious stuff on a quarter of the sky and across almost 14 billion years of time.

The result is once again a spectacular confirmation of Einstein's ideas."

[stewamax]

Hmm... there is an assumption in the BBC article (and elsewhere) that Dark Matter is 'stuff'.
Elucidating something that does not interact with electromagnetic radiation such as light but whose behaviour is only affected by gravity sounds like a new and meaty challenge for Roger Penrose...

[odysseus2000]

Hmm... there is an assumption in the BBC article (and elsewhere) that Dark Matter is 'stuff'.
Elucidating something that does not interact with electromagnetic radiation such as light but whose behaviour is only affected by gravity sounds like a new and meaty challenge for Roger Penrose...

WIMPS (weakly interacting massive particles) have been around as postulated dark matter particles for ages, a long with a whole sea of other particles that have also not been found.

Regards,

[XFool]

Hmm... there is an assumption in the BBC article (and elsewhere) that Dark Matter is 'stuff'.
Elucidating something that does not interact with electromagnetic radiation such as light but whose behaviour is only affected by gravity sounds like a new and meaty challenge for Roger Penrose...

Well, if it causes gravity then, presumably, it has mass - or something very odd is going on. In which case, IMO, it surely qualifies as "stuff"? But it is certainly currently unknown "stuff".

[9873210]

Hmm... there is an assumption in the BBC article (and elsewhere) that Dark Matter is 'stuff'.
Elucidating something that does not interact with electromagnetic radiation such as light but whose behaviour is only affected by gravity sounds like a new and meaty challenge for Roger Penrose...

Well, if it causes gravity then, presumably, it has mass - or something very odd is going on. In which case, IMO, it surely qualifies as "stuff"? But it is certainly currently unknown "stuff".

There are MOND proposals where "dark matter" it is not stuff but a law of physics. If one of these theories works out "dark matter" would go the way of "luminiferous aether". I like the view of Neil deGrasse Tyson that "dark matter" (and even more so "dark energy") are place holders for discrepancies between theory and observation. By the definition of "theory" we do not understand these discrepancies and should avoid getting too attached to any particular explanation until we get better data or a better theory.

[odysseus2000]

Hmm... there is an assumption in the BBC article (and elsewhere) that Dark Matter is 'stuff'.
Elucidating something that does not interact with electromagnetic radiation such as light but whose behaviour is only affected by gravity sounds like a new and meaty challenge for Roger Penrose...

Well, if it causes gravity then, presumably, it has mass - or something very odd is going on. In which case, IMO, it surely qualifies as "stuff"? But it is certainly currently unknown "stuff".

As far as I know all measurements are consistent with gravity acting at the speed of light, suggesting a force carrier (graviton) that is massless. Dark matter could emit gravitons just as the sun which is very bright, emits gravitons, but be transparent to electromagnetic radiation. Alternatively you can think of gravity like a deformation of space time & have dark matter being some kind of mechanism that distorts space time, but how one then has dark energy gets troublesome to think about.

Regards,

[ursaminortaur]

Well, if it causes gravity then, presumably, it has mass - or something very odd is going on. In which case, IMO, it surely qualifies as "stuff"? But it is certainly currently unknown "stuff".

As far as I know all measurements are consistent with gravity acting at the speed of light, suggesting a force carrier (graviton) that is massless. Dark matter could emit gravitons just as the sun which is very bright, emits gravitons, but be transparent to electromagnetic radiation. Alternatively you can think of gravity like a deformation of space time & have dark matter being some kind of mechanism that distorts space time, but how one then has dark energy gets troublesome to think about.

Regards,

Although he added it to his theory of General Relativity for the wrong reason, to make the universe static rather than expanding or contracting, Einstein's cosmological constant can with an appropriate choice of value perfectly accommodate the extra expansion of space-time associated with dark energy.
The only problem is that the modern expectation was that this cosmological constant would have the same value as quantum field theory's vacuum energy - unfortunately the calculated value from quantum field theory is out by 120 orders of magnitude.

https://en.wikipedia.org/wiki/Cosmological_constant

https://en.wikipedia.org/wiki/Cosmological_constant_problem

[odysseus2000]

As far as I know all measurements are consistent with gravity acting at the speed of light, suggesting a force carrier (graviton) that is massless. Dark matter could emit gravitons just as the sun which is very bright, emits gravitons, but be transparent to electromagnetic radiation. Alternatively you can think of gravity like a deformation of space time & have dark matter being some kind of mechanism that distorts space time, but how one then has dark energy gets troublesome to think about.

Regards,

Although he added it to his theory of General Relativity for the wrong reason, to make the universe static rather than expanding or contracting, Einstein's cosmological constant can with an appropriate choice of value perfectly accommodate the extra expansion of space-time associated with dark energy.
The only problem is that the modern expectation was that this cosmological constant would have the same value as quantum field theory's vacuum energy - unfortunately the calculated value from quantum field theory is out by 120 orders of magnitude.

https://en.wikipedia.org/wiki/Cosmological_constant

https://en.wikipedia.org/wiki/Cosmological_constant_problem

Penrose discusses Einstein’s mistake at about 1/3 the length & then goes on to explain his cyclic theory of black holes & experimental evidence for previous universe.

Regards,

[AsleepInYorkshire]

AiY(D)