Those were my thoughts exactly.
I read somewhere (I've no idea where!) that they are going to upgrade the LUX experiment - basically by having a bigger tank of xenon. The calculation that they can expect one particle of DM a century per litre of xenon makes this sensible.
Last edited by prendrelemick; 09-15-2016 at 03:35 AM.
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This is from my memory of a radio programme (BBC "In Our Time",) which is like a fount of all knowledge to me, so apologies if it seems a bit vague.Originally Posted by YesNo
The Earth based detector has many problems. It is a large 'L' shaped
structure. When a gravity wave comes along, space is distorted so that one arm stretches and the other contracts. This is measured by mirrors hanging on the ends of the apparatus that splits and re-combines light from a single source. It is an old technique called interferometry. If the wavelenghs of light are out of phase when recombined, then something has shifted.
Background 'noises' are a problem, and so is the small size of the detector. In fact the measurements are so fine even the vibrations of the mollecules within the mirrors have to be allowed for. It can even detect the Gravity field of a person walking past. But as G waves travel at the speed of light they can be discerned from the slower background stuff.
As you say this is not very satisfactory. There are plans to relocate into space where three satelites in a huge triangular formation can do a much better job.
All this is to confirm Einstein's prediction of the existance of Gravity Waves. They should be produced when something massive moves in an irregular way - or wobbles as you might say.
I think I remember something about G W's being detected recently with this equipment - but that was after the programme was broadcast.
Last edited by prendrelemick; 09-15-2016 at 06:08 AM.
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One thing I've wondered about is whether gravity waves move at the speed of light or slower. This would depend on whether the hypothetical graviton had mass: https://en.wikipedia.org/wiki/Speed_...tational_waves
Here is a post on Space by Hungarian researchers that consider whether a Fifth Force of Nature has been found: http://www.space.com/33750-fifth-for...rk-matter.html.
We'll have to see what happens to this possibly new protophobic force. It is interesting that when one finds a particle it could either be a form of matter or a force carrier.
"The experimentalists weren’t able to claim that it was a new force," Reminds me of something Sheldon Cooper might say - What can you expect from mere experimentalists ?
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I found John Moffat's "Reinventing Gravity" at a used bookstore and so I am looking into MOG or modified gravity. This theory does not have dark matter nor black hole singularities including a singularity at the big bang. I think this would eliminate any time travel possibilities, but it does have a beginning of the universe out of a vacuum (nothingness).
Often I read the concluding remarks in such books prior to reading the book itself. Moffat mentions that an experimental test of this could come with the gravitational wave projects (LIGO and LISA). The various theories have different predictions about what data should be observed from the gravitational waves at the beginning of the universe. Using the electromagnetic spectrum we can go only as far back as the recombination seen in the cosmic microwave background about 400,000 years after the beginning. LIGO and LISA should be able to get evidence even earlier than that.
Last edited by YesNo; 09-20-2016 at 05:30 AM.
This article in Universe Today seems to be drawing together our knowledge of stars to suggest a number of outcomes in the life and death of stars. Small stars like our sun have insufficient mass to go through the later stages of such development. Plenty to read here and discuss.
The first thing I realized from the article is that the Crab Nebula is the remains of a massive star's supernova.
I am still trying to distinguish between neutron stars and black holes mentioned in the artcile. Supposedly a more massive star is needed to make a black hole. Although it is out of date this article (2008) makes me wonder just how much anyone knows about these two objects: https://www.sciencedaily.com/release...0114162455.htm The matter in a neutron star is called "highly incompressible" where the electrons and the protons merge. This makes me wonder how matter can compress into something smaller.
I imagine it as the point where gravity can finally overcome the forces that keep neutrons as neutrons and they collapse or break up - Remember a neutron is not an elementary particle -and as quarks and gluons are infintely small there is probably a lot of space inside a neutron. that is because I can't think beyond my Newtonian world.
Last edited by prendrelemick; 09-22-2016 at 08:16 AM.
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If the star is just more massive and only compresses to neutrons that would give it more gravity. Here is an article about neutron stars and black holes that I am finding interesting, but don't quite understand: http://www.uni.edu/morgans/astro/cou...on2/new10.html
There is the idea of something being "neutron degenerate", which I don't understand. It means that a neutron star that gains mass would become smaller, but they would still have some size. There is also the idea of synchrotron radiation, a non-thermal radiation caused by electrons speeding up in a magnetic field.
One thing the article mentioned is that black holes have mass but they have no size. I am not sure why that has to be the case. Could not a neutron star have enough mass so the escape velocity required is the speed of light? However, if they had zero size, they would be "singularities" much like the big bang singularity. That is the part that puzzles me.
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In reading Moffat's view of gravity it looks like the problem with dark matter can be viewed in three ways:
1) The measurements are bad. (The current theory of gravity would fit the observations if they were accurate enough.)
2) The measurements are not bad. (The current theory of gravity does not fit the observations.)
...2a) The Newton-Einstein theory of gravity is correct. (The position of those looking for dark matter.)
...2b) The Newton-Einstein theory of gravity is not correct. (Moffat's position, as well as others offering competing new theories.)
Last edited by YesNo; 09-22-2016 at 09:32 AM.
The SOCIETY for POPULAR ASTRONOMY
Electronic News Bulletin No. 430 2016 September 25
PLUTO 'PAINTS' ITS LARGEST MOON RED NASA
In 2015 June, when the cameras on the approaching New Horizons spacecraft first observed the large reddish polar region on Pluto's largest moon, Charon, mission scientists had never seen anything like it elsewhere in the Solar System, and they couldn't wait to get the story behind it. Over the past year, after analyzing the images and other data that New Horizons has sent back from its historic 2015 July flight through the Pluto system, the scientists think they understand why the polar region on Pluto's largest moon, Charon, is red. The colouring comes from Pluto itself -- as methane gas that escapes from Pluto's atmosphere and becomes 'trapped' by the moon's gravity and freezes to the cold, icy surface at Charon's pole. That is followed by chemical processing by ultraviolet light from the Sun that transforms the methane into heavier hydrocarbons and eventually into reddish organic materials called tholins. The team combined analyses from detailed Charon images obtained by New Horizons with computer models of how ice evolves at Charon's poles. Mission scientists had previously speculated that methane from Pluto's atmosphere was trapped at Charon's north pole and slowly converted into the reddish material, but had no models to support that theory. The New Horizons team tried to determine whether conditions on the Charon (which has a diameter of 1,212 km) could allow the capture and processing of methane gas. The models using Pluto and Charon's 248-year orbit around the Sun show some extreme weather at Charon's poles, where 100 years of continuous sunlight alternate with a century of continuous darkness. Surface temperatures during those long winters dip to -257 C, cold enough to freeze methane solid.
The methane molecules bounce around on Charon's surface until they either escape back into space or land on the cold pole, where they freeze solid, forming a thin coating of methane ice that lasts until sunlight comes back in the spring. But while the methane ice quickly sublimates away, the heavier hydrocarbons created from it remain on the surface. Sunlight further irradiates those leftovers into reddish material -- called tholins -- that has slowly accumulated on Charon's poles over millions of years. New Horizons' observations of Charon's other pole, currently in winter darkness -- and seen by New Horizons only by light reflected from Pluto, or 'Pluto-shine' -- confirmed that the same activity was occurring at both poles. This study solves one of the greatest mysteries astronomers found on Charon, Pluto's giant moon, and opens up the possibility that other small planets in the Kuiper Belt with moons may create similar, or even more extensive, 'atmospheric transfer' features on their moons
http://astronomy.stackexchange.com/q...nto-black-hole I don't know how reliable it is, but this link describes the process - as far as it is known -It mentions Quark stars (I'd never heard of them,) and then plumps for unproven "strings" as the most fundemental matter. (Is that where mass and energy are finally the same thing?)
ps. it wasn't you who asked the question was it?
I can't answer your other question either, but suspect the answer is to do with the speed of light,( isn't it always!) eg the escape velocity reaches the speed of light just as the size of the massive object reaches zero.
Last edited by prendrelemick; 09-25-2016 at 05:08 PM.
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I hadn't heard of quark stars either, but they would be some way to put more mass into a neutron star without completely collapsing it to a black hole point. It is that collapsing to a point that puzzles me. If the escape velocity from the surface of the object is the speed of light does that mean that the "surface" must be an "event horizon" and no longer a surface?
Apparently Moffat has a way out of needing black holes, but I haven't read enough of the book to know what it is.
Although I have an account on the physics stack exchange, I have only posted items on the math stack exchange and that only after discussing number theory with desiresjab.
I Don't know, YesNo. All this about number theory is beyond me.
Lots happening just now, with a suspected supernova in Lupus: http://www.universetoday.com/131048/...covered-lupus/ that can be seen with binoculars. It is far south of us I'm afraid, bur supernovae are always a remarkable event - such incomprehensible force!
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