The idea is that dark matter annihilates producing standard particles that then decays into photons. We expect to be an X-ray signal from dark matter (in some models), the problem is that we don't know the frequency (free parameter) or the intensity (depend on some models).
25 posts • joined 20 Jul 2011
Re: Two words
Do you mean blocking the sun?
Re: Moon is a harsh mistress
I guess you have never played KSP...
To put something into the sun you have first to get rid of all earth orbital velocity. There are some tricks that will help you, so you can get down to half of that, but it's still a lot of energy to burn.
Also: space 1999
[Mandatory explosion icon for KSP related comment]
Re: I see no mention
If you install gnome tweak tool you can choose to have multiples desktop on both screens or just on the main one.
Re: I don't get it
The problem is that there are a lot of unity-specific patches that will not give you a clean gnome 3 installation for istance; so if you don't want just to try a new window manager but you have already decided to use it, the different flavour are the way to go.
However, being linux you are also free to apt-get install whatever you want
In 14.04 unity will have the ability to move the menu on the window bar, which make a lot more sense to me.
However I will stick to Ubuntu Gnome, I find it more beautiful than unity
I hope it's just rumors. I would like to buy a Tesla...
[we need an anti-apple icon. And anti-microsoft, anti-android, anti-linux, ecc..]
Re: The install package will (of course), be three times that of a vanilla install
nah... they don't have to put additional spyware, just change the server where data are send from nsa.google.com to chinese.goverment.cn
Re: First example?
Actually you explain with the assimetry of the asteroid, as it was hinted in the article...
"This YORP effect (named after the four scientists who contributed to the theory: Yarkovsky, O'Keefe, Radzievskii, and Paddack) has been suggested as a reason for the relative paucity of small, asymmetrical objects within our Solar System in comparison to rounder rocks, and the search is now on for more observations of the theory in action."
The concept of horizon in cosmology is a bit misleading. It is true that nothing can travel at a speed larger than the speed of light, however very distant galaxies are observed having a recession velocity larger than c. This is congruent with general relativity because its the space itself that is expanding. In fact, due to the accelerated expansion, in a distant future we will be able to see only objects in the local supercluster.
How to be downvoted
So, all of them...
Oh, the good old communist government trying to block a legitimate company to enter in a free market...
Re: @ Daniel B. - Unless...
You've missed a don't. It should have been:
"Apple would never ban a company that they don't think of as a fair competition."
Re: Modify about:config
Or just click on the tiny button on the right-upper corner
Yes, Italy has a space agency...
From Wikipedia https://en.wikipedia.org/wiki/San_Marco_programme
"The project resulted in the launch of the first Italian-built satellite, San Marco 1, on December 15, 1964. With this launch Italy became one of the first countries in the world to operate its own satellite, after the Soviet Union and the United States"
New Gravitational wave Observatory
This means that we will not have a space-based gravitational wave observatoty. NGO is the name of the LISA observatory after NASA left the project
Re: Is it really true?
It depends on the asteroids. On the earth, the heavy elements sunk in the core, while in the crust there are only light elements (and stuff bring up by volcanoes). Some asteroids were formed from the protoplanetary nebula, so they will have the mean composition of all earth. But others were formed from collisions of small planets and therefore there are asteroids with the same composition of the mantel and the core (basically iron, nickel and other heavy elements)
They are not compressing data, they are just throwing away uninteresting collision events
Re: Re: Re: Re: Can someone cleverer than me please explain?
And at those early times, the universe was very dense and ionized, so the electric attraction was far greater then the possible gravitational repulsion. It is very difficult to justify this segregation
Re: Re: Re: Re: Can someone cleverer than me please explain?
We don't know if antimatter is gravity repulsive (they are trying to measure this with anti-hidrogen experiments), but again, those experiments on decay ratios are showing that there's a measurable difference between matter and antimatter. The idea is that before the annihilation of the primordial matter and antimatter, around 10^-9 of the total antimatter decayed leaving a surplus of matter.
Of course this is science and this can be all wrong. It would be cooler if antimatter is repulsive because it could be stored more easily and solve lots of transportation problems ...
Re: Can someone cleverer than me please explain?
We should be able to se gamma rays from the annihilation in the border between the hemispheres. But we don't see them.
And also you have to find an explanation for this asymmetric distribution.
Those experiments, on the other hand, prove that there's a measurable difference between matter and anti-matter in the sense that the latter decays more easily. And that's the explanation of why just one out 10^9 survived annihilation. (we can use this decay ratio to find out if an alien is made of antimatter before shaking his hand)
Re: Does this answer some of that unexplained mass
Those planets (MACHOs) can explain just some of the dark matter.
From the analysis of the Cosmic Microwave Background radiation, we know that barionic (normal) matter is just 5% of the matter-energy of the universe, while gravitational matter is around 30%. So most of the matter of the universe has to be some kind of exotic (non baryonic) matter.
Actually one possible explanation is that neutrinos interact with the matter (I know that the cross section is very very small, but we still don't have lot of data about neutrinos' physics) and it's like sound through rock or light through plasma
No, we don't. Neutrinos from 1987's supernova arrived just at the precise time on which they were expected if they were travelling at c. They arrived 3 hours before the light just because they were emitted 3 hours before the light, being the light emitted only when the shock wave reaches the exterior of the star
Well, a space radio telescope is not the Russian answer to the Hubble Space Telescope. It's something quite different in the technology and also in the scientific targets