1
vote
1answer
45 views

How can fusion within the sun be possible if there is no such thing as helium-2 (2 protons, no neutrons)

As stated in the question where does the sun(or other star) get the necessary neutron in order to produce the Helium atom? and how does this process occur (explain how the neutron incorporates).
2
votes
1answer
46 views

Stellar remnants in a state of matter denser than neutron-degenerate

When discussing the stellar life cycle, it's often stated that if the collapsing core of a star is bigger than the mass limit for a stable neutron star, it must collapse to a black hole. However, ...
8
votes
1answer
176 views

$\Delta^+$ decay in GZK process

The dominant channels in the GZK process are $$p+\gamma_{\rm CMB}\to\Delta^+\to p+\pi^0,$$ $$p+\gamma_{\rm CMB}\to\Delta^+\to n+\pi^+.$$ According to the pdg, $\Delta\to N+\pi$ makes up essentially ...
2
votes
0answers
40 views

B-mode and circular polarization in BICEP2

In the case of the B-mode detected in BICEP2, at first they assumed there was no circular polarization and then the Q and U stocks parameter of the CMB is given by E-mode and B mode. If we have ...
1
vote
2answers
94 views

Could Gamma ray bursts be caused by matter-antimatter annihilation?

As far as I know a collisions of matter and antimatter leads to the complete annihilation of both, whereby 100% of the rest mass of the particles is converted into gamma rays. Could this mechanism be ...
1
vote
2answers
81 views

Are leptons, baryons and energy the only products of radioactive decay?

I recently visited my child's elementary school to speak to a science classroom about rocks and minerals. While trying to explain what a crystal is, I got sloppy and mis-spoke that an atom was the ...
10
votes
4answers
162 views

Observed composition of UHE cosmic rays

How much is known about the composition of ultra high energy cosmic rays (say $E>10^{20}\text{ eV}$)? I get the impression that the particles are often assumed to be protons or other heavier ...
2
votes
1answer
50 views

Would gravitons follow the same trajectory as photons through a gravitational lense?

Would gravitons follow the same trajectory as photons through a gravitational lense? would all other particles follow the same trajectory?
1
vote
0answers
73 views

Relativistic Black Hole? [duplicate]

So recently, looking at high energy particles through the lens of General and Special Relativity has peaked my interest. One thing I was considering, using the electron as the first example, is as ...
1
vote
2answers
211 views

Neutrinos: how can they carry information about universe?

I know that neutrinos are particles with a very small mass and no electric charge. They infrequently interact with matter and so they can give us information about the "old" universe. But how can they ...
1
vote
1answer
111 views

Relationships between different measure of opacity

I'm reading some papers that compare different values for a materials opacity to a particular particle. The first is given as $\frac{dE}{dX}$, a single particles energy loss per unit column depth (X ...
3
votes
1answer
217 views

In Klein-Gordon, why should infinite downwards photon cascades be possible?

Here is a simple point about the standard interpretation of the Klein-Gordon equation that for the life of me I've never been able to understand: Why would the existence of true negative energy ...
9
votes
2answers
837 views

How was the Oh-My-God particle observed?

How exactly was the Oh-My-God particle (ultra-high energy cosmic ray) observed and its energy measured?
5
votes
2answers
341 views

How convincing is the evidence for dark matter annihilation at 130 GeV in the galactic center from the Fermi Satellite data?

I listened to Christoph Weniger present his results at SLAC today. See his paper is here: http://arxiv.org/abs/1204.2797 and also see a different analysis here: http://arxiv.org/abs/1205.1045. The ...
1
vote
1answer
5k views

Negative and positive energy and Hawking [closed]

I don't have any physics background (except the material we did in high school-long time ago). I was watching a documentary with Stephen Hawking about whether God created the Universe and I could not ...
3
votes
2answers
103 views

Cosmic radiation cutoff at LOW energies?

The energy spectrum of the cosmic radiation (not CMB) is limited to both sides. I know about the GZK-cutoff at high energies. Basically the interaction probability for photons of energies above 10^20 ...
3
votes
3answers
428 views

How scientists estimated that our universe is 4% normal matter, 21% dark matter, and 75% dark energy?

Is there a simple way to understand how scientists estimated/calculated the following percentages?
3
votes
3answers
531 views

Energy of the electron-muon reaction

Lets see the reaction: $e^- \mu^- \to e^- \pi^- \nu_\mu \;\;\;\;\;\;\;\;\;\;\; {(1)}$ I suppose, that this reaction occurs as follows $e^- \mu^- \to e^- \mu^- \pi^+ \pi^- \to e^- \pi^- \nu_\mu$ Is ...