1
vote
2answers
51 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 ...
0
votes
2answers
68 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 ...
9
votes
4answers
132 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
42 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
63 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
182 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
90 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
175 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 ...
8
votes
2answers
734 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
331 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
4k 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 ...
2
votes
2answers
94 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
365 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
6answers
231 views

Are there free data available online from cosmology (or astrophysics) experiments that anyone can analyse?

One can understand a subject better in physics by trying to solve as many problems as one can from a textbook say. When it comes to experimental physics and data analysis, no book on experimental ...
3
votes
3answers
512 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 ...