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Scientists discover the highest energy gamma-rays ever from a pulsar

phys.org

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Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#11
post #7
post #3

So I was wondering if it could be that at the point of measurement it was moving very fast towards us. Napkin math says for photons to have 200 times more energy than expected it would need to be moving at 0.99995c. Huh.

It's a photon. Photons always have speed = 1C.

"If the emitter is coming towards us that would blue-shift photons," is, I think, the point of the previous person's comment.

Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#12
post #5

Earlier quoted context omitted.

When it comes to cosmic scales, it is literally unimaginable by the puny human mind. I don't know about others but I frankly can't really comprehend what does the mass of an entire mountain condensed into a single pebble mean. And there are stars full of this stuff. And there are stars spinning so fast its magnetic waves would rip the iron out of my blood and destroy the physics that hold my atoms together just becau…

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Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#13
post #7

Earlier quoted context omitted.

It's a photon. Photons always have speed = 1C.

Technically no, photons don't always have a speed of 1C, as C is the speed of light _in a vacuum_. In more dense matter the speed of light will slow down.

Technically true and also completely irrelevant for this thread.

Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#14
post #8

Earlier quoted context omitted.

When it comes to cosmic scales, it is literally unimaginable by the puny human mind. I don't know about others but I frankly can't really comprehend what does the mass of an entire mountain condensed into a single pebble mean. And there are stars full of this stuff. And there are stars spinning so fast its magnetic waves would rip the iron out of my blood and destroy the physics that hold my atoms together just becau…

I find all this really incredible as well. But at the same time I also find it really 'mindblowing' that I am able to think about why and how all of this stuff was made, and while thinking about it, there will always come a point where you have to at least 'think' about an creator. Not that I think it was made especially for us, but it's still very strange. Somewhere I read when you think about the universe it is lik…

I agree. I actually think that is a very common thought, at least from what I have seen with my colleagues who are mostly scientists in engineering and biotech. It could be because of our background but the kind of complexity and seemingly genius engineering solutions in some biological systems just boggle the mind and make us question how it happened. We often handwave them with evolution and sure we can come up with some ideas of how it actually evolved but at some point I personally felt some explanations we got became too contrived and overly convenient and nearly unfalsifiable...

To be honest though, I still don't think a creator is absolutely necessary. But I also think there is nothing wrong with the idea that there is one. I just personally don't think this creator, if exist, would belong to any of the major religion out there.

Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#15
post #2

> These dead stars are almost entirely made up of neutrons and are incredibly dense: a teaspoon of their material has a mass of more than five billion tons, or about 900 times the mass of the Great Pyramid of Giza Five billion tons packed within a teaspoon volume!? Incredible.

When it comes to cosmic scales, it is literally unimaginable by the puny human mind. I don't know about others but I frankly can't really comprehend what does the mass of an entire mountain condensed into a single pebble mean. And there are stars full of this stuff. And there are stars spinning so fast its magnetic waves would rip the iron out of my blood and destroy the physics that hold my atoms together just becau…

> I frankly can't really comprehend what does the mass of an entire mountain condensed into a single pebble mean.

Maybe turn it around. On a cosmic level, that mountain is nothing but a fluff of cottonwool, the earth a hot air balloon.

Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#16
post #7
post #3

So I was wondering if it could be that at the point of measurement it was moving very fast towards us. Napkin math says for photons to have 200 times more energy than expected it would need to be moving at 0.99995c. Huh.

It's a photon. Photons always have speed = 1C.

I'm talking about the pulsar speed.

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

Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#18

I have a question - what would happen if you were to drop one of these spoons of matter that weigh 5 billion tonnes onto the floor right now, where would it stop?

It would sink into the center of the earth and then oscillate around the center until friction stops it dead center. Materials in the earth's crust and mantle are not strong enough to stop that mass from sinking ever deeper.

But that assumes that this spoon of matter were stable in that state, which it isn't. That kind of density can only be held up with some force like gravity keeping up the pressure. The gravity of that spoonful is insufficient, so the internal pressure will drive apart the neutrons. The effects would probably look like a very very large nuke or large asteroid impact.

Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#19

I have a question - what would happen if you were to drop one of these spoons of matter that weigh 5 billion tonnes onto the floor right now, where would it stop?

Matter in neutron stars is compressed together by the enormous gravity. Once set free on your floor, this material would no longer be held together and will start expanding at close to the speed of light. The resulting explosion will probably obliterate the entire continent. A crude way to estimate it is to take into account the fact that the gravitational binding energy of matter at the surface of a neutron star is about 10% of the rest mass energy of the material, so once that material is removed it will liberate as much energy (If I got the numbers right, you get an explosion energy of 0.1 m c^2 ~ 10^13 megatons).

Re: Scientists discover the highest energy gamma-rays ever from a pulsar

#20
post #18

I have a question - what would happen if you were to drop one of these spoons of matter that weigh 5 billion tonnes onto the floor right now, where would it stop?

It would sink into the center of the earth and then oscillate around the center until friction stops it dead center. Materials in the earth's crust and mantle are not strong enough to stop that mass from sinking ever deeper. But that assumes that this spoon of matter were stable in that state, which it isn't. That kind of density can only be held up with some force like gravity keeping up the pressure. The gravity of…

Very large asteroid, too big for a nuke:

https://www.wolframalpha.com/input?i=%280.782343+MeV+%2F+neu...

~89 billion megatons of TNT equivalent

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