Can a gamma-ray burst hit the earth without being detected early enough?
Actually gamma-ray bursts start from the poles or sometimes sides of the object producing it. They are detected rarely and they occur very far from us like quasars. If the ray is pointing directly towards earth, there would be no way stopping it (except if there are some black holes or very high gravity objects in its path, it would fade away) though it could be detected. Those intense bursts could take many many years to reach us depending on the distance between us and the source. If it hits us it would surely lead to a mass extinction depending on the intensity of the ray. Many occur millions of light years away but it is hard to detect each and everyone .
Gamma-rays travel at the speed of light… because they are light… so they cannot be detected and reported before they could strike Earth. Even if you had a probe a billion miles away that could detect them and instantly send out a signal to warn us… that signal would have at best happened at the same moment that the gamma-rays passed the satellite. In which case, the signal would be traveling at the speed of light, right along with the front of the gamma-rays. No, until we develop Star Trek sub-space communications, nothing could warn us of a gamma-ray burst.
They happen about once a day. If we know about them, they’ve hit the earth. Don’t worry about it, our atmosphere should protect us. In space they could be hazardous, but down here they don’t pose any real threat. It is impossible to detect them before they get here. When something is detected as incoming before it arrives, it has to have a signal of some sort heading in our direction. The gamma ray burst is the signal. If one of the dangerous kinds were to hit us, we’d be doomed anyway so it’s not like we could stop it. But since the composition of the galaxy seems to suggest that the dangerous kinds are even less probable than they used to be, there’s no need to fret about it. The reason they say that they’re all so far away is because the composition of the galaxy seems to have some correlation to the probability of one of these gamma-ray burst events, and the high metallicity of our galaxy makes the probability of a local gamma-ray burst event even less likely.
The nearest Gamma Ray source is at least (hazarding a guess) 20,000 LY away, by an optimistic estimate. By inverse square law the radiation (power) density would be reduced by this distance to a factor of (again hazarding a guess) 10^37 th. At this power the Gamma rays are so weak that they will be giving away their power to the top layers of our atmosphere, ionising a streak of molecules there. That is the only detection possible. Someone (a crazy scientist) would photo-record a streak (or line) much above Stratosphere. Don’t ask me how he did it. He proposes a ‘theory’ in his next seminar. After a year or so, correlating with some Astronomer’s finding that the Gamma Ray source turned its stream towards Earth, a third scientist would conclude that it is so (that the streak is the same as the radiation of the quasar or whatever). That is how these things happen. But first to detect it we need to have something similar to X ray detecting ‘Chandra’, with an exceptionally high directivity
