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Comment by tyfon | Hacker News Reader

I always look at Betelgeuse when I am out walking an it's a clear sky. It's very easy to spot and you can pick out the colour difference with the naked eye.

I hope it will go supernova in my lifetime, it will be spectacular. This dimming might be a sign of that.

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There is a fella on the radio weekly here in Aus (and the BBC), Dr Karl Kruszelnicki. I always liked his take on it, "Could blow up any time between next Tuesday and 10,000 years from now. Don't worry about it."

FYI, if you want a few hours notice before (the very unlikely event of) a Betelgeuse supernova, there’s a mailing list you can join: https://snews.bnl.gov/alert.html

Re: I hope it will go supernova in my lifetime, it will be spectacular.

It could bleep up satellites and communication lines, nobody really knows. Be careful what you wish for. If Yellowstone and Betelgeuse go off at the same time, we are the New Dinosaurs.

> I hope it will go supernova in my lifetime

The inhabitants of any planets in the vicinity might disagree.

It doesn’t matter as it has already happened a long, long time ago. No matter what it was

Beatlejuice is 642 ly away. So it might have popped off already.

I was thinking it was a transit of some other celestial object in front of our vision.

Too much dimming to be a transit. Betelgeuse is so large that we can map its "surface"[0] and even planets in our own solar system are so small[1] that something so large to cause such a substantial dimming would have been detected a long time ago.

[0] see this from 2017 https://www.space.com/37344-alma-captures-clearest-image-of-...

[1] Jupiter is about the largest a planet can be, in the current conditions of our solar system -- that means Jupiter was larger when it was younger, but it's been cooling off and reducing its volume

My thoughts as well!

May be it's gone supernova already.

It’s possible but reasonably unlikely.

It's 'only' 642 light years away, if that's what you're referring to.

Not on my spacetime.

Some say it's better to regard anything with a lightlike separation as being simultaneous and that things with a spacelike separation essentially don't exist for practical purposes. So when the light reaches us is when it happens, because not even gravity can affect us beforehand.

Convenient perhaps, but the engineer in me doesn't want to accept that. Light is the fastest thing in the universe and it takes 642 years to reach us from this particular star. So we are lagging by 642 years. Those are the facts.

Except that those photons haven’t aged a single day, right?

Correct

Genuinely curious as to why you think they haven't aged a single day. Doesn't it depend on the point of reference? Earth is 500 light seconds from the Sun. So any photon hitting the eye is at least 500 seconds old. Hypothetically speaking, if a human were to be born on the Sun's surface and reach earth at the speed of light, he/she is at least 500 seconds old on Earth's clock?

Sure, but from the frame of reference of the human it’s not. If the human would travel at 99% of the speed of light, then time dilation would make it a lot less than 500 seconds.

If an object moves at the speed of light, Mathematically no time is passing.

It's also why we can detect muons on Earth, a particle that would have decayed by the time it reaches us if its age depended on our frame of reference.

I looked up after your reply, they decay by losing energy based on the matter they interact with. So in the vacuum of space they can travel great distances as long as they don't interact with the matter.

Source: https://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm

You are misreading the document. The muons are created in the top of the atmosphere and decays after a very short amount of time. The point is that they decay so fast that they shouldn't be able to reach the ground. They manage to do that because time passes much slower for the muon. Or to put it differently, from the point of view of the muon the thickness of the atmosphere has been compressed to become much smaller than from the point of view of an observer on Earth.

You are right, I misread the document. I stand corrected.

Yes I agree, from the object's frame of reference no time passes.

I thought that Einstein showed why "it happened long ago" and "it happens when we see it" are wrong? If the light strikes somewhere else and the effect of that changes the interaction between us and it then we have to admit that both places perceived the event relative to themselves - the origin and or perspective are not privileged... So if Jupiter is peterbed and earth is peterbed by the same event to make the sums for the future interacton of earth and Jupiter work we have to consider the events relative to both Jupiter and earth's frame of reference?

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