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Visually will the explosion appear any different than looking at a star with the naked eye?
Hours, and 21 million years, after it happened.
Hours, and 21 million years, after it happened.
Both space and time are relative, so if you're choosing Earth as your reference point, the supernova is happening right when you're seeing it.
Earlier quoted context omitted.
Thanks for pointing this out. I've obviously not gotten my head around the concept of space-time and the article fails to mention this. Also, http://newscenter.lbl.gov/feature-stories/2011/08/25/superno... is perhaps a more official story. They too don't mention that it's discovery was a few hours after it was possible to observe the explosion, not a few hours after the actual explosion.
These conversations are useless. Everyone knows that anything we see is strictly in the past and already has happened. Yet for practical purposes, a week ago there was no supernova there. Today a supernova is there. It may help you to look at it like this: a supernova is NOT the star exploding, it is the observation of the star exploding. In one sense, this is wrong, but in another it is really the only freaking thin…
Actually, that statement is nonsensical. Choosing the Earth as your point of reference, the supernova is happening exactly when we see it happening.
Earlier quoted context omitted.
These conversations are useless. Everyone knows that anything we see is strictly in the past and already has happened. Yet for practical purposes, a week ago there was no supernova there. Today a supernova is there. It may help you to look at it like this: a supernova is NOT the star exploding, it is the observation of the star exploding. In one sense, this is wrong, but in another it is really the only freaking thin…
> Everyone knows that anything we see is strictly in the past and already has happened. Actually, that statement is nonsensical. Choosing the Earth as your point of reference, the supernova is happening exactly when we see it happening.
Putting a specific time span on how far in the past it is without further specification is dubiously meaningful, saying it is in the past is not nonsensical. Everything we see is always in the past, even if it's just on the other side of the room.
Hours, and 21 million years, after it happened.
I always have to point this out at the risk of downvotes: it doesn't make sense to say that an event you're currently seeing on Earth "happened 21 million years ago." Both space and time are relative, so if you're choosing Earth as your reference point, the supernova is happening right when you're seeing it.
Relative time is a real thing, certainly and messes with the idea of simultaneous.
But transit time is not that. We and the supernova are more or less in the same frame of reference (we are not accelerating relative to one another, and there isn't much relative velocity difference either).
And because of that it is correct to say it happened xxx years ago.
Earlier quoted context omitted.
These conversations are useless. Everyone knows that anything we see is strictly in the past and already has happened. Yet for practical purposes, a week ago there was no supernova there. Today a supernova is there. It may help you to look at it like this: a supernova is NOT the star exploding, it is the observation of the star exploding. In one sense, this is wrong, but in another it is really the only freaking thin…
> Everyone knows that anything we see is strictly in the past and already has happened. Actually, that statement is nonsensical. Choosing the Earth as your point of reference, the supernova is happening exactly when we see it happening.
No, that is not true. You do not say point of reference, you say frame of reference - and for a good reason. Huge areas of space can all be in the same frame of reference.
Earlier quoted context omitted.
> Everyone knows that anything we see is strictly in the past and already has happened. Actually, that statement is nonsensical. Choosing the Earth as your point of reference, the supernova is happening exactly when we see it happening.
I don't think it's nonsensical. There is a meaningful way in which it is in the past. Even if you turn yourself into photons, match positions with the supernova remnants, then return to physical form, the supernova is going to evolve though time for quite a ways beyond the current state we observe it in before your physical form has its rendezvous, even if the trip has zero duration for you. Putting a specific time s…
Most educated people understand the principle of relativity (which states that the laws of physics behave consistent in all frames of reference) and the fact that the speed of light is constant regardless of your frame of reference, but we tend to forget the resultant phenomenon called the relativity of simultaneity. Two observers in different frames of reference can't even agree on the order of events, much less the "exact time" they occurred.
Now, you can certainly propose the semantic axiom that "everything happened in the past due to the finiteness of the speed of light," but I find that axiom to be pretty useless in scientific discussion. You can suppose that millions of years of stuff has happened to that supernova after "now," but none of those events could have any causal effects on us.