Scientists Predict Star Collision Visible to the Naked Eye in 2022
npr.org
npr.org
Write down (briefly) where you are in your life right now, on a blog, Facebook, or even some tweets.
Then write down where you think you'll be in your life in the five or so years when these stars collides. Hashtag it #whenstarscollide or give it a similar title so people can find it when the times comes.
At best i could note where i am when the light of the collision arrives here.
I've set a reminder for that "event" on Google calendar. I'm sure nothing major will happen, but at least I could host a "end of the world" party for my friends.
I wonder if that service (or Google for that matter) will be alive then. I wonder if I will be.
As far as I can remember, the star blowing up and the light reaching us are only simultaneous in the light's frame.
You could define the global time for a position to be the time at which light it sends reaches the earth, minus the time it took for the light to travel, but with things like gravitational lensing this can have some weird results, and may in fact not be well defined.
I imagine that if you define everything on the boundary of your past light cone as simultaneous to you, it requires that everything on your future light cone to be simultaneous too, which would mean that everything between them is also simultaneous. That kind of definition defines a 4D subset of spacetime as simultaneous. In that set are points in each others future and past light cones, which we can unambiguously say are not simultaneous to each other. I think that's the heart of the argument everyone's having. I never took GR, so maybe you can shed some light on it (heh) from that perspective?
Since the light hasn't reached us yet, it's perfectly valid to state that in some frame of reference, the event is happening right now. 2022 is the last possible time at which we could make that claim because the events become causally separated, which is I think what OP was getting at, though the wording was a bit off.
By the way, what's the need of talking about frames? Which other frame do you have in mind apart from ours?
For this reason, to avoid confusion, it is much better and customary to "tag" astronomical events by the time we observe them. That is to say that they happen when we observe them.
Large distances? Please, we are talking about a couple thousand years: what's that compared to the age of the universe?
Sir, honestly, this sentence of yours is just ridiculous.
Please write only if you have something useful to contribute to the discussion.
In a way what I'm imagining is speed of light being a kind of "clock signal" of digital electronics, except continuous, not discrete.
If you wanted to say that when a light signal goes from A to B its emission and reception should be considered simultaneous, then you'd have to say the same about a signal sent back from B to A when the first one is received. ... And then, if you also wanted to believe that "x is simultaneous with y and y is simultaneous with z ==> x is simultaneous with z", you'd get the absurd conclusion that two events in the same place but separated in time are simultaneous.
So here's the actual situation (at least in special relativity):
Once you define a frame of reference, which is basically the same thing as a velocity of motion, you then have a notion of simultaneity in that frame. If you fix your frame of reference, simultaneity has the nice properties you might want it to have (like transitivity, which I appealed to above). But you can have "x simultaneous with y in frame F" and "y simultaneous with z in frame G" without x and z being simultaneous in any frame.
If a signal can get from x to y (here x and y are locations in spacetime, not just in space) then there is no frame in which x and y are simultaneous. If it's possible only for a signal propagating at the speed of light, then it is (just barely) impossible to find a frame in which they are simultaneous. If it's not possible even at the speed of light, then there is a frame in which they are simultaneous.
So, in particular, consider the collision between these stars and the arrival of the light from the collision here on earth. In an (impossible) reference frame moving at the speed of light in the direction from there to here, the events would be simultaneous. Actually, they can't quite be -- but by considering a frame that moves fast enough, you can make the time difference as short as you like.
In an (equally impossible) frame moving at the speed of light the other way, they would be 3600 years apart. With actually-admissible reference frames, the time can be anywhere strictly between zero and 3600 years.
So far as I know, we and these stars are not moving very rapidly (in comparison with the speed of light) relative to one another. It seems reasonable to use a frame corresponding roughly to their motion and ours. That gives you a time difference of about 1800 years, and any plausible adjustment for our actual relative motion will make no difference to speak of because we're moving so much slower than light relative to one another.
But: There is another related notion that you may have in mind. You can compute a numerical measure of separation between any two points in spacetime, called the "interval", which is positive when the separation is "space-like" and negative when it's "time-like". If light could go from one to the other, this separation is zero.
(How does this escape the scenario I described in the first paragraph above? Because knowing the interval, as it's called, between x and y, and the interval between y and z, isn't enough to determine the interval between x and z any more than knowing the distances x-y and y-z is enough to determine the distance x-z. In fact the situation is worse for intervals than for distances because there isn't anything corresponding to the triangle inequality. And the "interval=0" relation isn't transitive. So knowing that the intervals x-y and y-z are zero tells you nothing at all about the interval x-z.)
J'Kaziof witnessed this event when s/he was n seconds [old] per their atomic clocks, and immediately set out in our direction.
What is the age of J'Kaziof in seconds when s/he arrives on Earth?
[p.s. assume their ships can instantanously accelerate to c and slow down to 0 from c.]
[p.s.s. In the year of our lord 222 here on Terra, Bardesanes of Edessa [2] went to meet his maker. Let's just say he passed away at the exact moment of J'Kaziof uttering 'make it so' to his 1st officer.]
That's right.
> in our frame it actually does happen in 2022
That's not. Read on clock synchronisation: https://en.wikipedia.org/wiki/Einstein_synchronisation
So you position your space ship in the middle between were earth and KIC 9832227 were 1795 years ago, about 900 light years away from each and sometime about the year 1122 you will see the stars colliding and at the same time, with a good enough telescope, what was happing on earth in the year 222 which establishes that the the collision of KIC 9832227 and the year 222 on earth were simultaneous in the frame of reference attached to the Milky Way.
So naively I would expect that you can attach a reference frame to almost all objects in the Milky Way and they would agree on simultaneity to within hours or maybe days. There are certainly some notable exceptions like the central black hole or particles traveling at an appreciable fraction of the speed of light and you can certainly just invent a reference frame with huge relative velocity changing simultaneity a lot.
But are there really places within the Milky Way so that simultaneity would be off by hundreds and thousands of years over a distance of just 1,800 light years? If yes, what is the cause of that, as far as I can tell it would have to be an effect of general relativity because, again as far as I can tell, there is no problem of defining simultaneity across extended distances in special relativity and the involved velocities are not large enough to have an appreciable effect to begin with.
EDIT: Just calculated an example Lorentz transformation, 500 km/s relative velocity and 1,800 light years distance, and the time difference comes out at almost exactly 3 years. That is certainly more than I expected and adds up to 166 years across the entire Milky Way, on the other hand 500 km/s is probably quite a bit above common relative velocities within the Milky Way.
So I am still not convinced that picking a reference frame for the entire Milky Way, say with the origin at the center of mass, one axis coinciding with the axis of rotation and rotating with the Milky Way so that the angular momentum vanishes, could not provide a good enough reference frame for the entire Milky Way for back of the napkin calculations.
Of course, relative to our own inertial reference frames as we experience them, i.e. where we are mostly not moving, the collision would be thousands of years in the “past”.
When he says “in our frame” he is clearly at least slightly confused.
No they cannot, unless you boost to a reference frame that's moving at the speed of light, which is a useless frame. In all other frames, including the ones we are in, the photon left the Sun before arriving to Earth.
But is that the reference frame that we experience?
You just constructed an argument that can be readily used to argue that all events are simultaneous. That should flip your internal bozo bit and help you see that the argument is not sound.
No, I haven't. I have studied relativity in University, have you? Lol @bozobit
I will make the statement more rigorous.
"Let event A represent the emission of a photon. Let event B represent the arrival of a photon elsewhere. Event here refers to a unique location in space-time i.e (x,y,z,t). As per special relativity, you can always find a reference frame such that the time separation between A and B can be arbitrarily small. It can't be made exactly zero, but it can be made as close to zero as you wish to."
Use this formula to figure out the reference frame of interest.
https://en.wikipedia.org/wiki/Length_contraction
The speed of light is constant. So decrease/contract the length until the time required = distance/c is one second or less.
If we see the collision in 2022 it means it happened in the distant past.
I guess the distinction is rarely made by professionals because
- It requires defining a reference frame.
- It makes no difference to the causality.
- Time is a function of distance, which usually has large error bars on it, so it's better to discuss the distance instead.
- Time as a function of distance gets more complex on cosmological scales.
On the last point, you can get the exciting realisation that, due to the expansion of space, objects actually start getting larger the further away they get beyond a certain distance.
People who are even more into astrology and stuff are probably losing their s.it.
How will we know when and where to look?
It's in cygnus, which is always visible in the northern hemisphere, and visible in a lot of the southern hemisphere low on the horizon in the winter months.
The event is not certain, but is highly likely to occur. The date is "2022 give or take a year", so if it occurs in Southern winter then it will likely be visible to the Southern hemisphere.
"we might be able to see this with the naked eye! why bother when you can see it through JWST?"
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