Light years?

[Dicart]

The speed of light is the speed limit for all of nature, so there's no universal "now".

This delay of the speed limit doesen't imply that there is not a universal now (even when parrots will not say this).

Still a third type of reality is illustrated by the outermost line of the present spatial surface of the Universe. This represents a sort of "universal present moment" in which we continuously participate. We receive influence from this sector of the Cosmos only by touch, for this part of the Cosmos contains all material objects. We encounter them only in the present moment when we physically touch them. This is the part of the Universe into which we send light signals, rather than receive them. (B's observer's circle is the trace of a light ray sent from Earth 4 billion years ago; it was invisible to us during its entire trip and its arrival "today" in the "universal now" will not be seen by us for another 4 billion years.) Light travels always in the "present moment" of the "universal now". Even though we see the light from the ancient history of distant galaxies, we see that light only in our portion of the "universal now", our personal "present moment".

https://arxiv.org/html/gr-qc/9911111v8

This only say that at a distant location you can not see this universal now (because you see things using light per example), and this point if total obvious.

The proof that a universal now exists, is that you can take any space traveler from any point of the space, let them travel toward a particular location and... every of them will arrive at the same "now" (so no multiple universe here).
Did i forget to mention that reality ("now" is the reality) is what happens localy ?

 

[Dicart]

Again: sure. Bu,t also, again: the post of Dave's is not "wrong" in that regard. It is not exhaustive, i.e., does not address expansion, etc., but neither does it profess to be. There's a difference between incomplete and incorrect, yes?

Science is not saying Dave is a good guy so i will believe him and not Dicart.
Here you are doing politic, not science.
Science imply using his own brain, try it.

 

[DaveC426913]

Please, for the sake of the OP, try to stay on-topic.
Trolling is not on-topic.

 

[parmalee]

Science is not saying Dave is a good guy so i will believe him and not Dicart.
Here you are doing politic, not science.
Science imply using his own brain, try it.

Jesus. I can't quite figure what you're saying here, but what little I do think I grasp kinda seems like advice which perhaps you oughtta heed.

 

[Dicart]

Please, for the sake of the OP, try to stay on-topic.
Trolling is not on-topic.

It is you who do some derivation with your "universal now" considerations.
Who will really understand this ?
Look, there are some specialists trying to understand it (you not for sure, you already know you know everything) :

A Debate Over the Physics of Time
According to our best theories of physics, the universe is a fixed block where time only appears to pass. Yet a number of physicists hope to replace this “block universe” with a physical theory of time.

https://www.quantamagazine.org/a-debate-over-the-physics-of-time-20160719/

Perhaps you will not only read the title and learn something new ?

 

[Dicart]

Jesus. I can't quite figure what you're saying here, but what little I do think I grasp kinda seems like advice which perhaps you oughtta heed.

Sorry i dont understand when somebody speak in slang.

 

[Seattle]

Sorry i dont understand when somebody speak in slang.

"I can't quite figure what you're saying here, but what little I do think I grasp seems like advice which perhaps you should heed."

 

[parmalee]

Sorry i dont understand when somebody speak in slang.

It's fine to expand and expound upon another's explanation, but stating that said explanation is "wrong"--as you do in post# 13--simply because it is not complete and comprehensive is not helpful, and it only confuses matters.

 

[Dicart]

It's fine to expand and expound upon another's explanation, but stating that said explanation is "wrong"--as you do in post# 13--simply because it is not complete and comprehensive is not helpful, and it only confuses matters.

In this case the question should have been formulated in physics (because it is a basic question), not in cosmology.
"Do i see the things like they are ?" Not; there is a speed of light.
Oh my gosh, its incredible !

 

[wegs]

But, it is incredible. Maybe for the first time, I’m realizing just how incredible the concept of light years really is. I was (in my mind) confusing it with time (as a measurement) and not as a measure of distance. Thus, this thread came to be.

As an aside, threads evolve. As more people chime in, the answers sometimes beg more questions. That’s the point of these discussions.

Why don’t you just discuss the topic with others, and not question the motives of everyone in the thread, Dicart?

 

[Dicart]

Why don’t you just discuss the topic with others, and not question the motives of everyone in the thread, Dicart?

Try to use your brain.
If you have a question, why dont you try to answer it yourself ?
Here you already have all the facts, and you think i am the one who agress other ?
I just give punches back, and you can verify this reading it carefully.
But you can also just repeat what other say. It is up to you.

I will help you.

I don't see how this complementary lecture is helping the OP get their question answered. It seems like more of an ego striking opportunity for you.

This is a very clever guy beeing able to identify my motivation ...

 

[parmalee]

In this case the question should have been formulated in physics (because it is a basic question), not in cosmology.
"Do i see the things like they are ?" Not; there is a speed of light.
Oh my gosh, its incredible !

Not a precise match, but I would posit that you were committing what is sometimes termed a numeracy bias or a precision bias:

Precision bias is a form of cognitive bias in which an evaluator of information commits a logical fallacy as the result of confusing accuracy and precision. More particularly, in assessing the merits of an argument, a measurement, or a report, an observer or assessor falls prey to precision bias when he or she believes that greater precision implies greater accuracy (i.e., that simply because a statement is precise, it is also true); the observer or assessor are said to provide false precision.

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

It's hardly the most heinous of offenses, but it does sometimes make things needlessly complicated, and confuses rather than illuminates.

 

[Dicart]

Not a precise match, but I would posit that you were committing what is sometimes termed a numeracy bias or a precision bias:

Precision bias is a form of cognitive bias in which an evaluator of information commits a logical fallacy as the result of confusing accuracy and precision. More particularly, in assessing the merits of an argument, a measurement, or a report, an observer or assessor falls prey to precision bias when he or she believes that greater precision implies greater accuracy (i.e., that simply because a statement is precise, it is also true); the observer or assessor are said to provide false precision.

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

It's hardly the most heinous of offenses, but it does sometimes make things needlessly complicated, and confuses rather than illuminates.

Do i really need to reply to this....?

 

[Bells]

Mod Note

Do i really need to reply to this....?

Whether you reply to a comment is up to you.

How you decide to reply to it, however, is dictated by the rules of this forum. If you are unsure about those rules, you can access them here: http://www.sciforums.com/threads/sciforums-site-rules.142880/

I would suggest you pay particular attention to the part about trolling and flaming.

So here's how we are going to address this. You will receive an infraction for trolling and flaming this thread and the participants in it. If you persist in acting this way, you will be barred from the discussion. And if you can't seem to stop yourself, you will receive more infractions until *poof*, the system will automatically ban you from this site.

I hope this clears up any confusion you may have.

 

[Dicart]

Mod Note



Whether you reply to a comment is up to you.

How you decide to reply to it, however, is dictated by the rules of this forum. If you are unsure about those rules, you can access them here: http://www.sciforums.com/threads/sciforums-site-rules.142880/

I would suggest you pay particular attention to the part about trolling and flaming.

So here's how we are going to address this. You will receive an infraction for trolling and flaming this thread and the participants in it. If you persist in acting this way, you will be barred from the discussion. And if you can't seem to stop yourself, you will receive more infractions until *poof*, the system will automatically ban you from this site.

I hope this clears up any confusion you may have.

The truth is you defend the trolls that drive users away, and that you never have recognized as such.
Not sure why but the result is that this website now sucks and nobody really care about.

Bye Bye (and i will not recommend this website for sure to anyone (more surely i will warn others that this website is full of trolls)) !!

PS : You can safely ban me, i will never log in anyway.

 

[exchemist]

The truth is you defend the trolls that drive users away, and that you never have recognized as such.
Not sure why but the result is that this website now sucks and nobody really care about.

Bye Bye (and i will not recommend this website for sure to anyone (more surely i will warn others that this website is full of trolls)) !!

PS : You can safely ban me, i will never log in anyway.

Splendid, splendid!

Bye.

 

[geordief]

But, it is incredible. Maybe for the first time, I’m realizing just how incredible the concept of light years really is. I was (in my mind) confusing it with time (as a measurement) and not as a measure of distance. Thus, this thread came to be.

As an aside, threads evolve. As more people chime in, the answers sometimes beg more questions. That’s the point of these discussions.

Why don’t you just discuss the topic with others, and not question the motives of everyone in the thread, Dicart?

You could say that LA is (guessing) 10 walking speed days from SF or 1 cycling speed day ,or 6 car speed hours or 1 plane speed hour
(Or 1 Trump corruption contagion second )

And ,maybe 1 tenth of a light speed seconds to get that same distance from LA to SF.

So the light years is the same kind of a combination measurement, combining the speed of something with the time taken and giving a distance as a result


You could measure the distance to the Sun from the earth as how long it would take a snail to get there if if could pull itself there eventually.

Probably 10 followed by millions of noughts of snail speed centuries.

8 light(speed). minutes is more sensible.

You also asked about the speed of light if the emitting object was moving or accelerating with respect to the observer.

As Dave (I think it was him) said the light would just be "red shifted" and the speed would be the same in a vacuum as if the emitting body was stationary


That seems a little strange but it does seem true (and it is very important in the mathematics of relativity)

 

[wegs]

Read something over the weekend that served as a light bulb moment (no pun)

If someone were to drive to my house with the starting point being one mile away holding a sticky note that read “it’s 2 PM,” by the time the person arrives to my home, the sticky note is meaningless, because it’s 2:30 PM by that point. Because the speed of the car traveling to me isn’t instantaneous. (This coincides with what Dave posted in terms of there not being an indisputable “now” when it comes to space.)

So, the light that I’m seeing from an object far away, has that same “delay effect” as the person traveling to me, except with light years, it’s much longer and the speed faster. One light year means it takes one year for the light of that object, to get to me.

Has anyone in this thread or forum ever taught science in high school or college? Just wondering.

 

[DaveC426913]

One light year means it takes one year for the light of that object, to get to me.

So now you're tapping on the lid of a can of worms.

That "object" cannot travel one light year in one year. No object with mass can travel at the speed of light.
It can travel at just under the speed of light (say, 99.99%), but if it did so, it will have experienced the journey as only about 5 days long!

But that's a whole 'nother thread.

 

[wegs]

So now you're tapping on the lid of a can of worms.

That "object" cannot travel one light year in one year. No object with mass can travel at the speed of light.
It can travel at just under the speed of light (say, 99.99%), but if it did so, it will have experienced the journey as only about 5 days long!

But that's a whole 'nother thread.

Oh. I posted the light of the object, not the object itself. lol If something is one light year away from Earth, it will take one year for the light of that object to reach me seeing it. Yes?