Seeing things in their past? You are full of beans!

[ChristineM]

Relative to an outside observer, yes.

Obviously, we are outside

 

[Kangaroo Feathers]

Obviously, we are outside

We are. But our perspective is not universal.

 

[ChristineM]

We are. But our perspective is not universal.

Certainly not physically

 

[TrueBeliever37]

And from the frame of reference of the light, it does.

What I don't understand is how you can say light does not experience time or distance, and yet has speed, which is by definition distance / time.

And then claims are made that we are seeing photons emitted hundreds of trillions of years ago, and astronomical mileages away. Yet turn around and say they experience no time or distance.

I'm sorry, but it is all so contradictory.

 

[Subduction Zone]

What I don't understand is how you can say light does not experience time or distance, and yet has speed, which is by definition distance / time.

And then claims are made that we are seeing photons emitted hundreds of trillions of years ago, and astronomical mileages away. Yet turn around and say they experience no time or distance.

I'm sorry, but it is all so contradictory.

In our frame of reference light can be billions of years old, but not in the frame of reference of the light.In

It would help if you could understand some basic concepts. Let's work on the concept of a "frame of reference" .

 

[TrueBeliever37]

A light year is based on a reference, that being the speed of light and the orbital time of Earth. We could also use parsecs for our distance which is based on the parallax of stars at the extreme ends of Earth's orbit. It is no different than the kilogram which is based on a reference. The light year is an arbitrary distance that we have chosen because we can define it with well known physical constants.



The meter can be defined using the speed of light.

"The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second."
Base unit definitions: Meter

And that is from the organization that has been put in charge of defining metric units.

Hi Thermos aquaticus,

I think even what you have shown with the definition for the meter kind of proves one of my points.

Even after they defined the meter using the speed of light. When you state the distance in meters , it tells you nothing about the time involved for the light to get here. That is without doing math.
Yet when you state the distance in light years, you inherently know the time involved. That was what I meant when I said it is a distance, but time (for light) is built in to it.

 

[TrueBeliever37]

In our frame of reference light can be billions of years old, but not in the frame of reference of the light.In

It would help if you could understand some basic concepts. Let's work on the concept of a "frame of reference" .

Let me try to explain it another way. Speed of Light = Distance / Time
The problem is you can't divide by zero.

 

[Subduction Zone]

Let me try to explain it another way. Speed of Light = Distance / Time
The problem is you can't divide by zero.

Let's forget your misunderstandings and work on the basics first.

 

[oldbadger]

A light year is a measure of c/dx , it is a time .

It is a distance.

Anyway............. the OP's incompetent watcher need not worry, because same won't be full of beans by the time the object arrives.

 

[TrueBeliever37]

The speed of light, c, is a velocity. In other words, the ratio between distance and the time it takes to go that distance. In particular, c is about 186,282 miles per second.

A year is a time. In particular, a year is about 3.15*10^7 seconds.

If you multiply a velocity (distance per time) by a time, you get a distance.

In particular, a light year is the *distance* that light travels in one year. This is approximately 5.88*10^12 miles.

Space is close enough to being a vacuum that the difference is rarely useful. There is approximately one hydrogen atom per cubic meter of space.

This is an example of the contradictory statements that are made.

Remember you have said light experiences no time or distance. Yet you say it travelled 5.88*10^12 miles in one year.

Speed of Light = Distance / Time

How can you come up with Speed if there is no time experienced? It is impossible to divide by zero, so how can you come up with a Speed ?

 

[TrueBeliever37]

Let's forget your misunderstandings and work on the basics first.

Will you please explain which part of what I said in post 427 is a misunderstanding?

 

[Polymath257]

What I don't understand is how you can say light does not experience time or distance, and yet has speed, which is by definition distance / time.

And then claims are made that we are seeing photons emitted hundreds of trillions of years ago, and astronomical mileages away. Yet turn around and say they experience no time or distance.

I'm sorry, but it is all so contradictory.

OK, times of hundreds of trillions of years are not discussed. The BB happened about 13.7 billion years ago.

Second, ALL uniform motion can be regarded as being at rest. So, someone going past at 50% of the speed of light is *at rest* in their reference frame.

Third, the amount of time measured between two events depends on the relative motion of the observer and those events. For example, if I determine two events happen at the same time, but at some distance apart, someone going past me at 50% of the speed of light would see those same two events as happening at different times (if you want specific numbers I can run a calculation). Time intervals are relative to motion.

As another example, if I watch a perfectly good clock going past me at 50% of the speed of light, it appears to be slowed relative to clocks at rest with respect to me. Clocks going past at 99%of the speed of light will be slowed more. The closer to the speed of light (in my reference frame), the slower the clocks.

This, by the way, is reciprocal: those at rest with respect to those clocks moving past me will see *my* clocks as going slower.

This is what is meant when we say space and time are relative. These are observed phenomena and are not in basic dispute.

Now, technically there is not a reference frame going at the speed of light. But, as we approach the speed of light, the clocks going that fast are slower and slower from our vantage point. This is what is meant when we say that time is 'experienced' slower under relative motion. In the limit as we approach the speed of light, the clocks are stopped: no time is experienced at all by the light. BUT, time is experienced for us since we are not going at the speed of light. And we measure light as going that same speed in any vacuum, no matter what.

 

[Polymath257]

This is an example of the contradictory statements that are made.

Remember you have said light experiences no time or distance. Yet you say it travelled 5.88*10^12 miles in one year.

Speed of Light = Distance / Time

How can you come up with Speed if there is no time experienced? It is impossible to divide by zero, so how can you come up with a Speed ?

OUR time, not that experienced by the light. WE measure the time and the distance. For the light itself, both the distance and the time are zero.

 

[Subduction Zone]

Will you please explain which part of what I said in post 427 is a misunderstanding?

The whole concept. But I would talk to Polymath for a more thorough explanation. I will give it a quick shot at any rate. You could have rewritten that as vt = d or velocity times time equals distance. If you did that there would be no divide by zero error. And you would find that in the frame of the photon v*0 = 0. At the speed of light distance to anywhere becomes zero. And time no longer exists. It is essentially zero. You will not understand this until you at least get a basic understanding of the concept of "frames of reference". If we start with Newtoninan frames of reference we can then move to relativistic ones.

 

[TrueBeliever37]

OK, times of hundreds of trillions of years are not discussed. The BB happened about 13.7 billion years ago.

Second, ALL uniform motion can be regarded as being at rest. So, someone going past at 50% of the speed of light is *at rest* in their reference frame.

Third, the amount of time measured between two events depends on the relative motion of the observer and those events. For example, if I determine two events happen at the same time, but at some distance apart, someone going past me at 50% of the speed of light would see those same two events as happening at different times (if you want specific numbers I can run a calculation). Time intervals are relative to motion.

As another example, if I watch a perfectly good clock going past me at 50% of the speed of light, it appears to be slowed relative to clocks at rest with respect to me. Clocks going past at 99%of the speed of light will be slowed more. The closer to the speed of light (in my reference frame), the slower the clocks.

This, by the way, is reciprocal: those at rest with respect to those clocks moving past me will see *my* clocks as going slower.

This is what is meant when we say space and time are relative. These are observed phenomena and are not in basic dispute.

Now, technically there is not a reference frame going at the speed of light. But, as we approach the speed of light, the clocks going that fast are slower and slower from our vantage point. This is what is meant when we say that time is 'experienced' slower under relative motion. In the limit as we approach the speed of light, the clocks are stopped: no time is experienced at all by the light. BUT, time is experienced for us since we are not going at the speed of light. And we measure light as going that same speed in any vacuum, no matter what.

ok you have given me a lot to think about. I want to mull this over for a while.
I want to go back to the link I looked at earlier, I could be mistaken, but I thought it said hundreds of trillions of years. But as far as concept, to me that would be a mute point.

 

[TrueBeliever37]

The whole concept. But I would talk to Polymath for a more thorough explanation. I will give it a quick shot at any rate. You could have rewritten that as vt = d or velocity times time equals distance. If you did that there would be no divide by zero error. And you would find that in the frame of the photon v*0 = 0. At the speed of light distance to anywhere becomes zero. And time no longer exists. It is essentially zero. You will not understand this until you at least get a basic understanding of the concept of "frames of reference". If we start with Newtoninan frames of reference we can then move to relativistic ones.

You should be able to arrange the equation any way you need to, in order to solve for what you are looking for.

It should hold up if true, no matter how it is arranged.

 

[TrueBeliever37]

It has traveled one light second or roughly 186,000 miles if you like English measurements or 300 million meters if you like metric. I can give you a more accurate figure if you desire.

Now my turn: What is a light year:

A. A unit of time.

B. A unit of speed

C. A unit of distance.

D. A peanut butter and jelly sandwich.

To me it is both C and A. It is a distance from the way they wanted to define it. But it is also provides the amount of time it takes light to travel a certain distance.

If it has traveled 1/2ly it has taken 1/2 year to go 1/2 the distance. Note that you have to actually multiply things out to get the distance.
It it has traveled 4ly it has taken 4 years to go 4 times the distance. So it provides both a time and a distance.

The number in front provides the time in years needed for light to travel that distance.

 

[Subduction Zone]

To me it is both C and A. It is a distance from the way they wanted to define it. But it is also provides the amount of time it takes light to travel a certain distance.

If it has traveled 1/2ly it has taken 1/2 year to go 1/2 the distance. Note that you have to actually multiply things out to get the distance.
It it has traveled 4ly it has taken 4 years to go 4 times the distance. So it provides both a time and a distance.

The number in front provides the time in years needed for light to travel that distance.

You do not seem to understand that both time and distance are relative and dependent upon relative motion. The traveling light undergoes no time.

 

[TrueBeliever37]

For you, time is moving by. Time ticks by at different rates at different velocities. This was confirmed by experiments:

Hafele–Keating experiment - Wikipedia



From the point of view of the photon, it does.

If light reaches it's destination instantly from the point of view of the photon, then why does it take light over 8 minutes to get here from the Sun?

How can it be here instantly but take us over 8 minutes to recognize it?

But then again how can it even get here, since you say it doesn't go any distance?

 

[TrueBeliever37]

You do not seem to understand that both time and distance are relative and dependent upon relative motion. The traveling light undergoes no time.

But that is not in agreement with the equation for the Speed of light.

That's what lets me know something has to be wrong with the theory that light doesn't experience time or distance.