I was thinking about the signals we crunch numbers for and noticing the dates that they were received at Arecibo. For instance my task right now says it was received on Oct. 4, 2008. So when was that signal sent out? Doesn't it take years for it to reach deep space? And wouldn't it take years in return to receive it back? Just curious. I am sure this has been asked before.

So when was that signal sent out?

Arecibo doesn't transmit, it just listens.

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... For instance my task right now says it was received on Oct. 4, 2008. So when was that signal sent out? Doesn't it take years for it to reach deep space? And wouldn't it take years in return to receive it back?

We are only listening for signals.

And when you consider the speed of light, you can consider distance as time (for that light-speed travel of the radio waves). So, for any signal being picked up, it is going to have been travelling for at least a few years from our nearest stars, and thousands of years if from the other side of our galaxy.

If we were to transmit a reply, then you get the same time delay again to get the transmission back to wherever.


We are about 499 light seconds from our sun. So we see the sun as it was about 8 1/2 minutes ago.

(A very curious effect is that we 'feel' the sun's gravity instantaneously, apparently without any delay...)


Keep searchin',
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

just how can we tell if gravity is from 8 minutes ago or not? since the sun and earth have the same mass from minute to minute and their pull is constant, How would we be able to distinguish this if all objects with mass exert gravitational forces on other objects? Doesnt Relativity come into play here?

---

In a rich man's house there is no place to spit but his face.
Diogenes Of Sinope

... For instance my task right now says it was received on Oct. 4, 2008. So when was that signal sent out? Doesn't it take years for it to reach deep space? And wouldn't it take years in return to receive it back?

We are only listening for signals.

And when you consider the speed of light, you can consider distance as time (for that light-speed travel of the radio waves). So, for any signal being picked up, it is going to have been travelling for at least a few years from our nearest stars, and thousands of years if from the other side of our galaxy.

If we were to transmit a reply, then you get the same time delay again to get the transmission back to wherever.


We are about 499 light seconds from our sun. So we see the sun as it was about 8 1/2 minutes ago.

(A very curious effect is that we 'feel' the sun's gravity instantaneously, apparently without any delay...)


Keep searchin',
Martin

Neutron stars may be a blessing for the neighborhood, and main sequence to consider orbit and mirages?

just how can we tell if gravity is from 8 minutes ago or not? since the sun and earth have the same mass from minute to minute and their pull is constant, How would we be able to distinguish this if all objects with mass exert gravitational forces on other objects? Doesnt Relativity come into play here?

It is all relative...

Light travels at the speed of... light. Hence we see the sun where it was 499 seconds ago. Meanwhile, the earth is moving around along the earth's orbit. Also, the sun has moved along its orbit around the solar system barycentre.

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.


Keep searchin',
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

Neutron stars may be a blessing for the neighborhood, and main sequence to consider orbit and mirages?

The present is embodied in Hexagram 14 - Ta Yu (Possession in Great Measure):

• There will be great progress and success.
  
• In the second line, undivided, we have a large waggon with its load. In whatever direction advance is made, there will be no error.
  
• The fourth line, undivided, shows its subject keeping his great resources under restraint. There will be no error.
  
• The fifth line, divided, shows the sincerity of its subject reciprocated by that of all the others represented in the hexagram. Let him display a proper majesty, and there will be good fortune.
  
• The situation is shifting, and Yin (the passive feminine force) is gaining ground.
  

The future is embodied in Hexagram 37 - Chia Jen (The Family):

• For the regulation of the family, what is most advantageous is that the wife be firm and correct.
  
• The things most apparent, those above and in front, are embodied by the upper trigram Li (Fire), which is tansforming into Sun (Wind). As part of this process, brightness and warmth are giving way to penetration and following.
  
• The things least apparent, those below and behind, are embodied by the lower trigram Chi'en (Heaven), which is transforming into Li (Fire). As part of this process, strength and creativity are giving way to brightness and warmth.
  

Thus quothed,
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

499 seconds to send anti matter to Sadalsuud?

The present is embodied in Hexagram 10 - Lu (Treading Carefully):

• One treads on the tail of a tiger, which does not bite him. There will be progress and success.
  
• The third line, divided, shows a one-eyed man who thinks he can walk well. He is one who treads on the tail of a tiger and is bitten. All this indicates ill fortune. We have a mere bravo acting the part of a great ruler.
  
• The fourth line, undivided, shows its subject treading on the tail of a tiger. He becomes full of apprehensive caution, and in the end there will be good fortune.
  
• The sixth line, undivided, tells us to look at the whole course that is trodden, and examine the presage which that gives. If it be complete and without failure, there will be great good fortune.
  
• The situation is shifting, and Yin (the passive feminine force) is gaining ground.
  

The future is embodied in Hexagram 5 - Hsu (Waiting):

• With sincerity, there will be brilliant success. With firmness there will be good fortune, and it will be advantageous to cross the great stream.
  
• The things most apparent, those above and in front, are embodied by the upper trigram Chi'en (Heaven), which is tansforming into K'an (Water). As part of this process, strength and creativity are giving way to danger and the unknown.
  
• The things least apparent, those below and behind, are embodied by the lower trigram Tui (Lake), which is transforming into Chi'en (Heaven). As part of this process, joy, pleasure, and attraction are giving way to strength and creativity.
  

Hence quothed,
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

Before thoughts meander into psychedelic dreams...

There is much food for cosmic thought on the slightly heavy-weight thread:

Gravity Waves

Keep searchin',
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

just how can we tell if gravity is from 8 minutes ago or not? since the sun and earth have the same mass from minute to minute and their pull is constant, How would we be able to distinguish this if all objects with mass exert gravitational forces on other objects? Doesnt Relativity come into play here?

It is all relative...

Light travels at the speed of... light. Hence we see the sun where it was 499 seconds ago. Meanwhile, the earth is moving around along the earth's orbit. Also, the sun has moved along its orbit around the solar system barycentre.

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.


Keep searchin',
Martin

If the Sun's position in the sky (as viewed with the naked eye) is from 499 seconds ago, and the Sun's position is actually 499 seconds further ahead, then how is it we can still point a telescope directly at the Sun and observe the sunspots directly on its surface? Or are the telescopes pointed 499 seconds ahead of the Sun when viewing its surface features?

Whenever this subject comes up regarding the Sun (or any object in our solar system for that matter), this is where I get confused.

If the Sun's position in the sky (as viewed with the naked eye) is from 499 seconds ago, and the Sun's position is actually 499 seconds further ahead, then how is it we can still point a telescope directly at the Sun and observe the sunspots directly on its surface? Or are the telescopes pointed 499 seconds ahead of the Sun when viewing its surface features?

Because you're forgetting that those telescopes are only pointed directly at the light (the optical image) emitted from the sun; they don't need to see the sun as it is right now instantaneously without the 8 1/2 second delay.

The same thing is true with the stars you see at night with your eyeballs. Some could be thousands of light years away and thus not actually in the position where they appear right now since the image you're seeing could be thousands of years of old.

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.

Not sure where you heard this Martin, but that's not correct.

Gravity propagates at exactly the speed of light. Experiments and observational evidence confirm this.

just how can we tell if gravity is from 8 minutes ago or not? since the sun and earth have the same mass from minute to minute and their pull is constant, How would we be able to distinguish this if all objects with mass exert gravitational forces on other objects? Doesnt Relativity come into play here?

It is all relative...

Light travels at the speed of... light. Hence we see the sun where it was 499 seconds ago. Meanwhile, the earth is moving around along the earth's orbit. Also, the sun has moved along its orbit around the solar system barycentre.

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.


Keep searchin',
Martin

If the Sun's position in the sky (as viewed with the naked eye) is from 499 seconds ago, and the Sun's position is actually 499 seconds further ahead, then how is it we can still point a telescope directly at the Sun and observe the sunspots directly on its surface? Or are the telescopes pointed 499 seconds ahead of the Sun when viewing its surface features?

Whenever this subject comes up regarding the Sun (or any object in our solar system for that matter), this is where I get confused.

We point the telescopes 499 seconds behind the sun's position if we want to see the light that was emitted 499 seconds ago. The information about where the sun is "now" is something we on earth don't know, in fact can't know, for 499 seconds. We always look into the past when we look out there.

Maybe this will help. If you want the see the light from "now" on the sun, first you have to wait 499 seconds. Now isn't now anymore is is past so you have to point to where now was 499 seconds ago to see the light.

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...
Keep searchin',
Martin

Gravitons are spin equals 2 massless gage bosons that travel at the speed of light.

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...
Keep searchin',
Martin

Gravitons are spin equals 2 massless gage bosons that travel at the speed of light.

Thats not true.

just how can we tell if gravity is from 8 minutes ago or not? since the sun and earth have the same mass from minute to minute and their pull is constant, How would we be able to distinguish this if all objects with mass exert gravitational forces on other objects? Doesnt Relativity come into play here?

It is all relative...

Light travels at the speed of... light. Hence we see the sun where it was 499 seconds ago. Meanwhile, the earth is moving around along the earth's orbit. Also, the sun has moved along its orbit around the solar system barycentre.

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.


Keep searchin',
Martin

If the Sun's position in the sky (as viewed with the naked eye) is from 499 seconds ago, and the Sun's position is actually 499 seconds further ahead, then how is it we can still point a telescope directly at the Sun and observe the sunspots directly on its surface? Or are the telescopes pointed 499 seconds ahead of the Sun when viewing its surface features?

Whenever this subject comes up regarding the Sun (or any object in our solar system for that matter), this is where I get confused.

We point the telescopes 499 seconds behind the sun's position if we want to see the light that was emitted 499 seconds ago. The information about where the sun is "now" is something we on earth don't know, in fact can't know, for 499 seconds. We always look into the past when we look out there.

Maybe this will help. If you want the see the light from "now" on the sun, first you have to wait 499 seconds. Now isn't now anymore is is past so you have to point to where now was 499 seconds ago to see the light.

The empiral proof of my assumption is;

Looking across a desert and the horizon and viewing the waves of the heat coliding with the surface of the planet {evaporating water} and watching the waves distort the view.
Mirage's occur when particular states of body fluid vary which is a direct result of the inference of magnetic kinetic shift {the esoteric body aligns with a magnetic stratespheric contortion}. The distance measured between the horizon point, the mirage/wave {distorted reality} and the stand position may be relevant and particularly to the individual observer regarding his food/water power energy to weight combination ratio.

I would suspect that individual vision perception would play a significant role as men and women with different colour blindness translate light signals to the brain using different neural path techniques.

just how can we tell if gravity is from 8 minutes ago or not? since the sun and earth have the same mass from minute to minute and their pull is constant, How would we be able to distinguish this if all objects with mass exert gravitational forces on other objects? Doesnt Relativity come into play here?

It is all relative...

Light travels at the speed of... light. Hence we see the sun where it was 499 seconds ago. Meanwhile, the earth is moving around along the earth's orbit. Also, the sun has moved along its orbit around the solar system barycentre.

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.


Keep searchin',
Martin

If the Sun's position in the sky (as viewed with the naked eye) is from 499 seconds ago, and the Sun's position is actually 499 seconds further ahead, then how is it we can still point a telescope directly at the Sun and observe the sunspots directly on its surface? Or are the telescopes pointed 499 seconds ahead of the Sun when viewing its surface features?

Whenever this subject comes up regarding the Sun (or any object in our solar system for that matter), this is where I get confused.

We point the telescopes 499 seconds behind the sun's position if we want to see the light that was emitted 499 seconds ago. The information about where the sun is "now" is something we on earth don't know, in fact can't know, for 499 seconds. We always look into the past when we look out there.

Maybe this will help. If you want the see the light from "now" on the sun, first you have to wait 499 seconds. Now isn't now anymore is is past so you have to point to where now was 499 seconds ago to see the light.

Space Balls anyone

---

In a rich man's house there is no place to spit but his face.
Diogenes Of Sinope

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.

Not sure where you heard this Martin, but that's not correct.

Gravity propagates at exactly the speed of light. Experiments and observational evidence confirm this.

For your comment "Gravity propagates at exactly the speed of light", what aspects of gravity are you describing?

There is the commonly accepted assumption that gravity waves propagate at the speed of light. However, it is not gravity waves that keeps us in orbit.

Then there is the gravity field through which we are 'falling'. If you assume that the gravitational influence from the sun to the earth responds to changes in position by a speed-of-light propagation for the new positions of the sun and earth, then the earth falls out of orbit and is lost into space.

The earth can orbit the sun as it does only if you assume an instantaneous line of gravitational attraction between the sun and earth.

This is demonstrated by orbital simulations and by direct measurement of orbits.


I know of no experiments that have measured whatever "speed" of gravity.


Quite perplexing!

Keep searchin',
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

Here's the killer...

We see the sun where it was 499 seconds ago. We feel its gravity from where it is instantaneously NOW. That is, the direction of the gravity gradient from the sun is at an angle that leads the direction of the light from the sun. We see the sun where it was, we feel where it is now without delay. Faster than light?...

This has been directly confirmed by observation. Simulations also confirm the observation.

Not sure where you heard this Martin, but that's not correct.

Gravity propagates at exactly the speed of light. Experiments and observational evidence confirm this.

For your comment "Gravity propagates at exactly the speed of light", what aspects of gravity are you describing?

There is the commonly accepted assumption that gravity waves propagate at the speed of light. However, it is not gravity waves that keeps us in orbit.

Then there is the gravity field through which we are 'falling'. If you assume that the gravitational influence from the sun to the earth responds to changes in position by a speed-of-light propagation for the new positions of the sun and earth, then the earth falls out of orbit and is lost into space.

The earth can orbit the sun as it does only if you assume an instantaneous line of gravitational attraction between the sun and earth.

This is demonstrated by orbital simulations and by direct measurement of orbits.


I know of no experiments that have measured whatever "speed" of gravity.

Nope, you're wrong.

Instantaneous gravitational attraction between the sun and earth is only required in Newtonian physics, not General Relativity.

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
http://einstein.stanford.edu/content/relativity/q197.html
http://einstein.stanford.edu/content/relativity/a10662.html
http://einstein.stanford.edu/content/relativity/a11134.html
http://www.newton.dep.anl.gov/askasci/phy99/phy99004.htm
http://www.qedcorp.com/pcr/pcr/speedg.html
http://www.mathpages.com/home/kmath451/kmath451.htm


Fairly comprehensive study regarding experimental confirmation of General Relativity and the speed of gravity:
"The Confrontation between General Relativity and Experiment"
http://relativity.livingreviews.org/Articles/lrr-2006-3/
(specifically, observations of the decaying orbits of Pulsars due to gravitational field energy loss)

Space.com- "Speed of Gravity Measured for First Time"
(this time using Jupiter)
http://www.space.com/scienceastronomy/gravity_speed_030107.html
http://www.newscientist.com/article/dn3232

"Light-speed gravity means that if the Sun suddenly disappeared from the centre of the Solar System, the Earth would remain in orbit for about 8.3 minutes - the time it takes light to travel from the Sun to the Earth. Then, suddenly feeling no gravity, Earth would shoot off into space in a straight line."

"It would be revolutionary if gravity were measured not to propagate at the speed of light - we were virtually certain that it must," says Lawrence Krauss of Case Western Reserve University in Cleveland, Ohio.

Though the Jupiter result is somewhat controversial, the scientists who claim the analysis was *not* a confirmation of the speed of gravity are NOT claiming that General Relativity is wrong, only that the experiment did not adequately verify the speed of gravity.

Despite what fringe practitioners of pseudo-science (in other words, researchers who purposely and selectively ignore hard evidence or incorrectly interpret equations without bothering to fully understand them) like Tom Van Flandern might want to believe, General Relativity has been directly supported by decades of observation and experiment, and the overwhelming consensus in cosmology is that gravity propagates at the speed of light, as required by General Relativity.
http://www.cosmosmagazine.com/features/print/1162/was-einstein-a-fake?page=0%2C0


Of course you're free to agree with Van Flandern and the disconnected blocks of text on his Metaresearch website, but the fact is that the scientific community does not.

Unless Van Flandern wins a Nobel Prize for proving Einstein wrong, and General Relativity is removed from text books all over the world, then for now I think it's probably safer to assume that gravity propagates at the speed of light.

Ok, (aside from the sun and gravity discussion, which is very interesting by the way...) we are just hearing signals that are being emitted from space. Correct? We haven't sent any out that have returned yet, right? So everything we are hearing comes from a star, pulsar, quasar, or (maybe someday) ET and other spacey goodness. Gotcha! When you work night, like I do, some crazy things pass through the brain and they don't always come out clearly, if that makes sense. ;-) Thanks for the great discussions everyone!

Ok, (aside from the sun and gravity discussion, which is very interesting by the way...) we are just hearing signals that are being emitted from space. Correct? We haven't sent any out that have returned yet, right? So everything we are hearing comes from a star, pulsar, quasar, or (maybe someday) ET and other spacey goodness. Gotcha! When you work night, like I do, some crazy things pass through the brain and they don't always come out clearly, if that makes sense. ;-) Thanks for the great discussions everyone!

No. The great majority of the stuff we hear comes from us. Mostly noise from our own receivers but a fair amount from our other activities. Once we get through that we find the rest of the universe.