1 hour ago, jalaldn said:

In Ole Rømer's time, people believed that light does not take time to travel. He proved that it does take time, and also proved its speed to be 220,000 kilometers per second. Of the two things he proved, one is wrong—it is the speed of light. Nevertheless, the discovery that light takes time to reach a destination belongs to him.

The number was incorrect, but I don’t understand your fixation with it, considering the relatively crude techniques involved, and the associated uncertainty in all of the values used in the calculations.

1 hour ago, jalaldn said:

Here at this point, what we are talking about is those eleven minutes when Io disappeared after emerging from behind Jupiter, at a time when there was no occultation (by Jupiter)

I don’t get why this is a mystery. Io emerges, and it takes 11 minutes for the light to get to earth.

59 minutes ago, jalaldn said:

Third possibility:

We are observing Io and Jupiter in real-time before Io hides. After Io hides, we see Jupiter without Io. When Io reappears, we still see Jupiter. However, Io's light doesn't arrive, but Io continues its journey without stopping. But when the light arrives, we see Io at the position it is at that time.

That means, instead of seeing Io at the position where it was when the light left, we are seeing Io at the position where it is now.

But we can do (and have done) other experiments/observations to confirm this, and you’re ignoring them.

19 minutes ago, jalaldn said:

Suppose we set up a flashlight on the io that blinks in a regular cycle: 30 minutes ON followed by 30 minutes OFF, repeating continuously.

If we observe this flashlight from Earth, we would see a strange pattern: it appears to stay OFF for 41 minutes, then ON for only 19 minutes, then OFF for 41 minutes again, and so on.

How would you explain this distorted timing using the concept of light-travel delay?

No we wouldn’t. You can’t make an assertion and also use it as established fact.

We see pulsars pulse at regular intervals. We get radio signals from satellites that don’t have these distortions.

2 hours ago, jalaldn said:

I have not published anywhere in full what the form of light is, and I will not publish it now. I am only talking about those things which have evidence to explain the properties of light.

I'm sorry you have chosen not to answer my questions.

For those with a genuine interest in what Roemer did, or did not do, there is a good readable account not only of his part but the events leading up to his work and the necessary conditions for him to be able to cary it out in this book.

It should be noted that the fact light has a finite speed was known to his employers Cassini and Picard at the Paris observatory.

5 hours ago, jalaldn said:

Suppose we set up a flashlight on the io that blinks in a regular cycle: 30 minutes ON followed by 30 minutes OFF, repeating continuously.

If we observe this flashlight from Earth, we would see a strange pattern: it appears to stay OFF for 41 minutes, then ON for only 19 minutes, then OFF for 41 minutes again, and so on.

When the light shuts off on Io, the photons from the previous 11 minutes are still traveling and will keep hitting Earth for 11 more minutes. So it still looks like a 30 minute ON period to the observer.

Let's say you were blind and could only know my position on a football field by me throwing a tennis ball and you feeling which direction it came from. I'm always fifty yards away and the ball always takes five seconds to reach you. So, from due north, I throw the ball, while I'm running a circle around you every sixty seconds. Ok. So after five seconds you are struck by the ball and determine, "That came from due north." But I am traveling around you at a rate of 6°/sec. So I am actually (5x6=) 30° off due north, when you register my position as due north. IOW, information always has a finite speed in reaching you.

6 hours ago, jalaldn said:

Suppose we set up a flashlight on the io that blinks in a regular cycle: 30 minutes ON followed by 30 minutes OFF, repeating continuously.

If we observe this flashlight from Earth, we would see a strange pattern: it appears to stay OFF for 41 minutes, then ON for only 19 minutes, then OFF for 41 minutes again, and so on.

How would you explain this distorted timing using the concept of light-travel delay?

As others have also pointed out, that is not what we would see. Leaving aside the complication of what would happen when Io passed behind Jupiter, we would see the light on for 30mins and then off for 30 mins.

You have still not explained what you mean by real time.

6 hours ago, jalaldn said:

How would you explain this distorted timing using the concept of light-travel delay?

Light travels at a finite time, when an object reflects light at a certain distance it will take certain time to reach us on earth, when it is further away it will take longer.

When the light shuts off on Io, the photons from the previous 11 minutes are still traveling and will keep hitting Earth for 11 more minutes. So it still looks like a 30 minute ON period to the observer.

Let's say you were blind and could only know my position on a football field by me throwing a tennis ball and you feeling which direction it came from. I'm always fifty yards away and the ball always takes five seconds to reach you. So, from due north, I throw the ball, while I'm running a circle around you every sixty seconds. Ok. So after five seconds you are struck by the ball and determine, "That came from due north." But I am traveling around you at a rate of 6°/sec. So I am actually (5x6=) 30° off due north, when you register my position as due north. IOW, information always has a finite speed in reaching you.

I can guess what all of you haven’t understood. If it doesn’t click for you immediately, there’s no mistake—it’s the very same thing that nobody understood for 350 years.

If light had the properties you think it has, Ole Rømer would never have had any chance to measure its speed.

Let me give an example with balls: Imagine you’re inside a room, and right above your head there’s a hole through which balls fall into a basket via a pipe.

You’re inside the room. You tell your friend outside: “Throw a ball in every five minutes. The distance is up to you, but once you start throwing, don’t change your position.”

You, inside the room, will see a ball arrive exactly every five minutes. Just from that, can you tell how far away he was when he sent the balls?

Let’s look at it from another angle: You throw 10 balls toward me. If I tell you that the first four balls never reached me—they vanished on the way—how would that feel? That’s exactly what those eleven minutes are.

In this place, something about the nature of light is unable to reach us; something else has reached us instead. It is up to us to separate them.

Edited November 24Nov 24 by jalaldn

2 hours ago, jalaldn said:

If light had the properties you think it has, Ole Rømer would never have had any chance to measure its speed.

He had a chance to do his measurement precisely because light has the properties we know it does.

2 hours ago, jalaldn said:

Throw a ball in every five minutes. The distance is up to you, but once you start throwing, don’t change your position.

But that’s precisely what he did not do. He measured the relative differences in Io’s timings at different points of the Earth’s orbit, and thus inferred a finite speed starting from differences in distance to Jupiter. Changes in position are the whole point of this setup.

6 hours ago, jalaldn said:

I can guess what all of you haven’t understood. If it doesn’t click for you immediately, there’s no mistake—it’s the very same thing that nobody understood for 350 years.

If light had the properties you think it has, Ole Rømer would never have had any chance to measure its speed.

Let me give an example with balls: Imagine you’re inside a room, and right above your head there’s a hole through which balls fall into a basket via a pipe.

You’re inside the room. You tell your friend outside: “Throw a ball in every five minutes. The distance is up to you, but once you start throwing, don’t change your position.”

You, inside the room, will see a ball arrive exactly every five minutes. Just from that, can you tell how far away he was when he sent the balls?

Let’s look at it from another angle: You throw 10 balls toward me. If I tell you that the first four balls never reached me—they vanished on the way—how would that feel? That’s exactly what those eleven minutes are.

In this place, something about the nature of light is unable to reach us; something else has reached us instead. It is up to us to separate them.

If the thrower drops 2 balls 5 mins apart when he is next to the hole, then sure, you will time them as arriving 5minutes apart. But if he then moves 50 metres away to throw the next one, you will note that the 3rd ball arrives slightly more than 5 minutes after the previous one. And if he then returns to his position next to the hole before dropping the 4th one, you will note that the interval between arrival of the 3rd and 4th balls is slightly less than 5 minutes. The differences are caused by the time of flight of the ball when it is thrown from a distance.

What Rømer observed was the difference in timing of occultation of Io, depending on whether the Earth was at its closest to Jupiter or at its furthest away. He correctly attributed this difference to differences in the time of flight of the light, according to the variation in the distance it had to cover between Io and the Earth.

It takes Io 1.77 Earth days (42 hours 29 minutes) or 2,548.8 minutes to complete one orbit around Jupiter.

If Earth is close to Jupiter, Io will be occulted for an average of 2 hours and 10 minutes.

If Earth is far from Jupiter, it will be occulted for up to 2 hours and 20 minutes.

When Jupiter and Neptune are on opposite sides of the Sun, Io will be occulted for 6 hours and 15 minutes when viewed from Neptune.

During those four hours and 10minuts, what happens to the sunlight that normally falls on Io?

26 minutes ago, jalaldn said:

It takes Io 1.77 Earth days (42 hours 29 minutes) or 2,548.8 minutes to complete one orbit around Jupiter.

If Earth is close to Jupiter, Io will be occulted for an average of 2 hours and 10 minutes.

If Earth is far from Jupiter, it will be occulted for up to 2 hours and 20 minutes.

When Jupiter and Neptune are on opposite sides of the Sun, Io will be occulted for 6 hours and 15 minutes when viewed from Neptune.

During those four hours and 10minuts, what happens to the sunlight that normally falls on Io?

Surely it is occulted for the same duration, regardless of the distance from Earth?

Where are you getting your information from?

It is the intervals between occultations that vary.

Edited November 24Nov 24 by exchemist

31 minutes ago, jalaldn said:

During those four hours and 10minuts, what happens to the sunlight that normally falls on Io?

It's not 'really' there, if you can see this post... ☠️

Surely it is occulted for the same time, regardless of the distance from Earth?

Where are you getting your information from?

Ole Romer's study also says the same thing.

He says that io was hidden for 11 minutes in addition to crossing the diameter of our Earth's orbit.

Edited November 24Nov 24 by jalaldn

1 hour ago, exchemist said:

Surely it is occulted for the same duration, regardless of the distance from Earth?

Angle would be different, so the arc it has to travel will be different, but they might have the numbers backward. (or wrong)

2 hours ago, jalaldn said:

It takes Io 1.77 Earth days (42 hours 29 minutes) or 2,548.8 minutes to complete one orbit around Jupiter.

If Earth is close to Jupiter, Io will be occulted for an average of 2 hours and 10 minutes.

If Earth is far from Jupiter, it will be occulted for up to 2 hours and 20 minutes.

When Jupiter and Neptune are on opposite sides of the Sun, Io will be occulted for 6 hours and 15 minutes when viewed from Neptune.

During those four hours and 10minuts, what happens to the sunlight that normally falls on Io?

Not sure where 4:10 comes from, but when it’s occulted as viewed from the sun, the sunlight is blocked by Jupiter. When occulted as viewed from earth, the sunlight may or may not be hitting it; that depends on where the sun is. We can’t see it because Jupiter is opaque. It will absorb or reflect light and we can’t see things behind it, like with any planet. Light reflected by Io doesn’t pass through it.

10 hours ago, jalaldn said:

You’re inside the room. You tell your friend outside: “Throw a ball in every five minutes. The distance is up to you, but once you start throwing, don’t change your position.”

I’m not sure why you think this is relevant, since the salient issue is that the distance does change.

Throw the balls, but vary the distance. You notice the first ball arrives at 12:00 and the next one at 12:05, then 12:10, so you confirm the 5-minute interval. Then he moves, but launches them on the same schedule. The ball you expect at 1:00 shows up at 1:01. If you know the change in distance you can determine the speed of the ball.

The ball took a minute to travel the additional distance

Angle would be different, so the arc it has to travel will be different, but they might have the numbers backward. (or wrong)

Not sure where 4:10 comes from, but when it’s occulted as viewed from the sun, the sunlight is blocked by Jupiter. When occulted as viewed from earth, the sunlight may or may not be hitting it; that depends on where the sun is. We can’t see it because Jupiter is opaque. It will absorb or reflect light and we can’t see things behind it, like with any planet. Light reflected by Io doesn’t pass through it.

Io takes two hours to pass behind Jupiter. After that, all the remaining occulted times depend on the distance.

That is, when Jupiter and Earth are close together, Io will be hidden by Jupiter for two hours. After those two hours, when Io comes out, it will be occulted again for about ten minutes (when there is nothing between Io and Earth), depending on the distance.

Moreover, when Jupiter and Earth are very far apart, Io will be hidden by Jupiter for two hours, and additionally for about 20 minutes when there is nothing between Earth and Io.

If we were perhaps watching from Neptune, Io would be hidden by Jupiter for two hours, and the remaining 4 hours would be occulted depending on the distance.

5 minutes ago, jalaldn said:

Io takes two hours to pass behind Jupiter. After that, all the remaining occulted times depend on the distance.

That is, when Jupiter and Earth are close together, Io will be hidden by Jupiter for two hours. After those two hours, when Io comes out, it will be occulted again for about ten minutes (when there is nothing between Io and Earth), depending on the distance.

Moreover, when Jupiter and Earth are very far apart, Io will be hidden by Jupiter for two hours, and additionally for about 20 minutes when there is nothing between Earth and Io.

If we were perhaps watching from Neptune, Io would be hidden by Jupiter for two hours, and the remaining 4 hours would be occulted depending on the distance.

What you leave out, though, is that we continue to see Io for about 10 minutes after it has actually been occulted, due to light already in transit after occultation starts.

Edited November 24Nov 24 by exchemist

What you leave out, though, is that we continue to see Io for about 10 minutes after it has actually been occulted, due to light already in transit after occultation starts.

It takes Io 1.77 Earth days (42 hours 29 minutes) or 2,548.8 minutes to complete one orbit around Jupiter.

We know where Io is in these 2,548.8 minutes, including being behind Jupiter. Those minutes that disappeared after coming out are lost and will never be get again.

According to the Wikipedia article, "Rømer's determination of the speed of light", it wasn't the occultation of Io that was used for the time measurements, but the eclipse of Io by Jupiter's shadow. And it was both immersion, when Io suddenly disappears into Jupiter's shadow, and emergence, when Io suddenly reappears from Jupiter's shadow, that was used (immersion and emergence cannot be observed from Earth for the same eclipse because one or the other will be hidden by Jupiter).

28 minutes ago, jalaldn said:

It takes Io 1.77 Earth days (42 hours 29 minutes) or 2,548.8 minutes to complete one orbit around Jupiter.

We know where Io is in these 2,548.8 minutes, including being behind Jupiter. Those minutes that disappeared after coming out are lost and will never be get again.

Whut?

12 hours ago, jalaldn said:

I can guess what all of you haven’t understood. If it doesn’t click for you immediately, there’s no mistake—it’s the very same thing that nobody understood for 350 years.

I think your description of light and of Ole Rømer’s observations deviates significantly from the established sources. Could you explain what personal idea or hypothesis you are pursuing that leads you to this different interpretation?

Whut?

Ask an AI to confirm the truth.

2 minutes ago, jalaldn said:

Ask an AI to confirm the truth.

That’s what an idiot would do.

On 11/22/2025 at 8:26 PM, swansont said:

This isn’t an issue.

Thanks!
(I incorrectly assumed a connection to the fact that immersion and the emergence cannot be observed for the same eclipse of Io)

That’s what an idiot would do.

There's nothing wrong with using AI to confirm whether the event I'm telling you is false or not.

1 hour ago, jalaldn said:

Io takes two hours to pass behind Jupiter. After that, all the remaining occulted times depend on the distance.

That is, when Jupiter and Earth are close together, Io will be hidden by Jupiter for two hours. After those two hours, when Io comes out, it will be occulted again for about ten minutes (when there is nothing between Io and Earth), depending on the distance.

Moreover, when Jupiter and Earth are very far apart, Io will be hidden by Jupiter for two hours, and additionally for about 20 minutes when there is nothing between Earth and Io.

If we were perhaps watching from Neptune, Io would be hidden by Jupiter for two hours, and the remaining 4 hours would be occulted depending on the distance.

This suggests it’s based on your preposterous misunderstanding of the situation and not on actual observation. IOW, you’re just making it up.

32 minutes ago, KJW said:

According to the Wikipedia article, "Rømer's determination of the speed of light", it wasn't the occultation of Io that was used for the time measurements, but the eclipse of Io by Jupiter's shadow. And it was both immersion, when Io suddenly disappears into Jupiter's shadow, and emergence, when Io suddenly reappears from Jupiter's shadow, that was used (immersion and emergence cannot be observed from Earth for the same eclipse because one or the other will be hidden by Jupiter).

Interesting detail, but I think the gross misconceptions on display are unrelated to this.

38 minutes ago, jalaldn said:

There's nothing wrong with using AI to confirm whether the event I'm telling you is false or not.

LLMs are not reliable sources of information

One misconception on display is that somehow we’re seeing distant things as they are right now, which is contradicted by mounds of evidence. Distant stars might not be there anymore, as we see them, as they could have gone supernova in the years it takes for light to get to us. We routinely have to account for delays for various electromagnetic signals. You can detect where a break in a fiber-optic cable is using a time-delay reflectometer (important for telling you which manhole is closest to there you need to go to do repairs). GPS receivers work by assessing the difference in the timing of signals from satellites so you can find your location by trilateration. All of this is being ignored with the fixation on this one set of observations.

1 hour ago, jalaldn said:

There's nothing wrong with using AI to confirm whether the event I'm telling you is false or not.

Yes there is. LLMs are programmed to tell you what you want to hear. You can get an initial idea from them but to confirm something you need to go behind the AI and get to the references it is relying on.