[modera]

I do not understand why people can predict when lunar eclipse or solar eclipse happen. What method do they use to predict?

[Dr David Thork]

They use the Saros cycle. A repeating pattern that tells you when the next eclipse will happen. Earth doesn't need to be round for that and no round earth maths are used.

Saros Cycle

[SteelyBob]

They use the Saros cycle. A repeating pattern that tells you when the next eclipse will happen. Earth doesn't need to be round for that and no round earth maths are used.

Saros Cycle

How would you go about predicting the start of a Saros series?

[Dr David Thork]

They use the Saros cycle. A repeating pattern that tells you when the next eclipse will happen. Earth doesn't need to be round for that and no round earth maths are used.

Saros Cycle

How would you go about predicting the start of a Saros series?

I don't need to. The Babylonians have already done it for me.

It is a repeating pattern. If I get an eclipse over London ... I know in 6585.3211 days I'm going to get a near identical one. Job done.

[modera]

They use the Saros cycle. A repeating pattern that tells you when the next eclipse will happen. Earth doesn't need to be round for that and no round earth maths are used.

Saros Cycle

How would you go about predicting the start of a Saros series?

I don't need to. The Babylonians have already done it for me.

It is a repeating pattern. If I get an eclipse over London ... I know in 6585.3211 days I'm going to get a near identical one. Job done.

Do you refer to lunar eclipse or solar eclipse?

[Iceman]

Maybe click the link he gave you?

[modera]

Maybe click the link he gave you?

From this website, it says 91 years.
https://www.rmg.co.uk/stories/topics/eclipses
Solar Eclipses in the UK
Last UK total solar eclipse
11 August 1999
Next UK total solar eclipse
23 September 2090

[SteelyBob]

They use the Saros cycle. A repeating pattern that tells you when the next eclipse will happen. Earth doesn't need to be round for that and no round earth maths are used.

Saros Cycle

How would you go about predicting the start of a Saros series?

I don't need to. The Babylonians have already done it for me.

It is a repeating pattern. If I get an eclipse over London ... I know in 6585.3211 days I'm going to get a near identical one. Job done.

Sort of, but not quite.

Solar eclipses are not visible in the same location after one Saros period - they shift by 8 hours, or 120 degrees of longitude, so if your London eclipse was solar, you'd have to travel 8 hours west to see the next one from that cycle. So if you wait three full cycles the eclipse will be back where it started, roughly speaking. Lunar eclipses are different - if the moon remains above the horizon, then a lunar eclipse will be visible from the same location after the next cycle. That's all in the link you provided us with.

There are, however, many active Saros cycles at any one time. This website says it's 40 at present - sounds about right - https://www.solar-eclipse.info/en/saros/.
The reason that the next total solar eclipse in London is out of sync with the Saros period (see Modera's post) is because Saros cycles include both partial and total eclipses, so the previous and next total eclipses at the same location aren't necessarily from the same series. The last total London eclipse was from series 145, whereas the next one is from series 155, hence the 91 year gap.

The next problem you have is that cycles are finite - they begin and end. So, if your eclipse in London was the last of a cycle, you won't have one anywhere on the planet from that series in one Saros' time. We therefore need some way of calculating when cycles will begin and end. To make things worse, there is no discernible pattern to them - whilst the period between eclipses in any series is roughly constant, the total number and type of eclipses in each series (partial or total) vary significantly, meaning the frequency of eclipses at any one time varies - unless you know all the active cycles, you can't say when the next eclipse anywhere on earth will be. So you need to be able to predict series starts and ends.

NASA, and other RE believers, use solar and lunar ephemerides derived from orbital models, using various levels of sophistication (the NASA website cites the VSOP87 model for the sun and the ELP-2000/82 for the moon, but plenty of others are out there, all with varying strengths and weaknesses) to predict eclipses and Saros series with remarkable accuracy.

So, my question again: how would you go about calculating the start of a new Saros cycle? Or indeed the end of a current one? 

[Dr David Thork]

NASA, and other RE believers, use solar and lunar ephemerides derived from orbital models, using various levels of sophistication (the NASA website cites the VSOP87 model for the sun and the ELP-2000/82 for the moon, but plenty of others are out there, all with varying strengths and weaknesses) to predict eclipses and Saros series with remarkable accuracy.

Total horse manure.
https://en.wikipedia.org/wiki/March_1504_lunar_eclipse#:~:text=Christopher%20Columbus%2C%20in%20an%20effort,29%20February%20in%20the%20Americas).
^No NASA. Just used historical tables ... from which you can determine the cycles. That's it. No round earth voodoo going on. 

So, my question again: how would you go about calculating the start of a new Saros cycle? Or indeed the end of a current one?

There is no start or end. They are perpetual. One after another after another. They began when God said "let there be light" and they'll stop when God declares the end of the world.

[SteelyBob]

NASA, and other RE believers, use solar and lunar ephemerides derived from orbital models, using various levels of sophistication (the NASA website cites the VSOP87 model for the sun and the ELP-2000/82 for the moon, but plenty of others are out there, all with varying strengths and weaknesses) to predict eclipses and Saros series with remarkable accuracy.

Total horse manure.
https://en.wikipedia.org/wiki/March_1504_lunar_eclipse#:~:text=Christopher%20Columbus%2C%20in%20an%20effort,29%20February%20in%20the%20Americas).
^No NASA. Just used historical tables ... from which you can determine the cycles. That's it. No round earth voodoo going on. 

So, my question again: how would you go about calculating the start of a new Saros cycle? Or indeed the end of a current one?

There is no start or end. They are perpetual. One after another after another. They began when God said "let there be light" and they'll stop when God declares the end of the world.

Follow your own link. Note the box on the side where it says 'Saros cycle 105, 53 of 74'. Click on that link. Note how that cycle began in 566AD and ended in 1864. How would you have worked that out from your ancient tables?

Are you suggesting that there aren't multiple saros series active at any one time?

[Dr David Thork]

Well when the one in 566 appeared I'd remark ... whoa ... a new cycle. This must be the start of one. 

There is no round earth NASA maths involved in following these patterns. Its not that complicated and hardly proves the earth isn't flat.

[Tumeni]

Saros might tell you when, but tells you nothing about where, how long, how the speed of the eclipse shadow varies over different areas of the planet, how wide the path of totality will be, how much less of the eclipse you will see if not on the path of totality, etc. etc.

This all fits in with globe mechanics.

[Dr David Thork]

Saros might tell you when, but tells you nothing about where, how long, how the speed of the eclipse shadow varies over different areas of the planet, how wide the path of totality will be, how much less of the eclipse you will see if not on the path of totality, etc. etc.

This all fits in with globe mechanics.

Prove it. Predict the next eclipse with your magic maths. No tables. Use magic NASA maths to predict the next eclipse. I trust they somehow solved the 3 body problem and didn't tell anybody. 



Its all done with tables.

[SteelyBob]

Saros might tell you when, but tells you nothing about where, how long, how the speed of the eclipse shadow varies over different areas of the planet, how wide the path of totality will be, how much less of the eclipse you will see if not on the path of totality, etc. etc.

This all fits in with globe mechanics.

Prove it. Predict the next eclipse with your magic maths. No tables. Use magic NASA maths to predict the next eclipse. I trust they somehow solved the 3 body problem and didn't tell anybody. 


Its all done with tables.

You don't have to analytically solve the 3 body problem, or indeed the n-body problem, in order to model it numerically. That's equally true of numerous partial differential equation problems - it's true, for example, of turbulent, compressible airflow over an aircraft wing. We can't solve the equations, but we can model the flow well enough to make good aircraft. As I said above, the NASA website Saros cycles are derived from a couple of ephemeris models, the basis of which are published and well reviewed. You can drill into a wide range of ephemeris models online - there's even some on GitHub which you can see the code for and play with yourself. There's no smoke or mirrors, or indeed hidden tables.

Well when the one in 566 appeared I'd remark ... whoa ... a new cycle. This must be the start of one. 

There is no round earth NASA maths involved in following these patterns. Its not that complicated and hardly proves the earth isn't flat.

That sounds very much like you've changed your position - well done - so you now accept that there isn't just one series of Saros-period separated cycles of eclipses, but rather multiple series that have finite and variable durations.

But the problem then is: if it's all done with tables, which table would have predicted, for example, the first eclipse from Saros series 156 on 1 July 2011, or could predict the start of the next new series, 157, on 21 June 2058? The start of 156 did not come as a surprise to anybody - it was predicted well in advance. I'm pretty confident that 157 will start as advertised as well, although I may not be around to verify it.

Again, NASA did it and does it with ephemeris data for the positions of the earth, moon and sun - they rinse through the data and look for occasions when the 3 line up and accurately predict position, time and nature of each eclipse.

[Tumeni]

Predict the next eclipse with your magic maths. No tables. Use magic NASA maths to predict the next eclipse. I trust they somehow solved the 3 body problem and didn't tell anybody.  Its all done with tables.

Already done, most recently for the Great American Eclipse, where the eclipse path tracked from Oregon to ... Louisiana, I think.

It was all there in the lead-up, predicted down to the last detail, with hosts of diagrams and page upon page of text telling the public what to expect. You could see how the speed of the shadow varied according to which part of the globe it was hitting. How the fall-off occurred for those outwith the path of totality. Etc etc

Far more detail than simply predicted a date in a calendar.

[Dr David Thork]

You're all saying the same thing.

You BELIEVE NASA has cracked the maths. You're not interested in looking at the maths. You've no idea what the maths entails or how it works. But you're convinced it exists and must therefore, despite not solving the n body problem, do so based on round earth maths and definitely not tables but you won't show me a shred of evidence to back your point.

Now I showed you proof you can predict eclipses with the saros cycle. I showed the Columbus historical example. We're all good for a way to predict if the earth is flat. You are trying to say there is no way to accurately do this unless you assume the earth is round ... but not one of you will show how or present evidence. Just saying "It has been done by NASA" isn't going to cut it, I'm afraid. NASA tell lies.

[Tumeni]

You BELIEVE NASA has cracked the maths. You're not interested in looking at the maths. You've no idea what the maths entails or how it works. But you're convinced it exists ...

Because the predictions all came true, in every respect.

Not a single person reported that the Great American Eclipse did not occur, nor that it differed in any significant way from what was predicted.

It was all laid out in advance. "Go here, at this time, this is what you will see, this is how long it will last".

And that's what happened. Didn't it?

As an aside, I've been through a big chunk of the maths and geometry involved. When the whole "the eclipse shadow is moving the wrong way" thing came up, I worked through it and satisfied myself it was moving the right way, and that NASA was not lying about this.

Look at the time intervals shown here, and how the eclipse shadow covers less surface distance in the middle of its transit, and more toward the outer edges; this variance is totally consistent with the shadow, moving in a linear fashion across the part of space occupied by the Earth, varying in speed across the surface of the Earth due to the global shape.

[Dr David Thork]

You're not giving me anything a saros cycle chart wouldn't.

[Tumeni]

You're not giving me anything a saros cycle chart wouldn't.

Show us how the Saros cycle would have predicted the change in length of the shadow's ground path in the 10mins between 17.00 to 17.10, and 18.20 to 18.30.

Or how the Saros cycle shows the location from which to view.

[SteelyBob]

You're not giving me anything a saros cycle chart wouldn't.

Still waiting for you to explain how you would use a saros cycle chart to predict the start of a new saros series, like the one I mentioned in 2011, or the one that hasn’t happened yet in 2058.