# Math Is Fun Forum

Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

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## #1 2014-11-29 14:45:39

mathaholic
Member
From: Earth
Registered: 2012-11-29
Posts: 3,251

### When would the eight planets line up?

If you have a theory or calculation about the title, you may do so here.

My current hypothesis:
Mercury
Revolution period: 0.24 Earth Years (87.97 Earth Days)
Venus
Revolution period: 224.7 Earth days
Mars
Revolution period: 686.93 Earth days
Jupiter
Revolution period: 11.86 Earth years
Saturn
Revolution period: 29.46 Earth years
Uranus
Revolution period: 83.75 Earth years
Neptune
Revolution period: 163.72 Earth years
Earth
Revolution period: 365.26 Earth Days

Could it be every 1 340 185 years 122 days 17 hours 59 minutes 16 seconds 800 milliseconds?

Long, right?

Mathaholic | 10th most active poster | Maker of the 350,000th post | Person | rrr's classmate

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## #2 2014-11-29 20:59:44

Bob
Registered: 2010-06-20
Posts: 9,299

### Re: When would the eight planets line up?

Right idea.  But how 'picky' are you about lining up.  The orbital planes do not quite coincide*, so an exact alignment would be so rare it probably won't happen in the expected lifetime of the solar system.

*  This is why a transit of the Sun by Venus doesn't happen as often as once per orbit.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

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## #3 2014-11-29 21:00:18

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: When would the eight planets line up?

Hi;

I did this calculation, or tried to. It is very difficult.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #4 2014-11-30 13:46:17

ShivamS
Member
Registered: 2011-02-07
Posts: 3,648

### Re: When would the eight planets line up?

They never line up perfectly. Planetary alignment does occur but it usually is between 3 or so planets with a discrepancy of around 30 degrees. The last time all planets came in an alignment of 30 degrees was in, I believe, 500. The next time should be around 2800. Each such alignment occurs every 500 years and there is usually a 30% chance of it being aligned within 30 degrees.

Last edited by ShivamS (2014-11-30 13:50:02)

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## #5 2014-11-30 20:12:26

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,965
Website

### Re: When would the eight planets line up?

bobbym wrote:

Hi;

I did this calculation, or tried to. It is very difficult.

Why?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #6 2014-11-30 20:19:02

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: When would the eight planets line up?

There was a book by a Dutch astronomer that showed the equations. I was doing it my own way and I think Chaos theory showed up.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #7 2014-11-30 20:22:44

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,965
Website

### Re: When would the eight planets line up?

What is wrong with julian's calculation?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #8 2014-11-30 20:23:30

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: When would the eight planets line up?

Try it out.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #9 2014-11-30 20:34:15

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,965
Website

### Re: When would the eight planets line up?

What?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #10 2014-11-30 20:37:10

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: When would the eight planets line up?

Do you see what I mean?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #11 2014-11-30 20:43:05

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,965
Website

### Re: When would the eight planets line up?

No but I suspect you will relate it to EM

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #12 2014-11-30 20:45:50

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: When would the eight planets line up?

Chaos is the enemy of numerical methods. We call it error analysis. Anyway, I failed to solve it for 3 planets. But it was a slightly different problem and that might make all the difference.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #13 2014-12-07 12:32:13

mathaholic
Member
From: Earth
Registered: 2012-11-29
Posts: 3,251

### Re: When would the eight planets line up?

I have searched about February 4 1962. This such alignment of six planets will happen every 97 years 270 days 13 hours 59 minutes 13 seconds 499.75 milliseconds. So, the next alignment is November 1 2059 at around afternoon in our time (Philippines). So, Americans are so lucky to enjoy the view of February 4 1962. And, I will be a 55-year old who would be blind already.

Last edited by mathaholic (2014-12-07 12:33:38)

Mathaholic | 10th most active poster | Maker of the 350,000th post | Person | rrr's classmate

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