# Gravity in the solar system
**URL:** https://boards.straightdope.com/t/gravity-in-the-solar-system/744208
**Category:** Factual Questions
**Created:** [January 25, 2016, 9:39pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208 "2016-01-25T21:39:32Z")
**Posts on this page:** 20
**Page:** 2
### Author:  [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)
#### Post date: [January 26, 2016, 5:48am UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/21 "2016-01-26T05:48:36Z")
> [@Henga](#):
>
> Nobody was around when it formed, so I don’t see how anybody can know with any kind of certainty.
We know the age of the Earth from radiometric dating and a comparison the proportions of the decay of heavy elements. In 1953 Clair Patterson determined the age of the Earth to be 4.55 ± 0.07 Bya by measuring the ratios of isotopes of lead in an nickle-iron meteorite that has a composition similar to that of the Earth. (Incidentially, while trying to get good estimates for the background ratio of lead isotopes, Patterson discovered that tetraethyl lead, used as an anti-knock additive in gasoline, had resulted in massive contamination of the environment with biosoluable lead, and spent the next three decades fighting to get the problem recognized.) Many other methods using various ratios have in the current estimate of 4.54 ± 0.05 Bya, which is the value universally agreed upon by scientifically literate people.
But lets stop dancing around the question. You’re a Young Earth Creationist, aren’t you?
Stranger
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### Author:  [@Mijin](https://boards.straightdope.com/u/Mijin)
#### Post date: [January 26, 2016, 6:56am UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/22 "2016-01-26T06:56:24Z")
> [@Chronos](#):
>
> Our actual Solar System is stable, but that’s because all those planets who couldn’t play nice have already been kicked out of the club.
Technically it’s chaotic, and we can’t rule out the possibility that, for example, Mercury gets kicked out in a few hundred million years as it’s perihelion precession gets in sync with Jupiter’s.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [January 26, 2016, 7:17am UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/23 "2016-01-26T07:17:24Z")
> [@Henga](#):
>
> Nobody was around when it formed, so I don’t see how anybody can know with any kind of certainty.
You’re aware of other situations where we can work out what happened without having been there in person, right? Investigation of unwitnessed crime, for example.
It’s essentially the same principle with any sort of investigation of the past. Examine the evidence; form an explanation; use the explanation to generate statements or questions, then go looking to see if those statements are true, or those questions have an answer.
This method (the scientific method) applied repeatedly, tends toward possession of a fuller set of evidence, and a more complete explanation of what actually took place.
Absolute certainty is the province of faith, not science, but certainty is not the same thing as truth.
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### Author:  [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)
#### Post date: [January 26, 2016, 9:22am UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/24 "2016-01-26T09:22:28Z")
> [@Henga](#):
>
> Nobody was around when it formed, so I don’t see how anybody can know with any kind of certainty.
Nobody was around when dinosaurs roamed the Earth, but we’re quite certain of their existence nonetheless.
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### Author:  [@Henga](https://boards.straightdope.com/u/Henga)
#### Post date: [January 26, 2016, 11:28am UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/25 "2016-01-26T11:28:42Z")
> [@Mangetout](#):
>
> You’re aware of other situations where we can work out what happened without having been there in person, right?
That’s called speculation.
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### Author:  [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)
#### Post date: [January 26, 2016, 11:37am UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/26 "2016-01-26T11:37:25Z")
> [@Henga](#):
>
> That’s called speculation.
Not when it’s based on scientific evidence and reasoning, it isn’t. Then it’s called a theory or hypothesis.
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### Author:  [@leahcim](https://boards.straightdope.com/u/leahcim)
#### Post date: [January 26, 2016, 11:52am UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/27 "2016-01-26T11:52:15Z")
> [@Henga](#):
>
> Nobody was around when it formed, so I don’t see how anybody can know with any kind of certainty.
That is incorrect. I was there watching it, and it happened just like modern cosmology says it does.
(And since you weren’t there (I know, I was there, and I didn’t see you) you can’t contradict my assertion that I was there. Especially with speculative inferences about human lifespan and ability to survive in pre-Earth environments. After all, I was there, you weren’t.)
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### Author:  [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)
#### Post date: [January 26, 2016, 12:32pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/28 "2016-01-26T12:32:45Z")
> [@Henga](#):
>
> That’s called speculation.
Many ideas about how the natural world actually is began with speculation. You take the idea, follow it logically, ask yourself “If this is not true, what would we see” and then come up with ways to find the things which would disprove your ‘speculation.’
When you find things that disprove your speculation then you either abandon the idea or you refine it to take into account these observations and measurements.
The more different things your ‘speculation’ can explain the stronger the likelihood that it is a valid model for the observed phenomena.
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### Author:  [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)
#### Post date: [January 26, 2016, 1:11pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/29 "2016-01-26T13:11:02Z")
The numbers might be off a bit, but I once read that 99% of the mass in the solar system is in the sun, while 99% of its angular momentum is in the planets. By Henga’s criterion this is all speculative, but then I have never met her, so her existence is also speculative (remember Umkay?)
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### Author:  [@Telemark](https://boards.straightdope.com/u/Telemark)
#### Post date: [January 26, 2016, 1:27pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/30 "2016-01-26T13:27:14Z")
> [@Hari\_Seldon](#):
>
> The numbers might be off a bit, but I once read that 99% of the mass in the solar system is in the sun, while 99% of its angular momentum is in the planets.
> **[(Factsheet) Masses Of Planets In Our Solar System - Smart Conversion](https://www.smartconversion.com/factsheet/solar-system-masses-of-planets)**
>
> A comprehensive factsheet on the mass of planets in our solar system
> **[Angular momentum in the Solar system](http://www.zipcon.net/~swhite/docs/astronomy/Angular_Momentum.html)**
>
> Comparison of angular momenta in solar system components.
> [@](#):
>
> So the rotational angular momentum of the Sun, which is 1.1e42, is less than 4% that of the total orbital angular momentum of the planets, which is 3.1e43.
> Based on this calculation Jupiter’s orbital angular momentum alone accounts for over 60% of the total angular momentum of the Solar system!
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### Author:  [@scr4](https://boards.straightdope.com/u/scr4)
#### Post date: [January 26, 2016, 1:29pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/31 "2016-01-26T13:29:22Z")
> [@Henga](#):
>
> Nobody was around when it formed, so I don’t see how anybody can know with any kind of certainty.
Were around now, watching many different star systems in different stages of formation.
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### Author:  [@scr4](https://boards.straightdope.com/u/scr4)
#### Post date: [January 26, 2016, 1:30pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/32 "2016-01-26T13:30:45Z")
> [@Henga](#):
>
> What produced the Big Bang if space didn’t exist before the Big Bang? Just how did the Big Bang also produce space?
We don’t know.
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### Author:  [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)
#### Post date: [January 26, 2016, 3:23pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/33 "2016-01-26T15:23:39Z")
The Big Bang Theory isn’t set in stone, it is changed as new information comes along. There’s more that we don’t know than do know. Christians are commanded to “Love your brother as you love yourself”, the age of the Earth is strictly vanity and vexation of Spirit … worrying about it only move one away from loving, and away from God.
Rasta man told me if you interpret anything in the Bible in the flesh, you’d be wrong.
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### Author:  [@Telemark](https://boards.straightdope.com/u/Telemark)
#### Post date: [January 26, 2016, 4:12pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/34 "2016-01-26T16:12:12Z")
> [@watchwolf49](#):
>
> The Big Bang Theory isn’t set in stone, it is changed as new information comes along.
The is true of literally everything in science. It’s not a new or useful distinction to make.
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### Author:  [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)
#### Post date: [January 26, 2016, 4:19pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/35 "2016-01-26T16:19:57Z")
> [@Henga](#):
>
> That’s called speculation.
Why are you asking questions about science if you’ve decided ahead of time that you won’t accept any of the answers?
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### Author:  [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)
#### Post date: [January 26, 2016, 4:25pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/36 "2016-01-26T16:25:46Z")
> [@Henga](#):
>
> That’s called speculation.
Nobody alive today has seen George Washington with their own eyes. Is it speculation to say that he was the first President of the United States?
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### Author:  [@Lemur866](https://boards.straightdope.com/u/Lemur866)
#### Post date: [January 26, 2016, 4:52pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/37 "2016-01-26T16:52:03Z")
> [@Henga](#):
>
> What produced the Big Bang if space didn’t exist before the Big Bang? Just how did the Big Bang also produce space?
That’s a good question. The answer is that nobody knows.
Why is there something instead of nothing? A simple answer would be that if there was nothing we wouldn’t be around to ask why there was nothing. So to ask the question there has to be something that can ask the question, so there has to be something.
We don’t know why the big bang happened, or if questions like “why” even apply before time and space existed. Our ideas about how the universe works depend on the universe existing, and before the universe existed the physical laws of the universe might not apply. So it might be that there is absolutely no way for human beings to learn about the cause of the big bang, because the cause happened before cause and effect even existed.
Or to put it another way. Where did God come from? If God created the universe, who created God? Nobody created God, right? But everything has to have a cause, so why doesn’t God have a cause? Why does God exist?
Point is, if God could exist without having a cause, why couldn’t the universe exist without having a cause? I mean, if we’re postulating the existence of entities that don’t require a cause, what do we gain by naming those things “God”?
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### Author:  [@DrCube](https://boards.straightdope.com/u/DrCube)
#### Post date: [January 26, 2016, 4:53pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/38 "2016-01-26T16:53:21Z")
> [@Henga](#):
>
> If it takes the earth’s motion to counter the sun’s gravity so the earth doesn’t crash into the sun, what causes the earth’s motion if not the gravitational pull of everything else in the solar system?
All the matter that _wasn’t_ moving in such a way as to stably orbit the sun ended up falling into the sun instead.
> [@Henga](#):
>
> If the earth’s solar system is made from matter left behind by an exploding star, is the matter older than the earth itself so the earth appears to be older than it really is?
No. We can’t determine the age of atoms. We can only determine the age of things like solid rocks. The earth was molten at first, so nothing like a complete rock survived the birth of the earth intact. Some meteorites fell later, but we can tell the difference between terrestrial rocks and meteorites.
So yes, the matter _is_ older than the age of the earth, but we know how old the earth is anyway. The fact that the atoms that make up the earth are older than the earth doesn’t change anything. Like the fact that the atoms in your water once made up dinosaur pee and cave man mud puddles doesn’t change the fact that you can tell how fresh your glass of water is.
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### Author:  [@doubleminus](https://boards.straightdope.com/u/doubleminus)
#### Post date: [January 26, 2016, 5:02pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/39 "2016-01-26T17:02:57Z")
> [@Stranger\_On\_A\_Train](#):
>
> We know the age of the Earth from radiometric dating and a comparison the proportions of the decay of heavy elements. In 1953 Clair Patterson determined the age of the Earth to be 4.55 ± 0.07 Bya by measuring the ratios of isotopes of lead in an nickle-iron meteorite that has a composition similar to that of the Earth.
> Stranger
If we’re at it - I wondered for a long time - If the heavy elements were ejected from a supernova then the isotope decay started with their formation. Thus the clock didn’t start to tick when the Earth was formed but a long time before that. So how do we know so exactly the age of the Earth ?
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### Author:  [@leahcim](https://boards.straightdope.com/u/leahcim)
#### Post date: [January 26, 2016, 5:29pm UTC](https://boards.straightdope.com/t/gravity-in-the-solar-system/744208/40 "2016-01-26T17:29:11Z")
> [@doubleminus](#):
>
> If we’re at it - I wondered for a long time - If the heavy elements were ejected from a supernova then the isotope decay started with their formation. Thus the clock didn’t start to tick when the Earth was formed but a long time before that. So how do we know so exactly the age of the Earth ?
Because we have both the decaying element and the end product of the decay. Before the material was formed into rock, when Uranium (say) decayed, the resulting elements would scatter. After the material formed into rock we have a baseline. The rock is not just losing Uranium, it is gaining Lead.
(And using multiple decay chains, or abundances of intermediate steps, we can control for initial levels of lead in the rock as well).
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