Pub Quiz Question

[Space Oddity6]

So I just got back from a pub quiz (which we somehow won ) and got the question: true or false, the Earth is older than the Moon.

All heads turned in my direction as I generally field the astro-questions and I thought true. My understanding is that there was an object (Earth) that was smashed into by a Mars-sized body that blew out a massive chunk of rock which formed the Moon. Surely the Earth had to be there in order to form the Moon?

The answer we gave therefore on my understanding was True but the right answer turned out to be False.

Is this wrong or would people care to enlighten me?

[Stinky_Pete]

what was the reason for it being false? If the giant impact theory is correct than the earth has to be older...unless they are suggesting that it was a proto earth (ie not THE earth as we now know it) that was hit by the big thing. IF thats the case then they have to be the same age?

[Anweniel]

I guess it depends on the model you feel has the most weight to it. To be honest none of us were present to tell the true answer. Trying to prove a theory is tricky, you may say it is far simpler to disprove a theory.

If all matter was created out of the big bang then surely everything in our universe is the same age?

If the earth was in a collision with a large object that through off material that formed the smaller moon then it could be that moon is still younger if you consider the earth may have been not entirely formed as what you may distinguish as a completed body of mass and the yet the moon came together and formed a 'final' state sooner.

Or as you suggest an Earth pretty much as we know it now lost a moon sized mass of material that got ejected from the earth as looser material that then got caught back again in its magentic field and condensed into what became the moon.

In short I dont think we know, it could be very simple or very complex and a matter of opinion, I would say same age based on the assumption that matter is neither created nor destroyed so both always existed since the dawn of time just in a different form

[philhas]

Apparently rock samples bought back by Apollo 17 are 4.5 Billion years old, the oldest rocks on Earth being aged at 3.5 billion years so it would appear the Moon could be older than the earth. I guess it boils down to how the rocks got on the Moon as other rocks sampled have been 3.5 to 4 billion years old.

[JamesF]

I'm not sure the question is even answerable without defining how you are going to measure age and define the point in history at which, for the purposes of the question, you decide that the earth is, well, the earth (which may well give away the answer to the question). I'd say your answer is correct if you're comparing how long a "blob of accreted matter" that we now know as the earth has existed compared with the moon, for exactly the reasons you say. I believe however that there are rocks on the moon that are older than the earliest datings for rocks on the earth. Saying the moon is older for that reason seems pretty poor logic though. They could, I guess, be considered the same age if you decided that the earth didn't actually exist until the time of the collision when it gained all that extra mass and threw out the matter that became the moon, but I'm unconvinced by that line of reasoning as well.

James

[Black Knight]

Apparently rock samples bought back by Apollo 17 are 4.5 Billion years old, the oldest rocks on Earth being aged at 3.5 billion years so it would appear the Moon could be older than the earth. I guess it boils down to how the rocks got on the Moon as other rocks sampled have been 3.5 to 4 billion years old.

Doesn't that have more to do with the Earth having an active geological system though? Most of the ancient rock on Earth would probably have been recycled several times by now. That's how I understand it anyway ... but then I'm not a geologist .

Isn't this one of the reasons space science wants to visit asteroids? I.e. to sample and investigate rock as old as the solar system, since we are unable to do that on earth because the geology has continually renewed itself.

[philhas]

Doesn't that have more to do with the Earth having an active geological system though? Most of the ancient rock on Earth would probably have been recycled several times by now. That's how I understand it anyway ... but then I'm not a geologist .

Possibly, Apollo 17's mission was to actually sample rock from the lunar highlands which was thought to be a region of volcanic activity on the Moon. It would appear strange that in all the time we have looked at the geology of the Earth not a single rock has been found to be older than 3.5 million years old. One of the great mysteries of the solar system I guess, there is loads of speculation however it's probably a question which will never be answered but from a purely scientific point of view which is provable the rocks on the Moon are older than the rocks on the Earth

[philhas]

And its amazing how a pub quiz can spark such healthy debate!

[Black Knight]

One of the great mysteries of the solar system I guess, there is loads of speculation however it's probably a question which will never be answered but from a purely scientific point of view which is provable the rocks on the Moon are older than the rocks on the Earth

TBH, I don't know it if really is a mystery. Earth is the only solar system body so far known with a system of plate tectonics (possibly triggered in the first place by a massive asteroidal/proto-planet impact), which continually recycles rock. So in many ways, perhaps it's not surprising we haven't found rocks on Earth that pre-date those found on the moon.

[banner001]

Possibly, Apollo 17's mission was to actually sample rock from the lunar highlands which was thought to be a region of volcanic activity on the Moon. It would appear strange that in all the time we have looked at the geology of the Earth not a single rock has been found to be older than 3.5 million years old. One of the great mysteries of the solar system I guess, there is loads of speculation however it's probably a question which will never be answered but from a purely scientific point of view which is provable the rocks on the Moon are older than the rocks on the Earth

not to be too blunt, but you are wrong, the USGS has samples from 4.6 billion years IIRC? i know that there are stromolites (bacterial mounds) that date from 3.5 billion years ago, and there had to be something here, cool and solid for them to grow on

as for the recycling, radiometric dating is not affected, thats why if you measure "fresh" magma it looks billions of years old, because its constituent radiochemical ratios are very old, its just that its only now bubbling to the surface. K-Ar dating i always remember having a half life of ~1 billion years, i think thats pretty widely used for geological time scales, also there must be some uranium dating methods as well.

as for the quiz, all methods for the formation of the moon IIRC involve a collision, i would therefore say that the two would be of equal age, maybe the smaller moon could have gained hydrostatic equilibrium quicker due to its smaller size?

[johninderby]

Rocks recently found in Western Australia (zircons from the Jack Hills) have been dated to 4.04 billion years old so there's not much difference betwen that and the 4.5 billion year old moon rocks.

John

[banner001]

The age of the Earth in the twentieth century: a problem (mostly) solved

there we go ~4.54 Ga (billion years), always good to find a paper

[philhas]

So going back to the pub quiz..........is the Moon older than the Earth!

[philhas]

Rocks recently found in Western Australia (zircons from the Jack Hills) have been dated to 4.04 billion years old so there's not much difference betwen that and the 4.5 billion year old moon rocks.

John

They also state "The source rocks for these zircon crystals have not yet been found"

[philhas]

The age of the Earth in the twentieth century: a problem (mostly) solved

there we go ~4.54 Ga (billion years), always good to find a paper

Interesting stuff, one thing to consider is only a small sample of rocks have been taken from the Moon. There is nothing to suggest even older rocks could not be present Lets keep this debate rolling!

[philhas]

not to be too blunt,

And don't worry about being blunt, I am here to learn.

[Space Oddity6]

I think to correspond to the correct answer according to the quiz, I'd have to agree with Anweniel in that the Earth before the Moon creating collision wasn't the Earth, just a celestial body.

Which takes us down another road; if we're saying the Earth was not the Earth until the collision, that means that the collision is the birth of the Earth as we know it, allowing for the development of life. Depending on the time between the pre-Earth's coming together as a body, and the collision, could there have been life or would pre-Earth have just been molten rock and dust - Venus-like? Could the collision that made the Moon (and the Earth as we know it) have been another life-extinguishing event?

This is getting very complicated and deep lol!

[philhas]

I think to correspond to the correct answer according to the quiz, I'd have to agree with Anweniel in that the Earth before the Moon creating collision wasn't the Earth, just a celestial body.

Which takes us down another road; if we're saying the Earth was not the Earth until the collision, that means that the collision is the birth of the Earth as we know it, allowing for the development of life. Depending on the time between the pre-Earth's coming together as a body, and the collision, could there have been life or would pre-Earth have just been molten rock and dust - Venus-like? Could the collision that made the Moon (and the Earth as we know it) have been another life-extinguishing event?

This is getting very complicated and deep lol!

Look what you started!

[banner001]

And don't worry about being blunt, I am here to learn.

im not normally blunt but after 12 hours in the lab irradiating myself with radioactive phosphorous-32 i am kind of tired and could not think of a better way to start the sentence

[philhas]

im not normally blunt but after 12 hours in the lab irradiating myself with radioactive phosphorous-32 i am kind of tired and could not think of a better way to start the sentence

No problem you put me right, 12 hours in a lab sounds like hard work to me.

[banner001]

No problem you put me right, 12 hours in a lab sounds like hard work to me.

12 hours a day, 60-hours a week, i wish i was paid by the hour and not on a salary

[Axe]

Earth is older.

[Nexus 6]

Good thread! I did think they were roughly the same age from what I've seen on tv and read.

Maybe we should do a poll with this one and see what comes out on top?

[stolenfeather]

Very interesting post since I would have answered the question exactly the same way being TRUE. I have to agree with Alan on this one. A poll would be very interesting!

Isabelle

[Shibby]

I would have answered True and got 0 points. Then I'd be irritated about the ambiguous quiz question for the rest of the evening!