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[Maximum Spin]

(passim)

Your proposal is kind of incomprehensible, but I get the feeling you seem to think that releasing methane would be good for the possible life on Mars? Which is actually the opposite of the case, if methane is being produced as a waste molecule – that would be like saying that humans release CO₂, so filling a room with CO₂ would make conditions better for the humans in it.

[Egan_BW]

I don't know, fellow human, that sounds like sound reasoning to me! Obviously we should release more CO2, which us humans totally can breathe. After all, it has oxygen in it!
*Plants roots into floor*

[Madman198237]

I didn't have time to respond yesterday.

Reelya, did you SERIOUSLY attempt to say that by attempting to generate drag from something moving WITH the planet, we could somehow change the planet's rotation?


That is not how the laws of physics work.

[Gentlefish]

There are a few huge problems with carbon-dating on Mars.

First, Carbon dating is only meaningful to around 50,000 years. Carbon-14 decays, so really old samples won't have meaningful amounts of it.

Second, Carbon-14 is made when a neutron hits Nitrogen-13. And Mar's atmosphere lacks the nitrogen we expect on Earth. So Carbon dating on Earth relies on the fact that stray Neutrons are bombarding Nitrogen atoms and replenishing the Carbon-14 in the atmosphere at a reasonably steady rate, while carbon locked in a dead organism retains only the Carbon-14 which it had at the time of death, and which slowly decays.

Third, we'd need calibration tables for the Carbon-14 concentrations in the air going back thousands of years, which we usually get from ice-cores in places like Antarctica.

Hence, the technique can't really be generalized to Mars, or to times long ago. At least not with Carbon dating as we know it.

I gotta challenge this on at least one point. Adding a neutron to Nitrogen-13 makes it Nitrogen-14. You'd need to add a proton to N-13 to make it C-13 and then a neutron to C-13 to make it C-14

[Maximum Spin]

Nah man, Z(N) > Z(C). You *remove* a proton from N-14 (and replace it with a neutron) to get C-14. Which, as it happens, is what happens when you bombard N-14 with a fast enough neutron.

ETA: Incidentally, because C-14 decays back to N-14 through beta emission, if you can moderate the speed of the leaving particles (say with an electric field) this is basically a sustainable way to convert high-energy neutrons into hydrogen. If you wanted to do that for some reason.

[Culise]

Nitrogen has one more proton than carbon: Nitrogen is atomic number 7; carbon atomic number 6.  Oxygen is the next atomic number up from nitrogen: adding a proton to ¹³N would result in an isotope of oxygen (at a guess, typically ¹³O, which is unstable and typically decays to ¹³N, or ¹²O which decays to either ¹¹N or ¹⁰C judging by this).  Carbon-14 is formed when a neutron strikes nitrogen-14, which results in carbon-14 and a free proton.  I assume that Reelya's comment that ¹⁴C comes from ¹³N is a typo, as 3 is next to 4. 

EDIT:
Ah, as is asserted more succinctly above.  Though, I'd add the caveat that it doesn't even need to be a fast neutron: a simple thermal neutron seems to be enough to pop the proton right off.  Epithermal on up to fast and ultrafast neutrons are not necessarily going to be absorbed as easily, oddly enough, which is why nuclear moderators are so important in certain fission reactors.  Slowing down the neutrons allows them to be more easily captured, continuing the reaction. 

[smjjames]

There are a few huge problems with carbon-dating on Mars.

First, Carbon dating is only meaningful to around 50,000 years. Carbon-14 decays, so really old samples won't have meaningful amounts of it.

Second, Carbon-14 is made when a neutron hits Nitrogen-13. And Mar's atmosphere lacks the nitrogen we expect on Earth. So Carbon dating on Earth relies on the fact that stray Neutrons are bombarding Nitrogen atoms and replenishing the Carbon-14 in the atmosphere at a reasonably steady rate, while carbon locked in a dead organism retains only the Carbon-14 which it had at the time of death, and which slowly decays.

Third, we'd need calibration tables for the Carbon-14 concentrations in the air going back thousands of years, which we usually get from ice-cores in places like Antarctica.

Hence, the technique can't really be generalized to Mars, or to times long ago. At least not with Carbon dating as we know it.

I gotta challenge this on at least one point. Adding a neutron to Nitrogen-13 makes it Nitrogen-14. You'd need to add a proton to N-13 to make it C-13 and then a neutron to C-13 to make it C-14

Wouldn't messing with the isotopes screw up the very thing you're trying to measure? At the very least, you wouldn't be absolutely sure that it's truly accurate due to messing with it.

There's other methods of chronologically dating rocks that should work just fine on Mars, we might develop a few methods that work specifically on Mars.

[Gentlefish]

Wow I was backwards thanks for correcting me guys.

[Reelya]

I didn't have time to respond yesterday.

Reelya, did you SERIOUSLY attempt to say that by attempting to generate drag from something moving WITH the planet, we could somehow change the planet's rotation?


That is not how the laws of physics work.

Friction does slow rotation. That's how tidal effects work. Friction is an energy transfer.

think about it this way, particles only want to move in straight lines. If a smooth planet was spinning with zero friction with the air, the atmosphere wouldn't rotate at all, it would stay in the same spot. The only way for the atmosphere to actually rotate with the planet is to be dragged around by a combination of friction with the ground and gravity.

So the energy for the atmosphere to move with the Earth in fact comes from the friction with the Earth. It's not "rotating" around the Earth by itself, because that's not how physics works.

[Maximum Spin]

Ah, as is asserted more succinctly above.  Though, I'd add the caveat that it doesn't even need to be a fast neutron: a simple thermal neutron seems to be enough to pop the proton right off.  Epithermal on up to fast and ultrafast neutrons are not necessarily going to be absorbed as easily, oddly enough, which is why nuclear moderators are so important in certain fission reactors.  Slowing down the neutrons allows them to be more easily captured, continuing the reaction.

Yeah, I meant that in a colloquial sense - as in "sufficiently energetic". Not necessarily literally a fast neutron, just one that's warm enough.

ETA:

Friction does slow rotation. That's how tidal effects work. Friction is an energy transfer.

think about it this way, objects in the atmosphere are slowed by friction with the atmosphere, you can't do geo-synced orbit in the atmosphere, drag still slows you down. If a bit of ground sticks up, then it's not immune to that just because it's connected to the ground.

It's the solid Earth that's spinning, free moving matter like air only wants to move in a straight line. It's not spinning with the Earth, because that's not how molecules move.

No. Sorry.

Okay, first. "Free moving matter like air" still feels gravity. Straight lines from the perspective of the air molecules are in fact curving toward Earth. In a sense, you might say that the atmosphere is orbiting the Earth, though it isn't in a stable orbit.

The atmosphere is moving along with the same speed as the Earth's surface (near the surface). This is why you do not feel a constant East wind. If something on the surface were moving more slowly than that, air drag would *speed it up* by pushing it in that direction. (In other words, it would feel a constant East wind.)

[Culise]

Ah, hence "fast enough" instead of just "fast." Sorry, I read a bit too fast, myself.  That would be my error, completely.

[smjjames]

I didn't have time to respond yesterday.

Reelya, did you SERIOUSLY attempt to say that by attempting to generate drag from something moving WITH the planet, we could somehow change the planet's rotation?


That is not how the laws of physics work.

Friction does slow rotation. That's how tidal effects work. Friction is an energy transfer.

think about it this way, objects in the atmosphere are slowed by friction with the atmosphere, you can't do geo-synced orbit in the atmosphere, drag still slows you down. If a bit of ground sticks up, then it's not immune to that just because it's connected to the ground.

It's the solid Earth that's spinning, free matter like air only wants to move in a straight line. So the atomsphere is not spinning, it's being dragged around by gravity. Adding more drag between the ground and the atmosphere will in fact slow the ground's spinning, because the ground is now pushing the air around more.

You can't geo-sync in the atmosphere ANYWAY because you're going too fast, seems a little silly to bring up attempting to geo-sync in atmosphere when you couldn't even if there was no atmosphere if you tried to orbit where the atmosphere is.

I get what you're trying to say with atmospheric drag, but the geo-syncing bit is a terrible way to explain it.

[Reelya]

Well the point as I re-edited in was that without any friction, the air would stay completely motionless around a round planet, no matter how fast the planet was spinning. It doesn't need to follow the planet.

Also, it's clearly not "orbiting" the planet by itself, because at that altitude, the orbital velocity is extremely high, much faster than the air is traveling. The air is in fact falling towards the planet (because it's below escape velocity), but being pushed sideways to maintain overall velocity.

So to maintain it's current speed around the planet, the air requires a constantly source of energy speeding it up, which comes from the rotation of the planet.

Think about a cog with teeth that's freely spinning, and there are loose stones being dragged around by the cog. If the cog has big teeth it's clearly pushing the stones around more than one with no teeth.

[smjjames]

There would actually still be movement due to heat convection, both from heat radiating from the core (though a smooth planet implies no volcanism, or a global ocean, which also works) and solar heat. See Gas Giants, though the primary driver for those in our solar system is core heat rather than solar.

But yes, you have a point as far as friction.

[Madman198237]

Here's the thing: You propose slowing down the orbit by using the "drag" inherent in the atmosphere.

Except, does the Earth get slowed down by pulling its atmosphere along?

And if it doesn't, but your hypothetical planet *would* be, why does the Earth not have 1000mph east winds as mentioned above?


It's late, so sorry if this doesn't really make sense right now. Trust me, it makes sense in my head and I'll explain it all later.