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Old 11th September 2019, 02:49 PM   #1
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First Exo-Planet with water!

https://www.space.com/alien-planet-k...arth-twin.html

Water vapour has been detected in the atmosphere of a super-Earth with habitable temperatures by UCL researchers in a world first.

K2-18b, which is eight times the mass of Earth, is now the only planet orbiting a star outside the Solar System, or 'exoplanet', known to have both water and temperatures that could support life.

Sadly we aren't going to be visiting anytime soon, first off, it's about 8x as massive as Earth, and second, it's 111 light years away.
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Old 11th September 2019, 04:47 PM   #2
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Eight times, Yikes. I thought it was only twice the size of Earth.

I hope we get new data soon. Could be fun stuff.
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Old 11th September 2019, 07:25 PM   #3
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Originally Posted by Skeptic Ginger View Post
Eight times, Yikes. I thought it was only twice the size of Earth.

I hope we get new data soon. Could be fun stuff.
If it's twice the diameter, that implies eight times the mass. Two cubed, and all that. Your density may vary.
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Old 11th September 2019, 09:10 PM   #4
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Originally Posted by Skeptic Ginger View Post
Eight times, Yikes. I thought it was only twice the size of Earth.

I hope we get new data soon. Could be fun stuff.
Originally Posted by Trebuchet View Post
If it's twice the diameter, that implies eight times the mass. Two cubed, and all that. Your density may vary.
Yep

The formula for the volume of a sphere is 4/3πr3

Double the diameter of a sphere, and the volume goes up by 8 times

10m diameter sphere = 524 m3
20m diameter sphere = 4188 m3
40m diameter sphere = 33510 m3


When you start cubing stuff, the numbers get very big, real quick!
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Old 11th September 2019, 09:27 PM   #5
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Dibs!
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Old 11th September 2019, 11:59 PM   #6
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I wonder what life would look like if it evolved there.
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Old 12th September 2019, 02:47 AM   #7
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Originally Posted by Cheetah View Post
I wonder what life would look like if it evolved there.
Flat?
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Old 12th September 2019, 02:56 AM   #8
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Originally Posted by smartcooky View Post
Flat?

Not Oceanic Life.
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Old 12th September 2019, 02:57 AM   #9
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If it's twice the diameter, 8 times the mass, and (big if) the same average density of earth, then the surface gravity would be twice that of earth. If gravitational compression has reduced its radius and increased its density, then the surface gravity would be higher.

Last edited by BillC; 12th September 2019 at 03:00 AM. Reason: oops
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Old 12th September 2019, 02:59 AM   #10
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Originally Posted by Cheetah View Post
I wonder what life would look like if it evolved there.
What does the life that evolved on earth "look like"? It varies a bit. There are petunias and there are kangaroos. The life on the other planet may look something like these.

But I would love to see alien living organisms. To my mind, whether or not life exists elsewhere is by far the most interesting outstanding mystery.
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Old 12th September 2019, 03:02 AM   #11
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Originally Posted by smartcooky View Post
When you start cubing stuff, the numbers get very big, real quick!
Yes, this is true, but each increase puts you further way from the centre of gravity, which obeys an inverse square law. For objects of equal density, surface gravity varies in proportion with radius.
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Old 12th September 2019, 04:10 AM   #12
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Originally Posted by smartcooky View Post
Yep

The formula for the volume of a sphere is 4/3πr3

Double the diameter of a sphere, and the volume goes up by 8 times

10m diameter sphere = 524 m3
20m diameter sphere = 4188 m3
40m diameter sphere = 33510 m3


When you start cubing stuff, the numbers get very big, real quick!
This is why a 3L bottle of Coke doesn't look much bigger than a 2L bottle of Coke.
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Old 12th September 2019, 04:15 AM   #13
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Something that is absent, understandably, from press reports on the subject is how they detected the water.

Are they sure? It's my understanding that exoplanets are detected by noting periodic variations in starlight as planets occlude their suns. How would this method allow you to determine the chemical composition of the planet and its atmosphere?
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Old 12th September 2019, 04:32 AM   #14
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Originally Posted by Craig B View Post
What does the life that evolved on earth "look like"? It varies a bit. There are petunias and there are kangaroos. The life on the other planet may look something like these.

But I would love to see alien living organisms. To my mind, whether or not life exists elsewhere is by far the most interesting outstanding mystery.
I think if there is complex life there is a lot you could speculate about, for example.

Carbon based.
Probably uses the same 20 amino acids as here if not all of them.
Something very similar to DNA & RNA if not exactly.
Made of cells.

If there are free swimming animals:
Bodyplan basically a tube with a mouth on one end and a pooper on the other.
Bilaterally symmetrical.
There is a lot more stuff like this.


Certain things just work better and it's likely evolution and chemistry will solve similar problems in similar ways.
I think it's quite likely alien 'fish' in similar niches to earth fish might look superficially very similar. Having a streamlined body with a flat tail on one end, to propel itself forward, and a mouth on the other end is just the best design.
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Old 12th September 2019, 05:07 AM   #15
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Originally Posted by Cheetah View Post
Probably uses the same 20 amino acids as here if not all of them.
That is excessively unlikely.

There are over 100 amino acids, I think. That any one set of carbon-based life would use the same combination we use is very very improbable. That's the main reason why we know that all life on Earth today descends from the same unique cell.
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Old 12th September 2019, 05:39 AM   #16
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Originally Posted by Belz... View Post
That is excessively unlikely.

There are over 100 amino acids, I think. That any one set of carbon-based life would use the same combination we use is very very improbable. That's the main reason why we know that all life on Earth today descends from the same unique cell.

They are not equal though. A whole mix was available and life 'chose' a few. Amino acids need to link together to form peptide chains to form more complex structures. Some amino acids form chains more readily and more efficiently. The best ones were selected for.


Why does all life use the same 20 amino acids?
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Old 12th September 2019, 06:30 AM   #17
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Originally Posted by Meadmaker View Post
Something that is absent, understandably, from press reports on the subject is how they detected the water.

Are they sure? It's my understanding that exoplanets are detected by noting periodic variations in starlight as planets occlude their suns. How would this method allow you to determine the chemical composition of the planet and its atmosphere?
They looked at the star light as the planet passed in front of the star and noted what absorption was occurring, because water and other chemicals absorb certain parts of the spectrum. Water has a very distinctive absorption in the IR part of the spectrum, so by looking at the light before and comparing it to that as the planet passes, if you see the absorption of those frequencies in the IR part of the spectrum, then you can say that the starlight had to pass through water, and the only source of that water is the planet.
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Old 12th September 2019, 10:08 AM   #18
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Originally Posted by Cheetah View Post
I wonder what life would look like if it evolved there.
Wet.
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Old 12th September 2019, 10:17 AM   #19
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Tastes remarkably like chicken.
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Old 12th September 2019, 10:43 AM   #20
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I didn't see mentioned ... would not the gravity of that planet preclude humans settling there ... could a landing party leave the planet (due to the increased escape velocity needed)

Realistically even a small increase in gravity, would cause a human's blood to pool in the legs, creating numerous medical problems.
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Old 12th September 2019, 11:20 AM   #21
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EARTH TO WATERWORLD:

"Prepare to be squished under the almighty heel of Earth's jack fins!!"
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Old 12th September 2019, 11:25 AM   #22
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Let me know when they find the first exo-planet with beer.
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Old 12th September 2019, 11:31 AM   #23
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Originally Posted by Cheetah View Post
I wonder what life would look like if it evolved there.
Underwater octopus-like.

Poor things never had a chance with fire.
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Old 12th September 2019, 11:41 AM   #24
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Almost everyday now a wild ass fantasy science fiction story of my youth hits the headlines as something brand new in the sight of Man.

You want to know about this world? Read Mission of Gravity the science fiction novel by American writer Hal Clement. The novel was serialized in Astounding Science Fiction magazine in April–July 1953. (per our friends at Wiki -- https://en.wikipedia.org/wiki/Mission_of_Gravity )

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Old 12th September 2019, 11:46 AM   #25
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Originally Posted by BillC View Post
If it's twice the diameter, 8 times the mass, and (big if) the same average density of earth, then the surface gravity would be twice that of earth. If gravitational compression has reduced its radius and increased its density, then the surface gravity would be higher.
I looked at the paper, and the density they derived was ~ 3.3 g/cm3. Earth's is ~ 5.5 g/cm3. My quick calcs showed a surface gravity of ~ 1.5 x Earth's. Not so bad if you evolved there.
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Old 12th September 2019, 11:48 AM   #26
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Originally Posted by Cheetah View Post
I wonder what life would look like if it evolved there.
Maybe like an entire world of Amazon Warrior Mermaids wearing svelte form fitting Neoprene™ ready to enslave all Earth men for the purpose of copulating with them!
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Old 12th September 2019, 12:51 PM   #27
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Originally Posted by Cheetah View Post
I think if there is complex life there is a lot you
Certain things just work better and it's likely evolution and chemistry will solve similar problems in similar ways.
I think it's quite likely alien 'fish' in similar niches to earth fish might look superficially very similar. Having a streamlined body with a flat tail on one end, to propel itself forward, and a mouth on the other end is just the best design.
Covergent evolution, I agree. Life finds a way, and that way seems to be whatever is the easiest solution.

When I was a child I was absolutely fascinated (and still am) by how strikingly similar in form and function many species of ichthyosaurs and modern cetaceans are despite how far removed they are from one another genetically.
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Old 12th September 2019, 08:35 PM   #28
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Scott Manley has done a YouTube on the subject https://www.youtube.com/watch?v=OG38Ei8R_08

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The water is in the atmosphere. The surface could be too hot for liquid water to exist.
It was detected by the absorption lines of the light that goes though the atmosphere.
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Old 12th September 2019, 09:38 PM   #29
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They detected water vapour in the atmosphere. And the planet is in the habitable zone in which liquid water can exist. But water is a greenhouse gas, and there could be other greenhouse gases in it's atmosphere. Venus has water vapour in it's atmosphere (0.002%) and is in the habitable zone, but there's certainly no liquid water on Venus' surface.

I'm not suggesting that there isn't liquid water on this planet, only that because we don't know the full composition and density of it's atmosphere it's premature to conclude that it has liquid water. Still, this is an exciting finding!
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Old 12th September 2019, 11:01 PM   #30
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Originally Posted by Cheetah View Post
I think if there is complex life there is a lot you could speculate about, for example.

Carbon based.
Probably uses the same 20 amino acids as here if not all of them.
Something very similar to DNA & RNA if not exactly.
Made of cells.

If there are free swimming animals:
Bodyplan basically a tube with a mouth on one end and a pooper on the other.
Bilaterally symmetrical.
There is a lot more stuff like this.


Certain things just work better and it's likely evolution and chemistry will solve similar problems in similar ways.
I think it's quite likely alien 'fish' in similar niches to earth fish might look superficially very similar. Having a streamlined body with a flat tail on one end, to propel itself forward, and a mouth on the other end is just the best design.
Basically, I agree with your thinking here.

Life is fundamentally just chemistry; complex chemistry for sure but chemistry nonetheless. Also, evolution and environment are inter-relational - if the environment of this planet was similar to that of the Earth at the equivalent time after its formation, then it seems logical to me that the chemical reaction known as abiogenesis might result in similar chemical reactions. Life on such a planet, at least at the microscopic level could be very similar to that on the Earth.
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Old 12th September 2019, 11:32 PM   #31
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If it has oceans and temperatures comparable to earth, the higher mass might not be a problem for fish-like creatures in the oceans. If there is also land, there could be land-based creatures adapted to the higher G.

Still hoping we find something closer to earth, but 111 light years is relatively close, on the galactic scale. The radius of the Milky Way is about 50,000 light years, so it's in our neighborhood, but not next door.
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Old 12th September 2019, 11:41 PM   #32
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Originally Posted by Gord_in_Toronto View Post
Almost everyday now a wild ass fantasy science fiction story of my youth hits the headlines as something brand new in the sight of Man.

You want to know about this world? Read Mission of Gravity the science fiction novel by American writer Hal Clement. The novel was serialized in Astounding Science Fiction magazine in April–July 1953. (per our friends at Wiki -- https://en.wikipedia.org/wiki/Mission_of_Gravity )

Quote:
The story is set on a highly oblate planet named Mesklin, which has surface gravity that varies between 700 g at the poles and 3 g at the equator.
That doesn't seem possible to me. There's a reason why the larger the planet, the closer to a sphere it becomes.
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Old 13th September 2019, 12:31 AM   #33
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Originally Posted by Puppycow View Post
That doesn't seem possible to me. There's a reason why the larger the planet, the closer to a sphere it becomes.
Saturn is more oblate than Earth.
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Old 13th September 2019, 12:36 AM   #34
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Originally Posted by sphenisc View Post
Saturn is more oblate than Earth.
Well, I stand corrected. I still doubt that a planet like the one in that story would be found in nature.
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Old 13th September 2019, 12:45 AM   #35
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Originally Posted by sphenisc View Post
Saturn is more oblate than Earth.
Saturn is like that because it spins rapidly. Once an object gets big enough (and that size is smaller than the moon) it is round and the main deformity would be due to spin. A planet going around the sun as close as this one would probably be tidally locked. If there was life on the planet it would be confined to a ring where the sun was low on the horizon.
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Old 13th September 2019, 02:25 AM   #36
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Originally Posted by rjh01 View Post
Saturn is like that because it spins rapidly. Once an object gets big enough (and that size is smaller than the moon) it is round and the main deformity would be due to spin. A planet going around the sun as close as this one would probably be tidally locked. If there was life on the planet it would be confined to a ring where the sun was low on the horizon.
I agree with you, though there was this in the article linked in the OP:

Quote:
The alien planet may therefore be "tidally locked" to its star, always showing the red dwarf the same face, just as Earth's moon only ever shows its near side to us. But this would not be a dealbreaker for the existence of life.

"A tidally locked planet can also be habitable," said Ingo Waldmann of CSED, a member of Tsiaras' team. Modeling studies suggest that "the energy from the dayside can be quite equally distributed to the nightside," Waldmann added.
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Old 13th September 2019, 04:25 AM   #37
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Originally Posted by Roboramma View Post
I agree with you, though there was this in the article linked in the OP:
I wonder if plants could grow without sunlight in the dark side? Come to think of it plant life would be a struggle if the sun is low in the sky and emits mainly in the infrared. Not much energy would get to the ground.
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Old 13th September 2019, 04:43 AM   #38
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Originally Posted by Craig B View Post
What does the life that evolved on earth "look like"? It varies a bit. There are petunias and there are kangaroos. The life on the other planet may look something like these.

But I would love to see alien living organisms. To my mind, whether or not life exists elsewhere is by far the most interesting outstanding mystery.
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Old 13th September 2019, 03:38 PM   #39
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Originally Posted by PhantomWolf View Post
They looked at the star light as the planet passed in front of the star and noted what absorption was occurring, because water and other chemicals absorb certain parts of the spectrum. Water has a very distinctive absorption in the IR part of the spectrum, so by looking at the light before and comparing it to that as the planet passes, if you see the absorption of those frequencies in the IR part of the spectrum, then you can say that the starlight had to pass through water, and the only source of that water is the planet.
The fact that they can do this is simply amazing.

Suppose that the planet is marginally Earth-like. Earth is a big rock, surrounded by a little envelope of gas, a small portion of which is water. You can't take a picture of the planet, but as the planet passes in front of the star, the light from the star gets a little bit dimmer. How much dimmer depends on the size of the rock. So, they can measure that change in brightness, and figure that if the star is getting dimmer at periodic intervals, there must be a planet passing in front of it. Now, to detect the water, they have to say that specific components of the starlight are dimmed by a small fraction of the size of the gas envelope surrounding the rock, which is partially transparent to some light, but less transparent to other light.

And from that they can figure out that there's an atmosphere with water.

It's pretty amazing stuff, really.

I must admit that as I see reports of really strange configurations of planets being discovered, especially if there are really huge planets with very short orbits, I have to wonder if there might be some other explanations for the periodicity of light shifts, and I wonder just how clear the light shifts really are. If you were to plot out successive light measurements on a graph, would it really be obvious that there were periodic changes in intensity, or is this the sort of thing that can only be sorted out by taking Fourier transforms and picking out the relevant frequencies, which are too faint to be noticed by humans looking at a chart?

I'm not expecting answers to that, by the way. I assume that these guys check each others' math and that regardless of how they are doing it, it's pretty clear that there are planets. I'm just marveling that it's possible.
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Old 13th September 2019, 04:24 PM   #40
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Originally Posted by Meadmaker View Post
I must admit that as I see reports of really strange configurations of planets being discovered, especially if there are really huge planets with very short orbits, I have to wonder if there might be some other explanations for the periodicity of light shifts, and I wonder just how clear the light shifts really are. If you were to plot out successive light measurements on a graph, would it really be obvious that there were periodic changes in intensity, or is this the sort of thing that can only be sorted out by taking Fourier transforms and picking out the relevant frequencies, which are too faint to be noticed by humans looking at a chart?

I'm not expecting answers to that, by the way. I assume that these guys check each others' math and that regardless of how they are doing it, it's pretty clear that there are planets. I'm just marveling that it's possible.

Here is some information about Kepler 37, which has at least four planets orbiting it. Light curves for three are shown.

https://www.researchgate.net/figure/...fig1_235681889

Kepler 37b is not very obvious without the resultant curve shown, but 37c and 37d are very obvious.


NOTE: Don't be confused by the notations - the chart marked "a" is 37b, "b" is 37c, and "c" is 37d.
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