What do you think is the best Planet/Moon for human colonization?

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IG2007

"Don't criticize what you can't understand..."
Apr 5, 2020
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One point I don't think has been mentioned. Given an emergency (asteroid strike) type situation, how much fuel -- how many ships -- are available on Earth to ferry humans to Mars (or wherever)? I think you are looking at a "two by two" into the Ark situation with many not very happy about being left behind.

Cat :)
I think we don't need to do that in an asteroid attack. We can just send two or three rockets to go to the asteroid and use their gravity (no matter how small a rocket is, it always has a gravity and that is enough) to change the path of the asteroid.
 
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Jun 1, 2020
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I think we don't need to do that in an asteroid attack. We can just send two or three rockets to go to the asteroid and use their gravity (no matter how small a rocket is, it always has a gravity and that is enough) to change the path of the asteroid.
Yes, it was two astronauts (Lu and Love) that presented their "tractor beam" (spacecraft gravity) idea. [Here (2005)]

I'm guessing that the larger, and more dangerous, asteroids may, ironically, be better for diverting since they would be found much sooner than the little suckers.
 
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Catastrophe

The devil is in the detail
Feb 18, 2020
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Helio

Eeeeeeek! Something the size of Titan might be seen far off, but how are you going to divert that?

OK That is at the large end of the size scale, but how about a 6 mile diameter object? Can you divert that?

Cat :)

This is what I had in mind:

The Chicxulub impactor had an estimated diameter of 11–81 kilometers (6.8–50.3 mi), and delivered an estimated energy of 21–921 billion Hiroshima A-bombs (between 1.3×1024 and 5.8×1025 joules, or 1.3–58 yottajoules).
 
Jun 1, 2020
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Helio

Eeeeeeek! Something the size of Titan might be seen far off, but how are you going to divert that?

OK That is at the large end of the size scale, but how about a 6 mile diameter object? Can you divert that?
Yes, that's the right kind of question I had in mind. The HST has found KBOs down to at least 30 mile diameter objects, so at that distance, I assume we would have ample time to get there and alter its trajectory. [The smaller size in your example would not be that much closer than KBO distances.]

But I'm not sure if there is a sweet spot as to when size helps us. Size will increase its visibility as the square of diameter, but the mass increases as the cube.

My guess is that size helps us more than we think. For instance, if we double the diameter of an object coming our way, we would be able to detect it twice as far out since distance works as the inverse square. But, and this is where it counts I think, the more distant objects will likely give us more than double the time as one 1/2 the distance since the extra distance will likely have much slower speeds.
 
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Catastrophe

The devil is in the detail
Feb 18, 2020
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Helio, just checking. Do I understand that the Chicxulub object would be no problem now? Cat :) :) :)

To KEEP THIS ON TRACK we are, of course, considering a safe future home as far as possible from impact dangers.
 
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Jun 1, 2020
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A simple equation is likely, IMO, as to our ability to respond favorably in altering trajectories.

I suspect the lead times to get a space tractor out to any object, once discovered, plus the early, albeit smaller, trajectory shift will favor the larger objects.
 
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Catastrophe

The devil is in the detail
Feb 18, 2020
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Helio, are not these objects normally (from opposite, rather than slow bump) travelling very quickly? We have to see them, prepare, and then get there - during which time they might still be approaching us very quickly. Is there really time for all this "saving manoeuvre"?

Cat :)
 
Jun 1, 2020
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Helio, are not these objects normally (from opposite, rather than slow bump) travelling very quickly? We have to see them, prepare, and then get there - during which time they might still be approaching us very quickly. Is there really time for all this "saving manoeuvre"?
Yes, but we have to both catch it early (detection) and have a "tractor" ready to roll in a reasonable amount of time.

The response time and travel time (and braking) are critical to any tractor efforts. Hence the larger object might be easier to alter, assuming earlier detection, than a small object. I'm only guessing.
 

Catastrophe

The devil is in the detail
Feb 18, 2020
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Helio, you know me. I am not argumentative but I can be a terrier on factual matters. My only REAL question is whether or not we could cope with any "object" prospective impact. Correction, can we now?

Cat :)
 
May 1, 2021
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Hmmm. You would need robots of greater intelligence than their makers. Don't forget, even at the nearest star, it will take about 4.3 years for you to receive a message from a robot asking how to act, and another 4.3 years for your advice to get back. The robot would be faced with situations of which we have no knowledge and thus have greater ability to act in unprogrammed situations - hence greater intelligence - which, of course, we would be unable to provide. Problems.

Cat :)
Robots already do some things better than we do, but I'm referring to advanced robots that can act on their own. The way AI is evolving, I see no reason why robots can't be smarter than we are by the end of the century.

An advanced species could have mastered communication via entangled particles, which apparently can communicate instantly with each other no matter where they are in space-time. Of course, I'm getting way ahead of our capabilities, but in a million years, we could be communicating with our robots or with other species on other planets many light years away as quickly as if we were face to face.
 

Catastrophe

The devil is in the detail
Feb 18, 2020
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"Of course, I'm getting way ahead of our capabilities, but in a million years, we could be communicating with our robots or with other species on other planets many light years away as quickly as if we were face to face."

Anything could happen in a million years, but in 100 years, we (humans) might be history.

Cat :)
 
Jun 1, 2020
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Would you bet your life on "suspect" and "guess"?
The "guess" part only means I'm too lazy to get serious about any math. :) I don't mind doing it since the math is very easy, but the physics (establishing all the physical restraints) is something I would have to be given.

P.S. Do you need tractors ready for all sizes and also options stony v iron?
I will continue guessing, I guess. ;) It would depend on the risk assessment for future incoming objects. If, somehow, we could determine the next, say, 20 years, of impact risks, then if warranted, perhaps one rocket to serve all needs is the best approach if few are coming. If many are coming, then it would be wiser to have several so that it would cost less for the little objects, and multiple units could go for larger ones, thus giving a back-up capability to the tractor fleet.

Given SpaceX and other's going to and fro in that time frame, we could perhaps divert their activity, with reasonable notice, to assist in the tractor efforts.

The guessing is clearly too great but the above may make more clear why we need to know what's out there and where it's going. Once we can establish the real risks, then we won't have to guess as much. :)
 
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Catastrophe

The devil is in the detail
Feb 18, 2020
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Helio, I commend your confidence. You have a clear idea about the dangers and the need for keeping a good look out for problems.
I have to differ only in the fact (imho) that there may be asteroids out there that are larger than we can cope with. One thing (amongst many) that worries me is the speed of approaching asteroids (or comets) compared with the speed it takes to reach them - even if we are ready to blast off immediately on recognition of imminent danger. And then there is slowing and stopping when we get there, and preparation (which hopefully is almost nil). And all the time this asteroid is approaching at "break Earth" speed.
Hopefully the "out of the Sun" problem is being solved by satellites further from Earth, but 360 degrees of space in 3 dimensions is a lot to cover. I seem to remember one recently coming in over a polar orbit.
I sincerely hope that you are right on all counts. Anyway, my greater worries are about survival long enough to worry about asteroids.

Cat :) :)
 
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Jun 1, 2020
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I have to differ only in the fact (imho) that there may be asteroids out there that are larger than we can cope with. One thing (amongst many) that worries me is the speed of approaching asteroids (or comets) compared with the speed it takes to reach them - even if we are ready to blast off immediately on recognition of imminent danger. And then there is slowing and stopping when we get there, and preparation (which hopefully is almost nil). And all the time this asteroid is approaching at "break Earth" speed.
I agree. We don't seem to have any plan to address the future threat. I would bet that the cataloging in recent years of all the major objects, along with the on-going work for smaller objects, has brought less immediate concerns. But given that a future threating impact is inevitable, likely far in time from now, some prep is wise.

[I like your "break Earth" speed term. :)]
 
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Catastrophe

The devil is in the detail
Feb 18, 2020
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"[I like your "break Earth" speed term. :)]" Thank you :) :)

For any not conversant with the idiom, my idea was based on the English term "breakneck" speed, which means very fast and probably recklessly. The breakEarth part of the pun is, I think, obvious.

Cat :)
 

Catastrophe

The devil is in the detail
Feb 18, 2020
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Helio, "We don't seem to have any plan to address the future threat." I agree.

What we have not discussed is the question of comets dislodged from the Oort Cloud. This has been postulated as a real threat when Earth passes through the galactic plane every 26-30 million years or so. It has been correlated with extinctions. There is a slight variation, but I don't think they mentioned the irregularities of matter in the galactic plane. Some passes we might have a 'get off' because we encounter less extraneous material. (A few passes have reduced corresponding disaster).

These comets are 'one offs' : they can come in at highly irregular angles : they may be difficult to identify and calculate orbit : their orbits speed up as they reach the inner Solar System. Trouble!

Cat :)
 
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What we have not discussed is the question of comets dislodged from the Oort Cloud.
Yes, if there are a trillion plus objects up there, then any percentage that fall is probably too many.

The free fall time ranges, per my calc., from 177,000 years (10k AU) to 2.6 million years (60k AU). Of course, an impulse on Oort objects would shorten the time.

But most I assume would have orbital perihelion distances far greater than 1 AU, so maybe (not that I know) such an event would be manageable in a not too distant future given our improving space faring progress.

These comets are 'one offs' : they can come in at highly irregular angles : they may be difficult to identify and calculate orbit : their orbits speed up as they reach the inner Solar System. Trouble!
It would be interesting to learn what the pros and cons are to observing incoming Oort objects. Will they have high albedos and with early tails, given that this would likely be their first pass toward Sol?
 
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Catastrophe

The devil is in the detail
Feb 18, 2020
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Has anyone seen calculations resolving momentum. Simple momemtum A and momentum B resolved to show change of direction vis a vis Earth impact?

Two items:

Point 1
In Newtonian mechanics, linear momentum, translational momentum, or simply momentum (pl. momenta) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If m is an object's mass and v is its velocity (also a vector quantity), then the object's momentum is:
{\displaystyle \mathbf {p} =m\mathbf {v} .}
In SI units, momentum is measured in kilogram meters per second (kgm/s).

Point 2
Application to collisions

By itself, the law of conservation of momentum is not enough to determine the motion of particles after a collision. Another property of the motion, kinetic energy, must be known. This is not necessarily conserved. If it is conserved, the collision is called an elastic collision; if not, it is an inelastic collision.
 
Nov 2, 2020
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Hmmm. You would need robots of greater intelligence than their makers. Don't forget, even at the nearest star, it will take about 4.3 years for you to receive a message from a robot asking how to act, and another 4.3 years for your advice to get back. The robot would be faced with situations of which we have no knowledge and thus have greater ability to act in unprogrammed situations - hence greater intelligence - which, of course, we would be unable to provide. Problems.

Cat :)
Hi Cat,
Imagine what would happen if aliens found us, instead of us finding them. This would be beautiful since I think that the more advanced a society is, the more clement it is (of course, our story surely doesn't teach us this, but I think the reason why this happen is because times aren't mature enough...)
Anyways, in this case in the round of ten years we would evolve in a society of the far future!
Of course, this is a little fantasy :tearsofjoy:
 
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May 3, 2021
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But how long does it take to get there? Just check this out.

Assuming (very reasonably) that you will have to travel at only a fraction of light speed, remember the fuel to accelerate and, what is more, if you want to stop when you get there, the fuel to decelerate.
Light speed is 6.706e+8 ( 186,000 x 60 x 60 = 6.696 x 10^8 ) miles per hour
The nearest star is approx 4.3 light years away, or 4.3 x 6,000,000,000,000 or approx 25.8 x 10^13 miles.

Thus 4.3 light years at 1% speed of light would take 25.8 x 10^13 divided by 6.7 x 10^6 or 3.85 x 10^7 hours, or 1.6 x 10^6 days or 4383.56 years. Of course, getting up to speed and slowing down would add to the time, but I think we can probably neglect these. They probably amount to only a few hundred years. Remember we have shown elsewhere that light sails are out.
Any other ideas?

Cat :)
the Alcubierre warp drive ship. It warps time and space to allow itself to go 10x the speed of light.
 
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