Did we ever really land on the moon?

I did not dismiss the idea of extra-planetary colonization as fantasy--i did point out the Mars is not a good candidate. For the effort to have a reasonable chance of success, we'll need to start by finding a planet or other satellite the conditions of which are as near as possible to those on this planet before our arrival.

Nor have i doubted the ingenuity of the human race. However, may people seem to lose their heads when the subject of travelling among the stars comes up. Modern science fiction takes as a matter of course, in almost all examples, that the human race would overcome or somehow sidestep the celestial speed limit of 186,000+ miles per second. But matters such as the speed of light, such as cosmic radiation, such as the effects of exposure to very low gravity are matters which cannot be ignored, and for with which human ingenuity would need to come to terms--they cannot, so far as our knowledge now runs, be "overcome," or ignored.

Which takes us back to the core of my argument--how are you going to convince people to make the necessary sacrifices over many, many years, and perhaps for generations, which would be necessary to overcome the daunting obstacles, given the technology and knowledge we now have? It is of course not only plausible, but very likely that the human race will be able to overcome those obstacles . . . in the distant future.

The Portuguese monarch known as Prince Henry the Navigator began sponsoring exploratory expeditions on the coast of Africa in the 1420s--it was nearly 200 years before the Jamestown colony was established on the coast of what is now the United States--and its survival was touch and go for many, many years. The navigators of that era had largely nothing more daunting to overcome than ignorance and superstition, they had already available to them the technologies necessary to accomplish their purpose.

Sailing to and among the stars could very well require more time than that on the scale of orders of magnitude. It might (and probably would) require centuries to develop the technology and systems necessary just to begin the process. Magellan's expedition, which he did not himself survive, was launched a century after Prince Henry's expeditions, and it took three years and four weeks to complete a circumnavigation. To circumnavigate the galaxy of which we are a part would require many tens of thousands of years--it's not unreasonable at all to suggest that it would take at least hundreds of years to attempt something on that scale.

So, let me hammer, once again--distant future.

Star travel!

Humans had been only a few light seconds away from earth and we have the whole solar system yet to explore and settle.

Mars is a great planet as it has at least some water for one thing and that mean we will have O2 and rocket fuel to start with.

With the level of technology we can have in less then a century without any unforeseen breakthroughs, we could begin mining the asteroids belt and begin to turn Mars into a far better place for humans by directing a few water bearing comets to hit Mars for example.

Unless there is one hell of a breakthrough in physic the stars will need to wait.

And that's assuming our civilisation survives that long which not so many people think it will. As Set implies- it's a fantasy. The crew would get so inbred that they wouldn't know how to steer the ship or even how to wash their thermal underwear.

The interesting thing is why so many people use the fantasy. One can leave the earth listening to Mozart.

That doesn't mean the mining can best be done by manned missions.

No matter how much water you put on Mars, you still won't have a magnetic field there which can protect humans from cosmic radiation, nor would it ameliorate the problem of low gravity.

First why do you think that the low gravity going to be a great problem? Zero g cause bone loss over months but what reason do you have to assume that low g not zero g will cause problems?

Second a few feet of dirt should take care of cosmic radiation background if that is proven to be enough of a problem to be of any great concern.

For that matter with technology not all that far in the future we could generate magnetic fields to cover large surface areas assuming once more if we find we need such protection.

Solar flares off hand should prove to be of far greater matter of concern then background comic rays!

Oh you do know that the earth magnetic field had been many times stronger then it is now and it had also drop to zero from time to time as the field have reverse signs in the history of life on this planet.

As far as I am aware there had been no indication that those times of very weak to zero field strength had result in any problem for animal life on earth.

Frankly given the above facts I do not see a great problem is at all likely for settling Mars due to the lack of a magentic field.

Is the Earth's magnetic field reversing now? How do we know?
Measurements have been made of the Earth's magnetic field more or less continuously since about 1840. Some measurements even go back to the 1500s, for example at Greenwich in London. If we look at the trend in the strength of the magnetic field over this time (for example the so-called 'dipole moment' shown in the graph below) we can see a downward trend. Indeed projecting this forward in time would suggest zero dipole moment in about 1500-1600 years time. This is one reason why some people believe the field may be in the early stages of a reversal. We also know from studies of the magnetisation of minerals in ancient clay pots that the Earth's magnetic field was approximately twice as strong in Roman times as it is now.


Even so, the current strength of the magnetic field is as high as it has been in the last 50,000 years, even if it is nearly 800,000 years since the last reversal. Also, bearing in mind what we said about 'excursions' above, and knowing what we do about the properties of mathematical models of the magnetic field, it is far from clear we can easily extrapolate to 1500 years hence.

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How quickly do the poles 'flip'?
We have no complete record of the history of any reversal, so any claims we can make are mostly on the basis of mathematical models of the field behaviour and partly on limited evidence from rocks that retain an imprint of the ancient magnetic field present when they were formed. For example, the mathematical simulations seem to suggest that a full reversal may take about one to several thousand years to complete. This is fast by geological standards but slow on a human time scale.
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What happens during a reversal? What do we see at the Earth's surface?
As above, we have limited evidence from geological measurements about the patterns of change in the magnetic field during a reversal. We might expect to see, based on models of the field run on supercomputers, a far more complicated field pattern at the Earth's surface, with perhaps more than one North and South pole at any given time. We might also see the poles 'wandering' with time from their current positions towards and across the equator. The overall strength of the field, anywhere on the Earth, may be no more than a tenth of its strength now.
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Is there any danger to life?
Almost certainly not. The Earth's magnetic field is contained within a region of space, known as the magnetosphere, by the action of the solar wind. The magnetosphere deflects many, but not all, of the high-energy particles that flow from the Sun in the solar wind and from other sources in the galaxy. Sometimes the Sun is particularly active, for example when there are many sunspots, and it may send clouds of high-energy particles in the direction of the Earth. During such solar 'flares' and 'coronal mass ejections', astronauts in Earth orbit may need extra shelter to avoid higher doses of radiation. Therefore we know that the Earth's magnetic field offers only some, rather than complete, resistance to particle radiation from space. Indeed high-energy particles can actually be accelerated within the magnetosphere.
At the Earth's surface, the atmosphere acts as an extra blanket to stop all but the most energetic of the solar and galactic radiation. In the absence of a magnetic field, the atmosphere would still stop most of the radiation. Indeed the atmosphere shields us from high-energy radiation as effectively as a concrete layer some 13 feet thick.

Human beings have been on the Earth for a number of million years, during which there have been many reversals, and there is no obvious correlation between human development and reversals. Similarly, reversal patterns do not match patterns in species extinction during geological history.

Some animals, such as pigeons and whales, may use the Earth's magnetic field for direction finding. Assuming that a reversal takes a number of thousand years, that is, over many generations of each species, each animal may well adapt to the changing magnetic environment, or develop different methods of navigation.

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I'm interested in a more technical description.

If what you claim is actually fact... Where is the documented timeline to determine whether there was any life on earth at the time of this 0 gravity. How was this revelation arrived at?

If what you claim is actually fact... Where is the documented timeline to determine whether there was any life on earth at the time of this 0 gravity. How was this revelation arrived at?
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Zero gravity where did you get from my writtings that the earth had have a zero gravity field?

The earth gravity field had always been roughly equal to 32 ft/sec^2 at it surface since the earth was done forming. The only way to change a gravity field is to change the mass of the object producing it. In this case the earth.

The magnitic field of the earth is what had and is changing in both strengh and sign and there had been plenty of proof of that lock into rocks. That field is depended on current flows in the iron core at the earth center.

What kind of an education did you recieved in your life?

Intrepid I am sorry I did not wish to be mean to you. Engineers and science nerds in general tend to assume that most everyone had a similar understanding of physics and that is hardly true.

I consider giving a very short lecture on the basic forces in the universe but that is a nerd thing to do also.

Respectfully you seem not to have the background to discuss this matter of whether a lack of a magnetic field on Mars would be a problem due to the lack of shielding that a magnetic field give to comic rays or if the lower gravity force of Mars compare to Earth would cause health issues due to bone loss.

What kind do you have since your previous post was total cut and paste. Did you even understand what you had pasted?

Courtesy dictates that you include the source of your cut and paste information.

How can u convince a star to WAIT ?



David

Extremely low gravity causes bone loss and loss of muscle tissue and muscle tone over weeks of exposure, not months. Just how long do you think it would take to reach Mars? A couple of days? Reality check, Bill.

It would also be useful to keep in mind that the gravitational field of Mars exerts one third the attraction of that of the Earth. Over just a few generations, "colonists" on Mars would be producing children who could not possible survive long-term on the Earth.

The few feet of dirt to which you refer means that people cannot live on the surface of Mars--and that is a point i've already made.

Your are living in La-La Land if you think that "we find we need such protection" against cosmic radiation. We already know we need it. Solar flares are simply a dramatic increase in the radiation to which we are exposed.

Changes in the magnetic field do not alter the fact that the magnetic field of this planet protects from the long-term effects of cosmic radiation. That is exactly why i have said that we need to find a planet as much like earth as possible

Your English really sucks.

You have demonstrated quite plainly that there is precious little about these topics of which you are aware. The cut and paste job you did (without attribution) points out that the Earth's atmosphere also provides protection from cosmic radiation. Are you aware of what kind of atmosphere there is on Mars? The surface pressure of the Martian atmosphere is somewhat less than 1% of the surface pressure on the Earth. From the Wikipedia article on Mars:

Mars lost its magnetosphere 4 billion years ago, so the solar wind interacts directly with the Martian ionosphere, keeping the atmosphere thinner than it would otherwise be by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected these ionised atmospheric particles trailing off into space behind Mars. The atmosphere of Mars is now relatively thin. Atmospheric pressure on the surface varies from around 30 Pa (0.03 kPa) on Olympus Mons to over 1155 Pa (1.155 kPa) in the depths of Hellas Planitia, with a mean surface level pressure of 600 Pa (0.6 kPa). Mars's mean surface pressure equals the pressure found 35 km above the Earth's surface. This is less than 1% of the surface pressure on Earth (101.3 kPa). The scale height of the atmosphere, about 11 km, is higher than Earth's (6 km) due to the lower gravity. Mars' gravity is only about 38% of the surface gravity on Earth. (Emphasis has been added)



Fortunately for those who would colonize Mars, if such a venture is ever actually undertaken, they won't be relying upon your ability to foresee problems in order to survive.

You do not seem to have such a background, either. In fact, i suspect that despite any lack of technical knowledge, Intrepid has a better grasp of these issues in this discussion than you do.

You kidding me correct?

You do know that we had have men and women in orbit for 6 months or so already?

Lord off hand I forgotten how long a Hohmann orbit tranfer between the earth and Mars would take but 6 months would be a large fraction of that time and that is the worst case situtation. If it turn out to be a problem you can away spin the ship in one manner or other. Two ships spinning around a cable for example to give the efffect of a g force but once more we had have men and women in zero g for long periods.

No one can live on the surface of Mars in a low tech hut for example anymore then they can live on the moon surface! In both cases you are going to need high tech shelters and includng rad. protection into the design is no big deal.

Walking and working on the surrface of Mars for hours a day protected in a manner similar to the moon should also not be enough to worry about.

Earth had been without a magnitic field for thousands of years at a time so how long term are you worry about?

I see no reason why we could not set up settlements on Mars but you might now wish to point out studies by NASA or other experts saying we can not do that for the reasons you gave or others.

II am sure that you view Intrepdi as someone with a better grasp then I have as he does agree with you. I will be waiting for the experts and their studies that you will shortly be posting that also agree with you that a settlement can not be set up on Mars.

Hopefully the experts you pick will know the difference between a magnetic field and a gravity field to start with! Hell it might be also nice if they know what a standard Hohmann orbit is but let not wish for too great an understanding on the part of your experts.

As NASA is planning on trips to Mars and in the long term outposts on Mars I do not think you will find many of those experts in the space community.

If the anti evolution groups can find people with PhDs after their names that will support their positions however you might find a few such people to support your after a good search using google.

You have erected another straw man. At no time did i state that no settlement can be set up on Mars. I know the difference between the gravitational well of a planet and a magnetosphere.

I have absolutely no idea why you posted that drivel about evolution. Do you assume that anyone who doesn't agree with you doesn't agree with a theory of evolution? You're a rare piece of work, you are.

Not that my observation is correct, but it seems like this thread has not attracted those posters that are on the other side of the pond? Is space really a U.S. domain (no Russian posters, I guess?) for A2K? Perhaps, less interest in space by the European/other continent posters?