Author Topic: Move to new planet, says Hawking  (Read 55359 times)

Offline publiusr

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Re: Move to new planet, says Hawking
« Reply #180 on: 05/21/2007 08:17 pm »
Quote
khallow - 22/2/2007  9:36 PM

Also, I'm dubious about the value of government trailbreaking.
In comparison, asteroid mining is simply expensive. What infrastructure is created?

I would like to respond to the above. I think DASH-80 was trailbreaking, and asteroid mining may not be too expensive--esp compared to wars.

You have heard me advocate cutting up an asteroid with cables and what not. The cables would also have tethers--not as long as Space elevator cables, but 100-200 miles or so. Asteroids spin, and this can be adjusted by release of one end of the bola. A two-asteroid bola might drag a tether trail and lift large payloads to orbit, or if small asteroid bits are on either end of the bola, one entire asteroid can be released as it swings down to the earth surface and actual mining take place here.

Sea Dragon inventor Bob Truax spoke about parachuting large items to the ground. With a tether, a large (force-flex) bagged space rock could be brought no violently to the surface with a lage chute and/or balute affixed just in case.

The empty tether may also be affixed to a chute under the water to drag the other remaining asteroid fragment down at sea, where it can use ballutes and be towed.

The object is to get massive amounts of payload up and down from orbit as you can. Avoiding assembly.
This large scale approach is what you will need to establish a real presence in space.

Offline vt_hokie

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RE: Move to new planet, says Hawking
« Reply #181 on: 06/12/2007 05:53 am »
I happened to catch part of a program on the History Channel where they were discussing gamma ray bursts.  I had no idea that they could be so devastating from such great distances.  Seems that moving to other planets might not be enough to ensure survival of the species!

Offline stargazer777

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RE: Move to new planet, says Hawking
« Reply #182 on: 06/12/2007 05:25 pm »
I happened to catch part of a program on the History Channel where they were discussing gamma ray bursts. I had no idea that they could be so devastating from such great distances. Seems that moving to other planets might not be enough to ensure survival of the species!

It is certain that we live in a dangerous universe -- gamma ray bursts (GRBs) are just one of the dangers.  If I understand the latest explanation of the phenomenon correctly, the deadly intensity of a gamma ray burst is not like a supernova -- going out with equal intensity in all directions -- but rather like a beam or jet emitted from the super-massive black holes at the center of our galaxy and other galaxies.  These are also understood to be -- for the moment at least -- extremely distant phenomena and thus very ancient.  However, if the GRBs are jetted, they may be more common than we realize or can observe at the moment.  There is a good discussion of this subject in Wikipedia (http://en.wikipedia.org/wiki/Gamma_ray_burst) that might be helpful to you.

Regardless of the danger posed by GRBs -- which was well understood by Hawkins -- the vital importance for humans to expand beyond Earth, and eventually beyond our solar system, to ensure our survival remains undiminished.  There are many more immediate threats that we face right here in the solar system that could easily extinguish human life on Earth.  The wider we spread human presence in our solar system and beyond, the better protected we will be from such catastrophic events.  

Addendum:  New article in 6/13/07 Space Daily (http://www.spacedaily.com/reports/Matter_Flashed_At_Ultra_Speed_999.html) indicates that matter  ejected by a GRB "explosion" has been measured with a velocity of 99.999% of light speed.  Moving pretty fast there boys and girls. 


Offline khallow

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Re: Move to new planet, says Hawking
« Reply #183 on: 06/13/2007 09:47 pm »
I happened to catch part of a program on the History Channel where they were discussing gamma ray bursts. I had no idea that they could be so devastating from such great distances. Seems that moving to other planets might not be enough to ensure survival of the species!

Actually, Earth (and for that matter any major planet or moon) is a good place to weather gamma ray bursts since one can use the planemo as a shield.
Karl Hallowell

Offline stargazer777

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Re: Move to new planet, says Hawking
« Reply #184 on: 06/13/2007 10:17 pm »

    Actually, Earth (and for that matter any major planet or moon) is a good place to weather gamma     ray bursts since one can use the planemo as a shield.

From Wikipedia article on GRB's:

Mass extinction on Earth

One line of research has investigated the consequences of Earth being hit by a beam of gamma rays from a nearby (about 500 light years) gamma ray burst. This is motivated by the efforts to explain mass extinctions on Earth and estimate the probability of extraterrestrial life. The consensus seems to be that the damage that a gamma ray burst could do would be limited by its very short duration, but that a sufficiently close gamma ray burst could do serious damage to the atmosphere, perhaps wiping out the ozone layer and triggering a mass extinction. The damage from a gamma ray burst would probably be significantly greater than a supernova at the same distance.

The idea that a nearby gamma-ray burst could significantly affect the Earth's atmosphere and potentially cause severe damage to the biosphere was introduced in 1995 by physicist Stephen Thorsett, then at Princeton University [1]. Scientists at NASA and the University of Kansas in 2005 released a more detailed study that suggests that the Ordovician-Silurian extinction events of 450 million years ago could have been triggered by a gamma-ray burst. The scientists do not have direct evidence that such a burst activated the ancient extinction; rather the strength of their work is their atmospheric modeling, essentially a "what if" scenario. The scientists calculated that gamma-ray radiation from a relatively nearby star explosion, hitting the Earth for only ten seconds, could deplete up to half of the atmosphere's protective ozone layer. Recovery could take at least five years. With the ozone layer damaged, ultraviolet radiation from the Sun could kill much of the life on land and near the surface of oceans and lakes, disrupting the food chain. While gamma-ray bursts in our Milky Way galaxy are indeed rare, NASA scientists estimate that at least one nearby event probably hit the Earth in the past billion years. Life on Earth is thought to have appeared at least 3.5 billion years ago. Dr. Bruce Lieberman, a paleontologist at the University of Kansas, originated the idea that a gamma-ray burst specifically could have caused the great Ordovician extinction. "We don't know exactly when one came, but we're rather sure it did come - and left its mark. What's most surprising is that just a 10-second burst can cause years of devastating ozone damage." [2]

Comparative work in 2006 on galaxies in which GRBs have occurred suggests that metal-poor galaxies are the most likely candidates. The likelihood of the metal-rich Milky Way galaxy hosting a GRB was estimated at less than 0.15%, significantly reducing the likelihood that a burst has caused mass extinction events on this planet [3].



Offline publiusr

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Re: Move to new planet, says Hawking
« Reply #185 on: 07/02/2007 10:07 pm »
If we ever do hear from ET--he would certainly be using something bigger than Delta II to hollow out asteroids and make mega transmitters in space.

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