Not far enough away. At least 20 light years would be sufficient, for me anyway.
If you’re travelling a c and you hit something it’s the same as you being stationary and something moving at c hitting you, surely?
The biggest problem with this scheme is if you hit a hydrogen atom at c (or vice a versa), all the available energy is liberated (from E= mc^2). So if seems, if this scheme is to work, it has to be sub luminal but with a very large scoop.
In his novel "Ringworld", Larry Niven imagined a ring with a radius of 93 million miles (the distance of the Earth from the Sun) with the Sun placed at the centre.
With an area three million times that of the Earth, the Ringworld could support trillions of people!
By rotating, the Ringworld could simulate Earth's gravity (if accelerated up to nearly 3,000,000 miles per hour!).
The image below shows how "sunshades" would have to be deployed between the Ringworld and the Sun in order to give its inhabitants the experience of night and day instead of being bathed in perpetual sunlight.
To construct a Ringworld we’re imagining a substance 100,000 times stronger than the best steel and carbon composites we have now. Larry Niven called it "Scrith". The tensile strength of Scrith would have to be on the same order as the strong nuclear force!
The Ringworld is described as having a mass approximately equal to the sum of all the planets in our solar system and we are told in "Ringworld's Children" that it took the reaction mass of roughly 20 Jupiter masses to spin up the ring!
SF fans call the Ringworld a "Megastructure" or less formally, a "Big Dumb Object"!
It has to be sub-luminal because no material object can travel AT the speed of light.
it will take atleast 1000 years to transform mars. that too if we start know. bombard mars with astroids. 2 things will happen mars will gain some weight and heat from bombardment might kick start the Dynamo. then again it will take 10,000 to settle things down.
I think I saw an idea by canting the ring and erecting high walls at the edges (which you anyway need to keep in the oxygen by gravity), you would also get alternating sunshine and shadow.
Oh, and the rotation would be sustained by Bussard ramjets at regular intervals, another invention.
Jan
I think that's the problem. It might actually be more sensible to make a number of smaller rings that're easier to spin up and can still hold many times earth's population. Then use reflectors to distribute the sun's light to them. Or make your own sun. I mean, how hard can that be?
OTOH if you can make a ring that big that can stand being spun up, the technology to spin it up is probably there too, and you're probably not bothered how long it takes either....
If you make the assumption that fusion is possible then it would also be possible to create a series of arcologies all relying on spin gravity, each housing a large cities worth (or more) of people.
Something like Alastair Reynolds Glitter Band demarchies. Or a Rama or three perhaps. Even James Blish Cities In Flight...
Something like Alastair Reynolds Glitter Band demarchies. Or a Rama or three perhaps. Even James Blish Cities In Flight...
Hard SF knows that a spaceship can only approach c and can never reach it. Just refer to Tau Zero by Poul Anderson!
Speculative SF simply gets over the c barrier by inventing super-luminal methods of travel.
You may see it differently, but I feel this is a distinction that has to be made when discussing spaceships. 🙂
Speculative SF simply gets over the c barrier by inventing super-luminal methods of travel.
You may see it differently, but I feel this is a distinction that has to be made when discussing spaceships. 🙂
Well, we believe that to be true. But there's a lot of pebbles on the beach of knowledge that remain uncollected.
There's more to be discovered. It may be too late for me but I'm optimistic for later generations as long as we don't stop looking up and wondering.
I mean, how can you look at those images from Hubble and not dream of being out there among the stars.
Generation ships the size of cities and powered by small fusion reactors.
Orphans of the Sky
Maybe the first SF book I ever read at 12YO
Orphans of the Sky
Maybe the first SF book I ever read at 12YO
This Robert A. Heinlein novel features a gigantic, cylindrical generation ship named Vanguard.
As a youngster, I loved the "Heinlein Juveniles" and still have several in my collection: https://en.wikipedia.org/wiki/Heinlein_juveniles
In "Tunnel in the Sky", a method of teleportation called the "the Ramsbotham jump" sends the excess population of Earth off to colonise other planets.
And is used to train High School students in advanced survival techniques!
Well, the only thing that actually moves at C are photons, which have zero rest mass. We have all experienced being hit by photons moving at C and it can be quite pleasant. But when you start planning on capturing non-zero rest mass particles like hydrogen molecules while you are moving forward at your imaginary C velocity, the physics are anything but pleasant. 119 years ago, Einstein revealed the very non-intuitive (to we non-Einsteins) principles of Special Relativity, and a few years later he expanded the perspective into General Relativity. Since then, no observation has refuted Einstein. So, if you want to do thought experiments about a hypothetical vehicle moving through the Universe at C and "catching" hydrogen molecules along the journey, you had best be prepared to confront Special and General Relativity.
The best available perspective is "we ain't gonna travel about at C or any respectable fraction of C because...physics!." We're waiting for the cogent perspective that offers an end-around on relativity and, so far, bupkus!
The maximum speed is c, according to our understanding of the universe. If we actually understood WHY, we might be able to do something about it. Until we know WHY, we ain’t goin nowhere.
Just observing something to be true every time you see it, and knowing why it IS that way are not the same thing. Im sure there is a way to change the gravitational constant of the universe, we just haven’t found it yet.
Just observing something to be true every time you see it, and knowing why it IS that way are not the same thing. Im sure there is a way to change the gravitational constant of the universe, we just haven’t found it yet.
OK...let's pretend! We understand precisely why...mass increases with velocity and the energy required to further increase velocity increases exponentially. Inconvenient facts are still facts.
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IIRC, the Spindizzy's that powered the Cities in Flight ran off a pair of AA batteries ;-)
Jan
Here's interesting research on giving Mars a magnetic field.
https://strathprints.strath.ac.uk/7...eate_an_artificial_magnetosphere_for_Mars.pdf
The conclusion seems to be that it's only possible after fusion reactors have been invented.
https://strathprints.strath.ac.uk/7...eate_an_artificial_magnetosphere_for_Mars.pdf
The conclusion seems to be that it's only possible after fusion reactors have been invented.
Not forgetting that's relative, observed mass. The person moving fast has the same mass in their frame of reference.