Sunday 27 January 2013

FTL?

OK. Poul Anderson's explanation of hyperspace in his Technic Civilisation future history makes sense and is easy to understand:

if a spaceship jumps from one set of spatiotemporal coordinates to a nearby set without traversing the space between them, then the jump can be instantaneous because only the traversal of space is limited by the light speed barrier so if the ship makes billions of such jumps per microsecond then it can move at a pseudo-velocity far greater than light speed.

But I am still trying to make sense of the alternative method of FTL (faster than light) travel offered in the same author's The Star Fox. Anderson's knowledge of the science of physics enabled him to devise several different verbal formulae as rationalisations of FTL but this one reached its conclusion very quickly.

The rationale:

inertia exists only in the inertial frame of reference of the entire universe;
inertial and gravitational mass are the same (Einstein);
equations of warped space describe gravity;
therefore, inertia is an inductive effect of the cosmic gravitational field on mass;
if gravitrons can bend space through a closed curve, then the ship has no resistance to acceleration;
so it has no top speed.

Does that make sense?

19 comments:

Sean M. Brooks said...

Hi, Paul!

A physicist might understand either version of these two hypothetical FTL drives, but I don't pretend to claim I do! Needless to say, I hope someday we do have scientists who discover a real world FTL drive. I want to know what is out there in the universe. I want other planets to be colonized by mankind.

Sean

Paul Shackley said...

The Technic History version is comprehensible. Moving from A to B by traversing the line AB is limited to light speed whereas disappearing at A and reappearing at B without traversing AB can be instantaneous. But PA needed to spell out the STAR FOX version a bit more.

Paul Shackley said...

I agree at least about getting some people off Earth for longer term survival.

Sean M. Brooks said...

Hi, Paul!

I was unclear. I do get the bit about disappearing at point A to reappear "intantaneously" at B. And various rumors I hear about tachyons somehow going FTL, as in the experiments at CERN, are very interesting (to say the least). But, even if a hypothetically workable THEORY is developed, the ENGINEERING necessary for moving untold tons of matter (including people) remains a formidable barrier to building FTL ships.

While we both agree in disliking most of Heinlein's later work, I think we can also agree with his comment that it's foolish for humanity to perist in keeping all it's eggs in the one basket called Earth. The danger of comets like Apophis hiting Earth should be enough, if we lived in rational times, to getting people off their duffs working for that!

Sean

Paul Shackley said...

Yes, I am very worried about comets. It is only a matter of time.

Sean M. Brooks said...

Hi, Paul!

Absoluutely! In fact, we are probably long overdue to getting smacked with a big comet. And we still FOOLISHLY persist in not doing what it takes to get off this rock!

I have wondered if the Tunguska incident occurring around 1905 was a comet hitting Earth. If so, the next is either going to be bigger or even if "small" hit a populous area. Either would be a disaster of the kind described in Jerry Pournelle/Larry Niven's novel LUCIFER'S HAMMER.

Sean

Paul Shackley said...

The comets that periodically fall into the inner system are getting progressively smaller (and disappointing in the night sky) because they lose matter every trip but something big and unexpected could be on its way.

Sean M. Brooks said...

Hi, Paul!

Agree, but it only takes one even "moderately" large comet hitting Earth to spoil everyone's day! And sooner or later, it will happen. UNLESS we have the means for fending them off. And that first necessitates getting off this rock.

But I know you agree!

Sean

Paul Shackley said...

Even if just getting off Earth to the extent of mounting an adequate laser defence system? But there are other good reasons for having populations in self-sustaining space habitats if not down on other planetary surfaces. All sorts of things could happen to Earth. As long as nuclear weapons exist, they could be used.

Sean M. Brooks said...

Hi, Paul!

I agree! For a really adequate big rock detecting and fending off system, we need to do it in SPACE. And founding settlements off Earth would act as insurance against us losing every thing due to a really big nuclear exchange.

If an English socialist agnostic like you and a Catholic conservative like me can see that, why can't OTHERS????? Sometimes, I do feel discouraged.

Sean

Paul Shackley said...

Signing off for about a week. This morning, driving to Leicester to visit my mother, 94, nearly bedridden, immediate future uncertain, but very resilient. I will have to go down there again soon. After that, don't know.

Paul Shackley said...

By the way, 2 days ago, 96 page views in the day, the most yet.

Sean M. Brooks said...

Hi, Paul!

Hope you have a happy visit with your mother despite the uncertain future. Good to know she is still so resilient.

And I hope some of those visitors to this blog will offer their own comments about both Poul Anderson and your notes!

Sean

Paul Shackley said...

Thank you. I am back home and trying to update this and other blogs. Page viewing has dropped off in my absence but that can't be helped. Rereading THE STAR FOX has been rewarding and now I have its sequel, FIRE TIME, to reread as well.

Sean M. Brooks said...

Hi, Paul!

I've also been thinking about THE STAR FOX, esp. the Aleriona leader Heim fought and why Alerion consides humanity a threat to her, even if humans don't WANT to be a threat to her.

I reread THE STAR FOX last year. Thinking I should reread FIRE TIME soon.

Sean

Jim Baerg said...

So you were talking about large meteor strikes just a few weeks before the Chelyabinsk meteor ;)

The Mach Drive in "Star Fox" & "Fire Time", might be based on this idea.
https://en.wikipedia.org/wiki/Mach%27s_principle

Any FTL drive in SF involves a good deal of 'handwavium', though 'wormholes' linking two points in spacetime seem the least implausible to me.
See the comment thread here:
http://www.rocketpunk-manifesto.com/2010/02/on-torchships.html
which deviates into a discussion of 'wormholes' and this post
http://www.rocketpunk-manifesto.com/2010/03/rapid-transit.html

Sean M. Brooks said...

Kaor, Jim!

All this about FTL drives is highly speculative, I agree! But I want so much to KNOW what might be out there that I would very glad if a real FTL drive is invented. And we do have real world speculations about such things in the proposed Alcubierre FTL drive.

More realistically, and hopefully, Elon Musk's work at SpaceX and Tesla in developing practical, reusable space ships and tech useful in space and the Solar System gives me some hope. As does what might be discovered thru the James Webb Space Telescope.

Ad astra! Sean

Jim Baerg said...

To the extent that I understand the speculations about Alcubierre drive & 'wormholes' the wormhole seems to allow FTL without the 'Closed Timelike curves' which would give all the standard time travel paradoxes, while Alcubierre warp drive would give time travel if it did allow FTL.
So that is the major reason 'wormholes' seem to me to be the least implausible FTL.

Sean M. Brooks said...

Kaor, Jim!

And I'm inclined to agree with you. The simplest possible FTL drive which just might be possible is to be preferred.

Ad astra! Sean