# Ding Dong, ALIENS CALLING

Sorry, sci-fi fans: pretty much anyone who's imagined what a near-light-speed spacecraft would look like has got it wrong, because they've forgotten its interaction with photons. Not only that, but according to a couple of scientists working for Raytheon, it doesn't matter whether Einstein's proposition that you'll never …

1. #### A baseball can do 30 megatons of damage?

You'd think they'd put a warning on them...

2. #### Re: A baseball can do 30 megatons of damage?

Methinks someone has been reading Randall Munroe's 'What If?'.

edit - Here

3. #### Re: A baseball can do 30 megatons of damage?

This explains some japanese comics.

4. #### Re: A baseball can do 30 megatons of damage?

In cricket, this eventuality is covered by the Duckworth-Lewis method.

5. #### @Loyal Commenter - Re: A baseball can do 30 megatons of damage?

Damn you beat me to the obligatory xkcd punch

6. #### As all real Scientists know

If it's on Arxiv, it probably could not make it through peer review at a Journal.

7. #### Re: A baseball can do 30 megatons of damage?

More likely is that the ship will hit a speck of galactic dust, perhaps one micron across. So 10**-18 cubic metres, or ca 10**-15 kg. The rest mass energy is therefore 90 joules, so its kinetic energy at relativistic speeds will be similar.

Suppose there is one such dust grain per cubic metre. At the speed of light, each square metre of the ship will hit 3x10**8 such grains, releasing at least 2x10**10 joules.

The ship will rapidly be reduced to galactic dust.

8. #### Re: As all real Scientists know

If it's on Arxiv, it probably could not make it through peer review at a Journal.

You completely misunderstand the nature of Arxiv (and vixra, for that matter), as well as peer review.

And the incentives behind peer review.

Go sit in a corner, dunderhead.

(Damn, I'm too serious again. Time for "venerable ancient bum" icon).

9. #### Re: A baseball can do 30 megatons of damage?

Some combination of electromagnetic, electrostatic & plasma shields needed I suspect to capture/deflect the particles, plus probably a massive container full of water to absorb that gamma radiation.

Its all just extreme engineering for near light speed travel...

10. #### Re: A baseball can do 30 megatons of damage?

I seem to recall reading, a large number of years ago, that there was a Project Daedelus proposed where we would head off at near-light speed to reach the stars.

If we detected something ahead of us, the craft would send out a fine mist, which, travelling at just below the speed of light, would smithereenerize (is that a word?) anything in it's path.

The craft would then sail serenely through the mist + pulverised remnants and carry on its way.

11. Isn't the idea of any kind of 'warp' propulsion that it moves a 'bubble' of spacetime rather than the contents, which effectively stay stationary. This is also known as 'frame-shifting'.

This might be bad news for anything in the path of that bubble, which presumably would get either bumped to one side, or torn apart, but the whole notion of accelerating anything to near the speed of light as a means of moving it astronomical distances is obviously a non-starter.

Relativity tells us that this would involve impractically (if not impossibly) vast amounts of energy for one, rising exponentially as you approach C. Your mass would increase accordingly, and time would slow down, which would be a definite problem if you wanted to go to another solar system and still stay in touch with your friends at home, who would all be long dead by the time you get there.

So what these guys are saying, is that if you tried to use an impractical method of transportation, it would be impractical. Nice tautology there...

12. This is also known as 'frame-shifting'.

This is also known as Harry Potter enabling.

13. #### @Loyal Commenter

I much prefer the EE Doc Smith solution in Skylark*:

"We're going faster than the speed of light!" says the scientist superhero.

"Doesn't that violate Einstein's Law of Relativity?" asks the plucky sidekick who is there just to ask such questions.

"Yes, but it's happening so Einstein was wrong. I'll figure it out later." answers the scientist.

*Some liberties may have been taken in transcribing the dialogue of this interaction.

14. #### Re: @Loyal Commenter

The liberties you took are sheerly, starkly unthinkable, you zwilnik!

Prepare to be shown the burned and pitted orifices of my twin DeLammeters!

15. #### Warp

I haven't read a sci fi book that relies on warp bubbles in.... ever. Most have either Generation ships, or some kind of lighthugger

http://revelationspace.wikia.com/wiki/Lighthugger

Generation ships trundling along between stars might be impractical but they do seem like the only option.

Good to know if a ship is approaching us they'll be visible.

16. #### Re: Warp

"Good to know if a ship is approaching us they'll be visible."

Would they, would they really? Articles like these fine hope to hostile invasions, but to presume you're enemy will be seen is generally a presumption the loser takes. In less than a hundred years it is only now that we can see most of Earth's deadliest lifeforms using technology. Encode an atom with a virus, send it across the galaxy, watch your enemy wither away. Galatic Bio-Weaponry, beautifully hideous...but effective.

17. #### Re: @Loyal Commenter

"zwilnik! DeLammeters!"

Wrong universe. Unless you are flying Gay Deceiver.

(A wrong author is less worse than wrong universe. At least that's true in my multiverse. :-p )

18. #### Gay Deceiver.

I've heard of The Flying Nun, but I don't think I've heard of a flying catholic priest.

I'll get my coat....

19. @Loyal Commenter

More like: physically impossible method of travel also impractical from an engineering and logistics standpoint.

Not that trying to solve a mooted technical problem like this would be necessarily devoid of useful insight, just that one must frame such research carefully.

20. This is also known as Harry Potter enabling.

Well, yes. Pretty much all SF non-local (inner-system) space travel involves a bunch of magical hand-waving rubbish. Oh, we have warp bubbles, y'see. And deflector shields. And the ship's hull is made of highly compressed fairies.

This is so patently obvious to anyone with a glancing acquaintance with physics that I really am baffled by Chirgwin's "pretty much anyone who's imagined what a near-light-speed spacecraft would look like has got it wrong". I'm not saying there isn't new work in this paper, but the general ideas of high-energy collisions with interstellar matter and blue-shifted photons are pretty common, surely?

I described both of them to my brother in an email many years ago when he was doing some research for an SF story - even did some back-of-the-envelope1 calculations. And I'm neither a physicist nor a spacecraft engineer. If those problems immediately occurred to me, it's vanishingly unlikely that they haven't occurred to a great many SF authors and readers. Who, presumably, ignored them or waved them away in order to get on with the story.

1In those days, still a physical paper object you could jot numbers and equations down on, with a pen.2

2In those days, a physical object you... ah, forget it.

21. #### Re: Warp

Encode an atom with a virus

Er ... do what, now? How do you "encode an atom"? As what? "See, this helium atom is actually an encoded hydrogen! We added another proton and electron for redundancy."

22. #### Re: Warp

@Michael

+10

I was gong to respond to the comment but just didn't know where to start.

23. #### Star Trek is already around it.

Deflector dish has that exact purpose, to push tiny weeny particles and fotons away from the front of the ship.

The way out is there, altough it is not thoroughly explained how. What I mean is that this was already considered, and a sci-fi coherent answer devised.

24. #### Re: Star Trek is already around it.

Honorverse novels acknowledge this too, the main limit on missile range being that coasting along at .99c without a gravity wedge is a recipe for fried ... everything in fact.

25. #### Re: Star Trek is already around it.

I know many people knock the crap out the Honorverse, but those frikkin battle scenes are AWESOME!

26. #### Re: Star Trek is already around it.

Odd that the Klingons, Romulans, Ferengi etc., etc., don't seem to need deflector dishes on their ships - ah, got it, Einstein wasn't a Klingon or Romulan etc., so presumably their physics is different.

27. #### Re: Star Trek is already around it.

Although Charles Hall tells of the fact that a fragment of space debris nearly demolished one of the Tall Whites's ships, so clearly shielding doesn't always work.

28. #### Don't they know anything?

"Not only that, but according to a couple of scientists working for Raytheon, it doesn't matter whether Einstein's proposition that you'll never accelerate matter beyond light-speed is right or wrong: collisions with matter will probably rip your spaceship apart anyway, and photons will slow you down."

That is what the Main Deflector is for. "The deflector commonly took the form of a dish-shaped force beam generator containing heavy-duty subspace accelerators at the extreme forward end of the vessel's secondary hull. It performed its primary function by emitting low-power deflector shields to deflect microscopic particles and higher-powered deflector beams and/or tractor beams to deflect larger objects."

What do you mean, Star Trek isn't real?

29. #### Re: Don't they know anything?

>What do you mean, Star Trek isn't real?

It is real.

It's just not real yet.

30. #### Re: Don't they know anything?

No, not the main deflector. That's for weapons fire. You're thinking of the navigational deflector, which while sufficiently powerful to deflect pretty much any 21st-century weapon, isn't capable of deflecting things like photon torpedos with kilogram-scale antimatter warheads.

31. #### Re: Don't they know anything?

It might very well real right now. Just not in our part of the universe. Hmm... or maybe not this universe....

32. #### Re: Don't they know anything?

Or, it isn't part of our human technology.

The universe is a big place. If something is possible in the realm of physics, then it is certainly possible that another intelligent civilization has implemented it, and may still be using it if they didn't die out before we grew to the point where we would observe them using it in our small corner of the universe.

There may be millions or even billions of other civilizations out there, maybe many of the able to travel through space faster than or at some significant fraction of the speed of light. But even if they could travel at some multiple of the speed of light, the distances are so vast that they may never visit anywhere near us.

So just because we don't know how, doesn't mean that many others don't know either - or didn't know when they still existed.

33. #### Re: Don't they know anything?

">What do you mean, Star Trek isn't real?

It is real.

It's just not real yet."

It's amazing how much of it is right now. Only 50 years after its debut. I have to wonder what the next 50 years will bring.

34. #### Re: Don't they know anything?

@TheOtherHobbes

"It's just not real yet."

From a technology standpoint, maybe - though much of it is fundamentally flawed, of course. (Even ignoring the Jar-Jar-verse.)

Once things are down to "it's an engineering problem", the only barrier is economics.

Unfortunately, there's a lot in Star Trek that is far more fanciful than warp drive and inexplicably compatible sexual coupling and reproduction. The idea of some kind of perfect egalitarian society in a post-scarcity, post-conflict, post-need human society is way behind things like deflector dishes in the list of things likely to happen.

Which reminds me - time to take my meds.

36. #### And if all that fails

just reverse the polarity of the neutron flux!

37. Captain, she canna take it, unless we drop out of warp now the manifold is going to explode. Even if we survive the explosion the dilithium crystals are shot.

38. explains that Einstein's universal speed limit applies to a vacuum

It's a "speed limit" in the same sense as the branch of a hyperbola is a "rotation limit" but okay...

39. #### Err duh!!!!

Just put your forward Shields up.

40. #### the radiation will tell us they're on the way.

Sounds like the premise for a sci-fi movie, except with aliens instead of asteroids. Call Bruce Willis.

41. #### Re: the radiation will tell us they're on the way.

I would rather have Sigourney Weaver for dealing with Aliens.

42. #### Re: the radiation will tell us they're on the way.

I will take both Bruce Willis and Sigourney Weaver...

And don't mess with Mama Bear, by the way.

43. #### Alternatively

Hook up the logic circuits of a Bambleweeny 57 submeson brain to an atomic vector plotter suspended in a strong Brownian motion generator (say a cup of hot tea), feed it the improbability for an infinite improbability drive, and away you go. No more mucking about in hyperspace.

Unless you want to deal with Bistromathics, of course

44. #### Ding Dong, ALIENS CALLING

Well, there's probably more chance of aliens taking note of my 'Cold Callers : Bugger Off' sign than fucking conservatory salesmen.

45. #### Re: Ding Dong, ALIENS CALLING

And I, for one, welcome our conservatory vending overlords.... with the mighty relativistic baseball of (30 megaton) power!

Boom! And yooouuurrr out!

46. #### Re: Ding Dong, ALIENS CALLING

Should be: "Boom! And yooouuurrr'e out!"

Even at near-light speeds, the laws of grammar still apply.

47. #### Re: Ding Dong, ALIENS CALLING

But your apostrophe - is it relativistically rrr'ed-shifted?

Even so, I believe it will still be "Boom! And yooouuu'rrre out!" for an observer on board...

48. #### Have they ever read any Sci-Fi

If yes, then how did they fail to notice the bloody big shields usually carried in front of relativistic spaceships?

If no, then The Songs of Distant Earth (1986) by Arthur C Clarke might be a good point to start...

49. #### Re: Have they ever read any Sci-Fi

Or like one story I read a long time ago (can't remember its title), the ships were basically large bundles of very thin, needle-like mini-ships. So when they ran into uncharted nebulae, they split up into a cloud of mini-ships and then reassembled themselves afterwards.

50. #### Re: Have they ever read any Sci-Fi

The Storm? had Delian and non-delian robots I think

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