Spice...Lots of spice.

quote:

Originally posted by MikeinNC:
I dunno, but always carry a towel.

Dude knows where his towel is.

Ask him



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quote:

Originally posted by B92F:
Spice...Lots of spice.

Exactly!! But then... how do you travel to Arrakis to get your first load of Spice?

^^^

Sit on top of a barrel and take a really good laxative.

How does one navigate to them? If we look at the light from them and point the ship in that direction, that's where it was hundreds of thousands or millions of years ago. How do we know where to point the ship so that we arrive at the intended destination, not where it was a long long time ago?[/QUOTE]

The real issue is whether or not the star will still be functional when we arrive! Especially if it is 1,000,000 light years away - it may have gone Nova in that time.

quote:

Originally posted by konata88:
Reading some of this sci-fi stuff. Distances to other systems can be hundreds of thousands or even millions of light years away. Let's assume that we have ships that can travel those distances in reasonable time periods.

How does one navigate to them? If we look at the light from them and point the ship in that direction, that's where it was hundreds of thousands or millions of years ago. How do we know where to point the ship so that we arrive at the intended destination, not where it was a long long time ago?

Hundreds of thousands or millions of light years isn't that far on the cosmic scale.
150M light years is about 1% of the visible universe (15B light years). That's equivalent to travelling 250mi on earth (1% of 25000mi). We know the requirements (technology, energy, etc) to move 250mi in a 'reasonable' time - now multiply that by 600,000. The requirements don't scale linearly, but it gives you a feeling of the lower-end of the problem. We need our 'reasonable' capabilities to be more than 600,000 times our current.

You'd navigate the same way we've predicted moon phases for 100s of years - you observe & track the motion, make sure it's regular, then make a mathematical model that predicts it's motion over time. You'd want to also model any object that could interact with the target in the timeframe since the light left. That's where it gets complex.

Here’s the bigger question…

How long did it take all those planets and stars to get that far away?

If it takes millions of light years, how long conventionally did it take as the mass of that material didn’t travel at light speed.

The answer lies in the fact that time is relative.

A photon from a far star witnesses no time and arrives in your eye at the same moment it was created. Photons experience no time.

Wow! Thank you for that observation! I had to research to understand it…from Perplexity:

Two different clocks, two different answers
From our clock (Earth’s frame):
The photon absolutely takes time to travel. Light from the Sun takes ~8 minutes. Light from Proxima Centauri takes ~4.2 years. Light from the Andromeda galaxy takes ~2.5 million years. Telescopes are literally time machines in this sense — the James Webb Space Telescope sees galaxies as they were 13+ billion years ago because that light has been in transit that long, by our reckoning.
Along the photon’s own worldline (its “proper time”):
Zero. The spacetime interval is null. If you could ride along, no time would pass and no distance would be traversed.
Both are true simultaneously. They’re not contradictory — they’re measurements made in different reference frames.
Why this isn’t a paradox
Relativity’s central lesson is that time and distance aren’t absolute — they depend on the observer. Two observers in different frames genuinely disagree about how much time elapsed between two events, and both are correct within their own frame.
For the photon:
• Earth frame: long distance × finite speed = long travel time
• Photon’s null worldline: length contraction shrinks the distance to zero, and time dilation shrinks elapsed time to zero. Zero ÷ zero, but the interval is well-defined and equals zero.
The practical upshot
When we say “telescopes see the past,” we mean it in our frame — the only frame in which “seeing the past” is a meaningful statement. The photon carries information about the star as it was when the photon was emitted, and by our clock that was a long time ago.
The “photon experiences no time” statement is a curious feature of the geometry of spacetime, but it doesn’t change what telescopes measure or how astronomy works. Astronomers do all their calculations in ordinary reference frames where light has a finite travel time.
So both statements are correct — they’re just answering different questions.

It’s easy; use the “suspension of disbelief” space drive.

quote:

Originally posted by MikeinNC:
I dunno, but always carry a towel.

quote:

Originally posted by Pipe Smoker:

quote:

Originally posted by MikeinNC:
I dunno, but always carry a towel.

Dude knows where his towel is.

Froody.

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^^

quote:

Originally posted by Doc H.:
As an interstellar navigator, you don't travel any distance at all.  Your position is a constant in the Universe, and has always been.  The position of your target is a constant,  and has always been.  You simply converge the positions by combining them, similar to quantum entanglement.  Your "travel" time is - almost - zero. "Almost" because there are some complicating factors, the constant of Universal expansion being only one. 

Except, isn't the Universe expanding faster than the speed of light?

Just press the button on the navigation computer and wing it.

"Hey Siri, what is the compass heading to that star?"

quote:

Originally posted by mdblanton:
^^^ - Georgeair, you typed your response faster than me

Slight tangent on your premise - and I'm paraphrasing what the physicist I was watching said: Spacecraft that could travel those distances in a reasonable timeframe would have to be incredibly small. He posited that a toothpick size or smaller would be optimal due the amount of 'dust' in space. He equated impacting one particle when traveling even a fraction of light speed would be equivalent to being hit by a baseball x 19,000.

don't recall the book, but there was one that had the space craft pushing a large block of ice in front to take care of space dust etc etc,

quote:

Originally posted by architect:

quote:

Originally posted by Doc H.:
As an interstellar navigator, you don't travel any distance at all.  Your position is a constant in the Universe, and has always been.  The position of your target is a constant,  and has always been.  You simply converge the positions by combining them, similar to quantum entanglement.  Your "travel" time is - almost - zero. "Almost" because there are some complicating factors, the constant of Universal expansion being only one. 

Except, isn't the Universe expanding faster than the speed of light?

At the inception of matter and energy, both increased their volume nearly instantaneously into what humans call "the Universe " at far greater than the speed of light if calculated by the increased distance between two objects.  Nothing physical however actually moved.  The volume of spacetime increased (measured by the separation of known objects) at a constant speed, reducing by a constant speed, for the first several billion years since inception, carrying its "objects" (including matter and energy) with it.  It then began accelerating (again by the separation of known objects), which continues.  The acceleration is not the same in all regions, but again is a constant regionally.  Very distant objects from Earth appear from observational data to have moved faster than the speed of light to get where they are.  They have not.  They have been "carried by the flow" of spacetime regionally increasing. The current regional acceleration is also a constant, following the introduction of metaphysical or extraphysical hidden energy to contribute to its flow.  That acceleration continues predictably to a certain border, where it will decrease again. It's complicated.  Regional physics matters in travel, through space or otherwise.  A corner drugstore 5 miles away takes half the time to get to at the same speed as a drugstore 10 miles away.  The moon is 30,000 miles closer to Earth at one point in time, 30,000 miles farther away at another.  Distance matters, locally, physically traveling by manual or assisted power, or in chemical rockets.

Distance does not matter in interstellar navigation.  Location matters, in the spacetime matrix.  The "farthest" star detectable with human instrumentation is almost 9 billion parsecs from Earth in this galaxy.  That number can be articulated by the human mind, but cannot be truly understood.  It is completely unreachable by any physical means of travel in a physical object, now or ever, the local and relative speed of light being only one physical limitation.  An interstellar navigator calculates positions, fixed along time coordinates, that can be superimposed for physical access.  That involves knowing those constants and accuracy beyond decimal places, as well as metaphysical and extraphysical actions taken briefly - very briefly - outside this physical Universe.  It's complicated.   But I'm not a navigator, and that's just my limited explanation. And I only work for the Librarian.

I’m proud to belong to a group so well versed in the subject that can also explain it in detail.

Am afraid there’s just one correct answer.

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