The aliens are silent because they're dead

[robinson]

The fears of a clown

[robinson]

funny typo

Funny enough to leave it in

[gnome]

I think there's also a corresponding mass increase such that if time dilation is 2:1, for example, your mass has effectively doubled, and at 40:1 your mass is 40 times heavier. (This is what I'm relying on.) Thus, the closer you approach to C, the more energy you need to get additional acceleration. I do wonder if some kind of electromagnetic field around the ship could deflect those micrometeoroids?

Something I never got to asking about related to this--Anax points to increasing energy requirements to keep up with the increased mass of the ship. If the whole ship is increasing in mass, then the fuel is too. Do you get more output from it as a result? Is the propellant also gaining mass, and thus more effective at pushing the ship? The laws of thermodynamics being the buzzkill that they are, maintaining some kind of parity between thrust and mass gain is probably wishful thinking. But has someone worked out that aspect of it before?

[Witness]

You don't get relativity. On board of the ship nothing changes. (Good luck to your heart trying to pump blood 40x more massive…) So the Δv from some fuel expenditure would be strictly the same – as measured by on-board instruments.

But seen from outside, by an observer supposed to be "at rest", velocities don't add in the simple Galilean fashion, you have to use:

new speed = (old speed + Δv)/(1 + (old speed)*Δv /c²)

See: Velocity-addition formula.

[gnome]

So if, by inside reckoning, I am accelerating at 1G, once relativistic effects become non-trivial, what does that look like from outside?

[robinson]

Nobody actually knows, because observation also depends on your relative motion. By "knows" I mean nobody has an image to show, and considering the distances and relative velocity, I wouldn't hold your breath waiting for a Youtube video.

Math and theory tell us things get much more massive as they "go faster", that shit actually swells up, but nobody observes this actually happening.

[robinson]

That opinion is of course, just my opinion. I would love to be proven wrong, and somebody slaps a video into this thread of a spaceship changing size as it goes faster. But I'm not waiting up nights.

[gnome]

I use "look" kind of loosely. I'd be satisfied with a description based on theory. And it's more about what kind of progress the ship looks like it's making from the observer's point of view. I'm told that the mass of the ship increases but you can't tell from inside. Does that mean that from inside it doesn't seem to be impeding progress or escalating the energy needed to maintain acceleration?

I have a grasp on a lot of relativity, just this point I get stuck on.

[Anaxagoras]

So if, by inside reckoning, I am accelerating at 1G, once relativistic effects become non-trivial, what does that look like from outside?

From the outside? I assume you mean a stationary observer.

Rulers get shorter (and of course, everything else too, including the spaceship) in the direction of travel. And clocks run slower.

[ed]

If I accelerate a gram of matter and direct it at an object, how much energy is released?

What are the implications for a craft being struck by atoms/molecules as it moves at high speeds?

If the mass of the object increases as it accelerates, does it not create a gravity depression that will tend to draw matter towards it?

Will the very act of accelerating provide an unavoidable quietus for the craft?

Could it be that every black hole that we observe is a failed effort a light speed by other civilizations?

I am turning into Robinson. Help me.

[gnome]

So if, by inside reckoning, I am accelerating at 1G, once relativistic effects become non-trivial, what does that look like from outside?

From the outside? I assume you mean a stationary observer.

Rulers get shorter (and of course, everything else too, including the spaceship) in the direction of travel. And clocks run slower.

That part I get--more the question of, which frame of reference most directly feels the problem of increasing mass requiring more force for acceleration?

[Anaxagoras]

So if, by inside reckoning, I am accelerating at 1G, once relativistic effects become non-trivial, what does that look like from outside?

From the outside? I assume you mean a stationary observer.

Rulers get shorter (and of course, everything else too, including the spaceship) in the direction of travel. And clocks run slower.

That part I get--more the question of, which frame of reference most directly feels the problem of increasing mass requiring more force for acceleration?

That would be the one that isn't moving. The mass doesn't really change from the perspective of people on the spaceship.

[robinson]

These questions are some of the really hard questions, just in case there is any question about that

[gnome]

So if, by inside reckoning, I am accelerating at 1G, once relativistic effects become non-trivial, what does that look like from outside?

From the outside? I assume you mean a stationary observer.

Rulers get shorter (and of course, everything else too, including the spaceship) in the direction of travel. And clocks run slower.

That part I get--more the question of, which frame of reference most directly feels the problem of increasing mass requiring more force for acceleration?

That would be the one that isn't moving. The mass doesn't really change from the perspective of people on the spaceship.

Right so my point being, is that an obstacle to my scheme of maintaining 1G and traveling so far from my own point of view, even if it's taking millenia from a stationary frame of reference?

[ed]

Avoid my really hard questions.

[gnome]

I liked them. I just have no idea.

[ed]

makes you think

[Witness]

I posted a small Relativity puzzle, just so we know what we're talking about.

[robinson]

Mass does not increase with speed or acceleration

There are no extra atoms, no increase in the size, no particles appear, this is just how it is. No matter how much you accelerate anything, more matter does not show up. What is being theorized is called relativistic mass.

And that is a touchy subject in physics, even when the majority agrees, that doesn’t mean it is settled, or even understood.


But no new “stuff” appears, so gravity does not change for an object moving or accelerating.

[robinson]

As for being “struck”, it’s the same as if the objects are moving and you are stationary. If you are moving relative to an object at very high velocity, it’s the same as if you are still and the object is hitting you at high velocity

[robinson]

If you are hammering down the road at 100 mph, hitting a stationary object, like a bowling ball hanging from a rope, is the same as the bowling ball hitting you at 100mph

Spaceships and grains of matter is no different, and gravity does not change

[ed]

You are avoiding my fucking question with arm waving misdirection.

Apologize immediately.

[robinson]

Accelerating a craft does not mean it is doomed. You just have to have a lot of expendable mass to take the hits, a shit ton of ice would work. Using h bombs as the driving force would be the greatest bang for the mass, so it’s theoretically possible to accelerate a huge space ship and protect it from impacts. Slowing it back down is the far bigger problem, but with enough h bombs you could reach another star in a reasonable amount of time, and have plenty of water when you get there.


The people starting off won’t live long enough, but their great grandkids will

[robinson]

None of this is original, it’s been in a sci-fi story or three already, in various forms

[robinson]

The secret knock might be launching multiple ships, like stages, each launched ship is already going very fast relatively speaking, but the ship doesn’t “know” it’s moving at high speed, so as it accelerates away it’s just accelerating from a rest state, then another one launched from it, and then another one, you could reach speeds enough to reach the nearest star in a 100 years or so.


But, slowing down is the real problem at that point

[robinson]

Since you have to turn the ship around to brake, now your giant ass steel plate you have been using for the h bombs to push you along is going to be taking the hits, and that’s a problem not solved

[Anaxagoras]

So if, by inside reckoning, I am accelerating at 1G, once relativistic effects become non-trivial, what does that look like from outside?

From the outside? I assume you mean a stationary observer.

Rulers get shorter (and of course, everything else too, including the spaceship) in the direction of travel. And clocks run slower.

That part I get--more the question of, which frame of reference most directly feels the problem of increasing mass requiring more force for acceleration?

That would be the one that isn't moving. The mass doesn't really change from the perspective of people on the spaceship.

Right so my point being, is that an obstacle to my scheme of maintaining 1G and traveling so far from my own point of view, even if it's taking millenia from a stationary frame of reference?

Actually, I think that's possible. From the point of view of people on the spaceship, a very long journey could happen in very little time.

Of course, there are still very difficult, probably insurmountable, practical problems with this, but General Relativity doesn't prevent it in principle.

From our perspective back here on earth, a light year is a light year, but from the perspective of those on this imaginary spaceship, the distances to other stars effectively shrink as time slows down. They would not experience it at time slowing down, but as outside distances getting shorter. At least that's my layman's understanding of it.

[robinson]

Day after day year after year your ice has been wearing away, but to slow down you can’t use ice against h bombs, they would destroy your mile thick shield, and you are fucked, shooting past your target at 1000 miles a second

[robinson]

And that’s why the aliens are all dead

[Anaxagoras]

Yeah, like I said. To stop again, you would need to spend as much time and distance decelerating as you did to accelerate in the first part of the trip.

[gnome]

Do I still gain the benefits of time dilation while decelerating?



"Ferris? It's not working. The miles aren't coming off, running it in reverse."

[Anaxagoras]

Do I still gain the benefits of time dilation while decelerating?

I believe that you would gradually revert to normal time as your velocity decreased.

[gnome]

Great then! I'm still confident that if we can get over the relativity hurdle the rest is a matter of innovation.

Even if only my descendants find out I made it back.

[robinson]

Time does not change for an observer

[robinson]

Just as the speed of light ( C ) does not change

No matter what your “motion” is, if you turn on a light the photons move away from you at C

[Anaxagoras]

[Pyrrho]

The aliens are silent because they've put us on ignore and have wished us into the cornfield.

[Rob Lister]

I can't be bothered to read the entire thread but I really, really, really believe that the reason no aliens have visited us is because we are first.

Somebody has to be.

[robinson]

The new world natives could have been explaining in 1491 that the reason the mythical people from across the sea haven't shown up, is because they are all dead

[robinson]

They really should have had kids and some dogs in the pic