New answers tagged space-travel
3
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Iron drive: does this fusion superengine require clarketech?
There's very little reason to fuse heavier elements in general, partially because it is technically much harder (you need higher pressures and higher temperatures even than the regular flavors of ...
- 72.4k
7
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Accepted
Iron drive: does this fusion superengine require clarketech?
Can we fuse hydrogen all the way to iron at your tech level? Sure, why not? If stars can do it so can we.
Would we use it for propulsion at your tech level? Probably not, no.
Why? Because the energy ...
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15
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Iron drive: does this fusion superengine require clarketech?
To fuse hydrogen (not deuterium or tritium) to helium alone is a slow process. Just getting a given proton to fuse with another to form a deuterium nucleus is said to take billions of years, which is ...
- 55.8k
0
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Avoiding time travel or causality stuff
If you travel back in the past, you are just no longer executed by the simulation that runs the universe. Its like beeing memory pasted into amber. You float forever preserved in some past flickering ...
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Assuming there was a spaceship that could counter-act the effects of being near a black hole, could a human observe the hole dissipating?
The fundamental problem here is that the event horizon isn't simply a one-way gate, but a transition in the nature of spacetime itself. Once you are below it you inevitably descend (just as we ...
- 30.5k
0
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Avoiding time travel or causality stuff
Differentiate between light cones and universal now
In theoretical physics, there is a concept of "universal now." People who don't actually understand relativity insist that there is no ...
- 14.3k
0
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Avoiding time travel or causality stuff
Well, let's break this down a bit.
First, what is the actual problem with FTL travel?
According to special relativity, kinetic energy is asymptotic as you approach light speed. This means that ...
- 3,520
8
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How would you get a ship out of a gravity well?
Obviously, bringing something that big down to Earth is just asking for trouble. It was built in space and operates in space... subjecting it to gravity and turbulence and weather and an atmosphere ...
- 72.4k
3
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How would you get a ship out of a gravity well?
Well, first of all, they wouldn't. Bringing something this ludicrously big (90,000 tons) down to the surface on anything atmospheric just wouldn't be done with the hard-scifi level you describe, just ...
- 21.1k
3
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How would you get a ship out of a gravity well?
The most likely answer, as has been pointed out in the comments, is that nobody would try to land such a large ship in the first place. Not with any expectation of launching it again. Or surviving the ...
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1
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Avoiding time travel or causality stuff
I'm going to re-post a modified version of an answer I made to a similar,previously asked question:
The simplest solution is to assume that the 'laws of physics' including those pertaining to the ...
- 15.5k
1
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Effect of molecular clouds on space travel and civilization
Interstellar gas and dust can block some frequencies of EM radiation, but I think not all. We know this from radio astronomy.
However, EM travels too slowly for any kind of intergalactic civilization: ...
- 13.8k
3
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Avoiding time travel or causality stuff
Time travel is not a consequence of no-preferred-frame
I am familiar with the problem you're worried about: it plays an important role in the novel Exultant by Stephen Baxter. But I think it's a ...
- 13.8k
5
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Avoiding time travel or causality stuff
No Loops
The easiest way to ensure that there isn't any time travel is to make sure that there are no loops in the wormhole network. They need to form a tree-like graph with only one path from any ...
- 1,308
13
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Accepted
Avoiding time travel or causality stuff
TL;DR: Decide whether any part of your system needs actual FTL (and wormholes do not require this by themselves, if the mouths get moved at sublight speeds). If you do need FTL, handwave a preferred ...
- 72.4k
0
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Assuming there was a spaceship that could counter-act the effects of being near a black hole, could a human observe the hole dissipating?
Unfortunately, no.
Singularity and event horizon are two entirely different things. Event horizon determines the point...er... surface of no return. Singularity is where time (apparently) stops, and, ...
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6
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Avoiding time travel or causality stuff
You could just say that time travel doesn't happen. No, really - this isn't a cop-put. Sometimes nature is just like that.
Suppose you are looking at the Andromeda nebula. If you have good sight and ...
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-1
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Assuming there was a spaceship that could counter-act the effects of being near a black hole, could a human observe the hole dissipating?
Yes, absolutely, with a little adjustment.
Just to clarify, if you want actual physics, there is no "falling into" a black hole. You can approach one, but time dilation will increase ...
- 14.3k
7
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Avoiding time travel or causality stuff
The universe may have an in-built mechanism for causality protection, preventing wormholes specifically from forming time machines.
Wormholes as we understand them don't always form time machines. ...
- 6,405
-2
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Avoiding time travel or causality stuff
It sounds like you are referring to a wormhole.
Think of space like a piece of paper. Ordinarily it may take quite some time to traverse from point A to point B on the paper. But if I were to bent the ...
- 995
-2
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Assuming there was a spaceship that could counter-act the effects of being near a black hole, could a human observe the hole dissipating?
You can never escape a black hole even if you could get enough anti gravity to cross back over the event horizon. This is because the black holes gravity is so strong it has bend spacetime back on its ...
4
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Could a creature which evolved in space using sunlight and gas for energy and propulsion, glide in our atmosphere?
If they've evolved to live in microgravity in a vacuum, then the experience of a warm planetary atmosphere would be a little like putting a human in a centrifuge, spinning them up to bone-crushing ...
- 72.4k
7
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Could a creature which evolved in space using sunlight and gas for energy and propulsion, glide in our atmosphere?
If the sails are also human-scale...
Not a Chance
A solar sail's force per square meter is 9.08 micro-newtons per square metre at Earth's orbit. Even assuming you could get sunlight through the ...
- 30.2k
6
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How much liquid hydrogen is required to veer a manned probe off course into an escape trajectory in deep space?
About 70.8 metric tons
To plot courses around the solar system, I find this chart handy:
Source: Slightly upgraded delta v map of the solar system
To get from one orbit to another, simply travel ...
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