231–240 of 391 posts
The trilogy _Three Body Problem_ is a good read, and has something to say about this. :)
There was a paper recently that argued that the habitable zone is smaller than anticipated because either the concentration of carbon dioxide will be too high (and thus toxic at least to life on Earth) or - for small stars like this - there will be (toxic) carbon monoxide in the atmosphere. https://phys.org/news/2019-03-complex-life-require-narrow-ha... (good article with link to the paper)
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If our current ideas about physics are correct, acceleration _never_ gets you to speed of light. The faster you go, the higher your relativistic mass, so if you accelerate by constant force, the lower your acceleration. Conversely, to keep acceleration constant, you would need larger and larger forces, in the limit ‘infinite force’. For more and better info, see https://en.wikipedia.org/wiki/Space_travel_using_consta…
> The faster you go, the higher your relativistic mass, so if you accelerate by constant force, the lower your acceleration. The Wikipedia article you linked to calls this (rightly) a "half-myth". It depends on your reference frame.
The spaceship's own reference frame will be a whole different story. If I understand correctly, it will perceive its own mass to be constant, the rest of the universe's relative speed to asymptotically approach the speed of light, but also the rest of the universe to get progressively squashed in the direction of travel (length contraction dual to time dilation), with the two effects multiplying up in such a fashion that the Newtonian relation between the integral of your acceleration and the time it takes to the destination seems to hold throughout.
In other words, for the spacefarer's schedule, it's as if the speed of light does not actually play a role: they can always accelerate more/go arbitrarily faster to get to their destination faster. However, from their point of view, it is as if the universe around them will deform in the process to accommodate this, and from the stationary observer's point of view, it is as if they are actually still moving slowly but tricking themselves into thinking otherwise by accelerating their passage of time.
The note that it's an old star makes me worry though. If they're older then us, and habitable, were they inhabited? Our current era is a few hundred years of real, directed technological development. A few thousands years either side of that and who knows what we'd be looking at, but you imagine that - hopefully - the general progression of technology is forward. So if they were inhabited, what happened to them? Are…
The note that it's an old star makes me worry though. If they're older than us, and habitable, were they inhabited? Many dwarf stars have more solar flares than our sun, while their planets are closer. Teegarden's star is supposed to be very calm right now. I have no idea if that is likely to be true over most of the past 8 billion years. The amount of water they gather may be smaller, and their closer planets may no…
The Drake equation has 7 terms. When it was first proposed, all but the first were complete unknowns. We're just barely starting to gather enough data to start tightening our guesses for the next two. The rest (which include the two you used) are complete unknowns. You say "those are actually pretty high odds", but by whose measure? There's exactly one data point to support that assertion, and right now that data point suggests that the odds are 100% (with an uncertainty also approaching 100%). We're still decades away from really having the data to assert anything at all about the presence of life outside of our solar system with confidence.
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It's incredibly improbable. While much of the planet's surface is recycled constantly, there are also huge swaths of land that are billions of years old and haven't changed enough to hide evidence of complex society. Dinosaur fossils are rare, but not that rare. Tiny ones are abundant. If all life on earth ceased today, you could come back here in a billion years and find plenty of evidence everywhere. Maybe it's not…
> there are also huge swaths of land that are billions of years old and haven't changed enough to hide evidence of complex society Do you have any examples? The article in the sibling comment to yours directly states that the oldest large-scale swath of land (in the Negev Desert) only dates to 1.8 million years.
[1]: https://news.nationalgeographic.com/news/2014/02/140224-olde...
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I think current technology makes no sense when talking about interstellar travel. I wonder how long it'd take, seen from the perspective of the ship, if we had an engine capable of delivering a constant 1g acceleration. That's the way we'll want to travel, after all.
constant 1g acceleration gets you to speed of light pretty quickly (around 1 year), so still around 12 years.
And to think that there is likely an Easy Mode system out there. A habitable planet on the low end of the mass spectrum needed for a stable atmosphere with other habitable planets in-system. And all that close to another star with habitable planets, possibly in the sub-lightyear range. Basically everything ripe for a spacefaring civilization to grow without too much trouble and with plenty of motivation. The Earth is…
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I think current technology makes no sense when talking about interstellar travel. I wonder how long it'd take, seen from the perspective of the ship, if we had an engine capable of delivering a constant 1g acceleration. That's the way we'll want to travel, after all.
constant 1g acceleration gets you to speed of light pretty quickly (around 1 year), so still around 12 years.
Seen from Earth, it'll be around 13 years (takes a year to got close to c and another to decelerate - that is two years to travel roughly a lightyear, then 11 to travel 11).
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Meh. 200 years aro they would have called you insane for wanting to fly between continents, let alone to the moon.
They also would have called you crazy for saying you wanted to turn lead into gold with alchemy. Fact is, most of the time the people who say something can't be done are right.
Which is doable but exceptionally expensive.
Not a strong argument against the ship unless you're calling it a waste of money.
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I'm locking the area to a specific region. If I divide the universe into 365 discrete areas, the problem is exactly the same.
If you're locking the area to a fixed area out of the 365 discrete areas, the birthday paradox isn't applicable anymore. Birthday paradox only says something about whether a pair exists among all areas.