First, you’ve got to realize that you’re making several very bold assumptions given current physics: (1) that we can build O’Neill cylinders with current or future materials that resemble anything like sci fi expects (probably not – pressure vessels are hard, mkay). (2) that we have a means to accelerate something larger than a probe to a significant fraction of light speed (this is actually the least difficult problem, but I suggest you look at the energy and travel time requirements). (3) that there’s any conceivable way for this thing to stop upon arrival (much harder problem without magic engines).
If all of the above are reasonable, then, well, you bootstrap manufacturing in situ in the asteroid belt or in a planetary ring or whatever. Not a huge problem. You obviously need to target a second or third generation solar system in order to find metals and heavier elements on arrival, but that’s trivial if you’ve solved the “stopping upon arrival using the energy and mass you brought with you” problem.
If you could send very small self replicating factories that could take their time to arrive, and upon arrival built a huge laser array used to slow down your larger shipments as they were inbound, you might be able to pull it off… With a few thousand years of preplanning. ;)
I agree with nearly all of your points. The stopping problem is the same as the accelerating problem. Assuming near infinite energy reserves, but limited power generation, then the ship would accelerate for half the trip, turn around, and then decelerate for the 2nd half. Depending on the amount of power that can be generated, earth gravity may be possible during the trip (except for the turn around in the middle).
The accelation problem is easier because you can build massive infrastructure in your home system that doesn’t need to make the journey, so it doesn’t incur the tyranny of the rocket equation. Still need massive infrastructure and huge amounts of energy, but it’s much easier to imagine a dyson swarm of lasers firing at the mirror at the back of the spaceship. :)
There’s no reason that we would expand out at the speed of light in one direction. It’s well within the realm of possibility that we can intercept rogue planets or large asteroids to use as long time habitats. Also we can expand in millions of directions at once at sub-light speed. The journey make take a million years, but we’ll reach a million places at once.
I didn’t say speed of light – just a significant fraction of it. Even 1% is extremely ambitious from an energy budget perspective. 10% or higher is probably achievable for small outbound probes using laser based acceleration – but they’ll just cruise by systems without any means to stop. For large “settlement” ships or similar, even getting 1% would be colossal amounts of energy (like percentages of the sun’s total output). So, yes, you’ll need to take the slow road.
Rogue planets come within a few light years of Earth. We could probably have a low speed, multi-generational ship to intercept one in a few hundred years. Once we’re on we’re hopefully good forever. Likely we’ll come close enough to some other interstellar bodies we could populate as we travelled. Exponential growth is bound to take off.
Yeah, if we aren’t in a hurry, and we can set up some fusion reactors and such on them and build whole civilizations on these rogue planets in the dark, it would work. Depends on how early and often we set up shop on passing planets, but in theory we could colonize much of the galaxy in a few revolutions around the milky way. So, under a billion years. ;)
The materials have been shown and proven in theory. It is simply a matter of building the space based manufacturing and infrastructure required. This is like Romans talking about what it will take to build nuclear power plants if they could somehow imagine them. I laid out the economy scale that I am talking about at the outset. This is an order of magnitude, or more, larger total human economic output. An era when this construction scale is not very novel.
Assuming we are talking about an era when Sol has a thriving space industry and the Solar system is broadly colonized.
If we are colonizing the rest of the Solar system, we figured out large scale and pressure vessels already. Once we are building in space with materials sourced from space, most of the problems go away.
Worst case, a ship can use nuclear detonations to both accelerate and decelerate easily within the limits of known materials. This has been thoroughly researched in a US program that was only canned as part of anti nuclear proliferation act. This system can easily handle both ends and traveling faster than any current method. It is a worst case. If we can master fusion, there are other ways as well.
I said generation ships too. I don’t care if it is slow and I think humans could cope just fine on a large enough ship, assuming we don’t find ways to put humans on ice.
I highly recommend checking out Isaac Arthur’s content on YT as he goes though all of this kind of stuff in detail but even further into possibility and future tech. I’m getting much more specific into a time and constraints than what IA does in general.
we figured out large scale and pressure vessels already
No. This is an assumption not borne of physics or engineering. There is no magic material that will make large scale pressure vessels suddenly viable. It (and space elevators) are mathematical constructs, not real things.
Use this calculator. checalc.com/calc/vesselThick.html – punch in 15 psi for pressure, and 100F for temperature. Play with your pressure vessel. Wall thickness of large scale habitats will need to be many metres of solid steel (or equivalent material). Even if you magically mass produce carbon nanotubes or something, you still need hundreds of millions of tonnes of carbon to pull off any large scale vessel. Your talking about ingesting entire asteroids just for building materials. You don’t launch that shit on an interstellar journey.
I would say degenerate matter in a neutron star is a better conductor of sound. It’s densely packed and doesn’t have to deal with pesky things like electromagnetism slowing down the sound wave.
Sinclair is ok. He wrote a book called “lifespan” that’s pretty well regarded. Also look up Aubrey de Grey. His book, Ending Aging, is also good. He himself is problematic though. If you’re interested in this sort of tech, also look up the SENS foundation (I donate there).
Fair warning, most everything focuses on increasing healthspan, not lifespan. I.e. Being able to be active and alert at 90. There’s no way for tech to guarantee an increase in lifespan within our lives, because we would need a few generations of evidence to guarantee that. So at most you’ll get partial evidence and animal models. But you gotta start somewhere. And if we’re lucky, we’ll stop be around for the ‘proof’ in 200 years :-)
Wouldn’t healthspan and lifespan go hand in hand tho? Like… I can’t imagine a 99 year old going for a marathon today and just dropping dead tomorrow due to old age. Wouldn’t an increased healthspan also include an increased lifespan?
Probably? I think the difference is the reasearch is going into meaningful things, such that would keep you healthy rather than just alive. I think it’s just a matter of semantics though.
Those two graphs have different scales on the y-axis. One is Irradiance per nanometer of wavelength, and one is Irradiance per terahertz of frequency. Both graph’s y-axis are called “spectral irradiance”, despite being different things. This causes most of the distortion between the two graphs, and can even change the location of the absolute maximum.
The graphs’ x-axis have different units. This causes some distortion too, but wouldn’t change the absolute maximum. It would help if they used a log scale in both cases, because wavelength and frequency are inversely related, so then the graphs could just be horizontally flipped.
So, look at the top graph (by wavelength), and see how much power is in that 1000-2000nm area. It’s still a lot, just spread out over a large area. It’s the same amount of power in the lower graph (by frequency) shoved into the much smaller area from 150THz to 300THz. Since it’s in a smaller area on the lower graph, it has more power-per-unit-of-x-axis.
Thank you. I understand most of your comment, and it makes sense. However, I still don’t understand how the change of units in the y-axis would cause a different maximum. It seems to me that the y-axis for both use the same formula with their respective x-axes: W/m^2/x.
It’s because the wavelength and frequency are inversely related. When the wavelength is low and the frequency is high, the wavelength is also moving very slowly, compared to the frequency which is moving very quickly. Since the frequency is changing so quickly, the power-per-unit-frequency is lower at higher frequencies, and higher at lower frequencies (at least relative to the power-per-unit-wavelength).
Let me try and use a car analogy:
You’re driving home through Wisconsin, and you live on the border between Wisconsin and Minnesota. The mile markers on the road decrease as you go, reaching 0 at the state border, where you happen to live.
The cows along the highway are evenly distributed, so if you count the cows as you drive, but restart your count every mile when you see the mile marker, you will reach the same number of cows every mile.
Now, the frequency is inversely related to the mile number. The frequency in this case refers to your children in the back seat asking, “Are we there yet?” They know damn well how far it is to home, because they can just look at the mile markers. Regardless, their rate of asking increases as the mile markers go down. When you’re at mile marker 100, they ask once every 10 minutes. When you’re at mile marker 1, they ask 10 times per minute.
If you instead look at the number of cows between “Are we there yet?” asks, then you will find that the cows-per-ask is much different from the cows-per-mile. At high distances (low frequencies), the cows-per-ask is very high, while at low distances (high frequencies), the cows-per-ask is very low.
Now, the article is looking at power-per-unit-frequency, so you’d actually have to measure the rate in change of how often the kids ask “Are we there yet?” And that would give you a little different result. You might need calculus to correctly calculate the derivative of the number of asks. But hopefully this illustrates that you can get different results, by using a different per-thing to measure your value.
This covers it all well, but I think a simple explanation is that although “W/m^2/x” looks the same on the axes, it’s not the same. f=1/w, so one axis is W/m^2/f and one is W/m^2*f. The article makes a big deal out of the differences as if the x axis were the only difference, but they’re just very different things being plotted.
For example: You eat too many potato chips and that’s bad for your health. Now you don’t go cold turkey on the snacks, but buy carrots instead and eat those.
How? You do it often enough. Do it for half a year, every other day and it’ll become the new habit.
The short answer is yes, you can trade one addiction for another and no, it doesn’t necessarily cause spiraling.
The long answer is yes, with a great deal of patience, you can condition yourself into just about anything. Breaking from an addictive personality is far from easy and requires a deep understanding of yourself and your triggers. Introspection and therapy aplenty. There can be relapses or worse if you try to hack together a treatment plan for yourself. Support groups can be helpful and leaning on friends and family, when possible, can make or break you.
While reading text your brain will bulk recognise what it interprets as common phrases and sentence fragments to build an internal lexical model to then interpret. After a while as you get more proficient at reading this becomes a mostly subconscious operation, which then hands concepts from what it’s read to your front of mind to further deal with.
If you blend contradictory common phrases together your brain will bounce through the phrase/fragment recognition part fine. Then it will trip over the lexical parsing of them, suddenly requiring a lot more mental horsepower to figure out what’s going on. Basically your front of mind task will be interrupted by your subconscious task basically going “what the hell is this!? I can’t make sense of this, you have a look” as it dumps a jumble of words on you.
For example, has anyone really been far even as decided to use even go want to do look more like? That phrase broke the internet about 10 years ago and it’s a pretty good example.
G is the gravitational constant, the m’s are the masses in question, and F is the force generated. The r is radius from the center of one body to the other; that is, height. If it didn’t decrease, orbits wouldn’t exist the same way and astronomers would have laughed Newton out of the room.
I could give you a link if you really want, but it’s the Newtonian gravity equation, so it’s probably just going to be “Gravity” on Wikipedia.
G is also fixed in GR, although it’s not guaranteed to manifest in a neat relation like that in every situation because spacetime curvature has a lot of components at every point, and they interact super nonlinearly.
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