Yepperz. Realistically, it will "cost" governments tens of trillions of dollars to solve the climate problem. Over the next ten to twenty years, it will become glaringly obvious that we have no choice. When people are like, "HEY, send me to start terraforming Mars RIGHT NOW!", I wanna tell them, "OK, have fun! I'll be here. Maybe you'll get the bandwidth to email me before you die, but maybe not". I think NASA is probably realizing that any serious attempt to colonize Mars needs to be an international endeavor if it will ever have a chance of succeeding (/affording it). With a staunchly anti-globalist president, there's no good reason for NASA to broadcast that, because they also probably realize that they're gonna have to pull a Vatican and think on timescales of human generations from the get-go, so what's four or eight years? I've been trash talking a Mars shot since I got here. The public simply doesn't understand how many challenges there are to colonizing Mars, and unlike asteroid mining, there are essentially zero business incentives for sending people to Mars. That I can think of, at least. It's not hydrogen emission, it's emission generated when hydrogen bonds to hydroxide and makes water. Had to look it up, I was so confused, I thought "Why would SETI be looking at... Lyman-Alpha..?". I don't think targeting water is a terribly bad idea. Water has so many unique properties (yuge heat index, less dense in the solid phase than the liquid, relatively small temperature difference required for phase changes, should occur everywhere in the universe near a previous supernova that produced the Oxygen, etc.), and although it certainly might drastically narrow the types of "life", it seems like a decent start. I think I've said this before, but I wonder if there isn't something encoded into quasar outbursts, like if advanced civilizations ever systematically arrange matter to fall into the supermassive black holes at the center of galaxies. I doubt it's really possible to encode much on very short timescales, because the processes in the accretion disk and jets that create emissions are super turbulent and non-linear. Actually, we think the most common non-linear process energizing things there is probably magnetic reconnection (muh jerb), but anyway. The dots and dits could be days, weeks, months, or years-long, though, I guess. That'd be the best way to have an omni-directional signal, because you'd be modulating gamma-ray and relativistic particle fluxes, which are rare enough that your signal-to-noise ratio is muuuuuuch better than other wavelengths or lower energy particles, especially if it were coming from the center of your own galaxy. There are many many other considerations, though. Didn't know that about Drake and the Navy. I still maintain that the galaxy might be teeming with life, and there's not really a reason for them to bother us. Apparently there are plenty of solar systems with rocky, watery planets. There might be only a relatively small span in a civilization's development when they broadcast radio waves up into space before switching to neutrino beams or whatever. Think of it like a spherical shell of radio waves, and however many years they broadcast for, that's how many light years thick it is, and the radius of the shell is obviously growing one light year per year. The strength of the signal inside the shell decays as a function of 1/r^2; quite quickly, as the radius expands outwards. Ho boy, here we go. Pinging Devac for peer review. Like, with the naked eye? OK, you'll need an apparent magnitude of at least +6. Let's make it +4, because I don't want to voyage into the central Pacific Ocean to see this, I don't even wanna squint. We'll assume that the Alpha Centaurians (probably centaurs) have tuned their laser's beam divergence such that when it reaches us, the beam diameter is the size of Earth's diameter. And btw, they'll have to aim 4.3 years in advance, so (being nowhere near precise enough) 0.3 orbits ahead of wherever Earth is when they flip the switch. From the apparent magnitude wiki article, we'll just convert the m=0 flux for the "V"(= visible) band to m=+4 using Pogson's ratio, 2.512, raised to the (+4 - 0 =) 4th power: 2.512^4 = ~40. OK, so to have enough visible photon flux per unit area (we start with cm^2) for it to appear as an m+4 for everyone on Earth, we need 40 x 3.64E-20 (= ~1.5E-18) ergs/(s*cm^2*Hz). We need to get rid of the Hz. If we assume they're using a monochromatic beam smack dab in the middle of the visible light spectrum, say 550 nanometers (yellow) = lambda, and c = lambda*f (where c is the speed of light), so f = 3E8 (m/s)/5.5E-7 (m) = ~5E14 Hz. So 1.5E-18*5E14 = ~1E-3 ergs/(s*cm^2). 1 erg = 1E-7 Joule, so now we're at 1E-10 J/(s*cm^2) = 1E-10 W/cm^2. Sanity check before the final step: I guess this sounds kinda right. If cat toy laser pointers are around 1 mW (1E-3 W) and we're instructed to never shine them in peoples eyes (which are roughly a square centimeter), it makes sense that barely-discernible blinking lights in the sky should be around 10 million times less powerful. OK, best for last. Finally, we multiply by the cross-sectional area of the Earth... in square centimeters. Earth's radius is ~6000 km, = 6E8 cm, and pi*r^2 = ~1E18 cm^2. So those guys are rollin' with a 1E8 Watt laser. 100 million watts. Let's make it a "jiggawatt" (1E9 Watts) for funsies. According to gubbmint, you'd need about 400 windmills to power your laser. Only(?) 40 windmills for the 1E8 Watt laser. Problem is, you might want a lotta lasers. And the results for red and blue will be more or less similar, certainly well within an order of magnitude. If they built a truly dispersionless laser (not quite possible, but play along), and knew exactly where your eyeball would be at all times 4.3 years in the future, they could just use something as powerful as the toy laser, and it'd still damage your eye. Hey, what're you up to just after January 28th of 2024? Asking for a friend.... not only is it going to be a lot less work to take our atmosphere from 400ppm to 250, we're already here.
SETI & Drake Equation paragraph
Give me the energy requirements for a tightbeam visual signal from, say, Alpha Centauri B. I wanna be able to read morse code at night.
So, the final formula is: where: p - Pogson's ratio [] (dimensionless) m - magnitude [] (dimensionless) F - flux [J / (s * cm² * Hz)] c - speed of light [cm / s] λ - wavelength [cm] r - Earth's radius [cm] π - pi [] (dimensionless) Checking units: Power = [J / (s * cm² * Hz)] * [1 / s] * [cm²] Power = [J / (s * cm² * Hz)] * [Hz] * [cm²] Power = [J / s] * [(Hz * cm²) / (Hz * cm²)] Power = [J / s] = [W] No problems here. Using our values: p = 2.512 m = 4 F = 3.64E-27 [J / (cm² * Hz * s)] c = 3E10 [cm / s] λ = 5.5E-5 [cm] r = 6E8 [cm] pi = 3.14 we obtain: Power = 8.94E7 [W] So… pretty close and the difference comes down mainly to rounding. Other than that, under your assumptions, I see no problems with reasoning or method. Sorry for taking so long to respond, though. You need to double it, that's when Centaurs would get your message. Power = (p ^ m) * F * (c / λ) * π * r² Power = ([] ^ []) * [J / (s * cm² * Hz)] * [cm / s] * [1 / cm] * [] * [cm²] Power = (2.512 ^ 4) * 3.64E-27 * (3E10 / 5.5E-5) * 3.14 * (6E8)²Hey, what're you up to just after January 28th of 2024? Asking for a friend.
Thanks for the unicode formatting and generalization! I was in a hurry to get a quick response in. I'm happy to see we agree within about 10%, but if there's no calculus involved, is it even math at all?? :/
It's a good estimate of the lowermost power consumption, and you've done all the legwork. Kudos! Might be a base for fun Fermi problems or a reference point to some other interstellar communication discussions. Does it even need calculus? Beam dispersion would probably be some Gaussian bundle, dissipation is most likely adequately described as a sum of elements in form of whatnot_optical_coefficient * distance, error correction is a bunch of algebra, and involving any fancy astrophysics is just going to make us look desperate. Also, it's been a while since I had to use actual numbers to solve a problem. :Pbut if there's no calculus involved, is it even math at all?? :/
No no, I mean, when I do arithmetic or algebra only, it feels like I've cheated and made unrealistic assumptions. I'm almost inclined to go looking for an integral or something, but it's like you said, there's not a point, here. Maybe I am desperate! Us chump experimentalists use real numbers all the time. Come join us on the dark side, Devac :D. edit: But be careful out there! I've already written a satirical public service announcement skit that culminates with my pilot friend, wearing full captain's attire in the cockpit of the jets he flies, looking deadpan into the camera and saying, "Remember: If it's math, on a plane, it's a bomb."Does it even need calculus?
I just handed over my homework which concluded that the derivation of thermodynamic parameters in our model is A-OK because second derivatives are finite everywhere and third derivatives only tend to infinities when T = 0, which is, like, acceptable in critical systems under fluctuation/perturbation regime. We're all chumps, experimentalists just get swaggerific toys. Can't believe I forgot about that incident. Also, would love to see that PSA.when I do arithmetic or algebra only, it feels like I've cheated and made unrealistic assumptions.
Us chump experimentalists use real numbers all the time.
sigh NO, you say "damn, dude, are you seriously doing math for fun?" and then listen to what he says. The best conversations I've ever had have been interacting with people doing weird shit on planes. Last flight I saw someone writing up an inspection report on a '75 Targa and told him not to hate me because I drive a 996. I proceeded to have a 2-hour conversation with one of the world's foremost Porsche experts, a guy who gets paid by Larry Ellison to fly around buying Porsches for him, a guy who has bought and sold Porsches since he was sixteen years old, a guy who had so many stories about nameless rich people that I sat through four bourbons just goading him on. ALWAYS ask an expert about their expertise. You will learn shit you didn't even know you'd find interesting.
On the way back from Santa Fe, I sat next to a woman around my age, and I was working out some unit conversions in my notebook, pen and paper, just numbers and abbreviated units. She asks, "Looks like physics?", and I say, "Yeah! That's right, how'd you know?". And then she mentioned minoring in chemistry or something, but I forgot, because just a few exchanges later, we both went back to our own little worlds. Not even any awkwardness, just two people having some quality alone time on a plane. Which is about the most precious thing in the world after sharing a room to cut costs at a week-long conference.
Sorry Klein, bad joke about economics having basic logarithms and economic theory being a threat to national security. Of course I would at least ask. I've read enough of those papers to make me want to cry in my salad though. On the way back from Rwanda I actually met a dude who was pretty high up in the U.S. military. He served on peacekeeping missions in the Congo and stuff, and you bet he was opinionated on Trump. He knew a bunch of former colleagues that ended up promoted in the Department of State because they basically played the game. Shifted their plans in support of the new leader. It was an interesting perspective into how the inside of the government actually works and how the chain of command functions.
It's a much lower number than I expected, probably because in sci fi it's never a signalling laser, it's always a launch laser and that's a whole 'nuther animal. FUN FACT - disturbing portions of the historical record thinks Sirius was red. There are two real ways to resolve this: (1) presume that the historical record, as evidenced time and time again, is faulty (2) presume that the Sirians were pointing a launch/signalling laser at us for a few hundred years back in antiquity. (2) is a lot more fun and could be the impetus for a pretty fun sci fi conspiracy tale, or so I've heard. Or, if you're Larry Niven and Jerry Pournelle, you take the idea and throw it in the distant future at a completely different part of the galaxy so that your social commentary doesn't have to include people. 100MW is chump change. I've worked with powerplants that big. You can buy them on Alibaba. Which leads me to believe that divergence is more important than we're accounting for but I'm too lazy to do more than throw some numbers at an online calculator and watch it choke on the light years.
Do remember that we're discussing a case of illuminating Earth (and only Earth) with some dispersionless, cylinder-like, 100% efficient laser beam with perfect accuracy. Even then, with those idealisations, power scales with the square of the radius of the thing we want to illuminate. Accuracy is also fun: in our case, it's like pinpointing something roughly the size of a credit card on the surface of our Moon, but without the joys of 4.3 years worth of one-way delay or tracking a moving object. Also, I didn't say that divergence isn't significant. Just that it likely won't involve higher maths to find an approximation, which is semi-true. Had to do a double integral over a disk to get from intensity [W/m²] to power [W]. Here's how we can calculate the power delivered by a Gaussian beam, and it's ripe for plugging numbers in. I took the formulae and symbols from the article. There's also a calculation of how narrow the beam would have to be at its narrowest point, which turned out to be essentially zero (which I, perhaps mistakingly, interpreted as equivalent to a point source). Pinging am_Unition for peer review and help in moving it forward. It's not pretty, though. My initial intensity assumption goes asymptotically to infinity the narrower the beam, so there's possibly a problem/fuckup. I absolutely encourage everyone to play around with the numbers. Maybe it could work for other wavelengths?
Are you saying I just need 40 windmills to blind inhabitants of every close planet around? So now: How many windmill do I need to exterminate them? Asking for a friend After all, its a rational thing to do while I still have windmills and before they come with unknown intentions
That's the funniest sentence that I've read in a looooong time. But you're on a list now, ooli, you'll never be allowed into the Galactic Order. Bummer, dude. Correction: You'd need 40 windmills to get their attention by blinking out a message like a star turning on and off. OH, and I forgot to mention above, you'll need to position your laser a long, long way from the planet, because it's too close to the star for us to see anything but the star if it's anywhere near the planets. If "your friend" wanted to blind them, you'll need around, well, 400,000,000 windmills. How many do you have? How quickly does "your friend" need to exterminate said planet? "Your friend" could just cook them slowly with microwaves, and watch with enjoyment as their world grew hotter over several centuries (and you wouldn't even need to move far away from the star to do it). What I'm trying to say is that global warming is obviously not man-made, and we're gonna be in an alien stew. They'll time their arrival with when the meal's done. See now THIS is science.After all, its a rational thing to do while I still have windmills and before they come with unknown intentions