Cheap Astronomy - Dear CA 131: What's The Point?

0:00It's the 365 days of Astronomy PodGa, coming in 3, 2, 1. Hi, this is Steve Nellick. Why, why, why, why, why, why? Why, why, cheap astronomy, oh me? Yeah, why? And this is D-cheap astronomy, episode 131, what's the point? So, here we are. But we are yet to determine how it is that we're here, let alone determine the point of why we're here. Although we do think there is at least one point. D-cheap astronomy, did the universe really start from a single point?

1:01This hypothetical concept is commonly stated in popular science articles and we are guilty of doing the same here at cheap astronomy. However, it's not necessarily correct. As with most things relating to the universe, all we can really talk about is the observable universe. All evidence we have available does suggest that the observable universe emerged from a single point 13.8 billion years ago. But if the whole universe is bigger than the observable universe, which it very likely is, then it's not clear whether the whole universe emerged from that point. Of course, it could have, if in some fraction of the first second, cosmic inflation pushed the proto-universe out to distances that we neither can nor will ever be able to observe. This gives some credence to a belief that the unobservable universe

2:04could be equivalent in nature and consistency to our observable universe, which is fairly homogenous and samey up to the limits of our observation. But it is best just to call that a belief. There's no way to confirm anything we may choose to assume about the unobservable parts of the universe. Nonetheless, the current consensus working model is that the observable and unobservable universe did emerge from the same point 13.8 billion years ago. No one's disproved this yet, so it's what we're choosing to run with for now. It can't say where that point was when it all started, since it popped out of nothing and nowhere and nothing and nowhere does not have a coordinate system to identify locations. The idea of a universe appearing out of nowhere may seem extraordinary, but it's perhaps less extraordinary than a universe having been around

3:08for all eternity. Things should have beginnings, and when you were talking about the beginning of everything, it does sort of make sense that before there was everything, there must have been nothing. What else could everything have started from? But as to a causal mechanism, that's still a long way off. Current thinking varies widely, but for example, it might be the case that potential universes pop out of nothing on a regular basis and last for varying durations. All assuming that each such pop of a potential universe involves a rapid expansion of space time, meaning that each potential universe will have a certain size and duration. We could also assume that each of those initial pops of space time contain a stupendous amount of energy, which begins to cool as the space time that contains it expands.

4:08The precise nature of that energy is not clear, which are saying energy in air quotes. But whatever it may be, things begin to freeze out of it as it cools. So you get leptons, such as electrons and neutrinos, and you get quarks, which towards the end of the first second mostly coalesced into protons and neutrons. And on top of all that, you presumably also get dark matter, which is whatever it is. Anyway, that is a story that fits our universe. Other universes may have different stories. For example, theoretically, our universe should have equal amounts of matter and antimatter, but at some early point in the proceedings, matter came to dominate. There's no consensus view on how or why this happened, and it does perhaps raise the possibility that while universes

5:09may pop out of nothing on a regular basis, if they do have balanced anti- and non-anti-contents, those contents will annihilate with each other. You'd only lose charged particles through that process, but that means you lose protons and electrons, so no atoms, no stars, no planets, and no beings. But since we know an imbalanced universe has happened at least once, it may be the case that imbalanced universes are more than normed in the exception, although it's pretty likely we'll never be able to confirm that. This is the middle bit. So the next time someone asks what's the point of us being here, you could just respond by saying that our presence is just one of a vast array of alternate possibilities that have quite possibly already happened. So, since we are here, why don't we try and stay here,

6:12rather than just becoming another failed attempt? Dear cheap astronomy is space-based solar power the solution to all our problems? Well, not all our problems, and while space-based solar power, SBSP is technically feasible, it may not be economically viable. The general idea of SBSP is that you have a solar collecting facility in Earth orbit, which then transmits the energy collected as microwaves down to the Earth's surface. Microwaves are preferred since they pass through the Earth's atmosphere relatively well, and should not harm aircraft, ground infrastructure, or people if they happen to get in the way. It might seem a bit daft to intercept light that can already pass through the atmosphere, convert it into a lower energy form of light, and then pass that through the atmosphere,

7:15pass the collection of solar energy in space as a lot of advantages over collect it on the ground. Firstly, passage through the atmosphere, scatters sunlight, and higher energy wavelengths in the ultraviolet just bounce straight off. A solar panel in space can generate two or three times more power than an equivalent solar panel on the Earth's surface. Also, you can collect solar energy in space for nearly 24 hours a day. Assuming your collector is in geosynchronous orbit, at nearly 36,000 kilometres altitude, Earth will really be directly between it and the Sun, so you can keep your collector eliminated for an average 99% of the time over the course of a full year. So, that all sounds great, but now here's the downside. Since we are talking about a microwave beam with a lower intensity than sunlight,

8:19you'll need a very wide beam to transmit a worthwhile amount of power to the surface. A transmitter aperture of around one kilometre in diameter is suggested. And since you are sending a 1 kilometre diameter microwave beam across a distance of 36,000 kilometres, with the last 10,000 kilometres being through Earth's atmosphere, the beam will spread. Meaning you need a much bigger receiving aperture on the ground, which might be 10 kilometres in diameter. That's some pretty serious infrastructure involving a substantial upfront investment, not to mention public opinion challenges, around fears of a death ray, plus no one really wanting a 10 kilometre wide microwave receiver in their backyard. This is where we say it's technically feasible but economically problematic, and there are actually bigger problems with the 1 kilometre space transmitter.

9:22Firstly, it represents a lot of mass to launch and get all the way out to geosynchronous orbit, and it's also a lot of infrastructure to maintain there. In geosynchronous orbit, above the Earth's magnetosphere, solar panel surfaces are quickly degraded by the solar wind, and micrometeor strikes on a 1 kilometre diameter surface area are going to be inevitable, if not frequent. Also, you are dealing with infrastructure which is designed to maximally capture radiation, and hence that infrastructure is going to get quite hot, and there's an inverse relationship between solar panel efficiency and how hot they are. You can deal with that by any cooling system, but really that's just a heat transfer system, you'd still have to get rid of the heat somewhere, perhaps through large surface area radiator panels. But of course, that's more mass, more structural complexity, and more points of potential failure.

10:29Nonetheless, in January 2023, Caltech's space solar power demonstrator was launched into low Earth orbit, aboard a SpaceX Falcon 9 rocket. The small satellite did demonstrate that components of a space-based solar power system could work in Earth orbit, and the unit did successfully transmit a tiny microwave signal back to Earth. So that confirms the technical feasibility, but the next step of scaling it up to a meaningfully productive, an economically viable system, is where all the question marks lie. The whole thing looks to be hugely expensive, and a cost-benefit analysis is difficult to undertake, until we actually build something to scale. So, we're not meaning to write the whole thing off as a bad idea, but the cost and uncertainties involved in implementing a working system mean that it's not going to happen anytime soon.

11:32There is a commitment from several government agencies to further develop small-scale trials, which is probably the best way forward for now. This is the end bit. So, there you go. A solution to all our problems is in plain sight, although please don't go staring at the sun. Nonetheless, that solution to all our problems is about as technically difficult to achieve as the other solution to all our problems, economically viable, nuclear fusion. It's hard to say if either option will eventually work out, but if we are looking for some point for us being here, it's probably for us to keep on being here. But that's it for another episode of Dear Cheaper Astronomy. If you've got a space science question, or you just want to be, why not write to cheapastroatgmail.com

12:33and we'll connect the existential dots for you. Thanks for listening. Steve Nellick, Cheaper Astronomy. You're losing to 365 days of astronomy podcast. Cool. The 365 days of astronomy podcast is produced by the Planetary Science Institute, Audiopost Production is by me, Richard Drum. Project management is by Aviva Yamani, and hosting is donated by Libsyn.com. This content is released under a Creative Commons Attribution, Non-Commercial 4.0 International License. Please share what you love, but don't sell what's free. This show is made possible thanks to the generous donations of people like you.

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