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The Current Transcript for January 2, 2018

Host: Anna Maria Tremonti

STORIES FROM THIS EPISODE

Listen to the full episode

Prologue

[Music: Theme]

SOUNDCLIP

VOICE 1: We will never be anywhere near the ideal which is the infinite knowledge. It wouldn't be very nice if all problems were solved because there would be nothing to think, and it would be a bit like death.

ANNA MARIA TREMONTI: Time to start your new year with a profound question. Is there a limit to what we human beings can know? As a species we're more knowledgeable about many complex things. But is there a limit to what our minds can understand? In an age of artificial intelligence and rapid technological innovation - is everything knowable? Today we've invited some very big thinkers to explore this. We have the United Kingdom's Astronomer Royal. We have the man credited for creating quantum computing and a philosopher who concentrates on knowing knowledge - all in an hour. Also today, our bodies instinctively know many things, including where we and our limbs are in the spaces around us. Actor Ruth Marshall never thought about any of that until she had to.

SOUNDCLIP

RUTH MARSHALL: I would lift that foot up and I would demand that it stayed. And I would start to notice the other leg was starting to wiggle its way off the side of the bed. It was really like they were plotting an escape and I had to capture them.

AMT: What she calls her perfectly awesome life was turned upside down with a diagnosis of a rare condition. She found a way to laugh about it. Hear her in half an hour. And...

SOUNDCLIP

VOICE 1: This is what we have temporarily set up. I've pretty much maxed out the power that I have available here at the house.

VOICE 2: How much money is this making you?

VOICE 1: Roughly about $10 a day.

AMT: That person maxing out the available electrical power in his B.C. home is a bitcoin miner - one of countless worldwide whose overheated whirring machines run night and day to create and process cryptocurrency. But so many machines are sucking up electricity and such great amounts that critics are now questioning bitcoins environmental impact and giving a whole new meaning to the phrase dirty money. We're starting there. I'm Anna Maria Tremonti. This is The Current.

Is bitcoin an environmental hazard?

Guests: Drew Taylor, Alex de Vries, and Leo Weese

SOUNDCLIP

VOICE 1: Are you ready?

VOICE 2: [Laughs] I'm ready. I'm ready.

[Sound: Warehouse machinery]

AMT: Well, what you were hearing behind that conversation was the buzzing of a warehouse in Iceland full of thousands of cryptocurrency computers. The specialized machines are working 24/7 earning bitcoin by solving puzzles and a process called bitcoin mining. Cryptocurrencies such as bitcoin are rapidly rising in popularity and value. One bitcoin is currently worth $13,500, which means cryptocurrency mining operations are popping up all over the world, including in Canada. But the huge amount of processing power and energy required to mine bitcoin has some people concerned that the cryptocurrency will be a disaster for the environment. We'll get to that in a few moments. But first, to find out how bitcoin mining works, I'm joined by Drew Taylor. He's a computer engineer and he is also a bitcoin miner. And he joins us from Montreal. Hi.

DREW TAYLOR: Hello.

AMT: Tell me a little bit about the setup in your home. How does the setup in your home to mine bitcoin compare with the sound that we just heard in that warehouse in Iceland?

DREW TAYLOR: Well I only have two machines. I would say roughly comparative to running a vacuum cleaner in my kitchen 24 hours a day. It's very noticeable noise. It's about $200 extra to my power bill each month. Essentially you can imagine the machines are plugged into the kind of outlet that you would have for your washing machine or your dryer. They're on [unintelligible] Volt electricity. And they're loud.

AMT: Do your neighbours complain?

DREW TAYLOR: No, it kind of is a bit of a white noise that blends into the background. It's very possible that my neighbours can notice something, but it doesn't sound like any sort of discernible thing that they would complain about. I've received no complaints.

AMT: How big are the machines - the computers?

DREW TAYLOR: They're actually not very big and they are computers, but they don't have a monitor. And the form factor is rectangular. It looks like a tiny brick and it is about the same weight as a brick - only slightly larger than a regular brick.

AMT: Okay, so you're using all this electricity. Do you have heat in that room that you wouldn't otherwise have?

DREW TAYLOR: I actually don't. In that particular room where the machines are I don't have the heat turned on at all. And the other rooms in the house. Yes, I am heating them. But essentially it is free heat for at least one room.

AMT: Okay. How does bitcoin mining actually work? What are those computers actually doing?

DREW TAYLOR: Essentially the way that it works is that, I am part of a mining pool which means that I share [unintelligible] that we get every time we solve a mathematical riddle. And what solving this mathematical riddle enables us to do is take a group of financial transactions, whether it's a purchase or a peer to peer transaction - two people exchanging money across the bitcoin network. It allows a bunch of transactions to be grouped into what's called a block, which is added to the block chain which is the database technology which powers these cryptocurrencies. And once transactions are grouped together inside of a block, all of the other nodes - different computers on the network will confirm that the transaction was valid and that the proof of work for the mathematical riddle is valid. And basically a point of having this mathematical [unintelligible] all of us bitcoin miner are racing to solve is that it's so computationally expensive. It takes a giant network of supercomputers to solve this mathematical riddle so it would be very difficult for a single person to solve this riddle alone. Whether it be on paper or just with their own computers because they would have to be faster than an entire network of millions of supercomputers. This is what protects our money. No one single person is going to have enough computational power to guess better than an entire network of people.

AMT: Okay. And so you let these computers run 24/7. Do you have to do anything to them or do they just keep running?

DREW TAYLOR: They do require a bit of maintenance. They run very hot. Heated temperature has to be regulated. They also produce quite a lot of wind energy. The fans on the machines - because it is a rectangular form factor and the small ends, one of them has a fan which sucks. The other side has a fan which blows. You can imagine that wind energy is going through the unit. And that is the majority of the noise that you hear from a bitcoin mining farm. It is fans. And they're going, on average, between six and seven thousand rotations per minute.

AMT: Okay. But that's physical maintenance. Do you have to do anything to maintain the computers from doing these puzzles or does it just keep coming to them and they keep solving and keeps turning over?

DREW TAYLOR: Well these machines are set up to do it out of the box, if you will. The main thing that you would have to configure - on a new machine it takes less configuration on an older machine there are more options and more maintenance which is needed. But the newer machines they tend to auto, which adjust to different heats and temperatures and different environmental conditions.

AMT: Right. What's in it for you? What does it earn you?

DREW TAYLOR: I'm currently earning at today's value which is just under $17,000 Canadian. I'm earning about $100 a day.

AMT: $100 a day to do that. Does that pay your bills? Is that good or do you want to earn more than that with those machines?

DREW TAYLOR: Of course more is better. And I do have more machines on the way from China. They'll be arriving probably at the end of the month.

AMT: Well let me just interrupt because we're almost out of time. What about the idea of the environmental footprint. You're using a lot of electricity.

DREW TAYLOR: It is using a lot of electricity. There are lots of stipulations which peg the networks electricity consumption or around that of a small country like Ireland. But I will say that it doesn't necessarily have to be this way. Of course it does use a lot of electricity. But you have, for example, the largest single known bitcoin mine - because there's a lot of unknown mines in the world. Bitcoin mining is somewhat secretive and there are a lot of miners which don't release their statistics. But the largest known mine is in Iceland and the majority of their energy is from geothermal and steam energy. It is very clean green energy. Not everyone is doing that of course.

AMT: Okay. Well Drew I'm going to talk to someone who's trying to track that. But thank you for explaining it all to us. Thank you.

DREW TAYLOR: Okay, thank you.

AMT: That's Drew Taylor. He's a computer engineer and a bitcoin miner. He is in Montreal and we apologize for that connection. That was Skype. As bitcoin mining grows in popularity from DIY operations to massive mining farms in Iceland - and apparently they are in China as well -some are sounding the alarm about just how much electricity is being consumed to power bitcoin. Alex de Vries is a data consultant and the creator of the Bitcoin energy consumption index. It tracks energy use by the Bitcoin network. Alex de Vries is in Amsterdam. Hello.

ALEX DE VRIES: Hi there.

AMT: Now, do I have this right, you used to be a bitcoin miner and you stopped?

ALEX DE VRIES: Well, to be honest I didn't mine bitcoin. I did use bitcoin in the past. But at some point I actually read an article somewhere in 2015 that stated that each bitcoin transaction was using the energy equivalent of one and a half U.S. households for a day, per transaction. At that point I abandoned bitcoin completely and I started wondering why nobody was writing about this because that was the first time I read about it. Bitcoin has been existing since 2009 and it was actually very little information I could find about it. To be honest as a user you're never confronted with these energy costs because [unintelligible]. As a user you don't get to see them and it's pretty hard to find information on that number. That's why I started publishing daily estimates for bitcoins energy consumption.

AMT: What is the daily estimate?

ALEX DE VRIES: Right about now, it's almost 37 hours [unintelligible] per year, which is the electricity consumption of a country like Bulgaria.

AMT: Okay, per year. And how does that compare with energy use by traditional financial institutions that are processing transactions?

ALEX DE VRIES: Right. Of course the real shocker here is that the bitcoin network only processes 350,000 transactions per day. If you average out the number I just mentioned per transaction you'll find that each bitcoin transaction uses the energy equivalent of about 300 kilowatt-hours per transaction, which is now enough to power the one U.S. household for almost 10 days. And if you compared that to a Visa transaction, Visa is doing maybe something like four to five watt-hours per transaction. For a bitcoin transaction that's 70,000 times more.

AMT: Obviously excessive electrical use for what you get on the other end.

ALEX DE VRIES: Absolutely.

AMT: And so how does this translate into an environmental impact? What are your concerns?

ALEX DE VRIES: I think the real concerning part is that the majority of these bitcoin miners are located in China and that makes sense because electricity is cheap in China, especially coal-based electricity is cheap in China. That's where it gets really painful because all of this coal-based electricity is going into the bitcoin network and coal electricity has a massive carbon footprint. That actually costs each bitcoin transaction to have a massive carbon footprint and I actually got an estimate for that as well. I'm currently estimating that each unique bitcoin transaction has a problem footprint of 150 kilograms of carbon dioxide. Now I don't know whether this is for a U.S. or Canadian household. But I do know that for a Danish household, each household uses - well has the carbon footprint of 800 kilograms of carbon dioxide per year. Compared to one bitcoin transaction being 150 kilograms of carbon dioxide, that's a massive, massive number.

AMT: Now we just talked to a man in Montreal. Apparently Quebec is attracting a lot of bitcoin miners because their hydroelectricity is cheaper. Any thoughts on that?

ALEX DE VRIES: Well I recently did publish some thoughts on that and it came down to this. In the end the whole bitcoin network is using so much more energy than our traditional system. No matter how you look at it it's going to be several thousands of times more than what we currently need for our traditional system. That can never outweigh any gains by doing this with hydro-electric power or any other form of clean energy.

AMT: Okay. Alex de Vries I want you to stay with me. We've got someone else who's waiting in the wings here. Leo Weese has been listening in. He's the president of the Hong Kong Bitcoin Association. Leo Weese is in our studio in New York. Hi.

LEO WEESE: Good morning.

AMT: First of all, what do you say to the calculations that Alex de Vries has just raised with concerns about the environmental impact of bitcoin mining?

LEO WEESE: The total energy consumption of bitcoin that Alex de Vries calculated - I don't think that's too far off. I think that's the right magnitude even though it's hard to say exactly. I don't think it's appropriate to calculate this down to the amount of transactions per day because the mining reward is largely dependent on new bitcoins being created and those bitcoins are very valuable. And this leads miners to essentially waste a lot of electricity to generate those new bitcoins. It's not that dependent on the amount of transactions per day. If a bitcoin block would not contain any transactions, it would contain 10 times as many transactions. It would still have the same reward and it would still cost the same electricity to produce.

AMT: It's still using a lot of electricity though.

LEO WEESE: It is, yes. And so are many other things. So is the Internet. And for somebody who doesn't use bitcoin it might seem very excessive. While for somebody who does use bitcoin it might seem perfectly natural and perfectly unnecessary.

AMT: Alex de Vries what do you say to that? That we're already using a lot of electricity on the Internet anyway.

ALEX DE VRIES: Well, I mean obviously that is true. The Internet is using a lot of electricity. But then again the Internet provides a lot of utility and if you compare what utility bitcoin is currently providing. I'm actually reading that the only utility bitcoin is providing is that people are using it or actually buying bitcoin in order to sell it at a higher price and they're not actually using it for anything else. That's not a whole lot of utility we gain from [unintelligible] such huge amount of electricity on that.

AMT: Leo Weese what do you say to that? That it's using the energy equivalent of Bulgaria. That it uses the energy equivalent of 10 days in a U.S. household.

LEO WEESE: The amount of energy consumed between two countries can be hugely different. Different reasons for why a country would use a lot of electricity or it would use a lot of energy, which are also not exactly the same thing. I think it has to do with us having a very difficult time to grasp how much electricity really is. A country using electricity as a whole - that might seem a lot. But at the same time that country might get its energy from other sources or that same time that country might not have electricity inefficient industries.

AMT: Okay. We know that China is using a lot of bitcoin mining and they use a lot of coal. Is it a dirty or kind of currency because of the electricity it uses?

LEO WEESE: Bitcoin mining incentivizes you to seek out the cheapest electricity you can find. And this type of electricity is usually excess electricity. It's usually electricity that would otherwise be wasted or burnt. And it's electricity inaccessible. It's electricity in faraway locations which is often hydroelectric power plants that have been built in the middle of nowhere often to attract industries, but that are lying dormant and whose operators are willing to sell that electricity for very cheaply as long as they can.

AMT: Lying dormant because they were made huge hydroelectric dams that they miscalculated on.

LEO WEESE: And they built those dams high up in the mountains where nobody is willing to build a factory because there's no highways up these mountains. There's no roads.

AMT: Alex de Vries what do you think?

ALEX DE VRIES: To be honest I think bitcoins energy consumption is exploding and the demand for bitcoin is increasing. That will mean that the demand for more bitcoin miners will continue to increase and that means the amount of electricity demand will be continue to increase. I mean even if we are using excess energy at the moment, it's really hard to get a pretty good view on that. Demand is increasing so far that pretty soon we'll need to build dams just to do run all these machines.

AMT: Leo Weese do you think that's a problem? Do you think there are new ways to power this?

LEO WEESE: Every four years the bitcoin mining reward halves. Meaning currently there are 12 and a half bitcoins being created. In three years it's going to be only a little bit more than six and eight years it's going to be just a little bit more than three. Even if the electricity consumption is dependent on how much these bitcoins are worth. Even if bitcoin were to double in price every four years, it would still not use more electricity than it does today.

AMT: Alex de Vries is there a way to lower the electrical consumption of bitcoin?

ALEX DE VRIES: Well the easiest way would be for the current price to crash because if there's no revenue then of course we can't pay for all electricity.

AMT: But who is paying for it by the way? Is it the regular taxpayer people? People are just operating this stuff out of their houses. Who's really paying for it?

ALEX DE VRIES: It would be helpful if the actual users were paying for the electricity because then it would make you more aware of how much costs are in the system behind the scenes at the moment. But it's just the miners, really. The miners are taking all the revenue and they are paying the electricity bill for all the machines that they have running. As a user you're not faced with that.

AMT: Okay. I'm sorry gentlemen, we're out of time. We're going to have to leave it there. Interesting discussion. Thank you for joining us today.

ALEX DE VRIES: Okay. Thank you.

AMT: That's Alex de Vries. A data consultant and the creator of the Bitcoin Energy Consumption Index. He's in Amsterdam. Leo Weese is the president of the Hong Kong Bitcoin Association. He's in our New York studio. The news is next and then in 2012 Canadian actor Ruth Marshall led what she called a charmed life until some odd symptoms led to a diagnosis that turned her life upside down.

SOUNDCLIP

RUTH MARSHALL: I had absolutely no sense of where my legs were and in fact I had completely forgotten how to walk.

AMT: Her story is coming up right after the news. I'm Anna Maria Tremonti. This is The Current on CBC Radio One.

What's it like to re-learn how to run, walk, pee, and have sex? 'Degrassi' actor tells her story

Guest: Ruth Marshall

AMT: Hello I'm Anna Maria Tremonti and you're listening to The Current.

[Music: Theme]

AMT: Still to come, is there a limit to human knowledge? Some say there is not. And that means there are also no limits to human progress. Others say there are things in this world that are just too complex for our brains to grasp. We have that debate in half an hour. But first, walking it off.

[Music: Adaptation Theme]

AMT: Well if you've watched Degrassi: The Next Generation you may recognize the voice of Ruth Marshall. She's the actor who played a mother to one of the teen characters in the iconic Canadian TV show.

SOUNDCLIP

VOICE 1: I called the real estate agent. She'll be here at four o'clock for the appraisal.

VOICE 2: Oh she's probably paying for it to put the house on the market.

VOICE 1: And hire one of those stagers.

VOICE 3: Your're selling our house. Did I miss the memo?

VOICE 1: We were going to tell you tonight. We just wanted to iron out some details first.

VOICE 3: But I love this house. It's like part of our family.

VOICE 1: It's time to move on.

AMT: Ruth Marshall in Degrassi: The Next Generation. She's also acted in such Hollywood films as Casino Jack, Dolores Claiborne. In 2012 she was living a charmed life. Her acting career was thriving. She was happily married with two boys. All of that suddenly changed when her feet started acting oddly. And that ended up leading her to a long and ongoing process of adapting to her new reality. Ruth Marshall is the author of Walk It Off: The True and Oddly Hilarious Story of How I Learned to Stand, Walk, Pee, Run, and Even Have Sex Again After a Nightmarish Diagnosis Turned My Awesome Life Upside Down. As part of our season long project Adaptation. She's with me in Toronto. Hello and welcome.

RUTH MARSHALL: Thank you so much.

AMT: Where do we begin. It's 2012 and your feet. How were they behaving oddly?

RUTH MARSHALL: Well they started tingling and I only became aware of it when I realized that they hadn't stopped tingling for some time. I was actually in a choir rehearsal and I spent a fair amount of time looking at my feet until the soprano next to me said, "Why do you keep staring at your shoes?" And I said, "My feet are tingling and it feels very strange."

AMT: You describe it a kind of like, where your feet are almost just starting to fall asleep. That kind of tingling at first?

RUTH MARSHALL: That's right. Sort of low grade, pins and needles that would not go away.

AMT: What other symptoms did you have?

RUTH MARSHALL: Well as time went on the tingling feeling started moving up my legs. It was causing me to trip. I was stumbling about a little bit. I couldn't quite - I couldn't quite master moving my legs as well as I used to.

AMT: And what did you think it was?

RUTH MARSHALL: I thought it was M.S. actually because I had consulted Google, which is a mistake. And I mentioned it to my mom and she thought it was because I did hot yoga and she didn't trust it. One of my sisters suggested that it was because I wore high heels too much. My husband thought it maybe was because I was ageing. Anyhow, it all resulted in me going to the doctor.

AMT: And you get a diagnosis. What is it? What are you diagnosed with?

RUTH MARSHALL: Well originally I got an MRI and I find out that I did not have M.S. It wasn't until many months later that I got a diagnosis.

AMT: And the name is...

RUTH MARSHALL: And the diagnosis was I had a spinal meningioma which is essentially a tumour - a non-cancerous tumor on my spine. It was big.

AMT: I'd never heard of a meningioma. Tell me more about it.

RUTH MARSHALL: Most people if they are discovered to have a meningioma - it's a brain meningioma the more common type. The less common type is a spinal meningioma. But in both cases, as I understand it, they usually are so benign that they don't affect you at all. And in fact many people live their whole lives not knowing that they had a meningioma until they die of some unrelated cause. And if an autopsy is done or what have you, a doctor might say, "Oh and she or he also had a meningioma and it never bothered them."

AMT: And yours was there for a long time then. It was growing I guess.

RUTH MARSHALL: It was growing apparently for at least 10 years that it had been growing on my spine unchecked and unnoticed.

AMT: Until it finally was at the size where it was starting to affect things.

RUTH MARSHALL: It was big. It was completely hardened. It was wrapped around my spine and it was sitting on my proprioceptive nerve which is the nerve which tells your body where it is in space.

AMT: You have surgery to remove this. What was your experience waking up from that surgery?

RUTH MARSHALL: It was crazy. It was supposed to only be a three-hour surgery. My husband and my parents were notified halfway through and the surgeon said, "This is rather difficult. We're going to be here longer and we'll just have to see what happens at the end." They did successfully remove the tumour, but I had absolutely no sense of where my legs were. And in fact I had completely forgotten how to walk.

AMT: And so describe the sensation in your legs at that point.

RUTH MARSHALL: It was as if I had no idea where they were. I really didn't. I would look at them, I could see part of my brain understood that my legs were there and attached to me. But I could not figure out how they were supposed to move and what they were doing. If I closed my eyes I couldn't even visualize them. It was almost like having vertigo. I felt very disoriented. I really had no sense of where my legs or feet had gone.

AMT: You talk about them going rogue essentially.

RUTH MARSHALL: Yes, that was exactly it. I would wake up in the night and I would open my eyes and I would see that one leg was very clearly trying to escape. It had left the side of the bed. And while I was sort of kind of chasing that one to put it back on the bed, I would feel pain in my other foot and I would notice that it had gotten itself caught between the tray table and my bed. And so I would lift that foot up and I would demand that it stayed. And I would start to notice the other leg was starting to wiggle its way off the side of the bed again. It was really like they were plotting an escape and I had to capture them.

AMT: You're very funny about this.

RUTH MARSHALL: Well, it was terrifying at the time. It was only funny the next day to me in a way when I was telling my husband what had happened in the night.

AMT: I was just going to say, it sounds very funny the way you say it. But it's because you have no feeling so you don't know that either leg is moving around.

RUTH MARSHALL: That's right. I just knew that eventually I had to get control of them so I would put them in lockdown.

AMT: And it's not funny at all, it's really serious. And it's scary.

RUTH MARSHALL: It was very scary.

AMT: And so what was the medical explanation for that?

RUTH MARSHALL: As my cousin who's a surgeon explained it to me, it is because you're proprioception - which took me forever to say properly and spell properly - is the nerve that tells you truly where your body is in space. And so it was as if the whole lower half of my body was lost in space. And so that was why I had to go to rehab to kind of relearn where my body was and how to use it.

AMT: And so what was the prognosis. When you got out of surgery and you were in that position where you have to tuck yourself in so you can control your legs, what were they telling you?

RUTH MARSHALL: My surgeon said that he was very hopeful that I would be able to walk again.

AMT: Hopeful.

RUTH MARSHALL: That's right. Hopeful.

AMT: And how did you hear that?

RUTH MARSHALL: Well luckily I was just on enough drugs to not register exactly how serious that was. I became very good for the several months leading up to the diagnosis. I became very good at denial. I heard that and then I just put it away.

AMT: What was your biggest fear then?

RUTH MARSHALL: Well my biggest fear was that I wouldn't walk again. But I tried not to think about that too much. I just did the work that I needed to do to move forward in the hopes that I would walk again.

AMT: You end up in a rehab facility shortly after the surgery and you have to relearn to do a whole bunch of things.

RUTH MARSHALL: Correct.

AMT: Not to get into too many details, but it's in your title to.

RUTH MARSHALL: Sure.

AMT: Going to the washroom became an ordeal. What was that about?

RUTH MARSHALL: Well it was as if all my nerves had been rewired. Completely rewired. My brain was not getting the message when I had to go to the washroom. Or it would get the message, but I couldn't figure out how to do it. That was something I actually decided to fully focus on because that seemed like the easiest problem to correct. I'll get to walking later. I just need to learn how to pee now. That was a huge focus while I was in hospital especially because many, many people who have spinal cord injuries are unable to figure out how to do that again.

AMT: What did it do to you emotionally to lose the ability to do even the most basic bodily functions?

RUTH MARSHALL: Well I tried to turn a lot of what was happening into a little bit of a joke. It was the only way that I could deal with it because it was really stunning to think that the thing that I was born knowing how to do for the first 47 years of my life I could no longer figure out how to do. I would rather than complain about it too much or talk about it too much with my family or my friends, I would write it down. I would just sort of vent on the page.

AMT: Now you had been cautioned that relearning things take time. How did your relationship with time change throughout this period?

RUTH MARSHALL: I counted everything. I counted the seconds until physio was over. The minutes until friends or family would come to bring me lunch. I counted how long it was between phone calls with my husband, when the kids were coming home from school. My day was divided actually much the same way when you have a baby. Your day is really divided between feedings and sleep. I just needed to get through each day and see the progress the next day.

AMT: And how long were you in the rehabilitation centre?

RUTH MARSHALL: I believe it was two months - a little over two months.

AMT: That's a long time.

RUTH MARSHALL: Yes, it was a long time.

AMT: How did all of this recalibrate your relationship with your husband?

RUTH MARSHALL: Well, my husband. He is the absolute best part of my life. He is an absolutely wonderful man. He always was. But he became very focused when I was in hospital. He just did what he had to do. He had to go to work, but work was not his priority. I was a priority, and then the kids, and then work, and whatever else happened after that. I guess some relationships falter when a partner is ill, but not this one.

AMT: Your book title mentions that you had to learn to have sex again.

RUTH MARSHALL: That's right. Well it was tricky. Your nerves are essential to every part of your life. And it took well a lot of practice to figure out what was going to work again. What might not work again and how to change that, and adjust to it. I mention in the book that I think sometimes my husband thought my body parts had been replaced with glass and so he was very, very careful. We were both super, super careful. But we wanted to get back to the place that we were before I had a tumour.

AMT: Do they do they tell you enough about that? They tell you a lot about walking in your legs and stuff. Does anybody tell you enough about sex and intimacy?

RUTH MARSHALL: Well I looked up that up.

AMT: You had to look that up.

RUTH MARSHALL: I had to look that up. I did speak to my nurses about that an awful lot. And I had one fantastic doctor who came to see me every single day at Lyndhurst and we talked about sex all the time which is something before the tumour I did not talk about sex with anybody. That was super, super private. But all bets are off when you're in hospital and I needed to have some answers. And yes, so I got coached.

AMT: And you found humour in the midst of it all. What moment stand out for you as funny when you look back?

RUTH MARSHALL: There was one story. Yes, I looked quite sloppy in my wheelchair. I didn't look particularly feminine or pretty - I don't think ever while I was in the hospital. But one day there was this one patient who I always found myself looking at. She's quite attractive as I describe her in a stripper kind of way. She had really nice flower tracksuits that she wore every day. But I finally noticed what was different about her from everybody else that I saw and that was that she crossed her legs. And I thought, 'oh I might be able to try doing that'. And so I worked really hard at learning how to cross my legs. And once I did that, I never looked back. I absolutely refused to sit, sort of, like in a man's spreading kind of way in my wheelchair again after that. She was a revelation to me.

AMT: There were difficult moments. You're very good at making light of stuff and laughing with them. But what memories have stayed with you as the most emotionally difficult?

RUTH MARSHALL: Well they would probably have more to do with the people that I was in the hospital with. And actually they’re about me because I was able to walk out of the hospital. I was able to regain my bladder and bowel function and my sexual function. What I'm left with is thinking about how the patients that I did in some ways by the end grow closer to - I do wonder how they are. And that is distressing to me to think that maybe they weren't as lucky as I was.

AMT: What things from all of that stay with you physically? What's changed for you?

RUTH MARSHALL: Oh, well my nerves are a little bit kooky still. I do still feel like - I describe it as static like the snow that you see on your television screen. That's kind of how my body feels from my bum right down to my toes. And possibly the most annoying thing, which is also sort of the funniest thing, is if I even have one drink my feet become just absolute idiots. They bang into each other. They cross each other. It's like they're really having a good time while the rest of me like, 'could you just walk normal, just be a person, just act normally'. That's what's remained.

AMT: And why is that? What's the explanation for that?

RUTH MARSHALL: I think I still have - I don't want to use the word struggle because I shouldn't call it that - but I still do have to manage some proprioception loss. Actually the most basic thing - when I'm putting in particular my left foot, which is somewhat more problematic than my right foot - when I'm putting my shoes on I have to hold my foot to put it in my shoe. I have to guide it in otherwise it waves around a little bit.

AMT: And so what was it like when you went home after the time you were there in rehab and you were able to walk out? What was it like for you to re-enter the normal wonderful life you had left?

RUTH MARSHALL: Well first it was absolutely fantastic. I couldn't have been happier to be home. But I figured, well I'm home and I'm walking. I was walking with two walking sticks. But I'm home. My life is perfect again. And it wasn't. The most basic things - I had to take a shower sitting down so I had to have a shower chair. That's fine. But when I got rid of the shower chair, and even now, I can't take a shower. I can't close my eyes at all because I do lose track of my body a little bit. I always have to be leaning on the wall. I did feel some frustration. I felt as if I wasn't there as much for the kids as I wanted to be. I mean I was there physically but I could do what I had done before. Initially it was quite exhilarating and frustrating at the same time.

AMT: You make the point that one of your sons leaves a musical instrument at home and normally you would just kind of run out the door with it and jump in the car, and you couldn't move like that.

RUTH MARSHALL: That's right. Yes, I had a little bit of a breakdown that day. My son left his French horn. My husband had to come back home which was no big deal. Come home, get the French horn, bring it back to his school. And I was an absolute mess. And he was fantastic the way he handled to me. He said, "Don't rush. Your home. Just give it time and everything will sort itself out. We don't know when, but it's going to sort itself out." I hadn't even been home a week. But I just wanted to be me again. And I was not me.

AMT: You end up spending time in your closet and you get rid of a whole bunch of things. What do you get rid of?

RUTH MARSHALL: Oh, yes. I did a very quick purge of all of my shoes. And I like shoes Anna Maria. That was really hard.

AMT: You like heels.

RUTH MARSHALL: I liked heels very, very much. I got rid of all of my heels, all of my wedges, all of my nice tall boots. I got rid of everything. And I couldn't wear slip-ons either because they - well they slipped off.

AMT: And you need your feet touching the ground. You can't have that height.

RUTH MARSHALL: That's right. Oh, no I couldn't. Actually even now, even looking at a pair of heels gives me a little sense of vertigo. I just know automatically I won't be able to wear those again, which is no great hardship. I just can't wear high heels again. But yes, I got rid of almost all of my shoes. Sold them all and kept two pairs of Oxfords and a pair of running shoes.

AMT: And has this experience changed the way you look at your life?

RUTH MARSHALL: Well it's hard to come out of this and not feel incredibly grateful. And I look forward to the time when I can walk down the street and not think about walking down the street and what my legs are doing. But I am incredibly grateful for what my body is able to do. Even with the continuing nerve issues I can handle all of that. As long as I can walk out of the studio I'm very happy.

AMT: And you're able to work again?

RUTH MARSHALL: Well I don't act anymore. I don't act on camera anymore. I stopped doing that. A few months after coming out of hospital it was my last episode of Degrassi that I had done. There are things that I had to deal with that I found really stressful. I had to make sure that I was taking my nerve medication, which I no longer take. That my feet weren't slipping out of my shoes. That I wouldn't fall off a seat when I sat on it because my bum feels so strange. Walking and talking at the same time with the camera on me was difficult, so I just thought I think I might be done acting on camera. I stopped that about four years ago and I continue to do voice work.

AMT: Do you like it?

RUTH MARSHALL: Voice work? Oh I love it.

AMT: Do you miss being on camera? Do you feel that you were cheated out of it or are you good with it?

RUTH MARSHALL: I'm so good with it. I acted for a long time. I think I had a very good career. I was really happy with what I managed to do and the 20 odd years I was doing it. I really felt ready to move on. I mean yes I was pushed a little bit out of it because my walking wasn't terrific. But I have really never looked back. I don't feel any regret, any jealousy from my colleagues and friends who are still acting. I'm very happy for them. But yes I was ready to move on.

AMT: And your family, what do you think you've learned as a family through this?

RUTH MARSHALL: That we're very resilient, my kids especially. They're just tremendous. They really came through it very, very well. I think it was not the greatest feeling to not have their mom at home for a long time and to not be quite sure what was going to happen with her. But they're very buoyant boys and they came back like champs. They're great.

AMT: And you can [unintelligible].

RUTH MARSHALL: I can. I can. I have moments where it'll come up out of nowhere. My husband Rich and I will be talking about just something that happened in rehab and I will cry. It surprises me. But I guess it has landed somewhere in my body that something major happened to me. But I am always aware that it could have been so, so much worse.

AMT: Well it's good to hear the positive side of you coming out of this. Thanks for sharing your story.

RUTH MARSHALL: Thank you so much for having me.

AMT: Ruth Marshall, author of Walk It Off: The True and Oddly Hilarious Story of How I Learned to Stand, Walk, Run, and Even Have Sex Again After a Nightmarish Diagnosis Turned My Awesome Life Upside Down. Ruth Marshall joined me in our Toronto studio. Let us know what you think of what you're hearing on The Current as you listen to us today. You can tweet us we are @TheCurrentCBC. Find us on Facebook. Go to our website cbc.ca/thecurrent. And stay with us in our next half hour. How do we know if we know all we're ever going to know? Does that make your brain hurt? My next guest will help unravel it as they debate whether there is a limit to human knowledge - a profound question on the second day of January 2018. I'm Anna Maria Tremonti and this is The Current on CBC Radio One Sirius XM, online on cbc.ca/the current, on podcast and on your radio app.

Here's a brain teaser: is there a limit to what we can know? Scientists say they know so

Guests: Martin Rees and David Deutsch

AMT: Hello I'm Anna Maria Tremonti and you're listening to The Current.

SOUNDCLIP

VOICE 1: Illustrated in movies like Star Trek, cosmic black holes have enormous destructive powers to consume entire worlds. Jeff Steinhauer single-handedly created this force of nature at his lab in Haifa, Israel.

VOICE 2: While working on a different experiment, I suddenly saw a phenomenon and I realized these atoms must be travelling at supersonic speed. This is an analogue black hole, a sonic black hole.

VOICE 1: Jeff's black hole measures a tenth of a millimetre and less two tenths of a second. This discovery, if confirmed by the scientific community, advances our understanding of the universe.

VOICE 2: Probably one of the main reasons that one studies black holes is not to learn about black holes themselves, but to learn about the new laws of physics.

VOICE 1: One more giant leap in unraveling the secrets of the universe.

AMT: The secrets of the universe. That CNN report says every day we're taking scientific strides that unlock new areas of knowledge and unravel something that until now has been a mystery. Black holes may seem like some of the biggest mysteries of all. But one of the most complex objects are not in fact in the far reaches of the universe. But right here on Earth with us. Some scientists argue that certain living organisms, animals, plants, and humans can in fact be more difficult to understand than parts of deep space. And that grappling with their complexity may be where humans reach the edge of how much we can know. I'm joined by two scientists who have extensive knowledge and differing perspectives on whether there is a limit to our human knowledge. Martin Rees is the United Kingdom's Astronomer Royal. And he joins us from Cambridge, England. David Deutsch is a visiting professor at the Centre for Quantum Computation at the Clarendon Laboratory of Physics at the University of Oxford. He is widely considered to be the father of quantum computing. David Deutsch is in Headington in Oxford. Hello to you both.

DAVID DEUTSCH: Hi.

MARTIN REES: Hello.

AMT: Martin Rees I want to start with you. You are an astronomer. Space may seem very complex to the rest of us, but what do you think. Will we one day be able to understand our universe fully?

MARTIN REES: Well never fully. But we can make great progress. And we already have. But the point I want to make to follow up your introduction. The most complicated things in the universe are neither the very small things - atoms - nor the very large things - stars, black holes, and galaxies - they're things in between, particularly living things because they have layer upon layer of structure and they are probably going to be harder for us to understand than either the atomic world or the cosmic world.

AMT: Tell me more about that in what ways are organisms or the human brain more complex than what we can see way out in the far reaches of the universe?

MARTIN REES: Well a star for instance is a very, very hot ball of gas and it doesn't have any very complicated substructure. It's so hot that no complex chemistry could exist inside it. Whereas, if you imagine, even the smallest insects that has layer upon layer of complexity and it will be very, very difficult indeed for us to fully comprehend that. We can have simulated if we had a super computer. But for us to actually grasp exactly what's going on inside the simplest insects is in my view a bigger challenge than to understand a black hole or to understand atomic physics.

AMT: What do you think - is there a limit to what humans can know?

MARTIN REES: I'm sure there's a limit to what humans can know. And it could be that the very deep elements of reality, which are as far beyond our grasp as quantum theory is beyond the monkeys grasp. I really think that's possible. And I think I'd like to distinguish between what we can actually grasp or compute. We could perhaps make a computer that could actually simulate some of these things. But that doesn't mean we could actually understand it - really grasp what's going on. I think there's a real limit to what human brains can actually comprehend and that may be important parts of reality that will be forever beyond that.

AMT: Do you not think our brains might be able to keep adapting forever to take in new knowledge?

MARTIN REES: Well we have a long way to go, obviously. The huge opportunities for us to understand things that we don't yet understand. We're nowhere near the limits. We are nowhere near hitting the buffers in many sciences. But I think there are almost certainly severe limit to what we know that brains think about a million times slower than even a small computer. We know that for 40 years we've had machines can do arithmetic better than us and we have computers that can analyze data millions of times faster than us; can play games like chess and go better than a human. And so we know already that we machines that are better than us and there are certainly going to be limits to the sort of wet hardware inside our skulls.

AMT: Well David Deutsch this is a good time to bring you into the conversation. Do you think humans will reach a point where we'll be at the limit of what we can know?

DAVID DEUTSCH: No. I don't think there can be such a limit. There are things that are unknowable. Mathematical things - all of them relating to infinity in some way. But I don't think there can be anything interesting that is anything relevant to humans or human problems that is unknowable. I think that idea is very akin to a belief in the supernatural. I totally agree that the mid-scale things like living things and brains are probably much harder to understand than the very small or the very large. But brains, especially human brains, have this special relationship with the laws of physics which other brains and other physical processes don't have. Namely, that they are universal at explaining things. And Martin said that we know that computers will be able to simulate everything, but he doubts that they will be able to comprehend everything or that we will be able to comprehend anything via them. But the thing is, comprehending, understanding, and explaining are all forms of computation and if we can't do them with our natural hardware, we can do them with artificial hardware as we have been doing for thousands of years. We couldn't even understand Newton's laws if it hadn't been for the invention of writing for example. There is only one type of computation in the universe. Our understanding and everything else must be a type of computation. Anything that goes beyond our abilities must be only because of things like speed and memory capacity, which we can improve artificially.

AMT: Martin has compared some of this to monkeys trying to understand Darwinism. What do you think?

DAVID DEUTSCH: Yes. Human brain is a monkey brain with add-ons. The fact that monkeys can't understand Darwinism - it's either because they don't have the physical capacity to hold the program. That is the program for human mind. That seems unlikely because their brains aren't smaller than ours by such a large factor. It's more likely human brains just have more computing power available - just more raw memory. Boring things, but which make all the difference when you add them on to the range of computations you can perform. And so I don't think there's that much difference in the computation in a monkey brain and the human brain. There can't be any difference in the computation of human brain and anything further because we know that the our existing computers are already universal.

AMT: Can human brains keep evolving to take in new knowledge, David do you think?

DAVID DEUTSCH: It could be done that way. My guess is that like in the past we weren't artificially make bigger brains like, any science fiction stories with humans with gigantic heads - post-humans with gigantic heads. I think we'll continue doing it as we have been doing it with technology. We already live largely - many of us anyway - inside our computers or inside our mobile phones and communicate via artificial means more and more. This can continue to whatever extent it's convenient and to whatever extent we find that it solves our problems. This difference between simulation and understanding is the difference between form and substance. It's solving problems or not solving problems. And it's all knowledge worthy of the name is problem solving. That's what we'll be using it for.

MARTIN REES: Can I come back and...

AMT: Yes absolutely. I was just going to bring you back in. Go ahead Martin.

MARTIN REES: Yes, well I think David [unintelligible] two very different things. One we can compute and one we can understand. Already we've had this machine that can play go and the world's expert go players can't understand why it made a particular move. That's an example of something that is computable, but not understandable. And when I say that we humans can't understand things, I don't deny that maybe a computer can compute them. But I'm still saying we can't understand them. But I'd like to make another separate point, which is that doesn't David Deutsch agree that it could be that the fundamental bedrock of space and time is describable by some 10 or 11 dimensional geometry as in M-theory. And this is what we know; some of the brightest brains in the world are now working on. But isn't it possible that they will never succeed simply because the maths is beyond the human brain. I think that's one perspective which we may hit the buffers. The other aspect is that already, as David admits, there are many things that can be computed, but we do have in our heads.

AMT: David what do you think?

DAVID DEUTSCH: Well I entirely agree that there may be many things. There already are many things that we can't do in our heads. In fact the basically the whole of modern science could barely be done in anyone's head entirely. I agree with that. But I think it's kind of parochial to care about what we can do with or without help. It's like saying, we will never run faster than 10 metres per second just because we would never move faster - sorry than 10 meters per second - just because we can run faster. We have a problem of how to get from A to B in a shorter time because it's more convenient and we can solve that problem provided that the laws of physics allow it. Again I also agree with Martin that a star is a very simple thing compared with a brain. But if you look in detail at the star, the more detail you look at - now we've got these pictures of close-ups of a star with lots of structure and curlicues and so on. And to predict that exactly would require a computer the size of the star. But we don't want to predict that precisely because it's not interesting. It's the same is true of Go-playing. If something can beat us at Go-playing just by sheer power and not by there being anything interesting there, that's not very surprising. And I don't count that as a limitation of knowledge any more than the details the surface of the sun our limitation on knowledge. But if there is something interesting there that means it affects something human. That means it affects a problem. And just because people don't understand it now, doesn't mean they won't.

AMT: David Deutsch you use the example of the hairs on Julius Caesar's head. Take us through your point there.

DAVID DEUTSCH: Well that's the same issue really. What are the limits of the science of palaeontology and paleoanthropology? We know an amazing number of things about the daily lives of people thousands of years ago and even hundreds of thousands of years ago. But obviously there are many things there that we cannot know. We cannot know whether the number of hairs on the head of Julius Caesar at the moment when he died was even or odd. And that is not a limitation of human understanding, only a limitation of information. And the distinction I'm trying to make is between understanding in the sense of problem solving and information of which there will always be too much.

AMT: In other words, we may not know but we don't always need to know what we don't know.

DAVID DEUTSCH: We don't care. And there's nothing to make us care. And if there were something to make us care, that very thing would be the lever by which we would discover it.

AMT: Martin Rees do you see technology or other organisms becoming smarter than us in the future?

MARTIN REES: Computers are already smarter than us in many respects. But I still think that being a human being I care about what human beings can actually understand and grasp. And I still repeat my point that there are limits to that. And that's rather sad because I think most of us as scientists want to understand things. We don't just want to be able to compute something. And I think there are going to be limits to that.

AMT: I think David Deutsch would agree with you on that level. Would you not David?

DAVID DEUTSCH: Yes, yes certainly. I think where we're disagreeing is that I think that machine assisted understanding is possible, as well as machine assisted prediction and machine assisted description. We already do machine assisted understanding. When we understand something about Maxwell's equations or Einstein's equations by writing symbols on a piece of paper, we are doing machine assisted understanding, not just prediction.

AMT: And so if we can use machine assisted understanding in progressively wider ways, does that mean there is infinite progress in what we can do?

DAVID DEUTSCH: Unlimited progress, yes. Of course we'll never reach infinity.

AMT: And does that mean we will head toward an ideal society? Could this lead us to do that?

DAVID DEUTSCH: No, because this is a different issue. But I believe there will always be problems. And there will always be soluble. But we will never be anywhere near the ideal which is the infinite knowledge or infinite perfection or all problems being solved. It wouldn't be very nice if all problems were solved because they'd be nothing to think, it would be a bit like death. But nor will we I think reach a stage where there are problems, but they can't be solved.

AMT: Martin Rees if you think humans eventually reach a limit of our knowledge, what happens to progress and everything from science to art when we reach that point?

MARTIN REES: Well I think the certain direction in which we can explore indefinitely - some areas where our brains are limited. But of course I agree with David, that humans are not the sum is in any sense of evolution. We are probably in a halfway stage in evolution. We've had four billion years of Darwinian evolution to lead from primordial life to us. And we know that there are billions of years ahead. I think there's going to be evolution. Whether that's going to be organic or electronic evolution is unclear. I suspect that the main intelligence evolution will be in the form of electronic entities, not souped up wet human brains. But I think we should remember we're just beginning and we should also remember that science is an unending quest. And as we settle some questions, then we are able to pose questions we couldn't even pose before. Science does progress and as it progresses the periphery between the known and the unknown gets longer. And there more questions that come into view that we are going to be challenged by.

AMT: Gentlemen, you've given us a lot to think about as we begin a new year. Thank you.

MARTIN REES: Thank you very much.

DAVID DEUTSCH: It's a pleasure.

AMT: Martin Rees is the United Kingdom's Astronomer Royal. He joined us from Cambridge, England. David Deutsch is a visiting professor at the Centre for Quantum Computation at the Clarendon Laboratory of Physics at the University of Oxford. He's in Headington in Oxford. Now knowing understanding, believing something to be true, the facts may be the domain of science, but thinking about what it means to know something often falls to the philosophers - the epistemologists to be precise. Jennifer Nagel is an associate professor of philosophy at the University of Toronto, and the author of Knowledge: A Very Short Introduction. Jennifer Nagel is with me in Toronto. Hello.

JENNIFER NAGEL: Hello Anna Maria. Pleasure to be here.

AMT: It's nice to have you with us. Coming at this from a philosopher's point of view, do you think there's a limit to human knowledge?

JENNIFER NAGEL: Absolutely. There are lots of limits to human knowledge. There are lots of things we'll never know. The kinds of facts you're talking about a moment ago - the number of blades of grass on Parliament Hill. I think the interesting question that was raised by your panel there, was the question of whether there are things that are humanly interesting, but unknowable and I think that's a sort of much deeper question. I think you can take any fact - this is actually something demonstrable - that doesn't happen to be known, that no human being actually knows. I like the fact about how a certain coin toss turned out. Let me just toss a coin here for a moment.

[Sound: Coin landing on table]

JENNIFER NAGEL: And I'll slap my hand down on it as it comes down on the table. Neither of us saw how that turned out and if I skewed the coin off onto the floor.

AMT: And you just did. Did you just throw it on the floor? [Laughs].

JENNIFER NAGEL: I just did. I just did. Neither of us will ever know. And you radio listeners out there will never know how that coin turned out. That's actually just an unknown fact. But there's an interesting epistemological theory. It's called Fitch's paradox of no ability that says, anytime there is an unknown fact, it brings with it in its trail some further facts that are not only unknown but unknowable. Or if you like, humanly unknowable.

AMT: An unknowable unknown? We are channelling Donald Rumsfeld here [laughs].

JENNIFER NAGEL: That is correct. Even if you had a God who knows everything. God, say who knows the outcome of that coin toss. If it's actually not known to any human being how that coin toss turned out then there's a further fact which is not only unknown but unknowable and it goes like this. It's the fact that, it's not humanly known that, that coin toss turned out heads let's say. Even an all-knowing God couldn't whisper in your ear, 'Anna Maria no human being will ever know that, that coin toss turned out heads, right?' That fact if God told you that then you'd know the outcome of the coin toss and it wouldn't be something that no human being ever knew. That's Fitch's paradox of no ability and it says that, actually it's not the case that truth in principle is just what can in principle be known. Truth always outstrips what can be known. It goes beyond what can be known.

AMT: What does it mean to know something?

JENNIFER NAGEL: To know something is to be securely locked onto the truth. Knowledge is a state of mind that you can have only towards the truth. That's actually the definitive characteristic of knowledge. It's what sets it apart from just thinking that something is so or being confident that something so. You can be confident something actually turns out to be not that way at all. Knowing is something that's necessarily a relationship that you can have just with truths.

AMT: Well it's interesting because your philosophical look at this actually is very grounded in what's going on in the world today. If we look at false news or fake news, if we look at alternative facts, if we look at the debates that happen in politics about what happened and conspiracy theories, people will insist they know something and people even believe things to be true that aren't true. How do we take different levels of knowledge and certainties that are uncertain?

JENNIFER NAGEL: Well I think the problems of fake news are in a sense not new. People have been attempting to deceive each other for a very long time. I think they arise in this new media climate in a way that is potentially very dangerous because we don't yet have good psychological and social immune systems to protect ourselves against the dissemination of what's false. I don't think this is necessarily a problem of epistemology fundamentally. I think this is a problem of social science. It's a problem of understanding exactly how media is working and how media is persuading people of things.

AMT: David Deutsch has said knowledge is not just information, knowledge is understanding, and knowledge and understanding is always relative to a problem. And it forces us to go deeper and learn more and discover. Do you see it that way?

JENNIFER NAGEL: I don't think the problem has to be given in advance. I think it can be the case that we discover something, encounters some little nugget of knowledge without having started out towards it without having a sort of antecedently defined problem. I think knowledge can hit us by accident. We can be lucky with what we know. There's something that David Deutsch said that I feel like I really want to respond.

AMT: What's that?

JENNIFER NAGEL: Well he said nothing is both interesting and unknowable. And he said the reason why it's not going to be unknowable is that you can augment human powers of knowledge, powers of computation with mechanical devices. Anything that's explicable at all is going to be explicable through some kind of type of computation - understanding itself as a type of computation. Let's just abstract away from the limitations of the human brain and add in all the powers that computers have and that's going to be enough to make any interesting problem knowable for us. But here's the thing, you can abstract away from the powers of the human brain. You can abstract away, sorry, from the contingent limitations of those powers. We've only got a certain lifespan. We're going to die and we think pretty slowly. The problem is that computers also only have a certain lifespan. We're going to hit eventually the heat death of the universe. They're going to have limitations of time and space as well. And we can know those in advance. We can know if we learn enough about astronomy when this universe is going to come to an end. We can't just sort of abstract away from all of those limitations and say, everything is going to be knowable. We've only got a finite time here. Even our computers only have a finite time here. It's perfectly possible that there could be interesting problems which can't be solved by any variety of available means in the time that we and our computer friends have got.

AMT: I don't know what to say to that [laughs].

JENNIFER NAGEL: But one thing to say about is that even being aware that there are these you know unknowable's glowering out there on the horizon or potentially glowering out there on the horizon. We can take courage in the fact that there's a great deal that is extremely interesting and is well within our reach as knowers, whether augmented or not.

AMT: Fascinating to talk to you. Thank you for coming in.

JENNIFER NAGEL: Such a pleasure Anna Maria.

AMT: Jennifer Nagel, associate professor of philosophy at the University of Toronto. She's the author of Knowledge: A Very Short Introduction. She joined us in our Toronto studio. That's our program for today. Stay with Radio One for Q and guest host Ali Hassan. Today he's speaking with Colin Mochrie. Remember you can always take The Current with you to go on the CBC Radio app, free from the App Store, or Google Play. I'm Anna Maria Tremonti. Happy New Year. Thanks for listening to The Current.

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