How's the echo, is it all right? Yeah, so thank you, devops days for welcoming me. I'm actually an iOS developer. It's been very interesting to hear some of the talks earlier. And so this talk's gonna be a little bit different, but I'm interested to hear your thoughts afterwards and so on. You can find me at one of the open spaces after this. I believe they're after lunch. I'd love to hear your feedback and what you guys think about what we talk about today. So before I begin, I want you guys all to think about the number of times and for how long total you've looked at your phone, your iPad, and your computer today. And what about in the time since the last talk? Or what about the amount of time that you did during the last talk?  I mean actually off, not silent, not airplane mode, shut down. I don't expect many of you to actually do this. We make excuses. Oh, I need to take notes on my iPad. I need to keep up with a Slack channel. What if my family needs me? To all those things I say, 20 years ago cell phones were a rare sight. People managed just fine. So take up my challenge, turn off your phone and computer and see how long you can keep it off. Also as a pointer, your faces glow when I use these things so it makes it pretty easy to tell if you lose faith in a few minutes. Okay, take a wrap. Put it in a box with a button. Wire the button to a food dispenser that can drop a pellet of yummy rat food into the box. You get to design the logic between the button and the food dispenser and let the rat use it. After 10 minutes of using it, we'll disable the food dispenser and over the next 10 minutes, I'll give you a dollar for every time the rat presses the button. How would you like to program the button and the food dispenser? A man by the name of B.F. Skinner tried this back in the 60s and the results of his study are changing the course of history to this day. Skinner defined five standard ways you can go about reinforcing your rat in the scenario. The first is continuous. This means that for every button press you give the rat a pellet of food, so one for one relationship instant reinforcement.  Once you decouple the button and the food, the rat will press the button a few more times, but quickly the button pressing behavior will extinguish. I won't go into detail about a few of the middle ones, but they could be things like giving the rat food every 30 seconds, regardless of button presses, or giving the rat food every fifth button press. But the best way to get the rat to press the button and continue pressing it without a reward is variable reinforcement. Variable reinforcement is a schedule of reward that is random. Button presses, heat of reward are randomly chosen. This could be like giving the rat food after the seventh press, the 15th press, the 22nd press, 25th press, 42nd press, et cetera. This variable interval reinforcement is the most effective form of reinforcement. But the variable interval strategy exists outside of the rat box. When you call your dog's name, Sparky, come here. Sparky comes to you. You don't always reward Sparky. Food is only sometimes a reward.  And sometimes you're taking him to get a bath. The lack of a pattern or the variability is what keeps Sparky coming back. Skinner's discovery isn't limited to animals. The slot machine is the quintessential human skinner box. Just swap out the rat food with money. Slot machines are designed to randomly give out small rewards on a variable interval schedule to make the user keep pulling that lever. The effectiveness of the human skinner box is why Las Vegas exists today. And maybe the Hoover Dam. The behavioral description of habit formation and reinforcement was discovered in the 1960s and quickly became the gold standard for understanding human habit behavior. In the time since Skinner's discovery, countless new fields have sprouted up, each with their own sections of behavioral studies. One significant field, for example, is the field of behavioral economics. Behavioral economics will explain why movie theaters sell popcorn, a small popcorn for $4, a medium popcorn for $6.50, and a large for $7. But I'm not here to talk to you guys about rats, Las Vegas, or movie theater popcorn. I'm here to talk to you guys about smartphones. I'm an iOS developer by trade, so I focus on smartphones. But my thoughts today extend beyond smartphones into a wide range of technologies. So I'm gonna mention five different scenarios, and I'd like you guys to stand up if it applies to you or someone you know. This is a cue to put your laptop down if you couldn't last five minutes. So get ready to stand. So please stand if you or someone you know uses their phone while driving a car and remain standing. Wow, this might go a lot faster than I expected. Remain standing, please. Please stand if you or someone you know uses their phone when they know it's getting late and they should probably go to sleep. Please stand if you currently have a desire to check your phone, or if you checked it during this talk. Please stand if you or someone you know uses their phone while in the middle of a face-to-face conversation. Sometimes you can be on the receiving end of that. And please stand if you or someone you know has lost their phone and felt a strong negative response, a stronger negative response than losing something of similar monetary value. Okay, all right, before you sit down, take a quick look around the room, including the balcony, and you might be hard pressed to find anyone who's sitting. All right, sit down, please, thank you. We are addicted to smartphones. Why do I say this? The American Society of Addiction Medicine uses five means of characterizing addiction. Inability to consistently abstain, impairment in behavioral control, craving, diminished recognition of significant problems with one's behaviors and interpersonal relationships, and a dysfunctional, emotional response. Now take a moment and think of someone who uses their phone a lot. Maybe it's a friend, maybe it's a spouse, maybe it's you, and using the five criteria I just mentioned, do you think they are addicted? Do you think that maybe you are addicted? I'd like to talk about a story that I experienced a few years ago. In an earlier life, I was a kayak tour guide, and so I'd take people out on, sit on top kayaks in the ocean, and we'd go into some caves that had swells and waves coming through, and it was, at times it was a little dicey. And I remember vividly one time I took out a group of people, and it was a man, while we were in the cave, I was swimming to keep his kayak stable in this cave. Big swells coming through, I probably in retrospect shouldn't have even taken him in, but the point is, I don't do that anymore for multiple reasons, but the point is, that while he was in the cave, and I was busy trying to keep him upright, he pulls out of his life vest, out of the cleavage of his life vest, if you will, he pulls out a cell phone in two plastic bags, and answers a phone call. I don't know what he did that was so important that he had to answer a phone call, but to think that he would put something, like, theoretically his life was at some small level of risk at that moment, and he had to answer a phone call and obviously let go of his paddle and stop listening to me. So he put his life at risk. And if that isn't obvious addiction, I can't think of anything more that is. One other interesting story, a few months ago, Honolulu, the local government, has started a process to make it illegal to use your phone while crossing the street, because even though you might be walking when you have a green light, people will not look at traffic coming and get hit by cars, it happens everywhere, and Honolulu's actually starting to pass legislation to prevent people from looking at their phone and crossing their streets. So we are addicted to smartphones, whether you like it or not. In a 2015 study, Deloitte calculated that the average American checks their phone 46 times a day. 81% of Americans reported checking their phones while dining out in a restaurant. And according to the National Highway Traffic Safety Administration, the percentage of drivers visibly manipulating their handheld devices more than quadrupled in the past eight years. There are many reasons to believe that these numbers are even higher today. Many schools now use texting and app-based services to quiz their students, take role and measure student understanding. We check our phones before we brush our teeth, before we eat breakfast, before we make coffee, before we get out of bed, and maybe even before saying good morning to our loved ones. It's literally the first thing we do in the morning and the last thing we do at night. We're addicted to smartphones. I mentioned this data not to scare you or to call for a decrease in phone usage, but as a tool to portray technology's growing role in our daily lives. We're addicted to smartphones, but the question is why? Why are we so attached to our phones? Why do we find ourselves putting our smartphones before our sleep, our safety, and our relationships? How did we let smartphones become such integral parts of our lives? But before we talk anymore about phones, I must point out that the core functionalities of even a basic flip phone, that is a phone and text messaging, these things are inherently addicting. These two basic features alone account for a significant amount of the addictive behavior that smartphones elicit. They follow patterns that easily fall into the skinner's most reinforcing category. It's an important note, yet it doesn't account for all pieces of the puzzle. The technology that we all make is the driver for the majority of smartphone dependency formation. Specifically, apps are in the ideal position to create strong levels of addiction. Each app has the potential to become its own skinner box, making the smartphone a collection of skinner boxes. An app like, so in other words, it isn't like a slot machine in your pocket. It's like all of Las Vegas in your pocket. Each app is its own slot machine. Take for example an app like Twitter. You open Twitter, you post something about your day, and then you close the app, okay? Over the next few days, at random times throughout the day, you get a notification. 10 minutes after posting, one retweet. 25 minutes after that, two likes. Five minutes after that, four more retweets. An hour after that, a friend replies, 10 minutes later, so on. This can go on for days. And then you add that you have at least five more apps just like it, and you get messages from your mother, you get hourly reminders to stand, you get breaking news notifications from CNN, and don't get me started on Lyft's promotions. The list of seemingly random notifications goes on. It's no wonder we can't be away from our phones for more than two minutes. There's one more thing to factor in. The timing on these notifications is not random. Many of the apps that send push notifications are trying to do better than random. Skinner's studies may have identified different types of reinforcement and ranked them by their strength, but he didn't master reinforcement. Mastering reinforcement is a task being taken up by a handful of tech-oriented companies. It's a small field, but it's growing quickly for obvious reasons, and the five employees at a company called Dopamine Labs seem to be leading the race to master human reinforcement. Dopamine Labs created what's called the Dopamine, or sorry, what's called the Reinforcement API. It's designed to make software more addicting. Two neuroeconomics, PhDs from the University of Southern California, are developing this API, and it's available to software engineers today. You can open your computer right now and look at it. The API is designed to help engineers increase the addictiveness of their products by determining if and when an action should elicit a reward. The API experiments with different methodologies to increase the strength of the product's reward schedule. Co-founder and COO Ramsey Brown explained that an effective method for forming habits is occasional bursts or clusters of rewards. Dopamine and other companies like it are studying human response to different reinforcement schedules, tweaking their strategy, and testing it out on large sets of people. Furthermore, these services are learning about unique user habits, providing personalized reinforcement schedules to each individual user. Technology isn't just maximizing the potential for addiction for mankind, but now we can maximize addiction for each individual. That includes you. The ability to create extremely addictive technology has tremendous value. Behaviorists have a coveted role in the tech world. Tech companies have a significant incentive to study particular psychological methodologies that can increase user engagement and usage. This is easily characterized in that software success today is measured by number of daily users, time spent using the software, et cetera. Software with ad-based revenue relies on users and high usage rates in order to make money. This means that for a significant portion of the software that is being distributed, tactics and changes that increase open rates and time and use are welcome with open arms. It's the logical step to take. It's simple economics. A great example is Snapchat. Snap Inc. is valued at over $15 billion. They have no significant revenue and they have never been profitable. Yeah, great company to invest in. In their March earnings report, after notifying shareholders of a $2.2 billion net loss in Q1, that's more than the whole value of the Domino's Pizza Corporation, Snap's report boasted an operational highlight of an increase in daily active users. Do you get this? A top 400 company on the New York Stock Exchange announces a loss of $2.2 billion, only a hundred million in revenue and then proudly announces an increase in daily users? I apologize if anyone works for Snap. If a company can be valued as highly as Snap, held up almost exclusively by usage numbers, why wouldn't companies be scrambling to increase their user's engagement? Well, they are and it's working. We're at an interesting point in time. Psychology and technology have a strong incentive to be tightly coupled. Tech companies can employ the decades of psychological research to increase their bottom line. From increasing user engagement to increasing click-through rate in sales, technology companies have strong incentives to look to psychology for guidance and advice. While tech companies are benefiting from the field of psychology, there's little evidence of tech companies returning favor. When I first began my studies in psychology and human behavior, I learned about how often people make irrational decisions. I learned of studies that showed how easily humans can be influenced and nudged towards certain decisions, even while feeling that they've been made free choices by themselves. This includes you guys as well. What's interesting is even if you're aware of the psychological tricks that are being done on you, it doesn't prevent the psychological tricks from working on you right then and there. It revealed the malability of human behavior. I wrote a paper about the psychological effects of social media, specifically how scrolling through a feed affects a subject's emotional state. In my research paper, I was specifically interested in the rates of depression between Facebook users who frequently scroll through news feeds and those who don't. I found that this data did not seem to exist. More importantly, I realized the potential value for collecting such data. This is what began my initial interest in the combination of technology and psychology. Sparked by anecdotal evidence, I proposed the question, does a news feed feature increase the rate of depression in social media users? As an aside, I used the term news feed to describe a list of posts or actions by friends on social media platforms. Like any good researcher, by the end of my studies, I found myself with many more questions and no closer to an answer. I found no data on not even a correlation between news feeds and depression. No studies have looked at this correlation. Even if I had found such a correlation, it could have been explained by claiming that the use of news feeds is a coping mechanism or a symptom of the cause of depression. I soon discovered that the whole field of data was sparse at best. There was little research available in the public domain. All I could find was a whole lot of unstudied questions. I discovered that the complexity and the depth to modern software created an ecosystem with great potential for counteracting effects. Surface-level data fails to reveal the smaller moving parts that we have widely differing impacts. For example, social media users as a whole may show no significant difference in depression rates from their controls. But under the surface, you can break social media users into two groups. You have active users and you have passive users. You might fall into one of these categories yourself. An active user is someone who spends the majority of their time creating content. That could mean posting text and photos and frequently sending direct messages to people. Passive users, on the other hand, are people who spend little or no time posting content, but instead scroll through their news feeds and their friends' photos and posts. Active users are the journalists. Passive users are the readers. Now, if you break the users into these two groups, I believe that the two groups would have significantly different rates of depression. Beyond this correlational study, users could have their experience altered to place them into two different experiment groups, one with exclusively passive features, one with exclusively active. This would be an ideal experiment to measure the effects. Unfortunately, we're not studying such detailed behavior. Just this year, one of the first experiments on Facebook usage was published by Tel Aviv University in Israel. A unique scenario allowed for a security company to split their employees into two groups, one that used Facebook and one that was banned from using Facebook. The results revealed that those using Facebook indeed showed a decrease in happiness compared to those that were banned from the platform. The study has been hailed as on the frontier of this type of research, but it didn't investigate different types of usage. There's still a lot more research to be done. But in such an ever-growing and changing field, this type of research is put on the back burner, arguably for good reason. The industry can change in a flash. Furthermore, this type of study is ideally conducted by the tech companies themselves, or us. It's no surprise that the companies would be hesitant to conduct this kind of research. The results could be bad. But Dalton Combs, the founder and CEO of dopamine labs, offered me some consolation. And now, as some tech companies begin to solidify their place in the majority of people's lives, I expect that studies like this will begin. Combs told me about his vision. He sees the future of software in a bright light. Combs and I see this addicting technology as an opportunity to provide tremendous value to users. People often look for easy ways to alter their own behavior. From snake oil to modern medicine, man has searched for ways to alter their own behavior for centuries. We look for weight loss pills, aphrodisiacs, antidepressants, stimulants, and many more tricks to improve ourselves, to get more out of our day. Many of these results can be achieved through changes to one's behaviors and actions. But making these changes is hard. We don't do them. That's why you set a weight loss goal every month. You don't, your weight's the same, but because all you have to do is eat less or exercise more, but we don't do it. It's hard. Many of these results can be achieved through changes to your behavior, but making it is hard. It takes significant willpower to change your habits alone, but we have just unveiled that the power technology has over man. Combs' vision is one where we can use technology to alter behavioral patterns. Users should be able to turn on the addictiveness of a product, turn it up or down depending on their personal goals. I envision a world where technology is the solution we use to help our personal problems. It provides guidance and direction on the path to self-improvement. This is already beginning to happen. We have apps that help us counter calories, exercise more, sleep better, limit our tech usage, organize our lives, manage our mental health, track our vitals and diseases, spend less, invest better, drive safer, care for our loved ones, et cetera. These self-improvement aids manifest themselves as both standalone software and features on software that serves a variety of purposes. Providing users with the ability to tailor their experience is an imperative step in the journey to creating ethical software. We owe it to our users to put them in control of their lives. The true value and power in software is its ability to serve as a tool that improves our lives. That's how we got addicted in the first place. That's why you went and bought your smartphone because it made your life better. People should feel better after using technology. With the increase in the strength of technology's effect on man, the importance of focusing on ethics increases in turn. It's not uncommon to have an initial aversion to this idea. It's normal to look at this as a poor financial decision or unnecessary risk. Michael, you may be asking yourself, why would I make the sacrifice for a greater good? Why should I be the one to take the risk that might not be as lucrative as sticking to our current ways? To these questions, I say look back in history. There are countless examples of companies and industries that were averse to such business decisions. Flexibility and the ability to pivot with the industry is what has led small startups to beat out major companies. The focus on adding value to the lives of users trumps the focus of maximizing profits in the current quarter. In 2006, General Motors released a statement claiming that the electric car was far from viable as a commercial success. Tesla, a young unheard of company at the time, was staring at a market that the big players wouldn't touch. Instead of joining the successful gas car companies, the founder of Tesla saw a product that consumers would want. Tesla took the chance, made an electric car, and now the 14-year-old company is worth more than the 110-year-old General Motors. Look at Apple, one of the biggest players in tech. They have made countless decisions that initially the public rejected. Yet, it's proven successful and its users tend to like it. They take away the CD drive and at first we complain. Eventually, most of us don't mind. They change the power cord and at first we complain, but then eventually we don't mind, et cetera. You get the idea. Apple doesn't give people what they want. They make things that people didn't know they wanted. So let's make technology that helps people in ways they didn't know was possible. Henry Ford is sometimes credited with the fitting quote, if I had asked people what they wanted, they would have said a faster horse. It's actually not true that he said it, but anyway. If we are the creators, we have to become, we have the power to change the future of technology and we can define what that future becomes. Not every engineer in this room has the power to make such a change. Some of us work for companies that don't give engineers the freedom to decide on the feature set for their product. This is where another opportunity arises. We must fill the hole in the data. I believe that every product has a strong incentive to collect some data. I don't care if you make a flappy bird clone, I think there's tremendous value in collecting user analytics. At a bare minimum, you should know where your users spend the majority of their time in your product and what features they do and don't use. On top of this, I believe that the more data we collect of our user's behavior, the better we can serve our users and improve the software that we make for them. I think this aggregate user data should then be shared on the public domain. By making the usage trends available to all, you provide the opportunity for others to stand on your shoulders and potentially add significant value to the world. By simply sharing the data we collect, we have the potential to spark novel ideas and innovations that are unimaginable today. There is no limit to the benefit we can have. Few people hold as much power as we do. We have the ability to create products that can be made available to more than billions, to made available to billions of people all over the world. Most users take our software with them everywhere they go. It's accessible on the internet. No time in history have customers been so accessible to their creators. Well, it may feel that the market is saturated with technology. I believe we're on the cutting edge of innovation. We can set the standards for future software. We are in the position to change the course of history, together we have the power and responsibility to create tools that further advance mankind. Thank you.


So, the first thing to look at is when we transmit, we want to transmit some data between two devices, look at the very basics in terms of the physics of how do we transmit some information between devices, well we use some form of signals, some physical signals and that's what this topic is going to mainly look at, the types of signals, the issues with the designing communication signals that can be sent between two devices. First some terminology, think of in the simplest case we have two devices connected via some link. We transmit data from one device to another, the source device is called the transmitter, it transmits the data, the receiver device receives the data and in between the transmitter and receiver is the medium. What is actually sent between transmitter and receiver? Some signals which are in the form of electromagnetic waves, so in basic physics we have some wave form carrying energy and they are our signals and these signals must carry some information, for example bits, zeros and ones, so between transmitter and receiver is a medium, well we can classify this medium into two types, guided and unguided. A guided medium is when the signals is guided by some material, the example is wired mediums, wires, cables, so we have a copper wire inside a LAN cable, again I don't have the LAN cable but a copper wire inside a LAN cable with some plastic coating around that copper wire, if we transmit electricity across that copper wire, an electrical signal, then that signal is maintained along the copper wire and does not disperse, or does not disperse much, you can think that signal as some wave form is guided along the copper wire. Similar if we have optical fiber, our signal is light, with optical fiber we have glass or plastic fibers and we send light into that fiber and it bounces over both sides and traverses through the optical fiber, the light, the signal is contained within the optical fiber, it doesn't disperse or not much at least, so that's a guided medium in that the signal is guided along a particular material, so wires and cables, twisted pair, copper cables, coaxial cable, optical fiber, we'll talk about some of these technologies in the next topic on transmission media. Unguided is essentially wireless communications where we transmit some signal and transmit it across the air, maybe through water or vacuum in theory and those signals may disperse in multiple directions, they're not guided by a particular material, by some cable or some wire, so when my laptop is using Wi-Fi, wireless LAN, it sends a signal to the access point up on the wall and you can think the energy there's an antenna built into the laptop, the energy is transmitted out of the laptop, some signal and it disperses in fact in multiple directions, if we could see that signal we would see some energy is traveling as a wave form to the access point but also the signal is being transmitted in that direction up, down and essentially all around, so the signal is not guided inside a particular medium, it's unguided in this case, so it's actually wired versus wireless, guided or unguided communication mediums, so this is the link between transmitter and receiver, we're just classifying and introducing some terminology, this link that we set up between transmitter and receiver we can configure it in two different ways, it can be a point-to-point link where we have one medium, one transmitter and one receiver, so just two devices sharing that medium or a multi-point link where we have more than two devices, multiple devices sharing the medium, so commonly we will see point-to-point links, I connect a cable from my laptop to this PC, two devices sharing that link, sharing that medium but we also see cases of multi-point communications where one device transmits and multiple devices may receive and therefore we have multiple devices sharing that medium and depending upon what we want to achieve in our communications we may choose one or the other, they have advantages and disadvantages, in either case when we have a communications medium, a link, the direction of communications may be either simplex, half duplex or full duplex, simplex communications is that the medium transmits signals in one direction only, the communication system just transmits in one direction from A to B, an example television with TV there's a TV station that transmits some signal and your TV at home has an antenna maybe that receives the signal, your TV does not send anything back to the TV station, so that's a simplex communication system, the data is all traveling in one direction, full duplex at the other end point is that we use the medium to transmit in both directions and at the same time that is we can transmit from A to B and at the same time using that medium we can be transmitting data from B to A, so both directions at the same time and in the middle half duplex both directions but only one at a time, so we have a link, A can transmit to B, B can transmit to A but they cannot transmit at the same time it's either one or the other, one direction or the other, so the direction the different technologies and systems maybe either simplex, half duplex or full duplex, this lecture when I'm talking to you are we using a guided or unguided medium, imagine the microphone is off, are we using a guided or unguided medium, unguided the medium is air in this case if the microphone is off I'm talking and the audio signal is in fact going in all directions it's not going across a cable it's going in all directions and those within range will receive and hear it, point to point or multi-point this lecture hands up for point to point let's see who's following hands up for multi-point hands up if you don't know hands down if you don't know that confused you okay it's multi-point that is you think of when I talk there are multiple receivers okay it's not one device just one other I'm the transmitter we have 20 or so receivers in this communication medium so it's point to multi-point or simply multi-point medium simplex half duplex or full duplex this lecture half duplex sometimes it's full duplex sometimes it's simplex it should be half duplex this lecture it means if I'm talking then no one else should be talking but if you have a question then of course you can be sending information back to me full duplex would be I'm lecturing and you're talking to your friends okay we try and avoid full duplex simplex is just me lecturing and lecturing and you falling asleep so let's try and keep it half duplex for this lecture so you can ask questions so what we want to focus on really in this topic is the signals that are sent from transmitter to receiver what are these signals how are they designed how do they carry information or some electromagnetic signals sent across our medium and we use these signals to represent data if you think of the data if we want to send a file as a sequence of bits my computer wants to send bits to some destination then I need to generate some signal that goes out of the computer that represents those bits we'll look at different ways to do that what we're going to see is that the communication signals that people use to transmit across systems we usually design them to be made up of multiple simple component signals that is we take some simple signals and combine them together to get one more complex signal and we're going to look at the mathematics of that and see how that impacts on our signal designer and performance we'll see that we can analyse signals from two different perspectives two different domains the time domain and frequency domain time domain you'll be familiar with frequency domain we'll explain as we go through starting with time domain and let's look at a very basic communication signal actually we still got a few more some terms to introduce and I think you know this thing difference between analog and digital you've seen this in in computing courses and in general physics courses okay we can differentiate between analog and digital waveforms analog the signal is continuous over time it continuously varying a digital signal we think is that it's some constant level then instantaneously changes to some other level like this square way the difference between analog and digital a simple concept we can have periodic or a periodic signals periodic as a signal that repeats both of these examples are periodic signals a periodic is one that doesn't have repetition over some period of over some time frame there's not an example here with a periodic signal we can measure its period and we'll see that through some further examples so I want to send information from one computer device to another using some form of signals whether it's light electricity some radio signals over wireless the person who designs the the transmitter and receiver designs the signals that are sent and how they carry information and the very basic way in which they design signals is based upon a sine wave so think of the simplest signal and usually come up with a sine wave something that is varying like this so you know the shape of a sign so a very simple signal s as a function of time can be expressed as a sine wave and here we can vary the shape of this sine wave using different parameters there's a multiplier at the front which is the amplitude if you can imagine a sine wave if you multiply by some value at the front then you increase the height so the amplitude of that signal a sine wave continuously varying you know it has some frequency in some period we can change the frequency from a low frequency to a higher frequency by varying some parameters so the sine function sine as a function of time t so depending on time we'll get a different value as an output and the general form is two times pi times the frequency where frequency is measured in Hertz so if we want a high frequency signal we increase the value of f so think of f as a parameter in this signal if we want a high frequency signal to increase f low frequency decrease f and you'll see if you plot this and we'll plot some as we go increasing f will get a higher frequency of our sine wave and a third parameter is the phase phi here it's a bit harder to visualize for most people but that is a shift of the that sine wave relative to some origin point so if we think of some signal that is generated by a transmitter here's one example where we take over time we take say time equal to zero the sine if we set these three parameters the amplitude or the peak amplitude the frequency and the phase just constants then we generate a sine wave that varies in some manner over time where we can think of the peak amplitude is the signal strength so measured in volts generate some electricity measured in volts coming out of the transmitter the frequency is the number of times the signal repeats per second the Hertz measured in Hertz and the phase some relative relatively shift of this signal is measured usually in radians some other parameters that are related to these three parameters of our very basic sine wave is the period and you know the period is simply the inverse of the frequency a frequency of two Hertz gives a period of half a second and another parameter is the wavelength the distance occupied by one cycle of our signal and calculated as the speed of light C divided by the frequency gives us the wavelength of that signal so in fact starting with a very basic communication signal a sine wave we can have three parameters that will change the shape of that sine wave the amplitude or the peak amplitude the frequency and the phase and related to them are the period and the wavelength of that signal this shows four examples of a sine wave with varying parameters the first one so we see on this plot it on the time is ranging from zero seconds up to 1.5 seconds and as the caption here we see the amplitude is one the frequency is one f is one and the phase is zero so if we write that signal the top left one the s1 of t some signal as a function of time the equation for this amplitude is one times sine two times pi times the frequency in this case the frequency is one write that times one times t plus a phase in this case the phase is zero or quite simply sine two pi t so with this function as t increases we get this output so when t is zero the s of t is zero when t is point seven five the s of t is minus one and so on so we get the the sinusoid and it keeps repeating by changing the amplitude the frequency and the phase we just change the shape of that sinusoid and the top right one we see the same equation except we've changed the amplitude to 0.5 the peak amplitude is now half frequency is the same phase is the same and you see the shape is just shrunk it's condensed so the peak goes up to point five and to minus point five here this the bottom left plot shows the same as the first except the frequency is now two so it would be one times sine two pi times two t plus zero which is simply sine four pi t for the bottom left signal and we see the difference now is that within one second we get two repetitions of the the cycle that is we have a frequency of two hertz in one second two repetitions here we have a frequency of one hertz sorry from zero to one second the period of our top left signal is one second that is one cycle the duration is one second it repeats every one second the period of our bottom left signal is half a second because it repeats every half a second change the amplitude change the frequency last one to change the phase amplitude is the same as the first one amplitude of one frequency of one the phase here is pi divided by four the fact phase is an angle but measured in radians and what does it do you can think it shifts that sinusoid along so take this one and shift it back and instead of starting at zero and going up it starts at this point and goes up so it's as if this one has been shifted by how much well by the phase of pi divided by four and as you change the phase you'll see a different shift of that signal so for now all we're doing is covering some high school mathematics or physics of the sinusoid okay a sine function and we've got three parameters we can change to change the shape of that function the peak amplitude the frequency and the phase and this just visualizes those changes the effect of those changes so a very simple signal that we want to transmit to carry information we can generate a signal which is simply a sinusoid a sine a sine wave and think of that comes out and the sine sine wave representing that the the the energy being transmitted is sent across the cable and received by the destination we can easily change the shape of the sine wave by changing these three parameters in fact we can change more than one at a time we can change the amplitude and the frequency and we can do more complex things we'll see is that we can take multiple sine sine waves and add them together combine them to get more complex output signals and that's the basics of how communication signals are designed we start with sine waves allowing us to vary these three parameters and combine them together in different ways to generate the signal that we want to transmit across the system across the communications link so in the very basics we can think of all of our communication signals are made up of different sine waves any questions that everyone remembers the sine function ask you to plot in the exam or the next quiz well I wouldn't ask you to plot but I would ask you to be able to recognize given this plot tell me the frequency so given this bottom left plot tell me the frequency well you look and you see it's a sine sinusoid and it's repeating in one second two times so every one second there are two repetitions so it has a frequency of two hertz or given this plot write an equation for it at least in this simple case well you see the peak amplitude is one the frequency f is two the phase because it starts at zero there's no offset or shift is zero so this one would be the signal as a function of time is sine 4 pi f at 4 pi t so you need to remember this general function here the signal is the peak amplitude times sine 2 pi f t plus the phase and then if you can determine those three parameters the value of the peak amplitude frequency and phase then you can determine the equation for that signal 2 pi times the frequency if the frequency is 2 we at 4 pi times t t is the parameter of the function the time let's let's draw some signals and then do some different combinations of them let me just check what pictures we have okay so with our basic sine wave we can vary those three parameters to change the shape but we can do more for example we can add two different sine waves together this is an example signal s of t sine 200 pi t plus one-third sine 600 pi t so we're taking one sine wave plus another sine wave and we'll get some different shaped signal as an output we'll plot that in a moment or a similar one so we can combine these sine waves together to get different shaped outputs and the communication signals that we deal with we can think as being composed of many different component sinusoid signals that made up of many different sine waves and usually at different frequencies in this top equation we can say there are two sinusoids what's the frequency of the first one 100 what 100 Hertz okay from the first component let's call this the first component sine 200 pi t map it back to our general equation that's our general equation well let's map it back and see okay we have in fact we have a multiply here 4 divided by pi times sine 200 pi t what's the peak amplitude of the first component in fact this multiplier is multiplied by both components so the peak amplitude of the first component is 4 over pi the frequency of the first component well it's sine 200 pi t the general form is sine 2 pi f t so what is f well 2 pi f t we have 200 pi t means f must be 100 Hertz because 2 times pi times 100 gives us out 200 pi times by the time plus a phase and in this case there is zero phase the phase is zero in this case there's no additional component here but we have a second sinusoid at it we're adding two together so we can give the same parameters for the second one peak amplitude of the second component write it down peak amplitude frequency and phase of the second component try and determine them there's this extra multiplier at the front we'll see the purpose of it soon but if we multiply 4 divided by pi times by one-third sine 600 pi t then that peak amplitude is simply 4 divided by pi times one-third that's the multiplier of the sine function sine 600 pi t what is the frequency of the second component 300 because our general form is 2 pi f t we have 600 pi t f must be 300 Hertz and the phase again is zero because there's no additional component radians the phase is measured so in fact this signal s of t is made up of two sinusoid's added together and both of them have different values of these three parameters the amplitude the frequency in the phase and in general our communication signals that we transmit we can think as being made up of as a combination of different sinusoid's be more complex than this but this is the principle that we can add them together to get a different shaped output I'll show you a plot of this one in a moment where each of the sinusoid signals have a frequency so in this case we have two components with two different frequencies 100 Hertz and 300 Hertz and also different peak amplitudes let's plot this before we go on to the next part actually I have it will plot another one later this is the plot of those the first two are the plot of the individual components and the third plot is the addition of the two now the scale on here doesn't exactly match the the equation here it's a general scale where uppercase t is the period but the shape matches what we have here we have a frequency of 100 Hertz we have to adjust t here and then a frequency which is three times as much 300 Hertz well you see the frequency of the second plot is three times as much as the top one and it's also one-third of the peak amplitude you see if this is a peak amplitude of one this will be one-third of that so the shapes at least match our our components here when you add them together and plot them you get this shape okay there's these humps here two humps at each point here importantly in this case that the frequency of the resulting signal is the same as the top signal we see the repetitions here here and if we keep going which is the same as the top signal and that was the way that the the equation was set up to produce that if we take some signal and we make it up by combining different sinusoids together when all frequency components are entered a multiple of one frequency then that one frequency is called the fundamental frequency and the others the other components are harmonic frequencies and our example equation first component was 100 Hertz second component was three times 100 Hertz which matches this condition here we have two components where this is one times 100 Hertz the second component is three times 100 Hertz so we say the fundamental frequency right f subscript f is 100 Hertz and this is a harmonic frequency 300 Hertz when we add these sinusoids together which match this condition then the resulting signal has a period equal to that of the fundamental fundamental frequency component the resulting signal has a period and frequency the same as this 100 Hertz signal and that's illustrated on this resulting signal here we have the first component the second component which has three times the frequency as the first component and the resulting signal when we add them together has the same frequency as the first component so if we structure our signal by adding sinusoids together we can get a resulting signal of a particular shape and having properties in this case the properties are that the same frequency as the the fundamental frequency in general by combining sine waves with different amplitudes frequencies and phases we can design or construct any communication signal we want so any real signal that we transmit we can think of it as made up of individual sinusoids sine waves and people use this to design signals so the people who create your wireless transmitter or design the standard for the wireless LAN or your ADSL modem and so on they need to create some hardware that generates signals well how do they design that hardware well they design it based upon these fundamental concepts of we can think of a signal as just a combination of many sine waves and we can use that concept to design the signal and look at its performance let's try and plot some different examples I'm going to plot them on the computer I have some software just some mathematics software that will produce some plots okay so it's not so important how I do it the important will be output plot that we see so we're looking at some time frame from zero up to one and I'm going to create a sine function and plot it and we'll see how we can combine them let me remember on a plot on the x access the time and on the y access the signal s of t and the first one remember our general our general form of a sinusoid amplitude time sine 2 pi f t plus phase let's set the peak amplitude to be one one time sine 2 times pi times the frequency and we can choose the frequency so I've chosen a peak amplitude of one a equals 1 sine 2 times pi times a frequency and let's just for this example choose a frequency of 2 2 Hertz times the time plus a phase let's make the phase to start zero zero phase and let's plot that as a blue line this is just the software I need to specify I'm specifying the color see if it works okay here's our our signal peak amplitude of one so it goes from plus one to minus one two times pi times 2 t so frequency should be 2 Hertz within one second there are two repetitions so we see that between zero and one we get two repetitions and there's no phase offset in this case let's try a couple of variations I want to do first I'm going to change something set the axes to be currently my axes range from minus one to plus one I'm going to change that which means it's the same signal except I've just changed the plot to go up to mine it from minus two to plus two we can change the peak amplitude so a new signal a red one and if we change the amplitude to say 1.5 simply increases the height if we have a green one with the original one amplitude and change the frequency to four so four Hertz we see it's the same height as the blue one except it repeats four times in this period of one second the green signal in this case so changing the amplitude and the frequency usually obvious to to visualize let's look at the impact of the the phase the start again so our first signal again and now let's introduce some phase shift and see how that impacts so before I had plus zero let's add pi over four so this is measured in radians so we can map it back back to degrees if we want but the input is radians and let's change the color we see the difference between the red one now has a phase of pi over four we see visually it's shifted by introducing this phase we have this shift of the from some point of origin and we can keep changing the phase pi over two another one three pi over four yellow it's hard to see and simply pi can you see the last one yep so by changing the phase we see this shift of this signal in the in the time domain from some point of origin so that's the change of the three parameters now let's consider if we combine two together take our original signal and then add a new one which is a third of the amplitude and instead of a frequency of two hertz change it to six hertz so I've shrunk the peak amplitude by a third and increase the frequency by three for the red one and now if we add the two together what we get take the first one two times pi times two t plus the second component so now we have it we're going to plot a signal with two components and we see the green one same frequency as the blue the original component but we have this different shaped signal we'll add some more components shortly and see how that impacts and what that results in first alright we're sending signals now so we can use sine functions and combine them to generate a signal of a particular shape but let's say we want to send bits from computer a to b what what can I do to send zeros and ones how can I shape my signal any ideas okay so but considering these basics these basic sinusoids what can we use how can we use them to represent zeros and ones so assign an amplitude to bit zero so if I want to send a zero I send a signal at one amplitude and if I want to send a bit one I send a signal at a different amplitude so that I'll send these signals and when the receiver receives a signal it will measure if the amplitude is low for example that means that someone just transmitted a bit zero if the amplitude is high it means they transmitted a bit one so that's the basic a basic way that we can use the signals to represent data let's say I want to send the sequence sequence of data with four bits the data I want to send zero one one one there's four bits of course if we focus on these four bits we want to get them from a to b so what we do is we generate a signal that represent this data and let's use the scheme that says if we want to send a bit zero we send a sinusoid with a low amp amplitude if we want to send a bit one we send high amplitude in fact we can simplify that and try and draw a case that captured that information let's try and what we do is for some period of time we send a signal to represent the first bit and then for another period of time the same period we send a signal to represent the second bit and so on let's see if we can use just a sine wave to do that so for this case we need to send four different bits so I'm going to do that over a period of one second our time frame so we'll break that into four different chunks of time I've set this up before so it's a bit simpler I'll explain it as we go so for the first if we imagine this one second is broken into four chunks each a quarter of a second long so for the time set one t1 we're going to plot our sine wave and in this case the frequency is to the peak amplitude is still one let's change the phase to be pi you'll see why in a moment and let's set the axis it'll be correct and for the second time time slot I'll use the same phase and the third time slot I'll use a phase of 0 and the fourth time slot a phase of pi so what I've done is over time I've changed the phase of this sinusoid this sine function so I've used the same peak amplitude over four time slots one one one one the same frequency two hertz two two two but I've simply changed the phase in this example and this is the resulting signal that say transmitted across our link where we're using the scheme when it's low it represents bit zero and when it's high bit one so zero one one one and by changing the phase I get the shape of the signal that represents the data I want to send whenever I want to send a bit zero I set the phase so that we go down and bit one the phase so that it shows a positive peak negative and positive a very simplistic way to transmit bits as some signal it may not be like that in real life but it captures the basics how fast did I send bits well no think of bits now think of how do we measure the speed of bits last week in fact on Monday data rate was one measure of how many bits we send per second how many bits per second do we send in this very simple example four bits were sent bit one two three four in a time period of one second four bits per second what was the frequency of our signal in all cases remember if we look at the sign the peak amplitude the frequency in this case is two hertz in all cases it's two hertz so I set that so using this simple scheme a negative value to represent bit zero a positive value to represent bit one we transmit this signal the receiver should receive a signal with similar shape and what it does for the first quarter of a second it measures the amplitude okay it's close to minus one therefore it must mean a bit zero was transmitted then it measures the amplitude plus one plus one plus one it must mean a three bit ones were transmitted in this simple case using a sinusoid with one component with a frequency of two hertz we had a data rate of four bits per second let's try using a different signal and see what happens when we change the signals that we use how that impacts upon our data rate and our other performance metrics let's draw it again instead of having one sinusoid component I'm now going to generate a signal using two components and it has some structure which you'll soon notice I hope it works now we have a signal which has two components sine 2 pi 2 time one plus pi peak amplitude is one frequency of this component is 2 phase offset is pi and a second component with one third amplitude frequency of six and a phase offset of pi we're missing a bracket there let's see how it goes and then we'll do that for the other time periods same concept but now we're just using a different signal where again negative amplitude represents a bit zero positive amplitude represents bit one so zero one one one the only difference is now I've used a different signal to generate the resulting signal here I use two sine components and you see the way that I've structured it is that the second component is one third of the amplitude of the first and three times the frequency here was two hertz here is six hertz I can keep adding components so this has two components if I add a third component using a similar structure we can get a similar shape signal but slightly different or add one more actually we'll see in general what I've done come back to that what we're doing is similar to this this is a signal with two sine components you can see in the caption sine 2 pi FT generally one third sine 2 pi 3 FT we see the shape with these two humps at the top in this case it's positive negative positive negative this is if we add a third sine component and the pattern we see is now plus one fifth sine 2 pi FT five times the frequency is the first one fifth of the amplitude this is with four components the last one is one seventh of the amplitude and seven times the frequency this is with an infinite number of components using the same pattern and we see we get a perfect square waveform now we can use this same approach to send our zeros and ones instead of just sending a sinusoid we can send in theory perfect square waveform where we'd say for example plus one represents bit one minus one represents a bit bit zero and we'd get a plot I'm not going to do it on the computer but we'd get a plot like this for our zero one one over our period of one second represents bit zero it's a negative value bit one one and one again we'd use the same signal except we can change the phase to determine the output shape the one I draw on the board represents the same data as this one different shape signals different signal transmitted but are carrying the same four bits zero one one one and at the same data rate four bits in one second and in this one over there we got also four bits in one second so we can choose and design signals differently to carry our data we'll look and compare which one is better is this square one better than the one on the screen to send data or we'll see that generally it is in terms of quality because the receiver in the presence of errors if there are errors in this one it's more likely that receiver will be able to still determine the correct bits if their errors in this one there's more of a chance that they'll get the wrong bit and we've got a detailed example of that later let's step back and see what else is different amongst the different signals so we skipped over a few slides here what we've been doing is taking sinusoids and changing the shape and now combining combining them together adding them together in this case to get a different resulting shape we can look at the some of the parameters or performance metrics of these signals and the way that we can make this easier this is the signal in the time domain let's look at it in the frequency domain and their mathematics Fourier transforms that can convert a signal in the time domain to a frequency domain we're not going to cover that we'll just look at the end results here is a plot of the same so looking at the bottom signal here made up of two components note the difference between the two components one has a the second one is a third of the peak amplitude it's a third of the size but three times the frequency and we add them together and we get this resulting signal in the frequency domain what we do is we consider the individual components and we consider their peak amplitudes and their frequencies this is a plot of the same signal the bottom one on the previous slide but in the frequency domain how we interpret this is say that at one F we have one component with a particular peak amplitude and a frequency three times that we have a second component with a third of the peak amplitude so this is the same signal but looking from the frequency perspective not as a function of time and the reason we do this is that because it makes analysis and design much easier for the for the engineers that must make the devices let's try and do that with a real example and then we'll define some terminology to finish let's take a signal and well I'll create a signal and then we'll draw it right out of space here's a signal with three components 15 times sine 2 pi 4t so 2 times pi times 4 times the time plus 5 sine 2 pi 12t plus 3 sine 2 pi 20t so I've created this signal let's analyze the individual components from our general sinusoid equation so we have three components what's the amplitude of the first component 15 easy just to multiply frequency of the first component keep helping me for okay remember the general structure 2 pi ft what's the frequency in this case I've written it easily I could have written 8 pi t that frequency is 4 4 hertz phase in all cases there's no plus anything so the phase is 0 I won't I won't write the phase second component amplitude is 5 frequency is 12 third component amplitude is 3 frequency is 20 hertz plot this signal in the time domain well I won't ask you to do that because you need a computer to get accurate so if I ask you to plot this signal in the time domain I could do it on the computer but it's not exactly the same but it would look something like this this would be the shape now for you to plot that in the time domain is again you need a computer to get the exact shape there but let's analyze this from the frequency domain and and we can first plot it in the frequency domain in the frequency domain the plot shows the the peak amplitude as a function of the frequency for each of the components here we have three components we know their peak amplitudes we know their frequencies so at a particular frequency we plot an impulse a spike I won't try and plot it in the time domain but in the frequency domain here's frequency in hertz and here is the peak amplitude of the signal as a function of f this is an uppercase s notation so at what have we got at 4 hertz we have a component may not be the greatest scale at 12 hertz and at 20 hertz we have three components we know their frequencies we know their peak amplitudes 15 5 and 3 so we'd plot an impulse 15 5 and 3 that is the plot of this signal the equation but given in the frequency domain the reason for using the frequency domain is to make the analysis and and the design of the signals easier it's much easier to do operations in the frequency domain than time domain and many signals are analyzed from this perspective now to finish let's introduce some concepts that we can gain from this we can say this signal s of t has three components the frequencies of those components of 4 12 and 20 hertz for any signal the spectrum of that signal is the range of frequencies it contains so for our signal we can say the spectrum is 4 12 and 20 hertz this signal contains three components with these three frequencies that's the spectrum of that one signal another term the absolute bandwidth of this signal is the width of the spectrum our spectrum ranges from 4 hertz up to 20 hertz therefore the absolute bandwidth is 16 hertz from 4 to 20 that's the width so the bandwidth in this case 20 minus 4 16 hertz some signals may have a DC component we'll not cover that yet so there's two new terms that we've introduced spectrum and absolute bandwidth spectrum of a signal the set of frequencies the bandwidth is the the maximum frequency component minus the minimum in fact on this plot it's very easy to see the bandwidth and the spectrum it shows us the spectrum and the bandwidth the absolute bandwidth is just the maximum minus the minimum 16 hertz in this case we'll see and we'll show some examples that indicate that the bandwidth of a signal and of a communication system impacts upon the data rate the number of bits per second we can send and in generally in general the larger the bandwidth with other things fixed the higher the data rate we can achieve so if we have another signal which with a larger bandwidth we can increase our data rate but there are some costs of increasing the bandwidth let's see if we can summarize with one more or finish with one more example same example let's say I now have a another signal with just two components I remove the last one what is its absolute bandwidth so a second signal two components what is the absolute bandwidth of this second signal it's 8 hertz because now we have two components amplitude 15 frequency of the first component 4 hertz second component amplitude of 5 frequency at 12 hertz so the spectrum is 4 hertz and 12 hertz the bandwidth is just 8 hertz in this case so we'd say this signal occupies a bandwidth of 8 hertz if we transmit this signal through our system it uses 8 hertz bandwidth the first signal used a bandwidth of 16 hertz in general the larger the bandwidth the higher the data rate the faster we can send bits so that the signal with a higher bandwidth is better from that perspective but another trade-off is that the higher the bandwidth we consume the higher the cost involved of transmitting that signal so we'd like a signal with a low bandwidth it's cheaper but we'd like a signal with a high bandwidth because we can send more bits per second so there's a trade off there in that when someone designs a signal what signal do I transmit across my Wi-Fi my wireless LAN then they need to consider that trade-off of do we design one with a large bandwidth or do we limit it so the trade-off between data rate and cost next week we'll go through that trade-off and look at some other factors as well with it with a detailed example what we want to summarize for today so we haven't gone through all of these factors let's go back all of our communication signals can be made up of we can think of it as sine waves where a fundamental sine wave is the peak amplitude times sine 2 pi times the frequency times time plus a phase varying those three parameters change the shape of that sine wave combining sine waves together we can get signals of different shapes as we see in this case adding these two we get this different shape signal and in fact if we added in in the pattern that we saw if we add an infinite number of components using this pattern we eventually get a square wave perfect square wave we can use this signal to represent bits for example transmitter high level to represent a bit one a low level for a bit zero so from that depending upon the hour our frequency we can get some bit rate number of bits per second one bit another bit and so on and determine a data rate these signals are in the time domain most analysis of communication signals performed is performed in the frequency domain and just going back in the frequency domain domain as a plot we look at the individual components determine their peak amplitude and their frequency and plotted impulse for a spike at that particular frequency and with that peak amplitude so this is a plot of the signal in the frequency domain we can also write an equation for that I'll do some analysis mathematically and the two terms so far we've defined spectrum and absolute bandwidth spectrum is simply the range of frequencies in that signal absolute bandwidth is the width of the spectrum what we'll do next week is show an example that connects all them together in particular bandwidth data rate and other factors like cost and errors


Earth Day Meteor Shower, presented by Science at NASA. On April 22nd, millions of people around the world will gather together at festivals and other events to celebrate our beautiful blue planet. It's Earth Day, an occasion to pause, reflect, and talk about how to sustain a clean, healthy environment on Earth. This year, Earth Day will end with a meteor shower. On April 22nd, 23rd, Earth will pass through a stream of debris from Comet Thatcher, the source of the annual Lyrid Meteor Shower. As Earth crosses the debris zone, flakes of Comet dust no bigger than grains of sand strike Earth's atmosphere traveling at 49 km per second, that's about 110,000 miles per hour, and disintegrate as streaks of light. Typical Lyrids are about as bright as the stars of the Big Dipper. As meteor showers go, the Lyrids are relatively mild. Most years in April, there are no more than 10 to 20 Lyrid Meteors per hour. But sometimes, when the Earth glides through an unusually dense clump of debris from Comet Thatcher, the rate increases, resulting in what is known as a Meteor Outburst. Sky Watchers in 1982, for instance, counted 90 Lyrids per hour, and even more impressive Outburst was documented in 1803 by a journalist in Richmond, Virginia, who wrote, Shooting stars were observed on Wednesday morning last at Richmond in its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From 1 until 3 in the morning, those starring meteors seemed to fall from every point of the heavens, in such numbers as to resemble a shower of skyrockets. Another published report from the 19th century lists an observer as having counted 167 meteors in about 15 minutes, and could not then number them all. No such Outburst is predicted for 2015, but then again, no Outburst were predicted on those previous occasions, either. If you're up late, take a look. The best time to catch the shower is between about 11 p.m. on April 22nd and sunrise on April 23rd, at any time zone in the Northern Hemisphere. Observing Tips Dress warmly. Bring a reclining chair or spread a thick blanket over a flat spot of the ground. Lie down and look up. Meteors can appear in any part of the sky, although their trails will tend to point back toward the constellation Lyra, from which the meteors get their name. The hours before dawn are best, because that is when Lyra is highest in the sky. Sometimes bright moonlight can spoil a meteor shower. That will not be the case on April 22nd. The moon is just a slender crescent, and it sets shortly after sunset, so lunar glare will not interfere with the lyraids. If you can, get away from city lights for the darkest possible sky and the best possible show. And enjoy Earth Day. And then enjoy Earth Night even more. For more news about meteor showers, stay tuned to science.nasa.gov.


This is one of those things where, to make that great comedy, you've got to follow a little bit of formula. I'm not really a big fan of romantic comedies in general. Hey everybody, welcome to another episode of Movie Feuds Presents Real Time Reviews. This week we had a great opportunity to see advanced screening of a film coming out this week called Killer Elite. We had an opportunity, and once again, I was so low because Cory doesn't go to new movies. I was there next to you. Ravenous. Game's over. This film went a little under the radar, but it did star some pretty big names like Robert De Niro, Jason Statham, and Claiborne. You know, there was no radar. I saw the poster before seeing this, and that was badass. He had the three guys with the guns and the mutton chops. Then I saw it and realized it was just transporter four. It's just Jason Statham. Another note about the characters is Robert De Niro really isn't even in this film. He's a little bit beginning, and then you see him again at the end, like they were filming Meet the Fockers Forward Next Door, and the director's like, really, De Niro's here? Let's see if we can get him here. Get over here, De Niro. You're in this. You're in this movie. How much time do you have? Two hours? Yeah, we can get you in. The last key player to this masterful picture, Claiborne, a former SAS member. What's SAS, you ask? I don't know. I still don't know. I mean, I looked at the IMDb plot description after the movie to find out what the hell I was just watching. This was just one really generic action movie. I mean, there were so many 30-second scenes that half the time you didn't even know where you were. Well, we did have nice little text notes at the bottom of it. Two days later. Two days later. Do I need that? You start by seeing Jason Statham being a really elite killer, then he retires from the game. I'm out. I'm out of the game. A year later, he gets a phone call saying he needs to get back in the game. I'm back in the game. Of course he's back in the game. That's never happened in a movie before. Two days later, he's getting off a plane in Morocco, and then the movie starts. Yeah, and then it's Indiana Jones from there. It's... Disappointment. He's in Morocco. Now he's in Paris. I mean, the scenes are 30 seconds long. He's in Morocco one time. I don't even know if Morocco is one of the places. It's just a tapestry of locations. Nothing adds up. We brushed over the plot, but to kind of piecemeal it, basically, Robert De Niro is the mentor. He gets kidnapped off-screen, and that's what brings Statham back into the mix. Now, you'll notice we're using their real actor names, because I have no idea what their character names are. There were so many characters in this film. It was ridiculous. Half the time, you didn't know where you were, but the other time, you didn't even know who you were talking to or talking about.   Unfortunately, none of these scenes are good. It was bad even for a Jason Statham movie, and the only really good part of the action you saw was one that was spoiled in the trailer when he flipped over on a chair on another guy, which was kind of cool, but... Once again, it relies on the shaky cam instead of actually well-thought-out choreography.  I don't know what 45 minutes in. I can't even see what's going on. For all I know, they were standing around drinking coffee, and the camera guy just shook the camera, so it looked like they were fighting. There's just so much awful here. I don't even know where to keep going with it.  The director likes one shot, and he uses it eight times, through the scope of a gun, through the scope of a camera. The film score was terrible, too. I felt like I was playing the facility on Gold 964, and Oddjob just popped out in front of me, and me, me, me, me, me. Oh, man, how do you make Statham shoot? Yeah, he's gonna do that anyways. Yeah, he doesn't have a gun, but he's got some broken piece of wood in his pant leg, and he'll pull it out and kill, like, eight people.  I mean, they break into a garage with a tennis ball, like, instead of, like, hot wiring or figuring out the code, he just puts a tennis ball on there and it opens. He's very resourceful. We need to find the best elite hackers in the world. No, no, no, no. We just need to go down to Shields. I got a gift card. We're gonna have this place figured out in a heartbeat. All right, give me a tennis ball, a loaf of bread, and a paper clip. I can get in here, no problem. But how are you gonna get past the guards? Well, let me see. We'll feed them the loaf of bread.  Statham style. This review is all over the place, but then again, so is the movie, so it's kind of fitting. I gotta go back to the plot and talk about how it goes. Bad Boys 2, about an hour in and just resets the entire movie.  Hold back. Jason Statham retires again and then comes back to the game to finish another job. I'm not gonna do it. Not that man anymore. I'm retired. It's like, we need you. Yeah, okay, yeah, that sounds good. I was gonna refurbish the porch, but this sounds better. I think actually, this time, I saw Ben Stiller in the background just drinking some coffee. He must have come over from to meet the father. If Stiller was there, he'd be on the poster front and center with Jinx the Cat. That's true. Let's get down to brass tacks. I'm a Statham fan.   Sands number three. But this has none of the good elements. Bad script. Bad characters. Even bad choreography. So it's got nothing to offer. We've wasted your time with this review. Just hit the stop button on YouTube. Just, you can hit that little like button. That'd be great. This movie was awful. Just stay away. Just walk away. Don't even see Contagion because I saw that too. It sucked. Want to go to that review now?  It's over. Alright, let's finish this. This guy is good. Oh, I do. Well, more than just reviews, this is Movie Feud to present real-time reviews. A lot of excitement closing this out. Really not much. So that's what this is all about. I gotta cover my expenses.


Income tax 2023-2024. Medical and dental expenses. Get ready, some coffee, and stay calm. Because as a taxpayer, you really don't have much more to lose. Most of this information can be found in the instructions for Schedule A Tax Year 2023, which you can find on the IRS website at irs.gov, irs.gov. Looking at the income tax formula, focused on what I would call the below the line deductions, more specifically on the itemized deductions. Remembering that the income tax formula is basically a funny income statement. Income statements typically having income minus expenses resulting in net income. Here having income minus various deductions resulting in taxable income, noting that for taxes deductions are good. Therefore, we're always looking for more of them. The major two categories of deductions being the adjustments to income or above the line deductions and the below the line deductions, the greater of either standard deduction or itemized deductions. Remembering that the above the line deductions are possibly less common, less familiar, but quite important if they qualify for an above the line deduction or adjustment to income because there's no hurdle that have to be cleared as is the case with the itemized deductions. With the itemized deductions, we would only generally be taking them if they add up to a dollar amount that is greater than the standard deduction, the standard deduction being based in part on filing status such as single versus married versus head of household and so on.