Science Articles

Cheat Sheet / Updated 11-13-2024

Botany is the study of plants. Plants are very similar to people in a lot of ways, but they also have some differences that can be hard to wrap your brain around. And, like any science class, botany can get a little overwhelming at times. So, here are a few items to help you grasp some of the big ideas in botany.

Article / Updated 08-08-2024

Hurricanes are scary, and few people think clearly under that stress. Additionally, a lot of what you need to do to best weather a storm starts well ahead of hurricane season — which runs from late May through November. Start your hurricane safety plan ahead of a storm, while things are calm. The following steps put you and your family in the best position to protect your home and yourselves when a hurricane is on its way. Have an evacuation plan ready. Determine whether you’re in an evacuation zone and watch for updates; the course of a storm may change. Scout your yard and remove any furniture or other items that may get picked up by the wind and fly through windows or otherwise cause destruction. Put any important documents in a watertight container, along with medications and insurance cards. Charge your phone and any other devices you plan to use or carry with you. Turn your fridge to the coldest setting and put a thermometer in there. You’re likely to lose electricity, and a colder starting temp will keep your food cold longer. The thermometer will let you know whether your milk is a lost cause when the electricity’s back. Look into hurricane insurance If you live in an area commonly hit by hurricanes, standard homeowner’s insurance isn’t going to provide everything you need. Such a policy addresses structural damage and typically includes a higher deductible whenever that damage arises from a hurricane. And it may be inadequate to cover your costs for rebuilding and the living expenses you pay while you rebuild. Be sure to look closely at coverage for additional living expenses (ALE), which are essential after extensive storm damage that requires you to rent living space while damage is repaired. Find out what your policy covers and what it excludes. For example, a standard homeowner’s policy probably doesn't cover damage from sewer backups, which are common after major storms. You actually can buy a specific policy for this instance. Much of the damage from a hurricane comes from flooding, which also requires a separate policy. To get the full value from the policies you do buy, make sure you have a complete inventory of what you own and how much it’s worth. Doing so will make filing claims later on much smoother. Keep this documentation and your policies in a water-safe container that you can easily move with you when you evacuate. If you rent or own an apartment in a co-op, you need your own insurance policies, but you also want to be aware of the coverage your building has in place. Hurricane “watch” or “warning?” What makes a watch different from a warning? These terms actually have very specific meanings. A hurricane watch tells you that hurricane-force winds may appear within 48 hours. If you hear a hurricane warning, know that you’re likely to encounter hurricane-force winds within 36 hours. Warnings usually are issued for about 300 miles of coastline at a time. Although satellite technology makes predicting a storm’s approach easy, determining exactly where it will make landfall is still difficult. If you are told to evacuate ahead of a hurricane, never hesitate. Leave as soon as possible. But, if whatever reason, you are unable to get out and find yourself caught in the storm, here's how to survive. Address kids, pets, and special needs during a storm Maybe one family member needs to keep insulin at a just-right temperature, or you have a dog who requires eye drops every four hours. Situations like these require more detailed planning. Be sure to think through a week’s worth of needs for each family member. That may mean finding a physician and forwarding medical records to a medical center in the city where you’ll wait out the storm at your cousin’s house, or it may require even more careful planning. Just make sure that as soon as you know a storm is possible, you carefully consider each family member’s needs for several days. Include the pets, the kids, and the grandma you’ll pick up on the way out of town. For pets and kids, concerns aren’t all that different: Be ready to feed and distract, at a minimum. You need to prepare whatever food, drinks, and toys or special objects will keep the kids and pets as content as possible during the storm. Make sure that your pets have been microchipped or that they’re wearing ID tags. It’s all too easy to become separated during the chaos of a storm. If your kids attend school or daycare, make sure that you know the schools’ evacuation plans. Laminate an “in case of emergency” card for each child that includes your contact information and that of a friend or relative who lives elsewhere and may be able to provide a safe place to stay if a storm arises. As much as possible, keep up your routines, which will reassure members of your family who rely on you. Your kids especially look to you for cues about how to act, so do your best to keep calm. Prepare a storm evacuation plan Uprooting your life in response to an incoming storm presents a host of challenges, like where you’ll end up and who’s in charge of the pet-food supply. Make the transition as smooth as possible by having an evacuation plan in place. It should cover the following: Where you’ll meet if you become separated: Pick a place close to home and one farther away where you can meet up, and choose a family member to serve as point person. This person is who everyone checks in with if you can’t stay in one place. Where you’ll stay: Identify a couple of options ahead of time. Shelters will arise nearby (use FEMA.gov to find them), or maybe a hospitable friend or family member lives outside the evacuation zone. If you have pets, this part of the planning is trickier; most shelters accept only service dogs. How you’ll get there: If you have a car, make sure it’s in good working order and your gas tank is full. If not, plan farther ahead for public transportation (which will shut down as the storm nears) or for someone to drive you. Supplies: Get your disaster supplies kit ready well ahead of time. Grab a phone charger for the car, and if you’re traveling far, have snacks and distractions ready — especially if you’re traveling with kids. Maps: Downed trees or flooding may require you to change your route at the last moment, so be ready with low-tech navigation that cannot let you down no matter the circumstances. IDs and cash: Appoint a family member to make sure everyone has an ID and a little bit of cash. Don’t let this be the time you’re caught with your wallet in your gym bag. Updates: If you don’t want to keep tuned to the weather on the car radio, ask one person to track the storm until you’re safely out of range. Emergency instructions sometimes change as the storm progresses, and you need to have the latest information as you evacuate. Notice: Identify a close friend or family member to check in with when you leave and when you have arrived at shelter outside the evacuation zone. Resolve: Staying in your home is tempting, even when you’ve been ordered to evacuate. Resolve, as a household, to follow those orders and accept no alternatives. Hurricanes are deadly. Agreeing ahead of time that you’ll evacuate can save valuable time debating the issue later. If you’re on the coast, get out well in advance of the storm surge When a hurricane pushes ocean water ashore, that push is called a storm surge and is responsible for more deaths and damage than any other part of the storm. Depending on how and where the storm hits, a storm surge — measured in how far above sea level the water rises — can bring almost 30 feet of water to land. This water moves at high speed, bringing tremendous destructive power to everything in its path. These surges are unpredictable, and they often arrive before the storms themselves. When they hit, water levels can rise ten feet in just minutes. Help cannot make it to you under these circumstances, and you are unlikely to be able to drive away from a storm surge. If you’re near a coast and anywhere close to a hurricane’s path, you must evacuate. If you see it coming, it’s too late. The surge can easily go from an inch to several feet before you even make it out of your driveway. Keep an axe in your attic so that if for some reason you are trapped in your home during a surge, you have an escape route through the roof. Travel to hurricane prone areas Because hurricanes happen near coastlines, a lot of popular vacation spots are susceptible. When you’re thinking about planning a vacation, take a look at the storm season before you book tickets and hotel rooms. Travel insurance that covers natural disasters can help, and you should check with hotels and airlines about policies regarding refunds or rescheduling in the event of a storm. For official communications related to hurricanes, please visit the websites of FEMA, Department of Homeland Security, and the National Hurricane Center for the latest information. Please note that this is general preparedness information, not specific to a particular storm.

Cheat Sheet / Updated 07-27-2024

Neurobiology has all kinds of real-world (and not so real-world) applications. From curing paralysis to the possibility of cyborgs, neurobiology has answers to many fascinating questions this Cheat Sheet addresses.

Cheat Sheet / Updated 07-27-2024

To estimate sample size in biostatistics, you must state the effect size of importance, or the effect size worth knowing about. If the true effect size is less than the “important” size, you don’t care if the test comes out nonsignificant. With a few shortcuts, you can pick an important effect size and find out how many participants you need, based on that effect size, for several common statistical tests. All the graphs, tables, and rules of thumb here are for 80 percent power and α = 0.05. In other words, the guidance applies to calculating sample size you need in order to have an 80 percent chance of getting a p value that’s less than or equal to 0.05. If you want sample sizes for other values of power and α, use these simple scale-up rules: For 90 percent power instead of 80 percent: Increase N by a third (multiply N by 1.33). For α = 0.01 instead of 0.05: Increase N by a half (multiply N by 1.5). For 90 percent power and α = 0.01: Double N (multiply N by 2).

Cheat Sheet / Updated 07-03-2024

Stargazing is a fascinating hobby, but there’s an awful lot to gaze at up there. Eighty-eight constellations and hundreds of other objects both bright and faint mean that wherever you look when you’re stargazing, there’s something to see. If you want to make sense of it all, and make sure that your kit is properly set up, this Cheat Sheet is here to help.

Cheat Sheet / Updated 05-10-2024

This Cheat Sheet is intended to supplement Quantum Physics For Dummies, 3rd edition, by Andrew Zimmerman Jones. It begins by reviewing some useful operators used in quantum mechanics calculations. Then it covers a useful method for solving the Schrödinger equation for the quantum wave function, and then how you can use that wave function to calculate probabilities in quantum physics. Finally, it lays out some key moments in one of the most important discoveries of quantum physics: the understanding of wave-particle duality.

Article / Updated 04-09-2024

Celebrate everything that is beautiful about our planet by reconnecting with nature, learning more about the natural environment, or picking up a new eco-friendly habit or two. April 22 is Earth Day — a world-wide celebration commemorating everything that makes our blue-marble planet unique and beautiful, and all the things we can do to protect it. Starting all the way back during the environmental movement of the 1970s, Earth Day has grown to become a powerful motivator for individuals and companies alike to become more environmentally aware and responsible. From local volunteer cleanups to nation-wide conservation initiatives, this year is no different, with numerous events happening at both the grassroots and state levels. Want to join in on the celebration? Find Earth Day events in your area, by visiting https://www.earthday.org/ The first Earth Day In response to public outcry to the Santa Barbara Oil Spill of 1969, U.S. Sen. Gaylord Nelson, a Democrat from Wisconsin, organized a nationwide "teach-in" on college campuses about environmental issues to take place on April 22, 1970. Rep. Pete McCloskey, a Republican from California, joined Nelson as his co-chair to organize the event. More than 2,000 colleges and universities, 10,000 public schools, and 20 million citizens participated. They demonstrated to raise awareness about the health impacts of 150 years of industrial development. Unfortunately, today, we face daunting threats from climate change. If you want to make a difference, there are plenty of ways to help and celebrate Earth Day — here are just a few. Plant a healthy diet You’ve probably already heard about the massive environmental impact that animal farming has on the planet. It is second only to fossil fuels in terms of contributing to human-made greenhouse gas emissions, the cause of climate change. And, while the jump from a traditional omnivorous diet to a full-blown vegan one is not something most people can accomplish overnight, cutting down on red meat is a great first step. Something as simple as committing to meat-free Mondays can have a significant influence on your health and the environment. Get started by taking a crack at one or two of our favorite plant-based recipes found in Plant-Based Diet Cookbook For Dummies. Channel your inner green thumb You don’t need to become an expert horticulturist to help save our planet. Simply buying local or better yet, growing some of your own food can help reduce your carbon footprint — not to mention, teach you valuable transferable skills like diligence and patience. Plus, there’s just something so satisfying about working with your hands, especially if you’re used to working in front of a screen all day. You can start by growing some common herbs like rosemary or thyme. They are fairly resilient and, depending on where you live, can even be grown indoors. If you lack the space to garden, look for farmers markets in your area or, better yet, join a community garden, these gardens are becoming increasingly popular, even in the most urban of cities. As you're planning your garden, think about irrigation and conservation: How can you use the least amount of water while growing your plants? Parts of the world, including in the U.S., are experiencing drought, and fresh, clean water is not something any of us can take for granted. If you need some ideas for conserving water, one excellent resource is: Low-Water Landscaping For Dummies. Don't worry if you have no previous gardening knowledge — beginner-friendly resources, such as Gardening Basics For Dummies, will help you get there. You can also find a farmers market near you using the USDA National Farmers Market Directory. Stay informed It’s no secret that our planet is in grave danger as a result of climate change. But, contrary to what you may feel after reading all the increasingly worrisome headlines, you must remember — there’s still hope. And, while the biggest contributors of climate change, like animal farming and fossil fuel burning, may seem so far removed from your daily life, you’d be surprised how much of a difference you as an individual can make. Staying informed is perhaps the easiest way to help environmental causes. As an informed citizen, you have the power to choose more wisely what products to buy, what companies and practices to support, and even who you vote for in the next election. Don't know where to start? Check out Climate Change For Dummies to help you navigate this complex topic. More ways to greenify your life There’s always something more we can do to reduce our environmental impact on the planet, but that should not discourage us from taking action — after all, every little bit counts. One small change in your daily routine today will lead you to more and more lasting changes in the future. If you’re ready to explore even more ways to go green, check out Green Living For Dummies for a more comprehensive guide to sustainable living. We also have a number of other books with invaluable information and ideas for reducing waste by recycling and reusing items in a different areas of our lives. Here are a few of the latest: Sustainable Travel For Dummies Recycling For Dummies Upcycling Furniture and Home Decor For Dummies Sustainable Fashion For Dummies From the team at Dummies, we wish all of our fellow earthlings a happy and green Earth Day.

Article / Updated 03-20-2024

Chemists aren’t satisfied with measuring length, mass, temperature, and time alone. On the contrary, chemistry often deals in calculated quantities. These kinds of quantities are expressed with derived units, which are built from combinations of base units. Here are some examples: Area (for example, catalytic surface). and area has units of length squared (square meters, or m2, for example). Volume (of a reaction vessel, for example). You calculate volume by using the familiar formula Because length, width, and height are all length units, you end up with or a length cubed (for example, cubic meters, or m³). Density (of an unidentified substance). Density, arguably the most important derived unit to a chemist, is built by using the basic formula Density = Mass / Volume. Pressure (of gaseous reactants, for example): Pressure units are derived using the formula Pressure = Force / Area. The SI units for force and area are newtons (N) and square meters (m²), so the SI unit of pressure, the pascal (Pa), can be expressed as N/m². Let’s try an example. A physicist measures the density of a substance to be 20 kg/m³. His chemist colleague, appalled with the excessively large units, decides to change the units of the measurement to the more familiar grams per cubic centimeter. What is the new expression of the density? The answer is 0.02 g/cm³. A kilogram contains 1,000 (10³) grams, so 20 kg equals 20,000 g. Well, 100 cm = 1 m; therefore, (100 cm)³= (1 m)³. In other words, there are 100³ (or 106) cubic centimeters in 1 cubic meter. Doing the division gives you 0.02 g/cm³. You can write out the conversion as follows:

Article / Updated 03-20-2024

Physics is filled with equations and formulas that deal with angular motion, Carnot engines, fluids, forces, moments of inertia, linear motion, simple harmonic motion, thermodynamics, and work and energy. Here’s a list of some important physics formulas and equations to keep on hand — arranged by topic — so you don’t have to go searching to find them. Angular motion Equations of angular motion are relevant wherever you have rotational motions around an axis. When the object has rotated through an angle of θ with an angular velocity of ω and an angular acceleration of α, then you can use these equations to tie these values together. You must use radians to measure the angle. Also, if you know that the distance from the axis is r, then you can work out the linear distance traveled, s, velocity, v, centripetal acceleration, ac, and force, Fc. When an object with moment of inertia, I (the angular equivalent of mass), has an angular acceleration, α, then there is a net torque Στ. Carnot engines A heat engine takes heat, Qh, from a high temperature source at temperature Th and moves it to a low temperature sink (temperature Tc) at a rate Qc and, in the process, does mechanical work, W. (This process can be reversed such that work can be performed to move the heat in the opposite direction — a heat pump.) The amount of work performed in proportion to the amount of heat extracted from the heat source is the efficiency of the engine. A Carnot engine is reversible and has the maximum possible efficiency, given by the following equations. The equivalent of efficiency for a heat pump is the coefficient of performance. Fluids A volume, V, of fluid with mass, m, has density, ρ. A force, F, over an area, A, gives rise to a pressure, P. The pressure of a fluid at a depth of h depends on the density and the gravitational constant, g. Objects immersed in a fluid causing a mass of weight, Wwater displaced, give rise to an upward directed buoyancy force, Fbuoyancy. Because of the conservation of mass, the volume flow rate of a fluid moving with velocity, v, through a cross-sectional area, A, is constant. Bernoulli’s equation relates the pressure and speed of a fluid. Forces A mass, m, accelerates at a rate, a, due to a force, F, acting. Frictional forces, FF, are in proportion to the normal force between the materials, FN, with a coefficient of friction, μ. Two masses, m1 and m2, separated by a distance, r, attract each other with a gravitational force, given by the following equations, in proportion to the gravitational constant G: Moments of inertia The rotational equivalent of mass is inertia, I, which depends on how an object’s mass is distributed through space. The moments of inertia for various shapes are shown here: Disk rotating around its center: Hollow cylinder rotating around its center: I = mr2 Hollow sphere rotating an axis through its center: Hoop rotating around its center: I = mr2 Point mass rotating at radius r: I = mr2 Rectangle rotating around an axis along one edge where the other edge is of length r: Rectangle rotating around an axis parallel to one edge and passing through the center, where the length of the other edge is r: Rod rotating around an axis perpendicular to it and through its center: Rod rotating around an axis perpendicular to it and through one end: Solid cylinder, rotating around an axis along its center line: The kinetic energy of a rotating body, with moment of inertia, I, and angular velocity, ω: The angular momentum of a rotating body with moment of inertia, I, and angular velocity, ω: Linear motion When an object at position x moves with velocity, v, and acceleration, a, resulting in displacement, s, each of these components is related by the following equations: Simple harmonic motion Particular kinds of force result in periodic motion, where the object repeats its motion with a period, T, having an angular frequency, ω, and amplitude, A. One example of such a force is provided by a spring with spring constant, k. The position, x, velocity, v, and acceleration, a, of an object undergoing simple harmonic motion can be expressed as sines and cosines. Thermodynamics The random vibrational and rotational motions of the molecules that make up an object of substance have energy; this energy is called thermal energy. When thermal energy moves from one place to another, it’s called heat, Q. When an object receives an amount of heat, its temperature, T, rises. Kelvin (K), Celsius (C), and Fahrenheit (F) are temperature scales. You can use these formulas to convert from one temperature scale to another: The heat required to cause a change in temperature of a mass, m, increases with a constant of proportionality, c, called the specific heat capacity. In a bar of material with a cross-sectional area A, length L, and a temperature difference across the ends of ΔT, there is a heat flow over a time, t, given by these formulas: The pressure, P, and volume, V, of n moles of an ideal gas at temperature T is given by this formula, where R is the gas constant: In an ideal gas, the average energy of each molecule KEavg, is in proportion to the temperature, with the Boltzman constant k: Work and energy When a force, F, moves an object through a distance, s, which is at an angle of Θ,then work, W, is done. Momentum, p, is the product of mass, m, and velocity, v. The energy that an object has on account of its motion is called KE.

Article / Updated 03-20-2024

When an object moves in a circle, if you know the magnitude of the angular velocity, then you can use physics to calculate the tangential velocity of the object on the curve. At any point on a circle, you can pick two special directions: The direction that points directly away from the center of the circle (along the radius) is called the radial direction, and the direction that’s perpendicular to this is called the tangential direction. When an object moves in a circle, you can think of its instantaneous velocity (the velocity at a given point in time) at any particular point on the circle as an arrow drawn from that point and directed in the tangential direction. For this reason, this velocity is called the tangential velocity. The magnitude of the tangential velocity is the tangential speed, which is simply the speed of an object moving in a circle. Given an angular velocity of magnitude the tangential velocity at any radius is of magnitude The idea that the tangential velocity increases as the radius increases makes sense, because given a rotating wheel, you’d expect a point at radius r to be going faster than a point closer to the hub of the wheel. A ball in circular motion has angular speed around the circle. Take a look at the figure, which shows a ball tied to a string. The ball is whipping around with angular velocity of magnitude You can easily find the magnitude of the ball’s velocity, v, if you measure the angles in radians. A circle has the complete distance around a circle — its circumference — is where r is the circle’s radius. In general, therefore, you can connect an angle measured in radians with the distance you cover along the circle, s, like this: where r is the radius of the circle. Now, you can say that v = s/t, where v is magnitude of the velocity, s is the distance, and t is time. You can substitute for s to get In other words, Now you can find the magnitude of the velocity. For example, say that the wheels of a motorcycle are turning with an angular velocity of If you can find the tangential velocity of any point on the outside edges of the wheels, you can find the motorcycle’s speed. Now assume that the radius of one of your motorcycle’s wheels is 40 centimeters. You know that so just plug in the numbers: Converting 27 meters/second to miles/hour gives you about 60 mph.