In one sentence, describe what the following article is about: A light year is a measure of distance equal to how far light travels in one Earth year. Because distances across the universe are so large, astronomers use light years. Without light years, discussing the distance between two stars would require the use of large, unruly numbers. Another measure of distance you may come across when learning astronomy is the parsec. It is equal to 3.26 light years. It is another way to simplify the numbers used to calculate and discuss astronomical distances. Using the common physics formula, distance equals rate times time or d = r x t, you can calculate how long a light year is: Light Year = (speed of light) x (one year). Since speed of light is represented by the variable "c", you can rewrite the equation as d = c x t, where d is the distance of a light year, c is the speed of light and t is time. If you want to know the distance of a light year in kilometers, you will need to find the speed of light in kilometers per second. If you want miles, you will need the speed of light in miles per second. You need to know the number of seconds in one Earth year for this calculation. Light in a vacuum travels at a velocity of 186,000 miles per second. This is the equivalent of 299,792 kilometers per second or 670,616,629 miles per hour. Here we will use the velocity in miles-per-second. For this calculation we will use the speed of light, c, equals 186,000 miles per second. This can be rewritten in scientific notation as 1.86 x 105 miles per second. To find the number of seconds in a year, you will do a series of multiplications by conversions units. To convert years to seconds you will multiply the number of days in a year times the number of hours in a day, times the number of minutes in an hour, times the number of seconds in a minute. 1 year x 365 days/year x 24 hours/day x 60 minutes/hour x 60 seconds/minute = 31,536,000 seconds. Again, we can rewrite this large number using scientific notation as 3.154 x 107. Now that you have defined the variables for speed of light and time, you can plug them into the equation d = c x t and solve for the distance of a light year. Replace c with 1.86 x 105 miles per second and time with 3.15 x 107 seconds. d = c x t d = (1.86 x 105) x (3.154 x 107 seconds) d = 5.8 x 1012 or 5.8 trillion miles. If you wanted to calculate in kilometers, simply replace the speed of light with the speed in kilometers per second: 3.00 x 105. The time in seconds remains the same because there is no conversion required. d = c x t d = (3.00 x 105) x (3.154 x 107 seconds) d = 9.46 x 1012 or 9.5 trillion kilometers.
Summary: Define the light year. Write the formula for distance. Define the speed of light. Calculate the number of seconds in a year. Plug variables into equation and solve. Calculate the distance in kilometers.

In one sentence, describe what the following article is about: Wait until you feel ready to eat something. Right after the surgery you probably won't feel like eating. You don't want to put something in your mouth until you're absolutely ready so that your wounds have a little time to heal first. The anesthetic can suppress your appetite for a few hours. Even if your surgery is in the morning you may not end up eating all day. Don't be afraid of not eating for a day your body will tell you when it's ready to eat. Make sure you are staying hydrated and drinking an adequate amount of water. By the second day, you should have a bit of your normal hunger returned. But even if you aren't hungry, you should at least eat a little something from the second day on. Avoid brushing your teeth on the day of the surgery, but resume brushing from the second day on. Brush gently, especially around the surgical areas. And be careful not to scrape the wound. Brushing will help keep your mouth clean and assist with the healing process, even if it is a bit uncomfortable. Beginning the second day after surgery, you should gently rinse your mouth every four to six hours with a warm salt water mixture. This can be made by adding teaspoon of salt with cup of warm water. Swish it around in your mouth for at least 30 seconds and then spit it out. Make sure you rinse your mouth immediately after you eat something. You should continue with regular salt water rinses for one week after the surgery.
Summary: Don't rush your hunger. Brush your teeth. Rinse your mouth.

In one sentence, describe what the following article is about: Treat your Social Security card with as much respect and care as your birth certificate, tax records, and other confidential documents. Unless you're required to show it, keep the original card locked in a safe at home. If a professional entity requests the card, see if you can bring a photocopy instead to avoid losing the original. To defend against fires, floods, and other disasters, keep your card in a weatherproofed container. In most cases, entities requesting your SSN will not need the actual card, just the number. The safest way to relay the number is by committing it to memory, that way nobody can steal the original paperwork from your wallet, purse, or briefcase. To help you memorize your SSN, try reading it aloud or writing it down multiple times. Test yourself daily until you can recall it without a visual aid. When getting rid of confidential documents, make sure to run them through a cross-cut or confetti shredder. This is especially important for documents that list your Social Security number, like financial statements. For extra security, try burning your documents in a fireplace or pit. Some public and private organizations require your Social Security number to function properly. Most, however, have no use for it. Before giving your number to an organization, ask what they intend to use it for. When in doubt, only give your SSN to entities like your employer, the IRS, and banks. If an institution has a spot on their forms for your SSN, check to see if it's required or optional. Many places, like doctor's offices, collect the info but don't actually need it. At some point, everyone gets targeted by e-mails or phone calls requesting private information. Unless you explicitly requested an e-mail or phone call from the person in question, do not give them your SSN or other identifying information. Never click on links or download attachments from phishing e-mails, as they often contain malicious software that will harm your computer or steal your information. Look for signs that an e-mail is a scam, like a suspicious e-mail address or bad grammar. Look for signs that a phone call is a scam, like suspicious reward offers or a reluctance to describe the reason for calling.
Summary:
Lock your Social Security card in a safe. Memorize your SSN so you don't have to reference your card. Shred used documents that list your SSN. Ask why an organization needs your SSN before giving it to them. Look out for phishing e-mails and scam callers.