Foundations of the Big Bang Theory

The Big Bang Model rests on two theoretical pillars:

General Relativity

Albert Einstein at the chalkboard The first key idea dates to 1916 when Einstein developed his General Theory of Relativity which he proposed as a new theory of gravity. His theory generalizes Isaac Newton's original theory of gravity, c. 1680, in that it is supposed to be valid for bodies in motion as well as bodies at rest. Newton's gravity is only valid for bodies at rest or moving very slowly compared to the speed of light (usually not too restrictive an assumption!). A key concept of General Relativity is that gravity is no longer described by a gravitational "field" but rather it is supposed to be a distortion of space and time itself. Physicist John Wheeler put it well when he said "Matter tells space how to curve, and space tells matter how to move." Originally, the theory was able to account for peculiarities in the orbit of Mercury and the bending of light by the Sun, both unexplained in Isaac Newton's theory of gravity. In recent years, the theory has passed a series of rigorous tests.

The Cosmological Principle

Survey of a 30 deg. swath of the sky, showing about 1 million galaxies out to a distance of almost 2 billion light years. After the introduction of General Relativity a number of scientists, including Einstein, tried to apply the new gravitational dynamics to the universe as a whole. At the time this required an assumption about how the matter in the universe was distributed. The simplest assumption to make is that if you viewed the contents of the universe with sufficiently poor vision, it would appear roughly the same everywhere and in every direction. That is, the matter in the universe is homogeneous and isotropic when averaged over very large scales. This is called the Cosmological Principle. This assumption is being tested continuously as we actually observe the distribution of galaxies on ever larger scales. The accompanying picture shows how uniform the distribution of measured galaxies is over a 30° swath of the sky. In addition the cosmic microwave background radiation, the remnant heat from the Big Bang, has a temperature which is highly uniform over the entire sky. This fact strongly supports the notion that the gas which emitted this radiation long ago was very uniformly distributed.

These two ideas form the entire theoretical basis for Big Bang cosmology and lead to very specific predictions for observable properties of the universe.

Image of the Day : Larsen Ice Shelf Meets Open Water

The edge of the Larsen Ice Shelf meets open water and sea ice, viewed from above during the 20th Ice Bridge flight in Antarctica. The flight, which lifted off on Nov. 16, 2009, surveyed the Antarctic Peninsula including the Larsen Ice Shelf and nearby glaciers. Credit: Michael Studinger, Lamont-Doherty Earth Observatory

Expedition 22 Crew Lands on Thursday

The Soyuz TMA-16 spacecraft is seen as it lands with Expedition 22 Commander Jeff Williams and Flight Engineer Maxim Suraev near the town of Arkalyk, Kazakhstan on Thursday, March 18, 2010. NASA Astronaut Jeff Williams and Russian Cosmonaut Maxim Suraev are returning from six months onboard the International Space Station where they served as members of the Expedition 21 and 22 crews.

Expedition 22 Crew Leaves Station, Set to Land This Morning after 167 days

Expedition 22 Commander Jeff Williams and Flight Engineer Maxim Suraev have completed their mission aboard the International Space Station after 167 days. They entered the Soyuz TMA-16 spacecraft, then undocked from the Poisk Mini-Research Module at 4:03 a.m. EDT. After entering the Earth’s atmosphere they will parachute to a landing in Kazakhstan at 7:23 a.m.

Staying behind are Flight Engineers Soichi Noguchi and T.J. Creamer and new Expedition 23 Commander Oleg Kotov. The trio, who will stay until June, joined Williams and Suraev after arriving in their Soyuz TMA-17 in December 2009.

Joining Expedition 23 and expanding the station crew to six will be Alexander Skvortsov, Tracy Caldwell Dyson and Mikhail Kornienko. They will arrive in the Soyuz TMA-18 on April 4.

Cassini Data confirm Ice and Rock Mixture inside Titan

By precisely tracking NASA's Cassini spacecraft on its low swoops over Saturn's moon Titan, scientists have determined the distribution of materials in the moon's interior. The subtle gravitational tugs they measured suggest the interior has been too cold and sluggish to split completely into separate layers of ice and rock.

The finding, to be published in the March 12 issue of the journal Science, shows how Titan evolved in a different fashion from inner planets such as Earth, or icy moons such as Jupiter's Ganymede, whose interiors have split into distinctive layers.

"These results are fundamental to understanding the history of moons of the outer solar system," said Cassini Project Scientist Bob Pappalardo, commenting on his colleagues' research. Pappalardo is with NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We can now better understand Titan's place among the range of icy satellites in our solar system."

Scientists have known that Titan, Saturn's largest moon, is about half ice and half rock, but they needed the gravity data to figure out how the materials were distributed. It turns out Titan's interior is a sorbet of ice studded with rocks that probably never heated up beyond a relatively lukewarm temperature. Only in the outermost 500 kilometers (300 miles) is Titan's ice devoid of any rock, while ice and rock are mixed to various extents at greater depth.

"To avoid separating the ice and the rock, you must avoid heating the ice too much," said David J. Stevenson, one of the paper's co-authors and a professor of planetary science at the California Institute of Technology in Pasadena. "This means that Titan was built rather slowly for a moon, in perhaps around a million years or so, back soon after the formation of the solar system."

This incomplete separation of ice and rock makes Titan less like Jupiter's moon Ganymede, where ice and rock have fully separated, and perhaps more like another Jovian moon, Callisto, which is believed to have a mixed ice and rock interior. Though the moons are all about the same size, they clearly have diverse histories.

The Cassini measurements help construct a gravity map, which may help explain why Titan has a stunted topography, since interior ice must be warm enough to flow slowly in response to the weight of heavy geologic structures, such as mountains.

Creating the gravity map required tracking minute changes in Cassini's speed along a line of sight from Earth to the spacecraft as it flew four close flybys of Titan between February 2006 and July 2008. The spacecraft took paths between about 1,300 to 1,900 kilometers (800 to 1,200 miles) above Titan.

"The ripples of Titan's gravity gently push and pull Cassini along its orbit as it passes by the moon and all these changes were accurately recorded by the ground antennas of the Deep Space Network within 5 thousandths of a millimeter per second [0.2 thousandths of an inch per second] even as the spacecraft was over a billion kilometers [more than 600 million miles] away," said Luciano Iess, a Cassini radio science team member at Sapienza University of Rome in Italy, and the paper's lead author. "It was a tricky experiment."

The results don't speak to whether Titan has an ocean beneath the surface, but scientists say this hypothesis is very plausible and they intend to keep investigating. Detecting tides induced by Saturn, a goal of the radio science team, would provide the clearest evidence for such a hidden water layer.

A Cassini interdisciplinary investigator, Jonathan Lunine, said of his colleagues' findings, "Additional flybys may tell us whether the crust is thick or thin today." Lunine is with the University of Rome, Tor Vergata, Italy, and the University of Arizona, Tucson. "With that information we may have a better understanding of how methane, the ephemeral working fluid of Titan's rivers, lakes and clouds, has been resupplied over geologic time. Like the history of water on Earth, this is fundamental to a deep picture of the nature of Titan through time."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the project for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL. Cassini's radio science subsystem has been jointly developed by NASA and the Italian Space Agency (ASI).

Picture of the International Space Station

On March 13, 2008, the International Space Station passed across the field-of-view of Germany's remote sensing satellite, TerraSAR-X, at a distance of 195 kilometers, or 122 miles, and at a relative speed of 34,540 kilometers per hour, or more than 22,000 mph.

In contrast to optical cameras, radar does not 'see' surfaces. Instead, it is much more aware of the edges and corners which bounce back the microwave signal it transmits. Smooth surfaces such as those on the station's solar generators or the radiator panels used to dissipate excess heat, unless directly facing the radar antenna, tend to deflect rather than reflect the radar beam, causing these features to appear on the radar image as dark areas. The radar image of the station therefore looks like a dense collection of bright spots from which the outlines of the space station can be clearly identified. The central element on the station, to which all the modules are docked, has a grid structure that presents a multiplicity of reflecting surfaces to the radar beam, making it readily identifiable. This image has a resolution of about one meter (about 39 inches). In other words, objects can be depicted as discrete units--that is, shown separately--provided that they are at least one meter apart. If they are closer together than that, they tend to merge into a single block on a radar image.

Since this image was taken, the station has expanded and is more than 90 percent complete, including a full complement of solar arrays.

A Mosaic image of Cassiopeia

This mosaic of images from the Wide-Field Infrared Survey Explore, or WISE, in the constellation of Cassiopeia contains a large star-forming nebula within the Milky Way Galaxy, called IC 1805 or the Heart Nebula, a portion of which is seen at the right of the image. IC 1805 is more than 6,000 light-years from Earth. Also visible in this image are two nearby galaxies, Maffei 1 and Maffei 2. In visible light these galaxies are hidden by dust in IC 1805 and were unknown until 1968 when Paolo Maffei found them using infrared observations. Both galaxies contain billions of stars and are located some 10 million light-years away. Maffei 1 is a lenticular galaxy, which has a disk-like structure and a central bulge but no spiral structure or appreciable dust content. Maffei 2 is a spiral galaxy that also has a disk shape, but with a bar-like central bulge and two prominent dusty spiral arms.

Huygens on Titan (Saturn's enigmatic moon)

In 2005 the robotic Huygens probe landed on Titan, Saturn's enigmatic moon, and sent back the first ever images from beneath Titan's thick cloud layers. This artist's impression is based on those images. In the foreground, sits the car-sized lander that sent back images for more than 90 minutes before running out of battery power. The parachute that slowed Huygen's re-entry is seen in the background, still attached to the lander. Smooth stones, possibly containing water-ice, are strewn about the landscape. Analyses of Huygen's images and data show that Titan's surface today has intriguing similarities to the surface of the early Earth.

Understanding Sun's Atmosphere

The 2006 launch of the multinational Hinode satellite changed the picture of the sun for astrophysicists. For two astrophysicists in particular, the resulting imagery offered a voyage of discovery and the thrill of unraveling a long-held solar mystery.

The Earth's atmosphere can obscure the view of unaided ground-based telescopes, but, unimpeded by this problem, the high-resolution telescope flying on Hinode captures images of the sun in unparalleled detail.

It is in these new images that Scott McIntosh, Bart De Pontieu, Viggo Hansteen and Karel Schrijver found the first tantalizing clues that led them to a new way of considering why the solar corona is millions of degrees hotter than the sun's visible surface.

"Among the regions observed by Hinode is the solar chromosphere, the area separating the sun's surface--the photosphere--from its extended atmosphere, the corona," explained McIntosh, an astrophysicist working at the National Science Foundation- (NSF) funded National Center for Atmospheric Research's (NCAR) High Altitude Observatory.

Intuitively, the sun's atmosphere should get cooler with distance from the sun's surface, but reality doesn't match supposition. Using Hinode imagery, De Pontieu, a scientist at Lockheed Martin's Solar and Astrophysics Laboratory, McIntosh, and colleagues discovered in the Hinode imagery a new type of spicule.

"Classic" Type-I spicules are jets of dense plasma that shoot up from the chromosphere and, more often than not, return along the same path, said McIntosh. The "Type-II" spicules, which McIntosh and De Pontieu have recently dubbed "radices," are hotter, shorter lived and faster moving than their Type-I brethren.

"In the Hinode imagery," added McIntosh, "the radices appeared to shoot upward and disappear, often moving at speeds in excess of 100 kilometers per second. These jets likely contain plasma that ranges in temperature from 10,000 to several million degrees Celsius, and have a life span of no more than 10 to 100 seconds. While astrophysicists, including NCAR founder, Walter Orr Roberts, have long studied Type-I spicules, it is known that the material in them does not reach typical coronal temperatures--about 1 million degrees--eliminating a connection to coronal heating."

But it was only during a 2008 scientific meeting about Hinode--when a colleague discussed seeing a subtle 100-plus kilometer per second upward velocity component in a coronal region with a strong magnetic field--that De Pontieu and McIntosh caught each other's eye, thinking exactly the same thing: Were they possibly seeing evidence of radices reaching coronal temperatures?

Together, they searched for the "ideal" Hinode data set, one in which they were able to trace the columns of plasma ejected from the chromosphere into the corona. Upon identifying the data, each approached the task from a different perspective.

In comparing their results, they realized that the locations of the radices and the upward velocity signatures seen in the corona were the same. They also found that the velocities of the chromospheric jets and those of the coronal events matched extremely well.

"This evidence indicates that radices may play an important role in supplying and replenishing the hot mass of the solar corona and wind, explaining the temperature differential between corona and photosphere," McIntosh said. "Our calculations indicate that radices can fill the corona with hot plasma even if only 1 to 5 percent of the radices reach coronal temperatures."

Not only did this work provide McIntosh, De Pontieu, Schrijver (also of Lockheed Martin's Solar and Astrophysics Laboratory), and Hansteen (of the University of Oslo) the thrill of discovery, and the excitement of tracing their idea to a breath-taking conclusion, their effort has direct implications for climate research on Earth.

"Understanding solar processes advances our knowledge of Earth-sun interactions, providing insights on how UV radiation generated by solar storms affects the Earth's upper atmosphere, stratospheric ozone and--potentially--global climate dynamics over both short and longer time scales," McIntosh explained.

One mission that will help advance understanding of radices is NASA's Interface Region Imaging Spectrograph (IRIS), which will allow scientists to investigate formation of radices at high resolution. A Hinode follow-up mission is also in the works, and the launch of the Solar Dynamics Observatory in February 2010 will provide an additional series of high-resolution coronal images, available every 10 seconds.

NASA Technology to develop 'Green' Building's Efficiency

NASA today announced that it is collaborating with Integrated Building Solutions (IBS), Inc. to develop a next-generation intelligent, automated, and integrated environmental monitoring and management capability for office buildings and research environments.

The building control systems being developed jointly by NASA’s Ames Research Center, Moffett Field, Calif., and IBS signal a new era in the evolution of 'green,' sustainable buildings. They will enhance energy efficiency, reduce energy consumption, and maximize worker performance and comfort. 'Sustainability Base,' the environmentally friendly building that is being constructed at NASA’s Ames, is expected to be completed in late 2010 and will be a testbed for these new 'smart' systems.

"We are thrilled to be applying NASA aerospace technologies to our everyday living and working environments," said Steven Zornetzer, associate center director at NASA Ames. "This collaboration represents the first of many research partnerships for Sustainability Base that will bring NASA technologies down to Earth and connect them with capabilities from the private sector to leverage taxpayer investment and improve the quality of life for everyone."

Ames engineers are working with their IBS counterparts to repurpose NASA-developed software systems for health and resource planning into a building environment. The NASA technologies were originally developed for everything from aircraft control systems to mission planning for the Mars rovers, Opportunity and Spirit. A suite of these NASA software tools is now being integrated with IBS's Intelligent Building Interface System. The latter provides centralized management, monitoring, automation, and analysis of building systems in an intuitive, browser-based console. The resulting building-control system will interpret data from sensors and merge this information with occupancy calendars and local weather predictions.

Multiple sensors deployed throughout the building will monitor its power demand, air temperature, moisture, air flow, light levels, and water consumption. The system will “learn” about the facility’s dynamics, including the human component, and will continuously evolve to produce better operational outcomes based on identifying connections, consequences, and trends.

Dangerous metals deposit on Contaminated Soil

You may not think about soil except for when you need to clean it off your clothes, sweep it off the floor, or wash it off your kids. But some soil’s trouble can be much more than just cosmetic.

Soil contaminated with heavy metals such as lead and arsenic can pose a public health risk, especially for children who might play, and inadvertently swallow it. If ingested in enough quantities, heavy metals such as lead and arsenic can lead to a variety of serious health effects.

But how do environmental managers and public health officials know when soil exposure is a health risk? Researchers at the U.S. Environmental Protection Agency are working to answer just that question.

Under current protocols, soils are tested for lead and arsenic content where contamination is suspected. That’s the easy part. While it is a relatively straight forward process to identify elevated levels of heavy metals, determining when levels pose a health risk is much more of a challenge.

EPA researchers are conducting laboratory and field research to estimate how much lead and arsenic humans are exposed to in soil and when these heavy metals are likely to be absorbed into the body after being ingested, a term scientists call “bioavailability.” Some soils can bind up contaminants, preventing them from dissolving or being absorbed, which reduces the exposure risk. Others contaminants are more readily available for absorption.

The research will help environmental managers identify those contaminated sites that pose the highest risk to public health so they can be targeted for clean up.

Atlantic salmon face the abrupt changing climate

Atlantic salmon are among the most imperiled species in the Northeast Region. While at one time hundreds of thousands of salmon made their epic migration from the oceans of Greenland to their natal rivers in Maine, now only remnant populations remain. Recovering this iconic species is a priority for the U.S. Fish and Wildlife Service.

The odds have been against the salmon. The construction of dams, overfishing, habitat loss, and water pollution have collectively caused their decline.

Biologists at the Craig Brook National Fish Hatchery, part of the Atlantic salmon recovery operation that Santavy oversees, are experimenting with ways to delay the spawning cycle that they’re seeing in the Penobscot River salmon. By artificially manipulating water temperatures and length of daylight they are attempting to bring the captive fish more in sync with seasonal river conditions. Hatchery-raised fish comprise 95-percent of the salmon population in the Penobscot.
Adult Atlantic salmon. Credit: Bob Michelson Adult Atlantic salmon. Credit: Bob Michelson

An additional concern in recovering the Atlantic salmon is that the rivers in the Downeast region of Maine are experiencing extreme fluctuations in water flows – heavier rainfalls happening less frequently, combined with earlier snow and melting river ice – that have been predicted in certain climate change models. During these weather events, the high-flowing water doesn’t have a chance to absorb into the river beds, which contain minerals that serve as a buffer to changing water chemistry. This lack of buffering can increase the acidity of the water. After the rainwater flushes out the system, river flows now tend to decrease rapidly unlike the gradual decline seen in the past.

According to Santavy, these shifting river conditions occur at a time in the spring when the juvenile salmon are very vulnerable. In the wild, the fish have just a one-month window of time to transform from parr into smolt before migrating to the sea.

Biological studies conducted by the U.S. Geological Survey (U.S.G.S.) show that it can take weeks for a salmon in this life stage to recover after being exposed to acidic conditions. Acidic pH levels in the water lower than 6 (7 is neutral) can cause naturally occurring aluminum levels in the water to become reactive to the fish. This can prevent calcium from binding to the fishes’ gills – a necessary process for their transition to the marine environment. If this is the case, Santavy says it could help explain the reason smolt are being lost in the estuaries, and would be devastating to recovery efforts.

The Right dieting plans

Dieting do’s

Eat breakfast every day! Skipping it won't help you lose weight. It'll just have you reaching for snacks later.

Drink water, juice, milk or smoothies instead of fizzy drinks. The normal kind are packed with sugar, and the diet kind have no nutritional benefits.

Drink 8 glasses of water a day - it's calorie free! The symptoms of dehydration can also be mistaken for hunger pangs.

Eat five portions of fruit and vegetables a day. Even a glass of fruit juice counts!

The odd treat's fine, just don't base your diet solely around chips!

Dieting don'ts

Don't diet! Instead, aim to get active and eat sensibly. This means eating enough starchy foods (bread, pasta), lots of fruit and veg and moderate amounts of meat, fish and dairy.

Avoid any eating plan that restricts your intake of dairy products. Growing bones need calcium!

Your body needs certain types of fats to look and feel healthy. But limit the saturated kind (found in foods like butter, hard cheese, fatty cuts of meat, pastry, biscuits and cakes) to an occasional treat.

Crash diets don't work in the long term and the weight will pile back on. The best way to achieve lasting results is to adapt your lifestyle gradually.

What is healthy eating all about?

Healthy eating is all about eating a range of foods which gives us a healthy and wholesome balance. It's really important to eat different food types so we get all the nutrients such as vitamins and minerals that we need. Fibre and whole grain foods are excellent too as they help us to digest food really well.

Healthy eating is about enjoying all the wonderful foods out there as well as understanding what we are eating and why? Healthy eating is not designed to be restrictive or un-exciting – there is tremendous variety in what we can prepare and cook.

Removing salt from our cooking and replacing with herbs and spices is a great way of adding extra flavour. Use small amounts of unsaturated fats (liquid at room temperature) in cooking or maybe a spray dispenser or just water for cooking if you want to keep it mega-healthy. We need a good balance of protein and carbohydrate but the least amount of sugar and fats.

Keeping hydrated as well is really key, sensible water intake keeps our bodies working just as they should be helping for example our joints, digestion, brains and skin.

If you would like to find out even more about healthy eating please have a look at the websites featured below, there is lots of information to guide you in eating healthily. And for the children there are some fun sites too!

Motivating kids to enjoy physical activity

Being a role model
Kids will usually follow what you do more than what you say. If they see you enjoying physical activity and having fun, it will motivate them to be more active. It also means they can’t use the classic excuse (either stated or just in their thoughts) of ‘Well, you don’t do anything yourself’.
Playing together is important too. Help your child practise basic sporting and movement skills such as throwing and catching or kicking a ball.

Providing the right conditions
With a bit of planning you can set up the conditions for getting active:
• Have a range of active ideas for when your child says ‘I’m bored’ – hide and seek, skipping, throwing and catching, etc. See activity ideas for more suggestions.
• Buy gifts that encourage physical activity, such as balls, bats or skipping ropes.
• Encourage active play with your child’s friends – bike-riding, kicking a ball.
• Provide some soft balls and equipment for active indoor games.
• Create fun and exciting opportunities for activity, e.g. after school or on weekends. It’s easy to think that your child is sufficiently active at school, but they need to be encouraged to be active at home as well.
• Encourage your child to be more active outside during daylight hours, to balance being less active when it’s not possible for them to be outside.
• Try and plan activities during school holidays, such as trying a new sport or going to a holiday camp.

If your child is inactive, gradually build up the amount of activity they do. Start with a moderate amount and set goals so you can chart progress over time.
Keeping it going

Long-term motivation is not so easy to achieve. Once your child is up and active, take some sensible steps to keep it going:
• Build up the amount of activity over time and chart their progress.
• Let your child try a variety of activities so they find ones they enjoy and want to continue with.
• Keep it interesting. Encourage them to try something different if they lose interest in one activity. Variety also ensures they develop a range of skills.
• Be flexible with the weather and different seasons. Have a list of activities for rainy days.
• Support your child’s choice of activity, whether it’s active play or organised sport.
• Recognise their achievements.
• Offer active rewards if your child attends an activity regularly and achieves their goals, e.g. take them to the pool or the beach.
• Attend practice sessions or matches whenever possible.

Go with Healthy Snacks

If you are trying to lose weight or maintain a healthy weight, snacking can be part of your diet. Use moderation and balance when selecting foods to snack on. Select foods that satisfy your hunger, supply your body with energy and provide important nutrients. Try to keep your snack at 100 calories or less. Choose your snacks from the following food groups:

• Fruits and vegetables give you a feeling of fullness with no fat and small amount of calories. These are low energy density foods so you can eat more for your 100 calories. They give you vitamins, minerals, fiber and water.
• Whole grains are rich in fiber and complex carbohydrates to give you energy that will last. Look for low-fat whole-grain crackers, whole grain pretzels and crisp breads.
• Nuts and seeds give you protein and make you feel fuller longer. They are high in healthy fats so be careful how much you eat.
• Low-fat dairy products like cheese, yogurt are good sources of calcium and protein and other vitamins and minerals. Look for the low calorie or “Light” varieties of yogurt.

Food safety guidelines in the kitchen

Clean. Wash hands and surfaces often

Wash your hands with warm soapy water for 20 seconds (count to 30) before you handle food or food utensils. Wash your hands after handling or preparing food, especially after handling raw meat, poultry, fish, shellfish, or eggs. Right after you prepare these raw foods, clean the utensils and surfaces you used with hot soapy water. Replace cutting boards once they have become worn or develop hard-to-clean grooves. Wash raw fruit and vegetables under running water before eating. Use a vegetable brush to remove surface dirt if necessary. Always wash your hands after using the bathroom, changing diapers, or playing with pets. When eating out, if the tables, dinnerware, and restrooms look dirty, the kitchen may be, too—so you may want to eat somewhere else.

Separate. Separate raw, cooked, and ready-to-eat foods while shopping, preparing, or storing
Keep raw meat, poultry, eggs, fish, and shellfish away from other foods, surfaces, utensils, or serving plates. This prevents cross-contamination from one food to another. Store raw meat, poultry, fish, and shellfish in containers in the refrigerator so that the juices don't drip onto other foods.

Cook. Cook foods to a safe temperature
Uncooked and undercooked animal foods are potentially unsafe. Proper cooking makes most uncooked foods safe. The best way to tell if meat, poultry, or egg dishes are cooked to a safe temperature is to use a food thermometer. Several kinds of inexpensive food thermometers are available in many stores.

Reheat sauces, soups, marinades, and gravies to a boil. Reheat leftovers thoroughly to at least 165° F. If using a microwave oven, cover the container and turn or stir the food to make sure it is heated evenly throughout. Cook eggs until whites and yolks are firm. Don't eat raw or partially cooked eggs, or foods containing raw eggs, raw (unpasteurized) milk, or cheeses made with raw milk. Choose pasteurized juices. The risk of contamination is high from undercooked hamburger, and from raw fish (including sushi), clams, and oysters. Cook fish and shellfish until it is opaque; fish should flake easily with a fork. When eating out, order foods thoroughly cooked and make sure they are served piping hot.

Chill. Refrigerate perishable foods promptly
When shopping, buy perishable foods last, and take them straight home. At home, refrigerate or freeze meat, poultry, eggs, fish, shellfish, ready-to-eat foods, and leftovers promptly. Refrigerate within 2 hours of purchasing or preparation—and within 1 hour if the air temperature is above 90º F. Refrigerate at or below 40º F, or freeze at or below 0º F. Use refrigerated leftovers within 3 to 4 days. Freeze fresh meat, poultry, fish, and shellfish that cannot be used in a few days. Thaw frozen meat, poultry, fish, and shellfish in the refrigerator, microwave, or cold water changed every 30 minutes. (This keeps the surface chilled.) Cook foods immediately after thawing. Never thaw meat, poultry, fish, or shellfish at room temperature. When eating out, make sure that any foods you order that should be refrigerated are served chilled.

Follow the label
Read the label and follow safety instructions on the package such as "KEEP REFRIGERATED" and the "SAFE HANDLING INSTRUCTIONS."

Serve safely
Keep hot foods hot (140º F or above) and cold foods cold (40º F or below). Harmful bacteria can grow rapidly in the "danger zone" between these temperatures. Whether raw or cooked, never leave meat, poultry, eggs, fish, or shellfish out at room temperature for more than 2 hours (1 hour in hot weather 90º F or above). Be sure to chill leftovers as soon as you are finished eating. These guidelines also apply to carry-out meals, restaurant leftovers, and home-packed meals-to-go.

When in doubt, throw it out
If you aren't sure that food has been prepared, served, or stored safely, throw it out. You may not be able to make food safe if it has been handled in an unsafe manner. For example, a food that has been left at room temperature too long may contain a toxin produced by bacteria—one that can't be destroyed by cooking. So if meat, poultry, fish, shellfish, or eggs have been left out for more than 2 hours, or if the food has been kept in the refrigerator too long, don't taste it. Just throw it out. Even if it looks and smells fine, it may not be safe to eat. If you have doubt when you're shopping or eating out, choose something else.

Food Safety Preparation Tips

Begin with clean hands. Wash your hands for 20 seconds with warm water and soap before and after preparing fresh produce.

Cut away any damaged or bruised areas on fresh fruits and vegetables. Produce that looks rotten should be discarded.

All produce should be thoroughly washed before eating. Wash fruits and vegetables under running water just before eating, cutting or cooking.

Many precut, bagged produce items like lettuce are pre-washed. If the package indicates that the contents have been pre-washed, you can use the produce without further washing.

Even if you plan to peel the produce before eating, it is still important to wash it first.

Washing fruits and vegetables with soap or detergent or using commercial produce washes is not recommended.

Scrub firm produce, such as melons and cucumbers, with a clean produce brush.

Drying produce with a clean cloth towel or paper towel may further reduce bacteria that may be present.

Follow 10 Tips for healthy eating and physical activity

• Start your day with breakfast.
Breakfast fills your "empty tank" to get you going after a long night without food. And it can help you do better in school. Easy to prepare breakfasts include cold cereal with fruit and low-fat milk, whole-wheat toast with peanut butter, yogurt with fruit, whole-grain waffles or even last night's pizza!

• Get Moving!
It's easy to fit physical activities into your daily routine. Walk, bike or jog to see friends. Take a 10-minute activity break every hour while you read, do homework or watch TV. Climb stairs instead of taking an escalator or elevator. Try to do these things for a total of 30 minutes every day.

• Snack smart.
Snacks are a great way to refuel. Choose snacks from different food groups - a glass of low-fat milk and a few graham crackers, an apple or celery sticks with peanut butter and raisins, or some dry cereal. If you eat smart at other meals, cookies, chips and candy are OK for occasional snacking.

• Work up a sweat.
Vigorous work-outs - when you're breathing hard and sweating - help your heart pump better, give you more energy and help you look and feel best. Start with a warm-up that stretches your muscles. Include 20 minutes of aerobic activity, such as running, jogging, or dancing. Follow-up with activities that help make you stronger such as push-ups or lifting weights. Then cool-down with more stretching and deep breathing.

• Balance your food choices - don't eat too much of any one thing.
You don't have to give up foods like hamburgers, french fries and ice cream to eat healthy. You just have to be smart about how often and how much of them you eat. Your body needs nutrients like protein, carbohydrates, fat and many different vitamins and minerals such as vitamins C and A, iron and calcium from a variety of foods. Balancing food choices from the Food Guide Pyramid and checking out the Nutrition Facts Panel on food labels will help you get all these nutrients.

• Get fit with friends or family.
Being active is much more fun with friends or family. Encourage others to join you and plan one special physical activity event, like a bike ride or hiking, with a group each week.

• Eat more grains, fruits and vegetables.
These foods give you carbohydrates for energy, plus vitamins, minerals and fiber. Besides, they taste good! Try breads such as whole-wheat, bagels and pita. Spaghetti and oatmeal are also in the grain group.
Bananas, strawberries and melons are some great tasting fruits. Try vegetables raw, on a sandwich or salad.

• Join in physical activities at school.
Whether you take a physical education class or do other physical activities at school, such as intramural sports, structures activities are a sure way to feel good, look good and stay physically fit.
• Foods aren't good or bad.
A healthy eating style is like a puzzle with many parts. Each part -- or food -- is different. Some foods may have more fat, sugar or salt while others may have more vitamins or fiber. There is a place for all these foods. What makes a diet good or bad is how foods fit together. Balancing your choices is important. Fit in a higher-fat food, like pepperoni pizza, at dinner by choosing lower-fat foods at other meals. And don't forget about moderation. If two pieces of pizza fill you up, you don't need a third.

• Make healthy eating and physical activities fun!
Take advantage of physical activities you and your friends enjoy doing together and eat the foods you like. Be adventurous - try new sports, games and other activities as well as new foods. You'll grow stronger, play longer, and look and feel better! Set realistic goals - don't try changing too much at once.

Choosing nutritious drinks

A short walk down the supermarket aisle shows how popular sugary drinks are, and there's no point denying that many children like them. But there is a point in limiting their intake and encouraging and offering healthier alternatives.

Encouraging healthy drinks – water and milk

Drinking water is the best way to quench thirst without providing additional sugar and kilojoules. Children should be encouraged to drink plenty of water each day. To make this easier, keep chilled water in the fridge and provide a jug of water with a slice of lemon or lime in it with dinner.

Reduced-fat milk (except for children under age 2) is a good source of protein as well as nutrients such as calcium and vitamin B12, important for strong teeth and bones. Reduced-fat milk contains the same level of nutrients as whole milk, but less saturated fat. Plain reduced fat milk is preferable, but flavored reduced fat milks are also acceptable. Milk drinks with fruit added, such as smoothies, are a good healthy option.
Reducing sugary drinks

Cordial, fruit juices, flavored mineral waters, sports drinks and soft drinks are usually high in some form of sugar. They contain few nutrients and may lead to tooth decay, excess energy (kilojoules) intake and weight gain. Even fruit juice, which has some nutritional value, still contains sugar and should be limited to small amounts.

Tips for parents

• Only buy soft drinks and other sugary drinks occasionally
• Dilute cordial drinks more than usual
• Use small glasses for sugary drinks
• Carry a bottle of water with you at all times for when children become thirsty
• Offer fruit, not fruit juice.