Like a book and a cover, you can't always judge a tree by how it looks. Fungus can rot a living tree from the inside, leaving behind a healthy-looking but hollow trunk. Typically the rot is only seen when the tree is cut down. When a tree decays, it releases carbon dioxide back into the atmosphere, contributing to climate change. And the tropics are home to 96 percent of the world's tree diversity, according to researchers, and those trees store a quarter of the world's terrestrial carbon. To get a better read on the health of tropical forests, researchers are now using sound to measure decay in trees. The <a href="http://www.bioone.org/doi/pdf/10.3732/apps.1600060">research</a>, published in the journal Applications in Plant Sciences, was conducted collectively by a group of college professors, grad students and high school teachers and students, who used a new way to examine 1,800 live trees in the Republic of Panama. <a href="http://www.seeker.com/oldest-pine-tree-fossils-discovered-1771048389.html">RELATED: Oldest Pine Tree Fossils Discovered </a> The group used a method for sending a sound wave through a tree and measuring how fast the sound wave travels - a process called sonic tomography. Sounds waves travel faster through solid trees, a measure of their health. In a decayed tree or one with cavities, where molecules are packed less tightly, sound waves travel more slowly. The process provides insights into how rotting affects tree mortality overall in a forest, said Greg Gilbert, lead author of the article and chair of the Department of Environmental Studies at the University of California, Santa Cruz, in a <a href="https://www.eurekalert.org/pub_releases/2017-01/bsoa-mtw010517.php">statement</a>. "Most of the decay is hidden," Gilbert said. "The tomography now allows us to see how many apparently healthy trees are actually decayed inside." And while the method won't work with some trees - including palms or any species that uses internal tissue to store water - it has benefits outside of the forest. The team used sonic tomography to perform a checkup on trees in Panama City, in part to highlight which ones might snap off in storms or heavy winds and cause injury or damage to property. WATCH: How Astronauts Grow Plants in Space

Like a book and a cover, you can't always judge a tree by how it looks. Fungus can rot a living tree from the inside, leaving behind a healthy-looking but hollow trunk. Typically the rot is only seen when the tree is cut down.

When a tree decays, it releases carbon dioxide back into the atmosphere, contributing to climate change. And the tropics are home to 96 percent of the world's tree diversity, according to researchers, and those trees store a quarter of the world's terrestrial carbon.

To get a better read on the health of tropical forests, researchers are now using sound to measure decay in trees.

The <a href="http://www.bioone.org/doi/pdf/10.3732/apps.1600060">research</a>, published in the journal Applications in Plant Sciences, was conducted collectively by a group of college professors, grad students and high school teachers and students, who used a new way to examine 1,800 live trees in the Republic of Panama.

<a href="http://www.seeker.com/oldest-pine-tree-fossils-discovered-1771048389.html">RELATED: Oldest Pine Tree Fossils Discovered </a>

The group used a method for sending a sound wave through a tree and measuring how fast the sound wave travels - a process called sonic tomography. Sounds waves travel faster through solid trees, a measure of their health. In a decayed tree or one with cavities, where molecules are packed less tightly, sound waves travel more slowly.

The process provides insights into how rotting affects tree mortality overall in a forest, said Greg Gilbert, lead author of the article and chair of the Department of Environmental Studies at the University of California, Santa Cruz, in a <a href="https://www.eurekalert.org/pub_releases/2017-01/bsoa-mtw010517.php">statement</a>.

"Most of the decay is hidden," Gilbert said. "The tomography now allows us to see how many apparently healthy trees are actually decayed inside."

And while the method won't work with some trees - including palms or any species that uses internal tissue to store water - it has benefits outside of the forest. The team used sonic tomography to perform a checkup on trees in Panama City, in part to highlight which ones might snap off in storms or heavy winds and cause injury or damage to property.

WATCH: How Astronauts Grow Plants in Space

Like a book and a cover, you can't always judge a tree by how it looks. Fungus can rot a living tree from the inside, leaving behind a healthy-looking but hollow trunk. Typically the rot is only seen when the tree is cut down.When a tree decays, it releases carbon dioxide back into the atmosphere, contributing to climate change. And the tropics are home to 96 percent of the world's tree diversity, according to researchers, and those trees store a quarter of the world's terrestrial carbon.To get a better read on the health of tropical forests, researchers are now using sound to measure decay in trees.The <a href="http://www.bioone.org/doi/pdf/10.3732/apps.1600060">research</a>, published in the journal Applications in Plant Sciences, was conducted collectively by a group of college professors, grad students and high school teachers and students, who used a new way to examine 1,800 live trees in the Republic of Panama.<a href="http://www.seeker.com/oldest-pine-tree-fossils-discovered-1771048389.html">RELATED: Oldest Pine Tree Fossils Discovered </a>The group used a method for sending a sound wave through a tree and measuring how fast the sound wave travels - a process called sonic tomography. Sounds waves travel faster through solid trees, a measure of their health. In a decayed tree or one with cavities, where molecules are packed less tightly, sound waves travel more slowly.The process provides insights into how rotting affects tree mortality overall in a forest, said Greg Gilbert, lead author of the article and chair of the Department of Environmental Studies at the University of California, Santa Cruz, in a <a href="https://www.eurekalert.org/pub_releases/2017-01/bsoa-mtw010517.php">statement</a>."Most of the decay is hidden," Gilbert said. "The tomography now allows us to see how many apparently healthy trees are actually decayed inside."And while the method won't work with some trees - including palms or any species that uses internal tissue to store water - it has benefits outside of the forest. The team used sonic tomography to perform a checkup on trees in Panama City, in part to highlight which ones might snap off in storms or heavy winds and cause injury or damage to property.WATCH: How Astronauts Grow Plants in Space

<blockquote>Related on TestTube: <a href="http://testu.be/1Jw2IVv">Astronauts Dine on Lettuce Grown on the ISS </a><a href="http://testu.be/1Kg7Vld">What Do Astronauts Eat in Space now?</a></blockquote>Recently astronauts aboard the international space station chowed down on the first bite of space lettuce. NASA astronauts Kjell Lindgren and Scott Kelly, along with Japanese astronaut Kimiya Yui got their dose of leafy greens while orbiting 240 miles above the surface of the the Earth. This an important step to self sustaining systems: NASA scientists grew the lettuce in zero gravity over a period of 35 days. It's not the first batch though, other plants have been grown aboard the station but were returned to Earth to be examined. A study published in the journal BMC Plant Biology in 2010 discussed the small white flowers grown in space to see how they would grow without gravity. And just last year lettuce was grown that was sent back to Earth to be analyzed for safety concerns. Once they got the okay from mission control, another round of plants were grown -- this time, for express purpose of being consumed. The ISS uses something called the "Veggie" system, developed by Orbital Technologies Corp. in Madison, Wisconsin. The system contains lighting and nutrients for a space garden. This particular garden contains red, blue and green LEDS. The red and the blue mostly for plant growth and health, the green?  So the plants don't look weird under the red and blue lights and resemble lettuce grown here on earth. The plants get their nutrients from a "pillow". And pillows can come in various sizes depending on what kind of veggies are grown in them. Pillows only work once though, but that's by design. That way there's a reduced chance of microbial growth from the system and plants. For plants that might have more microbes, a sanitization method they can do in the space station will have to be developed. Like Scott Kelly and his buddies for instance used citric acid-based, food safe wipes to clean the lettuce before eating it.Growing plants without Earth's soil will be crucial to any long-term trip to a planet like Mars or any long-term space travel. With limited resources and not a lot of chances for restocking along the way, expeditions would have to be self-sustaining. Scott Kelly called this experiment a "big step in that direction." And just in case you were wondering, Kelly said the lettuce tasted "awesome."  Learn More: <a href="http://www.space.com/30209-astronauts-eat-space-lettuce.html" target="_blank">Astronauts Snack on Space-Grown Lettuce for First Time</a> (Space.com) For the first time, at least officially, the NASA astronauts on board the International Space Station have tasted the product, or more specifically, the produce, of their work.

How Astronauts Grow Plants In Space

Earth & Conservation

Sound Waves Give Tropical Trees a Checkup

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After a decade of research and development, China is ready to test its first-ever thorium-powered molten salt reactor.

The Next Generation of Nuclear Power Is Here

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Sound Waves Give Tropical Trees a Checkup

Measuring how fast sound travels through a tree trunk can reveal whether it's rotting from the inside.