What is a sonar pulse and how can it injure humans under water?

Christine Erbe, Curtin UniversityOver the weekend, the Australian government revealed that last Tuesday its navy divers had sustained “minor injuries”, likely due to sonar pulses from a Chinese navy vessel. The divers had been clearing fishing nets from the propellers of HMAS Toowoomba while in international waters off the coast of Japan. According to a statement from deputy prime minister Richard Marles, despite HMAS Toowoomba communicating with internationally recognised signals, the Chinese vessel approached the Australian ship and turned on its sonar, forcing the Australian divers to exit the water. The incident prompted a response from the Australian government, who labelled the incident “unsafe and unprofessional”. But what exactly is a sonar pulse, and what kinds of injuries can sonar cause to divers? What is sonar? Light doesn’t travel well under water – even in clear waters, you can see perhaps some tens of metres. Sound, however, travels very well and far under water. This is because water is much denser than air, and so can respond faster and better to acoustic pressure waves – sound waves. Because of these properties, ships use sonar to navigate through the ocean and to “see” under water. The word “sonar” stands for sound navigation and ranging. Sonar equipment sends out short acoustic (sound) pulses or pings,...

Read More........→November 22, 2023

Polar bears may struggle to produce milk for their cubs as climate change melts sea ice

During their time onshore, polar bear mothers may risk their survival by continuing to nurse when food is not available. (Shutterstock) Louise Archer, University of TorontoWhen sea ice melts, polar bears must move onto land for several months without access to food. This fasting period is challenging for all bears, but particularly for polar bear mothers who are nursing cubs. Our research, published in Marine Ecology Progress Series, found that polar bear lactation is negatively affected by increased time spent on land when sea ice melts. Impaired lactation has likely played a role in the recent decline of several polar bear populations. This research also indicates how polar bear families might be impacted in the future by continued sea-ice loss caused by climate warming. Challenges of rearing cubs While sea ice might appear as a vast and perhaps vacant ecosystem, the frozen Arctic waters provide an essential platform for polar bears to hunt energy-rich seals — the bread and butter of their diet. Sea ice is a dynamic environment that can vary through time and in different regions of the Arctic. Polar bears in Canada’s western Hudson Bay area experience seasonal sea ice, which melts in the warmer summer months, forcing the polar bears to move onto land until cooler winter temperatures cause the sea ice to refreeze.While...

Read More........→October 09, 2023

Is it normal to forget words while speaking? And when can it spell a problem?

Greig de Zubicaray, Queensland University of TechnologyWe’ve all experienced that moment mid-sentence when we just can’t find the word we want to use, even though we’re certain we know it. Why does this universal problem among speakers happen? And when can word-finding difficulties indicate something serious? Everyone will experience an occasional word-finding difficulty, but if they happen very often with a broad range of words, names and numbers, this could be a sign of a neurological disorder. The steps involved in speaking Producing spoken words involves several stages of processing. These include: identifying the intended meaning selecting the right word from the “mental lexicon” (a mental dictionary of the speaker’s vocabulary) retrieving its sound pattern (called its “form”) executing the movements of the speech organs for articulating it. Word-finding difficulties can potentially arise at each of these stages of processing. When a healthy speaker can’t retrieve a word from their lexicon despite the feeling of knowing it, this is called a “tip-of-the-tongue” phenomenon by language scientists. Often, the frustrated speaker will try to give a bit of information about their intended word’s meaning, “you know, that thing you hit a nail with”, or its spelling, “it starts with an H!”. Tip-of-the-tongue states...

Read More........→October 05, 2023