Great Moments In Science

Trees are solid and dense. However, they're made from air. Wait, what?

About 95 per cent of the mass in the universe seems to be missing — what's going on!?

Our skin is like a personal space suit protecting us from the outside world. Skin is best when you are a child—because of the elastic protein keeping it fresh and supple—but, unfortunately, that freshness doesn’t last.

Host: Dr Karl Kruszelnicki

Producer: Diane Dean

An interesting demographics exercise is to add up the number of humans who've existed. This is different from how many people are in a population—which in late November 2022, is about 8 billion. But using data going back as far as possible, the number of people who've existed is reckoned at over 100 billion.

Host: Dr Karl Kruszelnicki

One might imagine that face masks work because the multiple layers will stop a virus getting through. But no, that's not it—they use a high-tech 'melt-blown' material, developed from a technique first noticed in volcano eruptions.

Host: Dr Karl Kruszelnicki

Producer: Diane Dean

Nowadays we're pretty familiar with wearing a face mask to reduce infection rates, and that some masks are better than others.But understanding why the N95 mask is a really good mask one came as a surprise.

Host: Dr Karl Kruszelnicki

Producer: Diane Dean

Nuclear weapons carry enormous destructive power in a very small package. A nuclear weapon weighing about a quarter of a ton can release as much energy as exploding 1.2 million tons of TNT – that’s a multiplication factor of about five million. During the Cold War the combined numbers of US and Soviet nuclear weapons reached about 70,000. There are not so many these days but there are still enough to end civilisation as we know it.

The further adventures of some of the most powerful events in our Universe: Gamma Ray Bursts. The biggest one recorded was in October 2022, in a galaxy far, far away. What would have happened if it had exploded inside our Milky Way galaxy?

First on the list of Most Energetic Events Ever in our universe is The Big Bang. No mean contender for top ranking is the "Gamma Ray Burst" - aka the GRB. GRBs can put out more energy in a few seconds than our Sun produces in its 10-billion-year lifetime.

The invention of the elevator made city-living possible. It made possible a rapid mixing of cultures and concepts, efficient use of energy—and ultimately, increased economic output. And now there's a further improvement called 'destination despatching'.