Amazing answers to your curious questions

Why was the Space Shuttle retired and what replaced it?

Sadly, the Space Shuttle turned out to be too dangerous. The disasters that destroyed Challenger on launch in 1986 and Columbia on re-entry to Earth’s atmosphere in 2003 were both caused by damage to the main orbiter during launch. It turned out that the design – which strapped the orbiter to the side of its booster rockets and fuel tank – was much riskier than traditional space vehicles where crew and cargo sit in a capsule on top of the rocket stages. Immediately following the retirement of the Space Shuttle in 2011, a variety of unmanned launch vehicles took its place for satellite launches, while Russian Soyuz spacecraft took crews to and from orbit. Commercial crew spacecraft like SpaceX’s Dragon have since succeeded the Space Shuttle, as well as NASA’s Orion on the Space Launch System.

IF THERE’S THE SAME AMOUNT OF IRON IN OUR BLOOD AS IN ASIXINCH NAIL, WHY DON’T WE ATTRACT MAGNETS?

Iron and other ferromagnetic materials – those that are naturally drawn to a magnet – are themselves made up of lots of tiny magnets. Put a chunk of iron next to a permanent magnet and these tiny magnets all line up in parallel. This allows the iron to produce its own magnetic field and attract the permanent magnet. For this to happen, a substantial number of iron atoms need to be in close enough contact to interact with one another. Most of the four grams or so of iron that can be found inside the average human body is bound up inside haemoglobin – the red-coloured protein in our blood which is responsible for carrying oxygen. Fortunately, as a result the iron atoms are not concentrated enough to join forces to generate their own magnetic field and attract nearby magnets.

WHAT EXACTLY IS DARK MATTER?

By measuring the motion of stars in our galaxy and others, astronomers can tell that galaxies in general contain much more mass than can be accounted for by their visible stars, gas and dust. In fact, normal, or baryonic matter – essentially anything with protons and neutrons – seems to account for just 15 per cent of all the mass in the universe. The rest is composed of something else… something that’s not just dark, but entirely transparent and unaffected by any kind of radiation. Dark matter plays an important role in the structure of the cosmos, too. Its enormous gravity causes baryonic matter to cluster around it, coalescing into galaxies and galaxy clusters. As a result, its distribution is similar to that of visible objects.