1. What would happen if a person fell into a black hole.
Physicists used to think you wouldn’t notice you were falling into a black hole until you crossed its event horizon. But new calculations in 2012 suggest you’d hit a wall of fire instead and be burnt to a crisp (ouch). If either theory is true, some basic laws of physics are in trouble.
2. Why it takes more genes to make a tomato than a human.
This problem has existed in various guises over the years and used to be known as the C-value paradox. But in 2003 botanists decided to downgrade it to an “enigma” – it’s still unexplained, though.
3. How the placebo effect works.
As long as you expect a pill to have an effect, it appears to – whether it is a real pill or a sugar-filled dummy. This is known as the placebo effect, and to make things even weirder it appears to still work even when you know you’re taking a sugar pill.
Oh and it’s not just pills – the placebo effect also works if you think you’ve had surgery but the crucial step is missed out. Yep.
4. If the Viking lander found life on Mars in the ’70s.
Viking, sent to Mars in 1976, carried three experiments to test for life. One came up positive. But the other two experiments did not, so the positive result had to be dismissed.
But in 2012 a team of scientists re-examined the data using a new technique and challenged the no-life verdict. So the jury is out.
5. How liquid water existed early in Earth’s history.
Early in Earth’s history the sun would have been fainter than it is now, and wouldn’t have had a big enough power output to melt ice on Earth. But from geological evidence we know that there was liquid water at the surface of our planet between 3.8 and 2.4 billion years ago, when life evolved. There are a few theories floating around but no explanation just yet.
6. Where all the aliens are.
This is known as the Fermi paradox and goes like this: There are billions of stars in the galaxy that are older than our sun. Some of those must have Earth-like planets, and presumably some of those have developed intelligent life. A smaller portion of those should have developed interstellar travel – so why have we not encountered these interstellar-traveling aliens?
7. Why some regions of the ocean have mysteriously low levels of phytoplankton.
There are regions of the ocean in the Antarctic where the nutrient level is high but the level of phytoplankton, a type of tiny plankton that create their own food using sunlight, is surprisingly low. Marine biologists have a couple of possible explanations for this, but no clear reason why, so it’s called the Antarctic paradox.
8. Why blue whales don’t get cancer more often than humans do, even though they’re much bigger than us.
There seems to be no correlation between the size of an animal species and the rate at which it gets cancer. This is known as Peto’s paradox, after biologist Richard Peto.
Given that cancer starts from mutations in an animal’s cells, scientists think that mammals with more cells should get cancer at a higher rate. Weirdly this does not seem to be the case.
9. Where all the lithium that should exist in the universe is.
One type of lithium is only about a third as abundant as it should be in the universe. Even in the earliest stars, whose composition scientists would expect to mirror that of the very early universe, don’t have enough.
10. Why magnets always have a north and south pole.
No matter how many times you divide a bar magnet in half the resulting object will always have a north and south pole. Quantum mechanics says that magnetic monopoles (a north or south pole on their own) should exist. But though magnetic monopoles have recently been made in a lab, we’ve never found one out in the wild.
11. Exactly how long the UK’s coastline is.
Coastal outlines are kinda fractal-like, meaning they are made up of lots of repeating patterns. If you zoom in on a fractal you just find the same shape at smaller and smaller scales, so their length is not well-defined.
The smaller the ruler you use to measure the outline of a coastline, the longer the answer you get.
(But you can approximate it depending on the scale you choose – according to Ordanance Survey, at a scale of 1:10,000, the outline of Great Britain is 11,072.76 miles.)
12. Why the sun’s atmosphere is so much hotter than its surface.
The sun’s atmosphere, known as the corona, extends more than a million kilometres from its surface and reaches temperatures of two million degrees. When compared to the mere 5000 degrees the surface of the sun reaches, there’s no explanation for why the temperature is so high.
13. Why the Eocene epoch was so warm.
From 56 million to 34 million years ago, during the Eocene epoch, geological evidence shows that temperatures could have been around 15 to 20C at Earth’s poles. But the reason for this period of warm climate is unclear.
14. Where these weird dark streaks are coming from on Mars.
They appear during warm seasons and travel downhill, before disappearing when the weather gets colder again. Scientists thought they might come from frozen water that heated up and flowed downhill, but measurements from Nasa’s Mars Reconnaissance Orbiter didn’t detect any water.
15. Where impossibly energetic cosmic rays come from.
The GZK limit is the theoretical upper limit on the energy of cosmic rays and is dictated by Einstein’s theory of relativity. But physicists at the Akeno Observatory in Japan have found cosmic rays that surpass this. There aren’t any sources that could be producing them near Earth, so their appearance is a mystery.