damu
Banned
- Apr 27, 2009
- 1,689
- 11
Physics is weird. There is no denying that. Particles that don’t exist except as probabilities; time that changes according to how fast you’re moving; cats that are both alive and dead until you open a box.
We’ve put together a collection of 10 of the strangest facts we can find, with the kind help of cosmologist and writer Marcus Chown, author of We Need To Talk About Kelvin, and an assortment of Twitter users.
The humanities-graduate writer of this piece would like to stress that this is his work, so any glaring factual errors he has included are his own as well. If you spot any, feel free to point them out in the comment box below.
Equally, if you feel we’ve missed any of your favourite physics weirdnesses off the list, do tell us that as well.
1.If the Sun were made of bananas, it would be just as hot?
The Sun is hot, as the more astute of you will have noticed. It is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. Just as a bicycle pump gets warm when you pump it, the pressure increases the temperature. Enormous pressure leads to enormous temperature.
If, instead of hydrogen, you got a billion billion billion tons of bananas and hung it in space, it would create just as much pressure, and therefore just as high a temperature. So it would make very little difference to the heat whether you made the Sun out of hydrogen, or bananas, or patio furniture.
Edit: this might be a little confusing. The heat caused by the internal pressure would be similar to that of our Sun. However, if it's not made of hydrogen, the fusion reaction that keeps it going wouldn't get under way: so a banana Sun would rapidly cool down from its initial heat rather than burning for billions of years. Thanks to people who pointed this out.
2.All the matter that makes up the human race could fit in a sugar cube
Atoms are 99.9999999999999 per cent empty space. As Tom Stoppard put it: "Make a fist, and if your fist is as big as the nucleus of an atom, then the atom is as big as St Paul's, and if it happens to be a hydrogen atom, then it has a single electron flitting about like a moth in an empty cathedral, now by the dome, now by the altar."
If you forced all the atoms together, removing the space between them, crushing them down so the all those vast empty cathedrals were compressed into the first-sized nuclei, a single teaspoon or sugar cube of the resulting mass would weigh five billion tons; about ten times the weight of all the humans who are currently alive.
Incidentally, that is exactly what has happened in a neutron star, the super-dense mass left over after a certain kind of supernova.
3.Events in the future can affect what happened in the past
The weirdness of the quantum world is well documented. The double slit experiment, showing that light behaves as both a wave and a particle, is odd enough – particularly when it is shown that observing it makes it one or the other.
But it gets stranger. According to an experiment proposed by the physicist John Wheeler in 1978 and carried out by researchers in 2007, observing a particle now can change what happened to another one – in the past.
According to the double slit experiment, if you observe which of two slits light passes through, you force it to behave like a particle. If you don’t, and observe where it lands on a screen behind the slits, it behaves like a wave.
But if you wait for it to pass through the slit, and then observe which way it came through, it will retroactively force it to have passed through one or the other. In other words, causality is working backwards: the present is affecting the past.
Of course in the lab this only has an effect over indescribably tiny fractions of a second. But Wheeler suggested that light from distant stars that has bent around a gravitational well in between could be observed in the same way: which could mean that observing something now and changing what happened thousands, or even millions, of years in the past.
4.Almost all of the Universe is missing
There are probably more than 100 billion galaxies in the cosmos. Each of those galaxies has between 10 million and a trillion stars in it. Our sun, a rather small and feeble star (a “yellow dwarf
We’ve put together a collection of 10 of the strangest facts we can find, with the kind help of cosmologist and writer Marcus Chown, author of We Need To Talk About Kelvin, and an assortment of Twitter users.
The humanities-graduate writer of this piece would like to stress that this is his work, so any glaring factual errors he has included are his own as well. If you spot any, feel free to point them out in the comment box below.
Equally, if you feel we’ve missed any of your favourite physics weirdnesses off the list, do tell us that as well.
1.If the Sun were made of bananas, it would be just as hot?
The Sun is hot, as the more astute of you will have noticed. It is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. Just as a bicycle pump gets warm when you pump it, the pressure increases the temperature. Enormous pressure leads to enormous temperature.
If, instead of hydrogen, you got a billion billion billion tons of bananas and hung it in space, it would create just as much pressure, and therefore just as high a temperature. So it would make very little difference to the heat whether you made the Sun out of hydrogen, or bananas, or patio furniture.
Edit: this might be a little confusing. The heat caused by the internal pressure would be similar to that of our Sun. However, if it's not made of hydrogen, the fusion reaction that keeps it going wouldn't get under way: so a banana Sun would rapidly cool down from its initial heat rather than burning for billions of years. Thanks to people who pointed this out.
2.All the matter that makes up the human race could fit in a sugar cube
Atoms are 99.9999999999999 per cent empty space. As Tom Stoppard put it: "Make a fist, and if your fist is as big as the nucleus of an atom, then the atom is as big as St Paul's, and if it happens to be a hydrogen atom, then it has a single electron flitting about like a moth in an empty cathedral, now by the dome, now by the altar."
If you forced all the atoms together, removing the space between them, crushing them down so the all those vast empty cathedrals were compressed into the first-sized nuclei, a single teaspoon or sugar cube of the resulting mass would weigh five billion tons; about ten times the weight of all the humans who are currently alive.
Incidentally, that is exactly what has happened in a neutron star, the super-dense mass left over after a certain kind of supernova.
3.Events in the future can affect what happened in the past
The weirdness of the quantum world is well documented. The double slit experiment, showing that light behaves as both a wave and a particle, is odd enough – particularly when it is shown that observing it makes it one or the other.
But it gets stranger. According to an experiment proposed by the physicist John Wheeler in 1978 and carried out by researchers in 2007, observing a particle now can change what happened to another one – in the past.
According to the double slit experiment, if you observe which of two slits light passes through, you force it to behave like a particle. If you don’t, and observe where it lands on a screen behind the slits, it behaves like a wave.
But if you wait for it to pass through the slit, and then observe which way it came through, it will retroactively force it to have passed through one or the other. In other words, causality is working backwards: the present is affecting the past.
Of course in the lab this only has an effect over indescribably tiny fractions of a second. But Wheeler suggested that light from distant stars that has bent around a gravitational well in between could be observed in the same way: which could mean that observing something now and changing what happened thousands, or even millions, of years in the past.
4.Almost all of the Universe is missing
There are probably more than 100 billion galaxies in the cosmos. Each of those galaxies has between 10 million and a trillion stars in it. Our sun, a rather small and feeble star (a “yellow dwarf
