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Weird Physics Facts

telegraph.co.uk

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Re: Weird Physics Facts

#11

Post by niyazpk »

ramchip wrote: post #9

[The sun] is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. But, isn't it hot because the confinement permits nuclear fusion? Just sitting there and having gravity is totally related to being hot or not; it's not like you can create energy out of nothing. If the sun were made of bananas, wouldn't it just become a very compact, c…

The huge mass causes a big gravitational pull towards the centre which in turn increases the temperature and pressure inside the core of the star. This enormous temperature and pressure starts nuclear reactions.

Re: Weird Physics Facts

#12

Post by rpledge »

Tichy wrote: post #3

"All the matter that makes up the human race could fit in a sugar cube" That makes me think: what is the size of an atom (or whatever kind of particle we are talking about)? What does it even consist of? It seems easy to think about "nothing" and "stuff", because we perceive solid things all the time - but I can't make sense of the solid things.

The real question is could all the matter that makes up sugar cubes fit inside a sugar cube? Inquiring minds want to know!

Re: Weird Physics Facts

#13

Post by theblackbox »

niyazpk wrote: post #11
ramchip wrote: post #9

[The sun] is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. But, isn't it hot because the confinement permits nuclear fusion? Just sitting there and having gravity is totally related to being hot or not; it's not like you can create energy out of nothing. If the sun were made of bananas, wouldn't it just become a very compact, c…

The huge mass causes a big gravitational pull towards the centre which in turn increases the temperature and pressure inside the core of the star. This enormous temperature and pressure starts nuclear reactions.

... which, in turn, resists the gravity (iirc?) i.e. supernovas are formed when this balance collapses and a series of fission/fusion reactions fail to stabalise the star. This helps create heavy elements, as the star explodes and some magnificent forces are unleashed, seeding the surrounding space with the necessary stuff for "further development" - later stage stars, planets, coments/asteroids and life.

I highly recommend Stardust by John Gribbin for a thorough and accessible read on the subject of stars and their evolution.

Re: Weird Physics Facts

#14

Post by gizmo »

ramchip wrote: post #9

[The sun] is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. But, isn't it hot because the confinement permits nuclear fusion? Just sitting there and having gravity is totally related to being hot or not; it's not like you can create energy out of nothing. If the sun were made of bananas, wouldn't it just become a very compact, c…

Banana's, if I'm not mistaken consist mostly of carbon and hydrogen. Since hydrogen is the easiest to fuse you'd get a hydrogen fusion reaction in the core of the bananasun. Over time heavier elements are created as the product of fusion.

The only thing that remains of the original bananas is the color yellow, which explains the color of the sun.

Re: Weird Physics Facts

#15

Post by pvg »

ramchip wrote: post #9

[The sun] is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. But, isn't it hot because the confinement permits nuclear fusion? Just sitting there and having gravity is totally related to being hot or not; it's not like you can create energy out of nothing. If the sun were made of bananas, wouldn't it just become a very compact, c…

It's going to become a very dense, very hot (due to the squishing) bananasphere. Which is roughly comparable to a ball of water. The composition of the Sun would change drastically, it will contain a great deal more heavier nuclei and dramatically less hydrogen. The banana-sun will probably have to get a lot hotter and denser a lot sooner and start fusing helium (the hydrogen fusion product) and given its mass probably end up somewhere around here in terms of stellar evolution.

http://en.wikipedia.org/wiki/White_dwarf

Although it would probably be a off-white bananaish dwarf.

Re: Weird Physics Facts

#16

Post by gizmo »

Tichy wrote: post #3

"All the matter that makes up the human race could fit in a sugar cube" That makes me think: what is the size of an atom (or whatever kind of particle we are talking about)? What does it even consist of? It seems easy to think about "nothing" and "stuff", because we perceive solid things all the time - but I can't make sense of the solid things.

The particle we're talking about are the nucleons (protons / neutrons) in an atom. You can simply count the nucleons in an atom (atomic table), then in a molecule, then in a cell, then in a person. Take the sum of all nucleons in all people and you know the total matter. Energy/electrons are insignificant, and not part of the calculation.

You could argue that because humans are warmer than our environment there is some extra heat energy which can be converted to mass (E=MC^2), which is should strictly be part of our weight. It's so little, though, that we can safely ignore it.

Nucleons themselves are made of quarks. Quarks have themselves mass, but they can also have mass as part of their field. I can't remember the details. I'm pretty sure nobody knows why a quark has mass in the first place.

Re: Weird Physics Facts

#17

Post by huntse »

So it's a bit of a stretch to claim (as this article does) that the "many worlds" interpretation of QM is a physics fact. It is a possible interpretation of the model which is impossible (at least I think that's the case) to empirically verify. Some pretty eminent physicists (Roger Penrose for example) believe that the "Many Worlds" interpretation is pretty much nonsense, and have said as much.

Re: Weird Physics Facts

#18

Post by gizmo »

rpledge wrote: post #12
Tichy wrote: post #3

"All the matter that makes up the human race could fit in a sugar cube" That makes me think: what is the size of an atom (or whatever kind of particle we are talking about)? What does it even consist of? It seems easy to think about "nothing" and "stuff", because we perceive solid things all the time - but I can't make sense of the solid things.

The real question is could all the matter that makes up sugar cubes fit inside a sugar cube? Inquiring minds want to know!

Easily.

Assume sugar cubes consist 100% of sugar. Then the question becomes, what has more mass: the world's population or the world's supply of sugar.

There definitely isn't enough sugar in the world to give everybody his own weight in sugar (including the sugar that naturally forms in plants / fruit), so there's your answer.

Re: Weird Physics Facts

#20

Post by roundsquare »

lt wrote: post #8
chrischen wrote: post #2

One more weird fact: scientists conduct experiment that show that reality doesn't exist! http://news.ycombinator.com/item?id=937329 Basically they found out that properties do not exist until after they are observed.

Physics has been a recent interest for me, for all its weirdness. I was thinking about this issue in particular yesterday. Made me think of Thirteenth Floor - the simulation doesn't need to happen until someone observes it Maybe we were written in a functional language with Lazy Evaluation. Maybe the issue isn't if it the tree makes a sound - does it fall at all if there's no one around?

Is it possible that when you get to the forest the tree has retroactively fallen down?
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