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Weird Physics Facts

telegraph.co.uk

32 pointsmikefrancis25 comments

This is a stunningly bad article. The author is a faker.

> If the Sun were made of bananas, it would be just as hot

Maybe, maybe not. The heat from the sun comes from fusion of hydrogen into helium. If it were mostly helium, it would be much much hotter. (That's a red giant.) With the carbon, oxygen, and whatever else in bananas, who knows.

> Events in the future can affect what happened in the past

Affect is an absolutely terrible choice of words for this. Events at a distance can be set up to be correlated in strange, "spooky" ways, but this in no way can be used to communicate back in time or faster than light. So "affect" is a tragically ill-chosen verb.

> Things can travel faster than light; and light doesn’t always travel very fast

I think a real physicist would weep at this faker's explanation here.

> There are an infinite number of mes writing this, and an infinite number of yous reading it

> According to the current standard model of cosmology,

There are wild theories (some may even be testable someday, some may not), but this is no "standard" model of cosmology.

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.

Another weird phenomenon is the Unhruh effect, one interpretation of which states that an accelerated observer will disagree with an unaccelerated observer as to the number of particles in a system. You get some weird stuff when you combine QFT and GR.

[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, cold sphere of crushed bananas?

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.

By mass, mostly oxygen and carbon (googling around, ~70+% water, ~20+% carbohydrates). Compared to the sun (~70+% hydrogen, almost all of the rest is helium), the amount of hydrogen is tiny . The density of the sun is substantially higher than its banana-replacement as well - 1.4 g/cm^3 vs a bit over 1 g/cm^3. It seems like you end up with a star that would fuse the limited amounts of hydrogen and resulting helium but is too small to get any further. The 'would be just as hot' thing seems like a bit of newspapery oversimplification - at solar masses (and below) bananium doesn't appear to be very good stellar fuel.

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.

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.

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.

It seems that, just like Haskell, the universe operates according to lazy evaluation.

I guess this makes human observation monadic.

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?

If realism is proven to be invalid, then that could be true.

The results are still debated though.

See http://news.ycombinator.com/item?id=925539

"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.

Well the perception of "solid" actually just comes from the repelling of like charges. The nucleus in the center is condensed positive charge and neutrons. When protons collide really what's happening is that they start repelling each other.

http://news.ycombinator.com/item?id=933534 You can see the carbon atom relative to 12 point font if you zoom in.

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.

The bits they're talking about are atomic nuclei, in which the vast majority of an atom's mass is concentrated.

http://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experime...

As to feeling 'solid things', Feynman has an engaging popular explanation:

http://www.youtube.com/watch?v=qhh32JYkQPk

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.

There are 7 Kg / person of sugar produced annually, I think the total amount of sugar on the planet is at least as large as the total amount of people.

I don't see how that follows. The amount of sugar produced is roughly equal to the demand for sugar -- and as sugar is eaten it immediately decomposes and ceases to be sugar.

So there is a fixed surplus of sugar in the world, and that's the only relevant amount. Production and consumption cancel each other out.

Assuming the average person weighs 50kg, there has to be a 5 year surplus in order for the surplus per person to be heavier than the person. I consider it highly unlikely we stockpile a 5 year supply of sugar (200+ billion kg) -- especially since there is no incentive to do so.

I feel this video is apt for this topic - Laurence Krauss - A universe from nothing.

http://www.youtube.com/watch?v=7ImvlS8PLIo&feature=playe...

It had me mesmerized and mystified for the whole run.

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