Ask a physicist anything. (7)

[Chalnoth]

If you were given the chance to explore a fictional world in person, like say the Star Wars universe or Narnia or whathave you, which genre would be most interesting from a physicist's perspective and why?

Sword and sorcery? Sci-fi? Steampunk? Religious?

Haha, well, I don't know about a physicist's perspective, but the dreams I have the most about going into fictional worlds involves dramatic situations where my knowledge could change the outcome. I then like to imagine all of the details of what would be different due to my intervention.

One set of novels that I read not too long ago that was very much like this was the Sword of Truth series by Terry Goodkind. The Libertarian ideology of the author gets a little grating at times, but he's really good at writing a story where little bits of ignorance of the main characters leads to all sorts of dramatic tension. I like to imagine what would happen if I were to visit this world and interact with the main characters there at just the right moments.

**spoiler warning**
For example, the main plot of the last few books in the series (not including The Omen Machine) was the unleashing of a spell called Chainfire, which erased the female lead, Kahlan, from everybody's memory but Richard (her husband and the male lead). And nobody would believe Richard when he said he had to go look for her. But there was a really, really easy way, revealed in the last book of this story line, for him to convince them of her existence. After reading those books in particular, I enjoyed mulling over in my head all of the various ways in which a little bit of knowledge inserted at the right moments could have changed the story.
**end spoiler warning**

This, to me, really goes across genres, and is more about narrative structure than anything else. Though I would very much like to visit some of the sci-fi situations to grab some of their sweet technology!

 

[Tuddrussell]

I liked the first book of SoT, but the whole S&M thing made me really uncomfortable.

 

[Chalnoth]

How do a soccerplayer spin the ball over 102 cm from its original course when kicking the ball. To me it seems like a impossibility to screw a ball, no matter it's baseball or soccer!

Ah, well, it's the same concept that gives an airplane its lift!

An airplane wing produces lift for a rather simple reason: the air on the top reaches the back of the wing faster than the air on the bottom. It's not too difficult to demonstrate that by moving faster on the top than the bottom, the pressure at the top of the wing is lower than at the bottom, so the wing is pushed upward.

In fact, the air flow around the wing can be separated into two flows: a flow of air where the air that flows above the wing and below the wing meet perfectly. This is known as laminar flow, and produces no lift. The rest of the flow is a circular flow around the wing. This circular flow actually produces the lift.

So if you take a ball, and throw it through the air so that it is spinning sideways, it causes a very similar effect. For example, if the right side of the ball is spinning towards the direction of motion, and the left hand side is spinning back towards the thrower, then this will increase the air pressure on the right side and decrease it on the left side. The ball is pushed to the left.

 

[Chalnoth]

I liked the first book of SoT, but the whole S&M thing made me really uncomfortable.

Haha, you mean the Mord Sith? Yeah, that was a bit extreme. I don't think he really goes down that particular road again in the following books. There is a fair amount of pain and suffering, but it isn't as related to sex as it was in that first one.

 

[Lillen]

Que?

 

[Chalnoth]

Que?

Are you responding to my last post, or my response to you?

 

[Tuddrussell]

If you had two left arms, would it be better for your right hand to have the thumb on top but facing the wrong way or for your thumb to be facing downward?

 

[hisgrace26]

hi there. sorry i am not well rounded in cosmology. but i am curious to find out what causes the expansion of the universe. in one theory there is the inflation theory where it acts sort of like an anti gravity that causes the expansion. more like an inflating balloon. does inflation theory supports that idea? any documentations on this matter? thanks.

 

[Wiccan_Child]

hi there. sorry i am not well rounded in cosmology. but i am curious to find out what causes the expansion of the universe. in one theory there is the inflation theory where it acts sort of like an anti gravity that causes the expansion. more like an inflating balloon. does inflation theory supports that idea? any documentations on this matter? thanks.

It's certainly a mystery. The evidence shows us what's happening, but as yet hasn't shed any light on why. Don't get me wrong, we do know that the universe is expanding, and did expand rapidly early on (known as 'inflation'), we just don't know why. Personally, I think it's impetus from whatever went on prior to the Big Bang.

 

[Chalnoth]

hi there. sorry i am not well rounded in cosmology. but i am curious to find out what causes the expansion of the universe. in one theory there is the inflation theory where it acts sort of like an anti gravity that causes the expansion. more like an inflating balloon. does inflation theory supports that idea? any documentations on this matter? thanks.

Well, there are two different things here.

First, General Relativity describes very accurately how the matter/energy contents of the universe change the rate of expansion over time. Lots of matter and not much of other forms of energy, and the expansion slows down. Not too much matter but a lot of dark energy, and the expansion speeds up.

Inflation is a sort of very high-density dark energy proposed to explain certain features of our early universe which matches the data very well. Inflation would have caused an early period where the expansion accelerated fantastically fast, growing a region smaller than a proton to the size of our entire observable universe in a fraction of a second.

Of course, inflation can only change the rate of expansion. It can't start expansion from a universe that isn't expanding. However, as it turns out, this isn't a problem: a static universe in General Relativity is unstable: it has a 50/50 chance of either collapsing in on itself or tipping the other way and expanding forever. But it can't stay static forever.

So if you have some theory for starting out a new region of space-time, it has roughly a 50/50 chance of collapsing in on itself or expanding. We wouldn't ever see a universe that just collapses in on itself before doing anything, there's really no reason to explain why ours happened to be one of those regions that started off expanding: if it hadn't, we wouldn't be here.

What really needs explaining, instead, is how these seeds of new regions of space-time are produced. There are many ideas, but in the end we just don't yet know. Lots of experimental work to do before we can nail it down.

 

[Lillen]

This is my question for today, and it is anatomic question How can the tear channels in your eyes produce tears when crying!!? And why are some people blunted to cry? and for most, why do we cry at all?

 

[CabVet]

This is my question for today, and it is anatomic question How can the tear channels in your eyes produce tears when crying!!? And why are some people blunted to cry? and for most, why do we cry at all?

I highly doubt a physicist will know the answer to that.

Do you want technical responses for the first two questions? As for the last one, we cry for a few reasons, the main two being strong emotions and irritation of the eyes.

 

[Chalnoth]

I highly doubt a physicist will know the answer to that.

Well, I certainly don't! There's probably some interesting biochemistry going on there that allows a large number of cells in the tear glands to excrete the tears in such quantities. But I have no idea what that biochemistry is.

There's always Wikipedia, though!
Lacrimal gland - Wikipedia, the free encyclopedia

 

[pgp_protector]

I highly doubt a physicist will know the answer to that.

Do you want technical responses for the first two questions? As for the last one, we cry for a few reasons, the main two being strong emotions and irritation of the eyes.

I thought the two main reasons were lubrication & cleaning of irritations. The emotional response is one that (as far as I know) only Humans do.

 

[CabVet]

I thought the two main reasons were lubrication & cleaning of irritations. The emotional response is one that (as far as I know) only Humans do.

Yes, tears are for lubrication, but she specifically asked about "crying", and crying is not for lubrication. We produce tears all the time for lubrication, "crying" is an excess, which in humans is related to emotions and irritation (not to mention whatever it is that actors do to cry).

 

[hisgrace26]

It's certainly a mystery. The evidence shows us what's happening, but as yet hasn't shed any light on why. Don't get me wrong, we do know that the universe is expanding, and did expand rapidly early on (known as 'inflation'), we just don't know why. Personally, I think it's impetus from whatever went on prior to the Big Bang.

What I like to know is where in that theory does it stated that it is one of the reason for the expansion?

 

[hisgrace26]

Well, there are two different things here.
Of course, inflation can only change the rate of expansion. It can't start expansion from a universe that isn't expanding. However, as it turns out, this isn't a problem: a static universe in General Relativity is unstable: it has a 50/50 chance of either collapsing in on itself or tipping the other way and expanding forever. But it can't stay static forever.

So if you have some theory for starting out a new region of space-time, it has roughly a 50/50 chance of collapsing in on itself or expanding. We wouldn't ever see a universe that just collapses in on itself before doing anything, there's really no reason to explain why ours happened to be one of those regions that started off expanding: if it hadn't, we wouldn't be here.

What really needs explaining, instead, is how these seeds of new regions of space-time are produced. There are many ideas, but in the end we just don't yet know. Lots of experimental work to do before we can nail it down.

Thanks that makes sense. if I may ask, what are the theories that account for these new space-time regions?

 

[Chalnoth]

Thanks that makes sense. if I may ask, what are the theories that account for these new space-time regions?

Two main ones are eternal inflation and quantum vacuum fluctuations.

 

[Lillen]

Parhaps i should rephrase myself. Why do strong emotion trigger crying and people to shed tears? the answer of the first question is penalism! Penalism causes people not to shed tears when they are sad. usually!

What is it good for? this is parhaps one of those questions that has alot of answers i guess!

 

[Lillen]

Now i know why you people cry, it is something i never can do!

Do you remeber the movie?