Ask a physicist anything.

[Chesterton]

1. What's your opinion of string theory?
2. How could anyone not know what a burrito is?

 

[Doveaman]

I'm enjoying these physics-related threads so...

Ask a physicist anything .

This one has always puzzled me.

We know that gravity pulls us down onto the planet. But what pulls the planet down onto the fabric?

And why isn’t the satellite making a dent in the fabric.

 

[Cabal]

This one has always puzzled me.

We know that gravity pulls us down onto the planet. But what pulls the planet down onto the fabric?

It's warping the fabric itself. Nothing is being pulled down. Think of it more like water around a rock.

And why isn’t the satellite making a dent in the fabric.

It would be. It's just incredibly small.

 

[Doveaman]

I'm enjoying these physics-related threads so...

Ask a physicist anything .

Another thing I forgot.

From my observation of this image I can see why those of us who live on the top half of the planet would be pulled or fall onto the planet. But what about those of us who live on the bottom half? Shouldn’t we be falling into the air?

I’m just asking.

 

[Cabal]

Another thing I forgot.

From my observation of this image I can see why those of us who live on the top half of the planet would be pulled or fall onto the planet. But what about those of us who live on the bottom half? Shouldn’t we be falling into the air?

I’m just asking.

Well, I'm not sure if this picture ties in, but if you wiki "spacetime" the first image on the page is very similar to the one you put and the caption indicates that it's a 2D description, not a 3D one. Not sure what the 3D one looks like though.

 

[Wiccan_Child]

Maybe I was misunderstood. Forgive me.

Meh, we all make mistakes. It takes balls to accept that.

OK, let’s try this: Lets say a plasma house was observed in space but because of lack of proper experiment on your part it was hypothesized by you to be a dark-energy house, without any experimental confirmation that dark-energy exist.

OK, I'm with you so far.

This would mean, then, that the hypothetical explanation you gave for that house has no basis in reality since you are not actually describing the plasma house but only a hypothetical dark-energy house that you think exist.

If the hypothetical explanation is flawed for lack of experiment then you end up seeing houses in space that are not really there.[/quote] Presumably, we had some means of detecting the house in the first place. So we can at least do that properly. But if our equipment isn't sophisticated enough to probe its properties, then we have to make do with the evidence we've got. A dark matter hypothesis could indeed explain the available data. We fully acknowledge that this hypothesis could be wrong, as we fully acknowledge that any scientific hypothesis or theory could be wrong. But that doesn't mean we should give up and go home. We have some data, limited though it may be, and, while it is hardly conclusion, it does suggest the existence of so-called 'dark matter' (specifically, matter that interacts gravimetrically, but not electromagnetically). This hypothesis is far from complete, and the few experiments designed to test it have yet to finish compiling data. But it's a valid hypothesis, and what evidence we have seems to support it.

 

[Doveaman]

It's warping the fabric itself. Nothing is being pulled down. Think of it more like water around a rock.

I am trying to think of it that way but my brain seem not to be electrically discharging the concept.

When I think of water around a rock I think of everything on that rock being washed away.

 

[Wiccan_Child]

are you a physicist?

I am indeed. At least, by day: by night, I'm wooer of mortals and drinker of ale.

Actually he's a detective - hot on the trail of God. Or a theologian with a speciality.

I'm not sure if I should be insulted or flattered

1. What's your opinion of string theory?

If it can do what people say it can do, it's a very exciting theory. But there's a bit too much speculation and conjecture for my taste. It reminds me of the spat of 'cold fusion' hype we had a few decades ago. Exciting if it worked, but the technology is still a long way away.

2. How could anyone not know what a burrito is?

I have a vague idea what a burrito is, but they're more of a Central/Northern American thing, aren't they? Case in point: my dictionary doesn't recognise the word 'burrito'.

 

[Wiccan_Child]

This one has always puzzled me.

We know that gravity pulls us down onto the planet. But what pulls the planet down onto the fabric?

It's a useful analogy, but every analogy falls apart if you poke it hard enough. Matter warps space in the same way a ball warps a rubber sheet.

And why isn’t the satellite making a dent in the fabric.

It does, but the image is a visual aid. Besides, the satellites own gravity well would be tiny, especially compared to Earth's.

Another thing I forgot. From my observation of this image I can see why those of us who live on the top half of the planet would be pulled or fall onto the planet. But what about those of us who live on the bottom half? Shouldn’t we be falling into the air?

The image is a bit misleading. It would be more accurate to show the lines being warped towards the centre of the Earth. Indeed, it would be more accurate to show a 3D grid, rather than a 2D plane. I can't find a good image of it though...

I’m just asking.

[/quote] Haha, ask away, that's what this thread's for.

 

[Cabal]

I am trying to think of it that way but my brain seem not to be electrically discharging the concept.

When I think of water around a rock I think of everything on that rock being washed away.

I wasn't referring to surface debris on the rock as such...more just how there is a variation in density around the rock as a result of it just being there in the medium.

 

[Chesterton]

If it can do what people say it can do, it's a very exciting theory. But there's a bit too much speculation and conjecture for my taste. It reminds me of the spat of 'cold fusion' hype we had a few decades ago. Exciting if it worked, but the technology is still a long way away.

A statement I read once is that the math involved in string theory requires the extra dimensions. Does this mean it a) demonstrates extra dimensions, or b) assumes extra dimensions?

I have a vague idea what a burrito is, but they're more of a Central/Northern American thing, aren't they? Case in point: my dictionary doesn't recognise the word 'burrito'.

Central/Northern America, uh, no, but given that you probably think in cosmic terms, you nailed the planet, the hemisphere and the continent, so that's pretty darn good!

 

[Jazmyn]

Is it true that string theory and quantum theory somehow don't match up together, and that if you mention this in a university interview they don't let you in? Light has a weight, right? If something were lighter than light, could it travel faster? Ever think of the 'foam of space'? What time is it at the north pole? Does the universe have an 'up'? What shape is the universe? Why is the sea salty? no really? 0_0

 

[Jazmyn]

Mwahhahahahah! On which side of a chicken are the most feathers? How far can a bear walk into the woods? A woman has 7 children, half of them are boys. How can this be possible? What lies on the ground, a hundred feet in the air?

 

[Thistlethorn]

Mwahhahahahah! On which side of a chicken are the most feathers?

The outside?

How far can a bear walk into the woods?

Until he reaches the end?

A woman has 7 children, half of them are boys. How can this be possible?

All of them are boys?

What lies on the ground, a hundred feet in the air?

Upside down centipede?

 

[Cabal]

Is it true that string theory and quantum theory somehow don't match up together

Can't say I've heard of that. You might be thinking of general relativity and quantum theory not matching up?

and that if you mention this in a university interview they don't let you in?

Er, no.

Light has a weight, right? If something were lighter than light, could it travel faster?

Nope, so no. That said....

Tachyon - Wikipedia, the free encyclopedia (sorry, not able to make hyperlinks on my browser tonight....rrrrr)

Ever think of the 'foam of space'?

Doesn't sound like anything more complicated than vacuum fluctuations at low scales, which is pretty typical for the quantum description of something on that length scale, but maybe I'm over-simplifying.

What time is it at the north pole?

I'm gonna be patriotic and say GMT (this is not a serious answer)

Does the universe have an 'up'?

Nope. There are no absolute directions or coordinates.

What shape is the universe?

I'm not sure what shape they currently think it is - a few ideas came out about a decade ago, but more currently than that....

*wikis*

Flat, apparently! (According to the WMAP satellite)

Why is the sea salty? no really? 0_0

Honestly not sure...

 

[Wiccan_Child]

Is it true that string theory and quantum theory somehow don't match up together, and that if you mention this in a university interview they don't let you in?

Only the more clandestine universities will do that. String theory is the next step up from quantum mechanics, just as quantum mechanics is the next step up from classical mechanics. Only if it's right, though.

Light has a weight, right?

No. Well, not as far as we can tell. Though it is affected by gravity.

If something were lighter than light, could it travel faster?

According to the standard model, yes. But it wouldn't travel faster than the so-called 'speed of light', which is a fixed number. If light itself had mass, then it would travel slightly slower than this fixed number.

Ever think of the 'foam of space'?

Yep. Nothing like a dose of virtual particles to make you go cross-eyed.

What time is it at the north pole?

Depends.

Does the universe have an 'up'?

No, since 'up' is a rather arbitrary designation.

What shape is the universe?

Either a bubble with a fixed edge, a bubble whose edge wraps around onto itself so you could travel in a straight line and end up where you started, or an infinite expanse of space, or anything else you care to imagine. I rather like the 'saddle' universe:

Why is the sea salty? no really? 0_0

Water picks up salt when it runs down mountains and through rivers. It then joins the sea, and gets evaporated by the Sun. But the salt (et al) stay behind. Thus, over time, the sea gets more and more salty. It's a little more complicated than that, such as the fact that the sea doesn't get much more salty than it is right now, but that's essentially what's happening.

Mwahhahahahah! On which side of a chicken are the most feathers?

The outside. On a side note, did you know that a chicken's right leg is always more tender than its left?

How far can a bear walk into the woods?

Half-way, then it's walking out again.

A woman has 7 children, half of them are boys. How can this be possible?

The other half are also boys.

What lies on the ground, a hundred feet in the air?

An upside-down millipede (though they have many hundreds of legs...).

 

[Thistlethorn]

As we're on the subject, don't forget the Simpsonian theory of the Universe: YouTube - The simpsons intro-universe It also hypothesizes the end of it all: YouTube - Simpsons best intro; Tree House of Horror XVI

 

[Wiccan_Child]

A statement I read once is that the math involved in string theory requires the extra dimensions. Does this mean it a) demonstrates extra dimensions, or b) assumes extra dimensions?

It assumes extra dimensions. So anything that demonstrates string theory is also demonstrating the existence of those extra dimensions.

Central/Northern America, uh, no, but given that you probably think in cosmic terms, you nailed the planet, the hemisphere and the continent, so that's pretty darn good!

 

[Wiccan_Child]

YouTube - Simpsons best intro; Tree House of Horror XVI

"You just destroyed the totality of existence!"

Best way to end a D&D campaign, methinks.

EDIT: Also, the forum has stopped being sucky! Yay!

 

[pgp_protector]

... I have a vague idea what a burrito is, but they're more of a Central/Northern American thing, aren't they? Case in point: my dictionary doesn't recognise the word 'burrito'.