Nice People Thread Number 10 -the official residence of Nice People

tomterm8

neverdespairgirl wrote: »

But then he said that some things, like gravity, are neither matter nor energy, and went off into a discussion about how curvature of space in 4 dimensions shows that Newton was wrong in some ways about gravity. He says he watched a programme about it on OH's computer before Christmas.

Is he right? I've tried looking it up online, but what I can find is either too simplistic or completely over my head. Are there other exceptions to the matter / energy idea apart from gravity?

Well, yes and no.

For a start, even Newtonian theory recognized three classes of things - matter, energy, and Forces that act on matter and energy.

If you believe relativity, the thing that appears to be the force of gravity is actually caused by curvature on space time. He's right on that.

So, under Einsteins theory it has a unique place; the other forces are caused by interactions between particles. Einstein also discovered there was a link between Energy and Mass ( the famous e equals mc squared one).

The problem is that Einstein's theories break down under some circumstances, for example in the very small scale where quantum theories hold sway, or in the middle of singularities - otherwise known as black holes.

You could say that we are quite sure that our best understanding of physics is wrong, and that at a quantum level it looks like mass, energy and force are concepts that don't hold at all. Instead, you have something called string theory, which if you look it up you will probably discover that it is something no one understands it at all.

GDB2222

silvercar wrote: »

Looks lovely Nicks, just needs a BBQ.

Was that a hint?



Today we had a fantastic walk on Hampstead Heath/Parliament Hill. I can't remember seeing so many people before.

For tea, we had Acid Rain cake - better known as lemon drizzle cake.

neverdespairgirl

Nikkster wrote: »

Can't you get him into Teletubbies or something instead?!

I have no idea, not my type of science. I bet Lydia has a good answer though...

Honestly, excuses, excuses....

tomterm8 wrote: »

Well, yes and no.

For a start, even Newtonian theory recognized three classes of things - matter, energy, and Forces that act on matter and energy.

If you believe relativity, the thing that appears to be the force of gravity is actually caused by curvature on space time. He's right on that.

So, under Einsteins theory it has a unique place; the other forces are caused by interactions between particles. Einstein also discovered there was a link between Energy and Mass ( the famous e equals mc squared one).

The problem is that Einstein's theories break down under some circumstances, for example in the very small scale where quantum theories hold sway, or in the middle of singularities - otherwise known as black holes.

You could say that we are quite sure that our best understanding of physics is wrong, and that at a quantum level it looks like mass, energy and force are concepts that don't hold at all. Instead, you have something called string theory, which if you look it up you will probably discover that it is something no one understands it at all.

Thanks very much.

Sorry to be thick, but under Newtonian physics, is gravity a force, but under Einstein's theory, it isn't?

I just did look up string theory, and I'm neither wiser nor better informed.

tomterm8

neverdespairgirl wrote: »

Honestly, excuses, excuses....



Thanks very much.

Sorry to be thick, but under Newtonian physics, is gravity a force, but under Einstein's theory, it isn't?

I just did look up string theory, and I'm neither wiser nor better informed.

Under Newtonian physics, gravity is a force.

Technically, under Einstein's theory gravity isn't a force.

Er... basically, things go in a straight line and at the same speed unless they are acted on by a force. (Conservation of momentum).

But, under Einsteins theory space time is curved. So, although from our perspective it looks like things are changing directions they actually are not. They're just following the curvature of space time.

Imagine putting a bowling ball in the middle of a trampoline. If you rolled a marble along the trampoline then the marble would change direction because the shape of the surface it was rolling on was curved.

This is all a bit wibbly-wobbly, but at least it makes more sense than string theory...

zagubov

tomterm8 wrote: »

Well, yes and no.

For a start, even Newtonian theory recognized three classes of things - matter, energy, and Forces that act on matter and energy.

If you believe relativity, the thing that appears to be the force of gravity is actually caused by curvature on space time. He's right on that.

So, under Einsteins theory it has a unique place; the other forces are caused by interactions between particles. Einstein also discovered there was a link between Energy and Mass ( the famous e equals mc squared one).

The problem is that Einstein's theories break down under some circumstances, for example in the very small scale where quantum theories hold sway, or in the middle of singularities - otherwise known as black holes.

You could say that we are quite sure that our best understanding of physics is wrong, and that at a quantum level it looks like mass, energy and force are concepts that don't hold at all. Instead, you have something called string theory, which if you look it up you will probably discover that it is something no one understands it at all.

What tom said! :beer:

The universe is filled with matter and this is acted on by forces which make it move.

Matter contains energy which enables it to resist the forces. The energy is related to and covertible to matter. although the reverse (matter turning into energy) is more likely to happen, and powers the sun and life on Earth.

Science has always known about matter ("material" shares an origin with "maternal" as Aristotle claimed we got our substance from our mothers), but known that there must be more than that or there would be no change in the universe. Newton introduced the concept of force. Others introduced the idea of energy.

I suppose matter generates the forces either by particle exchange (mesons and photons etc) or by physically distorting their surrounding spacetime, as gravity does.

Nikkster

GDB2222 wrote: »

Was that a hint?



Today we had a fantastic walk on Hampstead Heath/Parliament Hill. I can't remember seeing so many people before.

For tea, we had Acid Rain cake - better known as lemon drizzle cake.

Acid rain cake

You're all welcome to come over for a yellow-stckered burger/ sausage/ whatever else is lurking in the fridge freezer. As entertainment I can offer 'guess the plant' (no points for brambles, mint, dandelion, grass or buddleia, I've already worked those out)

LydiaJ

Thanks to the other physicists for answering Isaac's questions so brilliantly while I was driving across the country and back.

One tiny quibble - Newton didn't come up with the idea of forces; even Aristotle had some idea of a force, but his ideas about forces causing movement were very muddled and wrong, whereas Newton's are right unless you're incredibly small, incredibly heavy, or moving incredibly fast.

neverdespairgirl

LydiaJ wrote: »

Thanks to the other physicists for answering Isaac's questions so brilliantly while I was driving across the country and back.

One tiny quibble - Newton didn't come up with the idea of forces; even Aristotle had some idea of a force, but his ideas about forces causing movement were very muddled and wrong, whereas Newton's are right unless you're incredibly small, incredibly heavy, or moving incredibly fast.

Thanks Lydia - Newton's are also right unless you are an incredibly annoying 8 year old way outclassing his loving mother (-:

chewmylegoff

Nikkster wrote: »

Can't you get him into Teletubbies or something instead?!

I have no idea, not my type of science. I bet Lydia has a good answer though...

In the night garden has a gravity defying train called the ninky nonk which can go upside down along the underside of tree branches. That may help here.

Masomnia

Smart kid :eek: