Ask a physicist anything. (3)

[Maxwell511]

I know of several ways to commit suicide painlessly, but that doesn't mean it's polite dinner conversation.

Polite dinner conversation? Stop being so British. I assure you that the peasants will not revolt. Although I am concerned about the American colonies.

Don't be so close-minded you homophobic bigot! God! Jeez! Kuh, pfft!

So he doesn't have a great rack? I'm not interested then.

 

[AV1611VET]

What would gravity be like on a planet that is shaped like a torus?

 

[Maxwell511]

Why not? It seems to me that the colour of facial hair is as good a distinguishing mark as skin colour.

I agree.

Racial distinctions are funny in that they have no biological basis and they change arbitrarily.

I apparently belong to the same race as the English. My great great great great grandfather was of a different race to them.

 

[Nooj]

What would gravity be like on a planet that is shaped like a torus?

All I know is that it'd taste delicious.

 

[Nooj]

Arguably, a race is a distinct sub-group of human. I'm tempted to say 'breed' or 'sub-species', but they have horrible overtones. For example, white people are arguably a different breed to black people, given that there are distinct racial characteristics. Obviously it's not a perfect split, since people actually exist in a spectrum from whiter-than-white to blacker-than-black. But, like I said, discrimination would only be possible if there were characteristics people could discriminate against.

So a race is a sub-group of homo sapiens, and the thing that makes black people and white people two different races is that they have different amounts of melanin in their skin.

Do you think the Warlpiri people of Australia and the Shona living in Africa are the same race because they have black skin? Do you think Japanese and Spanish are the same race because they have white skin?

 

[AV1611VET]

All I know is that it'd taste delicious.

-- planet Dunkin' Doughnut:

 

[Wiccan_Child]

Why not? It seems to me that the colour of facial hair is as good a distinguishing mark as skin colour.

You'd have to ask those who endorse racial segregation. I daresay it's because white people where those who discriminated against black people, rather than blondes against brunettes.

 

[Wiccan_Child]

Polite dinner conversation? Stop being so British. I assure you that the peasants will not revolt. Although I am concerned about the American colonies.

Ah, they're just going through a phase. We have the biggest empire in the world! What could possible go wrong

 

[Wiccan_Child]

So a race is a sub-group of homo sapiens, and the thing that makes black people and white people two different races is that they have different amounts of melanin in their skin.

That's not what I said.

Do you think the Warlpiri people of Australia and the Shona living in Africa are the same race because they have black skin? Do you think Japanese and Spanish are the same race because they have white skin?

No and no.

 

[Wiccan_Child]

What would gravity be like on a planet that is shaped like a torus?

It'd be much the same as on a normal planet: you'd be pulled towards the surface. Even if you were on the inner 'ring', you'd still feel gravity pulling you 'down'. If a shell of matter, there's no gravity on the inside, interestingly enough.

 

[Tinker Grey]

But you would experience less gravity on the inner ring since there is mass "above" your head. This would apply to a degree on the upper surface--some offsetting mass (and hence gravity) would appear at various angles.

Depending on the size of the planet, these difference might not be discernible.

 

[Wiccan_Child]

But you would experience less gravity on the inner ring since there is mass "above" your head. This would apply to a degree on the upper surface--some offsetting mass (and hence gravity) would appear at various angles.

Depending on the size of the planet, these difference might not be discernible.

I would agree with you, but the shell theorem makes me wonder if that would indeed happen...

 

[Nooj]

You'd have to ask those who endorse racial segregation. I daresay it's because white people where those who discriminated against black people, rather than blondes against brunettes.

I meant something different. I mean why is black and white skin any more of a racial characteristc (that is, that defines one person as part of one race and another as part of another race) than different coloured hair.

That's not what I said.

Arguably, a race is a distinct sub-group of human. I'm tempted to say 'breed' or 'sub-species', but they have horrible overtones. For example, white people are arguably a different breed to black people, given that there are distinct racial characteristics. Obviously it's not a perfect split, since people actually exist in a spectrum from whiter-than-white to blacker-than-black.

What part of that did I get wrong? A distinct sub-group of human. White and black skin being a distinct racial characteristic, possibly the only relevant one, since you only mentioned the colour spectrum in your last sentence. I thought I restated it pretty well.

Please don't feel I'm attacking you. I'm interested in whether races have a biological basis, but everytime I look into it, I run into roadblocks. It's a politically charged area of science first of all, but I can't seem to find a good hypothesis of what race actually is. I've talked to people who I would categorise as racists, and while they flip-flop when I ask them what a race actually is, they usually don't stick to melanin differences as the most important thing. They instead point to IQ differences and 'cultural achievements' as proof that black people and white people are different.

 

[Tinker Grey]

I would agree with you, but the shell theorem makes me wonder if that would indeed happen...

I don't know what the shell theorem is. So my question to the physicist is: What is the shell theorem.

 

[AvalonXQ]

I don't know what the shell theorem is. So my question to the physicist is: What is the shell theorem.

When determining the force due to gravity on a point, if any of the mass being taken into account is in the form of a uniform spherical shell, then the contribution of gravity by that mass can be simplified:
1) If the point is within the spherical shell, the net force is zero.
2) If the point is outside the spherical shell, the net force is identical to that exerted by a point mass at the center of the shell that is the same as the total mass of the shell.
This allows us to greatly simplify gravity calculations involving large mostly-spherical bodies like planets.

 

[Tinker Grey]

When determining the force due to gravity on a point, if any of the mass being taken into account is in the form of a uniform spherical shell, then the contribution of gravity by that mass can be simplified:
1) If the point is within the spherical shell, the net force is zero.
2) If the point is outside the spherical shell, the net force is identical to that exerted by a point mass at the center of the shell that is the same as the total mass of the shell.
This allows us to greatly simplify gravity calculations involving large mostly-spherical bodies like planets.

Thanks.

And, welcome to the forum.

 

[AvalonXQ]

Happy to be here.
I'm a little disappointed that there are no active threads on relativity. That's my favorite physics topic.

 

[Wiccan_Child]

Happy to be here.
I'm a little disappointed that there are no active threads on relativity. That's my favorite physics topic.

Relativity? Excuse me while I run full speed into my barn with this ladder!

 

[AV1611VET]

Is it true that prokaryotes don't have telomeres?

 

[AvalonXQ]

Relativity? Excuse me while I run full speed into my barn with this ladder!

Are you referencing a thought experiment that demonstrates the necessity of the relativity of simultaneity? Or are you claiming that this creates a paradox that relativity cannot solve?