Light, Mass and Black Holes

[Uzzy]

This question came up, in all things, during a Philosophy lesson I was in earlier today. We were discussing the nature of immaterial substances (i.e. Substances without mass) and how they couldn't affect the world. This was in relation to Mind/Body duality, specifically the 'Mind'. Anyway, I was instantly reminded of how Black Holes affect light. Light, of course, has no mass, but it clearly affects the world and is affected by things like Black Holes.

So I'm curious. How can one immaterial substance, light, affect the world and be affected by the world, yet it's argued that another immaterial substance, the mind/soul/whatever, can't affect the world. How exactly does light actually affect the world? Or am I making some fundamental mistake in how light works?

[RecoveringYuppy]

What makes you think your mind is immaterial?

Don't see any fundamental mistakes in your statements about light though.

[Fnord]

How can one immaterial substance, light, affect the world and be affected by the world, yet it's argued that another immaterial substance, the mind/soul/whatever, can't affect the world. How exactly does light actually affect the world? Or am I making some fundamental mistake in how light works?

First, light and matter, while not equal, are equivalent. You may have heard of the famous "E equals M C squared" formula. This only states that a certain amount of matter, when its mass is multiplied by the speed of light, and then multiplied again by the speed of light, will be equivalent to a certain amount of energy measured in Ergs.

(Physics Nazis, please correct.)

Light is part of the material world, deriving it's emitted wavelength from state changes in matter, and imparting state changes in matter by allowing its wavelength to be absorbed by matter.

Fundamental mistakes? Probably ... any good college textbooks will set you straight.

As for asking how the immaterial world affects the material world, only God knows for certain, and even that concept is in dispute.

[Tubbythin]

First, light and matter, while not equal, are equivalent. You may have heard of the famous "E equals M C squared" formula. This only states that a certain amount of matter, when its mass is multiplied by the speed of light, and then multiplied again by the speed of light, will be equivalent to a certain amount of energy measured in Ergs.

(Physics Nazis, please correct.)


Well in SI units, mass is in kilograms and c in metres per second giving E in Joules. I think your answer is correct for cgs.

[Uzzy]

What makes you think your mind is immaterial?

I personally don't. I'm just trying to understand the arguments around it better. It was mentioned in the discussion about Mind/Body dualism that the Mind, in Rene Descartes view, was an immaterial substance. One of the counter arguments to that was immaterial substances couldn't interact with material substances, which made me think of Light and particularly black holes. I did ask my Philosophy teacher about this at the end of the class, but physics isn't really his strong suit. So I figured I'd ask here.

Thanks for your answer Fnord. I'll give it a proper look when it's not past midnight. :)

[gnome]

An "immaterial substance" seems to me to be a contradiction in terms.

But the mind does manifest physically in the form of neurons firing in the brain. I think cause and effect are a bit confused here. Does the mind cause the neurons to fire? Or do the neurons firing create the mind? I'm inclined to believe the latter.

[fuelair]

Mind is a function of the action of chemicals and electrical impulses in a mass of tissue. The function is not describable in a material way as it is not material. Do not confuse philosophy with physics or physiology - they are related in a vague way but they are vastrly different things. Philosophy is a function of the immaterial mind. Physics/chemistry(a subset of physics) and physiology (also a subset of physics)allow us to do philosophy.

[godless dave]

Light isn't immaterial. It's massless, but that doesn't mean it's immaterial.

[blutoski]

Light, of course, has no mass, but it clearly affects the world and is affected by things like Black Holes.

I think Fnord's explanation was almost entirely complete, but just to clarify: energy and mass are interchangeable, and both are material measurements. A photon is attracted to mass gravitationally because its energy has a mass equivalent - more energetic photons have a higher mass equivalence. This is also why photons also have momentum proportional to their energy value and can 'push' things.

To be frank, I predict you will have trouble with this approach because it sounds like you're destined for an argument about the meaning of words, which unfortunately is very characteristic of discussions about consciousness.

[sol invictus]

Shadows have no mass or energy, and yet they affect the world.

They can also move faster than the speed of light.

[blutoski]

Shadows have no mass or energy, and yet they affect the world.

They can also move faster than the speed of light.

Oh, absolutely, and that's the risk when you get into arguments about terminology involving materialism, consciousness, &c.

My favourite is: "My attention was in the Andromeda Galaxy, then a moment later it was in the Milky Way Galaxy. My attention moved faster than light; therefore, things can move faster than light; therefore GRT is wrong; qed."

Light is not immaterial the same way that my attention is immaterial.