/sci/ - Science & Math

[Anonymous No.3827986]

If light has no mass, how can it be affected by gravity?

srs question, thanks

[Anonymous No.3828007]

Gravity bends waves, too (See: Light refracting off of large bodies of water, pun intended) as well as particles. When there's enough gravity like the sun the light of the sun is bent around it because it draws the waves in which the light travels through. It would take a supermassive star to affect the light that much though.

[Anonymous No.3828014]

light follows the curvature of space as if it were any other medium
odd thing is spacetime isn't to be called a medium

[Anonymous No.3828019]

Light travels along geodesics, the shape of geodesics is determined by the energy-momentum in the universe.

[Anonymous No.3828021]

>>3827986
It doesn't.
Gravity warps space.

[Anonymous No.3828026]

Random thought: What if the mass of a star was exactly the right amount that light hitting it at a specific angle would get bent 360 degees around the star? Would that light orbit the star? How would it look to an observer?

[Anonymous No.3828031]

Okay that kinda makes sense to me I guess, but then I don't get how that fits in with what I'm studying at the moment really.. we're doing gravitational fields. is curvature of spacetime another way of modelling a gravitational field, or is it a consequence of a gravitational field, or is a gravitational field defined as the curvature of spacetime? I just don't get it haha.. and how do you calculate the effect of gravity upon light? Use its relativistic mass, or what? Sorry for all the questions!

[Anonymous No.3828069]

halp!

[Anonymous No.3828359]

well i kinda has mass

it has energy right?

using E=mc^2 can be used to give light a mass depending on it's wavelength, much like it has momentum


however it's m_0 is still 0

[Anonymous No.3828373]

>>3828021
>implying that converting Earth into electromagnetic radiation would suddenly cause its gravitation to cease to exist.

The implications of that are pretty mindblowing. I thought matter was just a wave function anyway?

[Anonymous No.3828384]

It has a mass, although it's so ridiculously small it's neglegible. It's 10 orders of magnitude less than the mass of a proton. There's no such thing as "no mass", there's always something drawn to something else, although the smaller the object is in comparison with the comparative object, the less of an affect.

[Anonymous No.3828390]

>>3828031
The current theory (1916 to present) is that gravity warps space. As for calculating it, what you want to look into is what's called a gravitational lens
http://en.wikipedia.org/wiki/Gravitational_lens
The angle formula is there and I assume it works, but I didn't read squat because you can do that for yourself.

>>3828019
said it very succinctly.

[Anonymous No.3828393]

Fucking Miracles

[Anonymous No.3828411]

>>3828359
>>3828384
No. Photons have momentum but they do not have mass, the momentum operator at relativistic speeds is not simply mv.

>>3828373
Not just matter but all forms of energy make up the stress energy tensor which is what causes the curvature of space. So no, it's gravitation would not cease.

>>3828026
Yes you could get a photon of the right energy to "orbit" a star (or any other object of the proper mass/position) however that orbit would be incredibly unstable, the photon would be pushed off by quantum randomness or other EM radiation long before it revolved completely. As for what it "looks" like think about the question. The photon itself is in a closed circular path so you could not observe it directly (i.e. see it) and if you bounce another photon off of it in order to "see" it the way we do with radio telescopes you have imparted more than enough energy to decay the orbit, no matter how low frequency waves you use.

[Anonymous No.3828422]

If neutrally charged liquid travels in a charged pipe, how come it can be deflected by another source of charge?

It pulls the medium of travel, not the traveller in the medium.

[Anonymous No.3828613]

>stress energy tensor .. causes the curvature of space

so the description causes what it seeks to describe

science, the magical approach.

[Anonymous No.3828619]

>>3828411
>pushed off by quantum randomness