If gravity acts at the speed of light and not instantaneously

Why?

>If light only propagates at the speed of light then why aren't all the planets dark because they are never being shined on "directly"?

>>8625448
Planets are pulled - continuously - toward their sun, and thus orbit that sun. Orbital perturbations arise from attraction between planets.
What question/issue are you asking about?

>>8625533
If the sun is moving through space in a path that is not perfectly straight then all the bodies orbiting it will have a "lag" since they are being pulled toward a location behind and to the side of the sun at all times. The faster the sun in question is travelling the longer the lag. Does this lag have any measurable effect? It seems so counter intuitive that an orbit can be stable since the planet has to adjust to its suns own trajectory while also "keeping up" with it

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>>8625548
The forces are "instantaneous", it's the principles of a vector field.
Basically every single point of the universe "feels" the action of our sun, albeit of course with a diminishing effect. (precisely, the effect is proportional to the inverse of the square of the distance.)

Don't think of gravity as vectors travelling through space at the speed of light, think of it as a vector field.

>>8625553
Thanks Anon!

>>8625548
>it will have a "lag" since they are being pulled toward a location behind and to the side of the sun at all times

The speed of light is so much faster than the relative speeds of orbiting objects, there wouldn't be much lag, certainly not enough to disrupt the orbit.

How far could the sun move in 8 minutes relative to the earth? in 5 hours for Pluto?

>>8625448
Who said gravity is limited to the speed of light?

Gravity bends light. Gravity can be forced to turn at a 45 degree angle, but nothing physical (photons) can do this without stopping.

Only my own theory dealing with structural engineering. There are certainly some geeky science guys here I defer to in specifics though not in common sense.

>>8626079
Einstein did.

>what is general relativity?

>>8625448
Planets don't "drift" or get "pulled", they are continuously falling.

>>8625448
Your view of orbits is incorrect. You're assuming something like a yo-yo on a string.

>>8625553
>The forces are "instantaneous"
This is incorrect.

>>8625553
Completely incorrect. I guess this anon's never heard of gravity waves (which would be impossible to deserve as spacetime perturbations if they went from A to B instantaneously). As others have mentioned, there is a lag but the pull is continuous. A star one light year away takes roughly a year to tug on me, but at every moment I'll feel the previous tugs. You'd never notice this, though, as gravity and EM fall of sharply as distance (so can often be approximated as instantaneous even though that's super incorrect theoretically)

>>8626123
Only true for a 2 body system. Bet you're killing HS right now.

>>8625553
>every single point of the universe "feels" the action of our sun
this souns like some new age bullshit

>le we are all connected and shit
>electric field from my pubes are felt in the whole universe

>>8627139
well, depending on the size of the universe, and the age of the sun, that might be true

everything in the observable universe feels the gravity at least

>>8627153
does that feel even do anything

>>8625448
Because the waves are continuous
Sun doesn't send one gravitational wave and wait for it to reach to send another one (at least that's what I assumed you thought), it continuously sends waves

Or if what you're asking is that why gravitational waves aren't pulling planets to the previous locations, it's because it doesn't take that long for it to reach
http://image.gsfc.nasa.gov/poetry/venus/q89.html

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>>8627171
that feel does many things anon

>>8627083
Which is why I put quotations mark on it. It's a simplification, right, but at our scale it doesn't matter much.

If a firehose doesn't shoot water to its destination instantly, why can you ever hit moving targets?

>>8628214
Because cognition of the relative locations in timespace is necessary first?

Jesus Christ /sci, I am disappointed

all the responses in this thread so far are wrong or irrelevant

>>8625448

https://en.wikipedia.org/wiki/Speed_of_gravity#Aberration_of_field_direction_in_general_relativity.2C_for_a_weakly_accelerated_observer

The correct answer is that planets are attracted not towards the position of where the Sun was, but (almost) towards the position where the Sun is at the present, even tough the speed of light is finite

this only works if accelerations are very low, which is a very good approximation for our a solar system, but fails for example for quickly orbiting black holes, which do inspiral over time precisely because the speed of light is not instantaneous

>>8626079
Structural engineer here.

You're fucking dumb.

Thanks.

File: Screenshot_20170125-162301.jpg (277KB, 1374x898px) Image search: [Google]

277KB, 1374x898px

White circle is lightbeam
Black circle is mass before it recieved light
>light rotates and bends around mass trough reflection?

>>8629066
Brown = projection?
Red = energy