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/sci/ - Science & Math

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5646675 No.5646675 [Reply] [Original]

Does light have a weight?

>> No.5646678

>>5646675

it has a relativistic mass that's affected by gravity, if that's what you're asking

>> No.5646685

>>5646678
a yes or no would suffice you nerd

>> No.5646692

>>5646685

it doesn't have a weight like you or i do, but it does have a weight, yes

>> No.5646696

>>5646692
ok thanks.
sorry for calling you nerd

>> No.5646715

Does the sun get lighter over time?

>> No.5646749

>>5646715
Yes

>> No.5646756

It has momentum.

>> No.5646823

>>5646675
E=MC^2

Question answered

>> No.5646843

but does weight even have a light?

>> No.5646850

it has weight when affected by gravity, it has mass either way

>> No.5646867

Not OP.

Is anything not affected by gravity?

>> No.5646869

Light leaving the Sun has to weight about 8 minutes to reach Earth.

>> No.5646871

>>5646749
Is that the reason it grows in size?

>> No.5646873

>>5646871
yes

>> No.5646885

>>5646867
Electromagnetism maybe? Just guessing.

>> No.5646887

It if it didn't have a mass it wouldn't get trapped in a black hole would it?

>> No.5646889

>>5646885
Maybe, but I wouldn't be surprised if spacetime curvature from gravity affects them as well.

>> No.5646890

>>5646675
Not in basic Newtonian mechanics. Yes in more up-to-date theories, which contain more complicated definitions of mass.

>> No.5646896

>>5646867
What about time?

I don't reall yknow alot about all this stuff.

>> No.5646898

>>5646873
So, if there isn't enough gravitiy to contain the suns internal expension it pops like a balloon? But why do only bigger stars explode?

>> No.5646900

>>5646896
Time is effected by both gravity and velocity

>> No.5646901

Let me start answering by clarifying one thing.

Weight is the result of a gravitational force acting on an object. So say something has a mass of 1kg, And it's being pulled into the earth at a rate of 9.81 <span class="math"> ms^-2 [/spoiler] then it would have a weight of 9.81 Newtons.

Mass is simply a measure of how much "Stuff" there is in an atom, or group of atoms. So 1kg of iron can have no weight in outer space.

Mass doesn't change, no matter where you go.

Now that we have that little mass/weight thing out of the way let me start by telling you, Light has no mass. None at all. Yet it is effected by gravity!

We can see this by light being bent by the sun/black holes/ large celestial body's. So light IS effected by the curvature in space time.

It also depends on what theory you're looking at, if you apply a wave model then it almost seams silly to think that a wave can have mass.

But if you look at a particle model and take into consideration Einsteins famous <span class="math"> E = mc^2 [/spoiler] then in theory they can have relativistic mass.

So do photons have weight?

We aren't sure.

>> No.5646902

>>5646898
Because you touch yourself at night

>> No.5646906

>>5646900
In what way is it affected by gravity?

>> No.5646907

>>5646901
I appreciate it.

>> No.5646908

>>5646906
Isn't velocity some sort of gravity?

>> No.5646915

>>5646908
But then why would it be affected by gravity and velocity if it's both the same thing?

>> No.5646918

>>5646915
I'm not sure if it's the same thing, I'm just thinking velocity acts like gravity because of the laws of motion.

>> No.5646924

>>5646906
Time flows slower inside a gravitational field, or maybe faster I don't know.

>> No.5646932

>>5646930
Whoops messed up on the greentext

>> No.5646930

>>5646924
I've found the answer i think

>Einstein also suggested that space-time wasn't flat, but curved or "warped" by the existence of matter and energy. Large bodies in space-time, like the Earth, aren't just floating in orbit. Instead, imagine an apple resting on a stretched out blanket -- the weight of the apple warps the sheet. If the Earth is an apple, then we can imagine the Earth's blanket as space-time.

This means that someone moving through space-time will experience it differently at various points. Time will actually appear to move slower near massive objects, because space-time is warped by the weight. These predictions have actually been proven. In 1962, scientists placed two atomic clocks at the bottom and top of a water tower. The clock at the bottom, the one closer to the massive center of the Earth, was running slower than the clock at the top. Einstein called this phenomenon time dilation.

>> No.5646934

>>5646918
no

>> No.5646935

>>5646924
But gravity is everywhere, and doesn't it essentially have an infinite range? What would happen to time if gravity wasn't there?

>> No.5646933

>>5646915
gravity acts to slow the passing of time, and velocity acts to speed it up
http://en.wikipedia.org/wiki/Time_dilation

>> No.5646942

>>5646934
As a rocket acclerates you're pressed into the seat. Isn't that some sort of gravitiy?

>> No.5646943

>>5646935
Then time goes by with the speed it traveling by? I don't know just a guess

>> No.5646949

>>5646942
that's inertia. it's not an attractive force arising from mass

>> No.5646972

>>5646678
Nobody uses the term relativistic mass anymore. They just use mass, of which a photon has none.
Weight, in general relativity, is taken to mean 'effects on motion due to gravity', in which case light has weight.
>>5646885
>>5646889
Light IS electromagnetism. Photons carry electromagnetic force.

>> No.5646991

>>5646942
That's the basis for the equivalence principle in GR

>> No.5647142

>>5646949

but, how can you tell the difference?

>> No.5647193

Does dark have a weight?

>> No.5647201

>>5647193
Defines darkness.

>> No.5647216

>>5647142
You can't. Differentiating between inertia and gravity is one of the unsolved problems of physics.

>> No.5647275

>>5646869
I'm just here to appreciate this comment.

>> No.5647286

>>5647142
You shine a flashlight at the wall; If you're in a gravitational field, the curve of the photon due to gravity will be very slight; but if the perceived force is due to you accelerating, then the light will appear to accelerate in the opposite direction of the force (due to the speed of light being so goddamn fast, this will also appear very slight, but will be more pronounced than the gravitational curve. You'll still need a pretty amazing microscope to tell, but there's a difference)

>> No.5647287

>>5647216
>unsolved problems of physics
wat

>> No.5647292

>>5647286
nope

>> No.5647300

>>5647287

not? what's the difference between the two mass components, and what causes them to correlate?

>> No.5647303

>>5647216
Well, this might sound stupid, but couldn't gravity just be inertia happening in a higher dimension? If that makes sense.

>> No.5647307

>>5647292
What? It's the truth.

>> No.5647313

>>5647300
thats not what you said in >>5647216

>> No.5647316

>>5647307
no, its impossible to distinguish between the 2.

>> No.5647323

>>5647216
Practically speaking, at least; gravity is a radial force, while acceleration is vector. If you drop two similar objects at different points under gravitational pull, they should each fall in very slightly different directions (as each is offset from the source of the force differently and heads toward the center) If you're in an accellerating vehicle, doing the same will lead to both 'falling' paralell.

You could also drop said balls at the same spot in different heights. In gravity, the initial acceleration will differ between the two (due to force depending on distance), whereas in an accelerating vehicle the observed acceleration in both objects will be the same. Of course, this doesn't work if you're limiting tests to one single point, but practically speaking that's impossible anyway.

>> No.5647326

>>5647316
>I clearly outline how to distinguish between the two
>BUT IT'S IMPOSSIBLE BECAUSE I THINK I'M RIGHT

Throw some actual facts that disprove what I said and then we'll talk, buddy.

>> No.5647333

>>5647326
well, general relativity is derived from the fact that you cant tell the 2 apart, and its been tested a lot, do you really need any more? and where did you actually show that scenario can actually tel,l it apart? you didnt.

>> No.5647338

>>5647333
That isn't what general relativity is derived from, buddy, and I clearly stated that the difference in the bend of the light would be how you would tell whether you were in a gravitational field or accelerating.

>> No.5647345

>>5647338
>That isn't what general relativity is derived from
lol, do you actually know any GR? pointcare invariance along with equivalence can be used to derive all of general relativity.

>> No.5647353

>>5647323
> In gravity, the initial acceleration will differ between the two (due to force depending on distance),
that wont work in a uniform gravitational field.