How much does light weigh?

Question

I've heard that in a black hole, light that passes the event horizon is trapped forever in a black hole. Gravity apparently is so strong that light doesn't have the velocity to escape. Does this mean that light has mass? if so, If you took all of the light emitted by the sun in 1 day how much would it weigh?

Answer 1

Technically, light does not possess weight. The reason light cannot escape the event horizon is because of the effect that the mass of the black hole has on space.

To use a reference made by Stephen Hawking, think of the space around an object as a stretched out balloon (so that it forms more of a plane... if you like you could skip this reference and think of the surface of a trampoline... same concept). Whenever you place an object into the balloon, it will flex downward and form a cup around the object. As you place heavier objects onto the balloon, the farther the balloon will flex downward around the object.

Now think of a black hole as an extremely massive object. We'll say that the black hole is a bowling ball and the balloon is very thinly stretched. When you place the bowling ball into the balloon, the weight of the bowling ball will flex so far downwards that it will do two things. First, it will turn the balloon inside out, so that it doesn't form a cup around the object, but will actually form around the object entirely since the balloon can't hold the weight of the bowling ball. Second of all, it will turn the balloon inside out so much that the balloon will break (this is why some theoretical physicists believe that black holes can help us reach other places in the universe or perhaps different times or even different universes).

Now with this being said, let's think of a particle of light as a marble rolling along the surface of the balloon. As for most objects, the velocity of the marble will carry the marble past the object, but it will bend slightly with the cup that is formed around the object. Now think of the marble being rolled into the "bottomless pit" formed by the bowling ball. The marble will have no choice but to fall into the "bottomless pit" and will not be able to come out on the other side.

This is a very good explanation of how a black hole effects the space around it (bowling ball on a thinly stretched balloon) and also of how light is captured by the event horizon (marble rolling into a "bottomless pit"). After explaining this, I want you to know that the light isn't "pulled" into the black hole by gravity, but instead, the path that the light travels is affected. Essentially, the light "falls" into the event horizon and cannot escape because the weight of the black hole turns space "inside-out". The event horizon is that point where space is basically turned "inside-out".

Hope the analogies were useful. Technically, you could still figure out how much the light would weigh since there would be a specific amount of energy associated with the light emitted by the sun. Figure that out and then use E=MC^2. Now that I've written a novel, I'll press enter.

Answer 2

A black hole is initially created with matter, a large star or collection of them. Nobody knows if the light that enters a black hole adds to the mass. we can only assume and write theories.

Remember, mass is energy and energy is mass. E = mc^2

The luminousity of the sun is 4 x 10^26 W or J/s

Using E = Mc^2 you can convert this into Mass per second:

Mass = (4 x 10^26)/(3 x 10^8)^2 = 4.4 x 10^9 kg

So... a lot of mass is burned out in the sun per second.


EDIT: Light is definatly not a stream of electrons... light can be described as packets of energy or photons which have no mass in that form. Mass connot travel at the speed of light. Energy can.

Answer 3

Yes light has mass. It is a travelling stream of electrons or charged particles and electrons have mass. Einstein found the formula E=mc^2 which relates energy to mass. Thus simply find out how much energy is released by the sun (as light) in 1 day and divide by the speed of light squared to determine it's mass. The trouble is in finding how much of the sun's energy is released as light and not infared or UV radiation.

Thank you, Good day.

Answer 4

Light does not have real mass, IE it does not weigh anything.


However, light has relative mass, thus gravity can effect light. Relative mass simply means that it has energy, and from E=mc^2 we know that if it has energy, it has mass; however, it has mass in the form of energy.

An odd concept, but simple if you think about it for a bit. I mean, if it had real weight you'd be getting hit by it! ouch!

Answer 5

Light has no mass. Gravity effects light because, according to Einstein, it causes a curvature of space. This means that gravity can effect a zero mass object, like a photon of light.

Answer 6

There is no scientific answer to that question. It is still a fundamental topic that we don't understand about light. It has momentum, but it doesn't appear to have mass. It appears to be mass-less, but it is still tugged by gravity.

Discover that and win a Nobel prize.

Answer 7

Light has no mass ,if it had a minute mass the kinetic energy would knock u down.

Answer 8

light is massless.
but it has momentum though..
kinda weird...
but the momentum is due to its very very very very fast speed...
i don't know the physical laws that govern in a black hole...
black is an absorber of light...so i guess light 'can't escape'...

Answer 9

A couple of pounds of light would be tons of it!

Answer 10

no light does not have mass