Posts: 3676
Threads: 354
Joined: April 12, 2015
Reputation:
42
How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 1:46 pm
This is the $50 million question
If gravity only affects objects that have mass and photons are massless, why does light curve around a planet or get trapped in a black hole?
The god who allows children to be raped out of respect for the free will choice of the rapist, but punishes gay men for engaging in mutually consensual sex couldn't possibly be responsible for an intelligently designed universe.
I may defend your right to free speech, but i won't help you pass out flyers.
Those who can make you believe absurdities, can make you commit atrocities.
--Voltaire
Nietzsche isn't dead. How do I know he lives? He lives in my mind.
Posts: 2412
Threads: 5
Joined: January 3, 2018
Reputation:
22
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 1:50 pm
Gravity does affect things with no mass in general relativity. it does so by curving spacetime, which affects anything, whether it has a mass or not.
Also, the converse is true. Anything with energy produces gravity, whether it has mass or not.
Posts: 3260
Threads: 179
Joined: April 29, 2012
Reputation:
24
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 1:51 pm
Gravity does not affect light directly, but it does bend the spce-time that the light is moving in
The meek shall inherit the Earth, the rest of us will fly to the stars.
Never underestimate the power of very stupid people in large groups
Arguing with an engineer is like wrestling with a pig in mud ..... after a while you realise that the pig likes it!
Posts: 2412
Threads: 5
Joined: January 3, 2018
Reputation:
22
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 1:52 pm
(March 2, 2018 at 1:51 pm)zebo-the-fat Wrote: Gravity does not affect light directly, but it does bend the spce-time that the light is moving in
In that sense, it doesn't affect *anything* directly. The reason planets orbit the sun is because of the curvature of spacetime the sun produces. It is that curvature that makes the planets move the way they do.
Posts: 19789
Threads: 57
Joined: September 24, 2010
Reputation:
85
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 1:57 pm
(This post was last modified: March 2, 2018 at 2:04 pm by Anomalocaris.)
(March 2, 2018 at 1:46 pm)Rhondazvous Wrote: This is the $50 million question
If gravity only affects objects that have mass and photons are massless, why does light curve around a planet or get trapped in a black hole?
Energy and mass are interchangeable directly, and for the purpose of gravity. Photons have energy, E=MC^2, hence photons have equivalent of mass.
Think of it this way, by E=MC^2, all forms of energy have equivalent of mass, and therefore are both affected by gravity, and exert their own gravity. If global warming heat the earth up, the gravity of the earth actually increase because the added kenetic energy of the molecules makes the earth slightly more massive.
If you annihilate a mass particle with its anti-partlcle, the mass of those two particles will convert into photons. If you somehow trap the photons so they don’t speed away, you will find the gravity well around the these photons remains exactly the same as before the annihilation.
Posts: 2886
Threads: 132
Joined: May 8, 2011
Reputation:
31
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 2:02 pm
General relativity: Mass warps spacetime. Photons travel in spacetime so to an outside observer they follow a warped path when passing an object with mass.
Special relativity: E=MC2. Photons have relative mass even if they don't have resting mass.
Save a life. Adopt a greyhound.
Posts: 2412
Threads: 5
Joined: January 3, 2018
Reputation:
22
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 2:06 pm
(March 2, 2018 at 1:57 pm)Anomalocaris Wrote: (March 2, 2018 at 1:46 pm)Rhondazvous Wrote: This is the $50 million question
If gravity only affects objects that have mass and photons are massless, why does light curve around a planet or get trapped in a black hole?
Photons have energy, E=MC^2, hence photons have equivalent of mass.
Think of it this way, by E=MC^2, all forms of energy have equivalent of mass, and therefore are both affected by gravity, and exert their own gravity. If global warming heat the earth up, the gravity of the earth actually increase because the added kenetic energy of the molecules makes the earth slightly more massive.
One aspect of this that is a bit strange is that massless particles, like the photon, actually move along a different path (a null path) than a massive particle of going very close to the speed of light would. The deflection of the light is *double* what would be expected from a naive equivalence between the mass and energy. that was actually one of the distinguishing experiments differentiating special and general relativity when applied to gravity.
Posts: 3676
Threads: 354
Joined: April 12, 2015
Reputation:
42
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 2:51 pm
(This post was last modified: March 2, 2018 at 3:06 pm by Rhondazvous.)
(March 2, 2018 at 1:57 pm)Anomalocaris Wrote: (March 2, 2018 at 1:46 pm)Rhondazvous Wrote: This is the $50 million question
If gravity only affects objects that have mass and photons are massless, why does light curve around a planet or get trapped in a black hole?
Energy and mass are interchangeable directly, and for the purpose of gravity. Photons have energy, E=MC^2, hence photons have equivalent of mass.
Think of it this way, by E=MC^2, all forms of energy have equivalent of mass, and therefore are both affected by gravity, and exert their own gravity. If global warming heat the earth up, the gravity of the earth actually increase because the added kenetic energy of the molecules makes the earth slightly more massive.
If you annihilate a mass particle with its anti-partlcle, the mass of those two particles will convert into photons. If you somehow trap the photons so they don’t speed away, you will find the gravity well around the these photons remains exactly the same as before the annihilation.
This explains a lot, with one nagging caveat. Photons mediate the electromagnetic field. While the mediator of the gravitational field has not yet been discovered. So we have mediators in two separate fields affecting one another. If photons create gravity, then the electromagnetic field is also the mediator for the gravitational field. Is it possible there is no gravitational field? Like heat, maybe gravity is just a property of matter or a property of spacetime when massive or energy particles come close.
(March 2, 2018 at 2:02 pm)popeyespappy Wrote: General relativity: Mass warps spacetime. Photons travel in spacetime so to an outside observer they follow a warped path when passing an object with mass.
Special relativity: E=MC2. Photons have relative mass even if they don't have resting mass. And this explains why although photons existed before recombination, there was no matter and therefore no gravity to counter the dark energy pushing everything apart. only after things got so apart that they lost energy was the strong force able to bring quanta together to form atoms and then large bodies with measurable gravity.
The god who allows children to be raped out of respect for the free will choice of the rapist, but punishes gay men for engaging in mutually consensual sex couldn't possibly be responsible for an intelligently designed universe.
I may defend your right to free speech, but i won't help you pass out flyers.
Those who can make you believe absurdities, can make you commit atrocities.
--Voltaire
Nietzsche isn't dead. How do I know he lives? He lives in my mind.
Posts: 67223
Threads: 140
Joined: June 28, 2011
Reputation:
162
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 3:07 pm
(This post was last modified: March 2, 2018 at 3:12 pm by The Grand Nudger.)
Quote:Is it possible there is no gravitational field?
No, even within the context of your proposal you're simply wondering whether or not some other x might effect that grav field...there's a grav field in that proposition all the same. Regardless of what gravity is a property of, gravity, then, would exist as a property of that x.
To demonstrate this in another context. We don't know whether or not there are gravitons, a hypothetical fundamental particle in qft that mediates the force of gravitation. We've never identified one. Suppose there aren't. There's still gravity, there are still grav fields.
I am the Infantry. I am my country’s strength in war, her deterrent in peace. I am the heart of the fight… wherever, whenever. I carry America’s faith and honor against her enemies. I am the Queen of Battle. I am what my country expects me to be, the best trained Soldier in the world. In the race for victory, I am swift, determined, and courageous, armed with a fierce will to win. Never will I fail my country’s trust. Always I fight on…through the foe, to the objective, to triumph overall. If necessary, I will fight to my death. By my steadfast courage, I have won more than 200 years of freedom. I yield not to weakness, to hunger, to cowardice, to fatigue, to superior odds, For I am mentally tough, physically strong, and morally straight. I forsake not, my country, my mission, my comrades, my sacred duty. I am relentless. I am always there, now and forever. I AM THE INFANTRY! FOLLOW ME!
Posts: 19789
Threads: 57
Joined: September 24, 2010
Reputation:
85
RE: How Cn Gravity Affect Light When Light Has No Mass?
March 2, 2018 at 3:53 pm
(This post was last modified: March 2, 2018 at 3:58 pm by Anomalocaris.)
(March 2, 2018 at 2:51 pm)Rhondazvous Wrote: And this explains why although photons existed before recombination, there was no matter and therefore no gravity to counter the dark energy pushing everything apart. only after things got so apart that they lost energy was the strong force able to bring quanta together to form atoms and then large bodies with measurable gravity.
I don’t believe that is accurate for two reasons:
1. Recombination refers to electrons pairing up with protons. They existed separately as ionized plasma before. So there were matter before recombination, just not electrically neutral matter.
2. Even if there were not electrons and protons, If there were photons, there were gravity. Gravity is an artifact of energy in all forms, not just in matter form. If I am not mistaken, most of the gravity of normal matter is not from the rest mass of the particles with rest mass, but from binding energy that holds These particles together.
|