Is light matter or energy?

Question

I've heard that light is energy, but it moves through vacuums and is affected by gravity. All the other forms of energy (i.e. electrical, thermal) seem to based in matter, but light seems completely independent from it. What is light?

Answer 1

___The better question is to ask whether or not the categories "mass" and "energy" are absolute or absolutely mutually exclusive. The properties of light seem to lie somewhere in between. Some refer to a wave-particle "duality", but it might be better to talk of a wave-particle "ambiguity". Light may be better described as neither energy nor mass, but something in-between or encompassing both. How to deal with this matter is a philosophical question as much as a scientific question.
___Consider this, an old question in philosophy: Is the universe one thing or many things? If you answer "one thing", then all the distinctions and differences in the universe are illusions. If you answer "many things", then the connections in the universe are all illusions. Questions of quantity do not allow for ambiguous answers, and it would be hard to make sense of the answer, "well, sort of one thing, but also sort of many". But both unambiguous answers lead to absurd, skeptical conclusions.
___Consider this: by any usual proceedure of assigning properties to things, gravity is a property of all material things. Even Newton referred to it as such. But with respect to this one property, every material thing extends to infinity, and occupies the entire universe, though at different "densities" at different locations. This is a messy universe, so Newton stipulated that we treat gravity as a separate entity, an "invisible force" (a "thing" that is unlike other kinds of physical "things"). Treating it separately allowed him to figure out the math. But this stipulation, how are we to treat it when we talk about the way the universe really IS?
___Material objects are in some respects plural and distinct, and in other respects not-plural, but integrated in a universe that is in this respect "one thing".
The situation is more complicated than can be handled within the mechanics of the language of a "simple" question. The question "Is the universe one thing or many things?" asks for either "one thing" or "many things", and cannot handle the complexity of the answer.
___Now we can sort it out with a more complicated answer, like the "in this respect..." answers above, but then we are left with the problem of whether "this respect" is absolutely, unambiguously distinct from "that respect". Or put another way, whether "this property" is absolutely, unambiguously distinct from "that property". They may be conceptually distinct (color is distinct from mass or taste or solubility), but when has anyone ever been able to separate color from mass in a physical separation?

___Humans evolved in this world, and our senses evolved according to the requirements of getting food, etc, in this world. We and other animals "fortunately" evolved at a non-quantum scale, we evolved at a scale at which material bodies are relatively stable and at which molecular forces determine fixed boundaries for material solids. Our bodies are also made of molecules, and do not slip through the molecular boundaries of material solids. Further, at our scale, light reflects off of molecular boundaries, and we have eyes that are themselves molecular constructions that are affected by the light that hits them. And the spectrum of radiant energy that we see, just "happens" to be light of the wavelengths that reflect off of molecular boundaries of matter, and not the radiant energy that passes through them. (Otherwise, all solid things would be transparent or translucent with regard to some "colors".)
___And with respect to gravity, we don't experience it as an impenetrably-bounded thing, but a contextual element within which we can sense our orientation (balance).
Our senses simplify physical reality for us, and to some degree, disambiguate it for us. We only sense the distinct boundaries of things, and do not sense them as connected.
Though, if you want, you can spend a day imagining that everything you "pick up" is a part of the planet, whose elastic connection to the planet you are merely stretching, until you let go, as if it were connected by some slippery bungee cord to the earth's center of gravity. This conceiving would be as accurate as the usual one, but not very efficient in terms of getting things done.
___So don't be bamboozled by ambiguities like that of light. Our simple senses and minds can't comprehend all the complexity of the world when we take it on "all at once", so we break it into manageable, intelligible, unambiguous units. Accept the limits of human cognition, and accept that the world is complex, not just in terms of the accumulation of a lot of little details, but in terms of the connectedness that makes it seem "ambiguous" to us disambiguating beings.
___The world is as it is, and it doesn't have to conform to the requisites of our intelligibility for it to exist.

Answer 2

Modern science has dichotomy of understanding about many
aspects of nature. Light is one of them. I will tell you
something about light which most of you do not know.

Who were the first to calculate the velocity of light?
Rig Veda Bhashyam by Sayana Madhava gives the following
Sloka praising the Sun:

Yojanam sahasre dve, satadve, dvecha yojane
Ekena nimeshardhena kramamaana namosthuthe

One Yojana equals 15788.8 meters, and half of Nimesha
equals 8/75 fraction of a second. This gives the velocity
of light as 325940 km/s. We have to remember here that the
above value is an approximate one intended for easy
remembrance, like remembering the value of pi as 22/7. It
is better than the value 215000 km/s given by Danish
astronomer Ole Roemer in 1676. Having discovered so many
things, it is only logical to expect that our ancestors
must have used light as the standard for length
measurements; after all, modern science considers velocity
of light to be a Universal Constant! The word "kramamaana"
of the above Sloka has the hidden meaning of gradual
minute change.

Our ancient seers did not use light as a standard for
length measurement. Albert Einstain found that light
bends if it passes by the side of a large mass. How can
that "which bends" be called unchangeable? Every
created thing is subject to change by time; there is
nothing like an universal constant. And the velocity of
light is no exception to this law. The velocity of
light of our Sun was greater in Krita Yuga than what it
is now, even if it is by a small fraction. The velocity
of light is proportional to the stored energy in the
Sun or any other star. Modern science also accepts that
the Sun has lost a lot of energy over billions of
years. Then, there must be some other stars in the
universe which have greater stored energies than the
Sun, and are emitting light which is faster than that
of the Sun? Yes. Modern science will confirm this after
it develops more sophisticated equipment than what they
have at present.

Answer 3

Light is electromagnetic energy. You're quite right, that light differs from other forms of energy in existing in space without being attached to matter. Light is the basic form in which energy travels through space. Gravity does not affect light directly. Instead, gravity warps the space that light travels through. Light always travels in a straight line; it's just that "straight" in a gravitational field appears bent from outside that field.

Answer 4

Light is made up of photons which are little "packets" of energy. Light is affected by gravity because gravity is a "curve" in space-time. Light rays simply follow this curve just as matter would.

Answer 5

light is both matter & energy...

matter & energy is the same. both can neither be created or destroyed...only converted or changed to another form. everything is made up of atoms...atoms are the building blocks of energy/matter because both energy/matter are made up of atoms. you can split it (fission) or combine it (fusion)...either way, it's there & cannot be destroyed.

definition of matter = anything that has mass and/or occupies space.... light has mass and occupies space. yes...it occupies space...if you put anything solid in front of it, light will either be scattered (rough surface) or reflected (smooth surface) either way, light cannot occupy the same space taken by the solid object in front of it.

Answer 6

Human vision is utterly amazing in its ability to receive and process a wealth of information concerning levels of light intensity, colors, motion, and stereoscopic depth of field. However, as wonderful as our eyesight is, we are able to see only electromagnetic waves between 400 and 700 nanometers (4 to 7 x 10-9 meters) in wavelength. Young Isaac Newton in 1666 used a prism to break visible white light down into the rainbow colors of the spectrum giving impetus to the development of what is now the vast science of optics. Discovery of the wave-nature of light soon led to the realization that our universe is permeated with electromagnetic waves ranging in wavelength over at least 16 orders of magnitude--from ultra low frequency radio waves which are tens of kilometers in wavelength to cosmic rays with wave crests and troughs only a millionth of a millionth (10-12) meter apart. Just in our century science has quickly extended the range of the eye for exploration purposes. Many different kinds of electronic sensing instruments now tell us vastly more about the cosmos than our eyes alone can tell us directly.




Light from the sun arrives at the top of the earth's atmosphere at a power level of about one kilowatt per square meter. It is this heat and light from a modest star (surface temperature only 5500 degrees C), that all life-processes on earth are ultimately driven. Without the sun's constant energy input our planet would quickly radiate away its latent heat and freeze us and everything else very very solid in short order.

Heat and light from the sun are obvious, but we are unaware of cosmic rays penetrating our bodies at the rate of perhaps 10 per second. Nor do we realize that radio and television signals from a hundred stations fill our living rooms. Many of these "rays" pass through our bodies unimpeded. Light waves, radio waves, heat signals, X-rays, and the like, are electromagnetic (EM) radiation all forms of which can transmit energy and carry useful information even across vast reaches of "empty" space. The signal speed of EM waves ranges upwards to a maximum value which is the current speed of light, ~3 x 108 meters/sec.

In this century has also come the realization that we can equally well describe light and other EM radiation as if it were corpuscular in nature. EM radiation is a result of moving electrical charges (currents) and all forms of EM radiation can be described mathematically as consisting of streaming photons. Each photon constituting a "particle" of light has an energy equal to Planck's constant times the speed of light divided by the wavelength. (Photons are very small, yet the human eye is sufficiently sensitive that we can sometimes detect even a single light photon with dark-adapted eyes). Whether one uses a wave model or a particle model for light is largely a matter of convenience for the physicist. The concept of "wave-particle duality" is well established by experimental evidence and the excellent models of Quantum Mechanics

Answer 7

Light is energy. If it were matter, it would have mass.

Answer 8

light is energy. without light energy there will be no electricity and also your telescope would not work.

Answer 9

Go with kdesky3's answer. He da man..!