10 Trillion Electron Volts

I've never understood how light can have energy. Speed is constant and mass is zero. Or did they change it?

Mike.

Rest mass is 0, but relativistic mass applies :



Regards, Dana.

Pommie said:

I've never understood how light can have energy. Speed is constant and mass is zero. Or did they change it?

Mike.

Click to expand...

Have you never heard of 'light sails' - a common SciFi technology, which is based on real facts.

Pommie said:

I've never understood how light can have energy. Speed is constant and mass is zero. Or did they change it?

Click to expand...

Energy has equivalent mass; the inverse of E = M C^2

danadak said:

Rest mass is 0, but relativistic mass applies :

What is the mass of a photon?

Regards, Dana.

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What do you multiply zero by to get the relativistic mass?

Mike.

To all, to answer my own question, yes, they changed it.

Mike.

Pommie said:

I've never understood how light can have energy. Speed is constant and mass is zero. Or did they change it?

Mike.

Click to expand...

There must be energy in there of some sort, or solar panels wouldn't work.

There's no mass, but there is momentum. That momentum is energy. That linear momentum is converted to angular momentum when it interacts with mass. This tilts a proportion of particles in the mass. A collective field. This rings(vibrates) the mass. And we measure that ring as a wave. A frequency. But the "wave" that hits the matter is NOT a wave. It's a series of discrete hammers.

BR-549 said:

There's no mass

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So how does something without mass have energy? How can 0.5MV^2 (cant do symbols in ubuntu) equal anything but zero if M=0? As I said, they must have changed it since I was at school. And I vaguely remember, something travelling at the speed of light has infinite mass. Time for coffee.

Mike.

One photon of visible light contains about 10-19 Joules.

M = E / C^2

The equivalent mass of the photon, due to its energy, is around 1.1 x 10^-32 grams.
(If my brain is working right, half asleep..)


Reference - see the "Photons" section:

Does sunlight have mass? It powers life and climate. Mass is not required for energy. Only EM field density is required. Propagated EM field density has perpendicular gradients. Charge particles which make mass also has perpendicular EM fields around them. These fields socialize and nest with the other fields of mass.

When an EM fields enters from without, those fields interact and apply two torques or tilts on a portion of those charges. If that proportion number is large enough, both the M and the E of the charges, will line up and create a larger collective field. If there is free charge present, current will flow. If not, an net EM field is still created and can be measured.

And generates heat in the mass. But only half the heat generated comes from the light. The other half comes from the mass reacting to it.

Pommie said:

So how does something without mass have energy?

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Ask your solar panel how it is able to convert that mass-less alight to energy. If your solar panel won't answer, as the oak tree.

BR-549 said:

Mass is not required for energy.

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You cannot have one without the other!

That's again where E = M C^2 comes in.

Energy has equivalent mass; that's how the mass of an object increases with acceleration - the addition of kinetic energy.

If you write a program loop to continuously increment the velocity of an object & calculate the energy used for that acceleration, adding that in to the original mass at each pass, you will get a numeric overflow as the velocity reaches near 300,000,000 metres per second (at which point the mass sum would be infinite, if the computer could handle it).

The added mass due to the stored kinetic energy is the reason for relativistic mass increase.

Plus, light is directly affected by gravity, though the effect is only visibly around massive objects such as stars or larger - gravitational lensing.

A real physics site's take on it -

In short, the special theory of relativity predicts that photons do not have mass simply because they travel at the speed of light.

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Based on outdated ideas, from a quick look.

There was a massive gap in the speed of light <> infinite mass concept when Einstein came up with it; it's all based in classical physics which in turn is based on objects (masses) only being moved or accelerated by external means.

As I noted in #14, relativistic mass is added by the action of external acceleration, adding energy and equivalent mass; projectile or ballistic physics. That now appears to be a generally accepted explanation.

A photon is never accelerated, it is created with it's natural velocity.

Escape velocity is a good example or the classical physics omissions; nothing being able to leave a gravity well without reaching that velocity - a purely ballistic physics concept.
It does not apply to any vehicle with continuous propulsion that can exceed the attraction of gravity for a sufficient time. There is nothing yet that could work like that in earth gravity, but possibly such as an ion drive for low gravity moons or asteroids etc.

And the never-talked-about one - If relativistic mass increase is due to external energy input, a self-contained spacecraft can never experience any mass increase at any velocity, as there is no external energy input.


Remember that the scientific community has phenomenal inertia against acceptance of change to existing standards, even when the existing explanations of a concept or phenomena are blatantly incorrect - probably the craziest example being that it took near enough a hundred years for the explanation of how aircraft fly to be updated from it purely relying on the greater upper curvature of the wings meaning a longer, faster, airflow path than the lower surface. That of course meant inverted flight is impossible, which has been known to be very obviously incorrect since not all that long after aeroplanes were invented. It was stupidity to the point that some scientists in the early or mid 20th century claimed that inverted aircraft or those with symmetrical profile wings or blades were not technically "flying".

Thanks all for some very educational replies. Obviously, ideas have changed a lot since I was at school.

The explanation of flight reminds me of a question I asked of my flight instructor, if you stand behind a propeller then the air moves much faster than in front therefore being at lower pressure. Hence, the plane should go backwards. Note, never stand anywhere near an active prop.

Mike.

Pommie said:

if you stand behind a propeller then the air moves much faster than in front therefore being at lower pressure. Hence, the plane should go backwards. Note, never stand anywhere near an active prop.

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You are under the impression that, the air pressure is lower on the down-wind side of the propeller than the upwind side? Really?

Energy and mass are not entities, there are properties of a physical entity. That entity science calls charge. But knows little about it. We have all kinds of forms of energy, and all kinds of ratios and conversions for energy.

Has any of your instructors every defined what energy is? What is energy? Energy is the property of motion. That's it. Isn't that mysterious? All this hoopla over describing motion or movement. It takes a PhD.

What is mass? Mass is simply how confined that motion is. This is why you can ratio it.

Charge has a structure that can convert a linear EM field into an angular EM field, and visa-versa.

E = Mxc2. The c2 is NOT a math square, it's a physical square. It's a perpendicular acceleration. TWO accelerations at 90 degrees. It takes a minimum of two accelerations for a charge rotation.....or any other rotation.

And that is just a ratio. IT does NOT say that mass is required for energy. AND it does not say that mass is a part of energy.

Scientists really don't have a 100% consensus on what photons are "made of", though lots of theories abound.

I find the Higgs' Field Theory very appealing, in which space is pervaded by a "soup" in which energy & mass are constantly being exchanged, much like liquid water and water vapor are interchanged at the water's surface.

The Higgs' Field Theorem essentially proposes that this soup is very much like the "aether" in Maxwell's "luminiferous aether" - except that the Higgs' aether is not considered to be fixed in space. It is the properties of this aether are believed to be what determine the permeability and permittivity of free space, and these determine the propagation velocity of photons and other electromagnetic waves AND are responsible for the relationship between energy, wavelength, and propagation velocity.

This soup/aether also appears to be (at least part of) what constitutes "dark energy" and "dark matter", and it appears to conform to many aspects of String Theory.

I suggest that anyone interested in the weirdness of space at the quantum level study the Higgs' Field Theory. Truly fascinating stuff, even if it eventually turns out to be completely wrong!