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And, how many million megatons of heat are decending upon our earth from the sun at any given instant? How much does the light weigh that we see around us on our earth?

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Since sunlight has energy, it also has a mass associated with it as indicated by Einstein's famous equation E = mc^2 or m = E/(c^2).

An elementary textbook says the sun converts 4.2 x 10^9 kg of mass to energy every second. Using this number, we can estimate the amount of energy (mass) from the sun hitting the earth by calculating the fraction of the entire solid angle the earth intercepts as seen by the sun. Since the diameter of the earth is about 1.3 x 10^7 m and it is 1.5 x 10^11 m from the sun, it subtends an angle of about 8.7 x 10^-5 radians. If we square this angle and divide by 4 pi = 12.6, we get the solid angle fraction subtended by the earth, which I calculate to be about 6 x 10^-10 of the entire solid angle. Multiplying this by the 4.2 x 10^9 kg burned by the sun every second and we obtain 2.5 kg/s as the mass of the photons (light) from the sun striking the earth every second.

There is another way to guesstimate this number using the rough estimate of 1 kW/m^2 as the energy of the sunlight striking the earth. Multiplying this by the area of a disk with the area of the cross section of the earth (pi x R^2 = 1.3 x 10^14 m^2) gives 1.3 x 10^17 J/s. Dividing this by the velocity of light squared (c^2 = 9 x 10^16) gives 1.4 kg/s. I consider this to be in excellent agreement with the figure of 2.5 kg/s obtained above.

Please let me know if you find this less than clear or would like more information or explanation.

Best, Dick Plano, Professor of Physics emeritus, Rutgers University

http://www.newton.dep.anl.gov/askasci/phy00/phy00644.htm

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ORIGINAL: Musicmystery

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And, how many million megatons of heat are decending upon our earth from the sun at any given instant? How much does the light weigh that we see around us on our earth?

The mass of the photons (light) from the sun striking the earth every second is 2.5 kg/s.

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Since sunlight has energy, it also has a mass associated with it as indicated by Einstein's famous equation E = mc^2 or m = E/(c^2).

An elementary textbook says the sun converts 4.2 x 10^9 kg of mass to energy every second. Using this number, we can estimate the amount of energy (mass) from the sun hitting the earth by calculating the fraction of the entire solid angle the earth intercepts as seen by the sun. Since the diameter of the earth is about 1.3 x 10^7 m and it is 1.5 x 10^11 m from the sun, it subtends an angle of about 8.7 x 10^-5 radians. If we square this angle and divide by 4 pi = 12.6, we get the solid angle fraction subtended by the earth, which I calculate to be about 6 x 10^-10 of the entire solid angle. Multiplying this by the 4.2 x 10^9 kg burned by the sun every second and we obtain 2.5 kg/s as the mass of the photons (light) from the sun striking the earth every second.

There is another way to guesstimate this number using the rough estimate of 1 kW/m^2 as the energy of the sunlight striking the earth. Multiplying this by the area of a disk with the area of the cross section of the earth (pi x R^2 = 1.3 x 10^14 m^2) gives 1.3 x 10^17 J/s. Dividing this by the velocity of light squared (c^2 = 9 x 10^16) gives 1.4 kg/s. I consider this to be in excellent agreement with the figure of 2.5 kg/s obtained above.

Please let me know if you find this less than clear or would like more information or explanation.

Best, Dick Plano, Professor of Physics emeritus, Rutgers University

http://www.newton.dep.anl.gov/askasci/phy00/phy00644.htm

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ORIGINAL: Aswad

Is, by mass-energy equivalence, the thermal energy of an object part of its effective gravitational mass?

Or, phrased differently, does the gravitation of an object depend in part on its heat?

The intuitive answer seems to be yes, but IANAP.

IWYW,
— Aswad.

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ORIGINAL: Musicmystery

Ah . . . no.

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the earth is simultaneously reradiating almost exactly the same via reflectance and infra red.

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ORIGINAL: epiphiny43

The problem is that temperature is a metric of energy, and energy has mass, but the temps we experience mean kinetic motions that are only relativistically Very small. Increase in kinetic energy (vibration of molecules) increases mass but only in relation to that Delta (change of) speed divided by C, the speed of light. This is hard to measure with common household objects?

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ORIGINAL: Aswad

The actual question was one about whether an object's kinetic energy influences its gravitational mass.

That said, as regards thermal radiation, a blackbody radiates based on its temperature, and absorbs as effectively as it radiates. Reflectors of thermal infrared do not radiate well. Water is a very close approximation of a blackbody. The Earth does radiate close to what it absorbs. Not sure how you arrived at the conclusion that blackbodies don't radiate, Hillwilliam.

IWYW,
— Aswad.

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ORIGINAL: mnottertail

collapsed stars are hot, because they are collapsed.

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The actual question was one about whether an object's kinetic energy influences its gravitational mass