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Energy?

Started by Crispy Apr 9, 2005 at 6:18 PM 56 replies 3.5k views

Original Post

Apr 9, 2005 at 6:18 PM

The Earth is constantly being fed with a flux of energy spat out by the Sun. A quote from this place expresses this fact quite vividly: "Each day more solar energy falls to the Earth than the total amount of energy the planet's 6 billion inhabitants would consume in 27 years". This webpage writes: "Where does all this energy go? About 15 percent of the sun's energy that hits the earth is reflected back into space. Another 30 percent is used to evaporate water, which, lifted into the atmosphere, produce's rain-fall. Solar energy also is absorbed by plants, the land, and the oceans. The rest could be used to supply our energy needs.". Now, that's all nice and dandy, but it gives us absolutely no answer as to where that energy really goes. If 15% is reflected back into space, then it would be a safe bet to say that 85% eneters the Earth's atmosphere and is "used up". Let's put things in persepctive - there's this thing called The Law of Energy Conservation, which states that "the total inflow of energy into a system must equal the total outflow of energy from the system, plus the change in the energy contained within the system". Every school kid knows that you can't pour more water into a glass than the glass is capable of holding or you'll get a spill. Where is that spill going in the case of a planet? We consume a small part of the energy, one way or the other, biologically or otherwise, a part is "used up" by the planet itself to keep the vital meteorological and geological processes going, but nowhere can we say that our planet is in any way capable of just making that 85% disappear. I do realize that there is a marginal amount of energy that is emitted back into space in the form of radiation. Low-density outer atmosphere that is washed off into space as the planet moves can cause some marginal loss of heat energy, but where is the rest of the energy going? Momentum? Kinetic energy? If so, then what does that kinetic energy go into?

Raduprv

Apr 9, 2005 at 6:21 PM

The rest heats the earth, duh.

Crispy

Apr 9, 2005 at 6:23 PM

Quote:
Original post by Raduprv
The rest heats the earth, duh.

My question starts where your remark ends: and then what?

Raduprv

Apr 9, 2005 at 6:25 PM

And then it dissipates into the ether. The 15% that is reflected is reflected imediately (which makes the earth glow, from the moon), and the rest is slowly radiated away, in time (IR radiation).

Dmytry

Apr 9, 2005 at 6:26 PM

earth radiates heat into space. In stable situation, all that energy is radiated back into space. It's not marginal, it's where all energy go. When there is more greenhouse gases, earth surface must have higher temperature for same amount of IR radiation getting into space.

Uthman

Apr 9, 2005 at 6:28 PM

and then its lost back into space. thats why it gets cold at night

Nathan Baum

Apr 9, 2005 at 6:38 PM

Listen to what Doctor Clickenstein has to say.

Although 15% of the Sun's heat is directly reflected, eventually almost all of it is radiated away in other forms. Whilst you might expect that keeping the Earth cool was a big deal, our atmosphere actually needs to trap heat in order for life as we know it to survive.

Crispy

Apr 9, 2005 at 6:38 PM

Alright - let me put it this way: heat energy can't be "lost into space". Heat isn't a "flow of energy" - heat is the definition of interaction between particles: the faster a set of particles is moving in relation to each other, the "warmer" the mass is. I can't see a way of losing that 85% into space without casting away a substatial amount of matter from the Earth's atmosphere. Is that what's happening?

Now, if matter really is being shaved off the Earth and heat cast into space (which means that there should be a substantial dissipating trail of matter in the path that the Earth has recently travelled, much like the tail of a comet), then where does that energy go from there on?

Or, in the form of an example: suppose you spill a bowl of warm soup into space: the soup forms a mass of a particular shape and starts to give off energy until it freezes and becomes a solid mass. This means that particles inside the blob of soup have become stagnant and are no longer moving (and thus no longer giving off energy). The question is: where (or in what form) is that energy (in) now?

Dmytry

Apr 9, 2005 at 6:40 PM

Quote:
Original post by Crispy
Alright - let me put it this way: heat energy can't be "lost into space". Heat isn't a "flow of energy" - heat is the definition of interaction between particles: the faster a set of particles is moving in relation to each other, the "warmer" the mass is. I can't see a way of losing that 85% into space without casting away a substatial amount of matter from the Earth's atmosphere. Is that what's happening?

Now, if matter really is being shaved off the Earth and heat cast into space (which means that there should be a substantial dissipating trail of matter in the path that the Earth has recently travelled, much like the tail of a comet), then where does that energy go from there on?

Or, in the form of an example: suppose you spill a bowl of warm soup into space: the soup forms a mass of a particular shape and starts to give off energy until it freezes and becomes a solid mass. This means that particles inside the blob of soup have become stagnant and are no longer moving (and thus no longer giving off energy). The question is: where (or in what form) is that energy (in) now?

heat radiation, man. That's why termos not only use vacuum between walls, but also nice shinny silvered coating inside.

It's same way how Sun radiates it's energy into space, just sun is hotter, wavelength is shorter, and we call it "visible light" because we've evolved to see it.

Raduprv

Apr 9, 2005 at 6:43 PM

Quote:
Original post by Dmytry
heat radiation, man. That's why termos not only use vacuum between walls, but also nice shinny silvered coating inside.

It's same way how Sun radiates it's energy into space, just sun is hotter, wavelength is shorter, and we call it "visible light" because we've evolved to see it.

Not really, the sun radiates all kind of wavelengths (light, uv, ir, radio, gamma, etc.)

Dmytry

Apr 9, 2005 at 6:47 PM

Quote:
Original post by Raduprv
Quote:
Original post by Dmytry
heat radiation, man. That's why termos not only use vacuum between walls, but also nice shinny silvered coating inside.

It's same way how Sun radiates it's energy into space, just sun is hotter, wavelength is shorter, and we call it "visible light" because we've evolved to see it.

Not really, the sun radiates all kind of wavelengths (light, uv, ir, radio, gamma, etc.)

indeed, but most is visible light and (near IR and near UV). That was my point. Comparing to earth, spectrum is kind of similar (aside of spectral lines), just all wavelengths is shorter.

"theoretically", earth and any other object radiates at all wavelengths, as spectrum curve is nice and smooth...

Kaze

Apr 9, 2005 at 6:57 PM

Quote:
Original post by Dmytry
Quote:
Original post by Raduprv
Quote:
Original post by Dmytry
heat radiation, man. That's why termos not only use vacuum between walls, but also nice shinny silvered coating inside.

It's same way how Sun radiates it's energy into space, just sun is hotter, wavelength is shorter, and we call it "visible light" because we've evolved to see it.

Not really, the sun radiates all kind of wavelengths (light, uv, ir, radio, gamma, etc.)

indeed, but most is visible light and (near IR and near UV). That was my point. Comparing to earth, spectrum is kind of similar (aside of spectral lines), just all wavelengths is shorter.

"theoretically", earth and any other object radiates at all wavelengths, as spectrum curve is nice and smooth...

it more smooth from the sun than it is here though, the reason we evolved to see visable light inseted of UV is becouse most of the electromagnetic spectrum dosent penetrate the atmosphere very well

Raduprv

Apr 9, 2005 at 7:01 PM

Quote:
Original post by Kaze
it more smooth from the sun than it is here though, the reason we evolved to see visable light inseted of UV is becouse most of the electromagnetic spectrum dosent penetrate the atmosphere very well

IR does, and we can't see IR. Other animals, such as bees, for example, can.
And it's not about evolution, it's about design :)

try_catch_this

Apr 9, 2005 at 7:01 PM

The question is: where (or in what form) is that energy (in) now?

IR radiation. "Commonly known as Heat".

Hedos

Apr 9, 2005 at 7:04 PM

I'm still a n00b in physics, so let me ask a question..
Light from the sun is heat radiation, right?
From what I know, light is a wave, but it also contains particles: photons.

So, as you said that any object will lose its energy as heat radiation, will it also emits its own photons or is it totally unrelated?

Kaze

Apr 9, 2005 at 7:07 PM

it dosnt contain particles, it just sometimes acts like one

Raduprv

Apr 9, 2005 at 7:08 PM

Quote:
Original post by Hedos
So, as you said that any object will lose its energy as heat radiation, will it also emits its own photons or is it totally unrelated?

Yes, of course. If emits light (or other radiations) it will emit photons.

Hedos

Apr 9, 2005 at 7:31 PM

Quote:
Original post by Raduprv
Quote:
Original post by Hedos
So, as you said that any object will lose its energy as heat radiation, will it also emits its own photons or is it totally unrelated?

Yes, of course. If emits light (or other radiations) it will emit photons.

Thanks for the information.

Quote:
Original post by Kaze
it dosnt contain particles, it just sometimes acts like one

Really?
Photons are not particles? I have a hard time understanding how could a wave move through void, thus I guess light is not simply a wave. What is the difference between photons and real matter particles then?

I should read up on photons, it's quite interesting.

Raduprv

Apr 9, 2005 at 7:35 PM

Quote:
Original post by Hedos
Photons are not particles? I have a hard time understanding how could a wave move through void, thus I guess light is not simply a wave. What is the difference between photons and real matter particles then?

AFAIR the photons are virtual particles, because they carry the electromagnetic force. They do exist only as long as they move. When they stop, they die (dissapear).

Kaze

Apr 9, 2005 at 7:41 PM

im not exactly an expert on this but i thinks its to do with e=mc^2- meaning energy and matter are interchangeable, so rater than absolute energy or matter so energy can sometimes act like matter and vice versa, some think dark matter is a transiton between energy and matter

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