Traveler and the Mysterious Case of the Missing Radiation Pressure

[traveler]

Nonsense. Gravity would overcome any radiative pressure.

 

Nonsense. The heat from the sun would force the Earth away like a piston is forced down on the power stroke of an internal combustion engine.

 

The Earth wouldn't have a leg to stand on. It would be forced away as the sun got closer.

[iNow]

Nonsense. The heat from the sun would force the Earth away like a piston is forced down on the power stroke of an internal combustion engine.

No, it would not. Your analogy does not support your assertion. The only reason the piston is forced to move in an internal combustion engine is because the explosive pressure from ignition is contained by the cylinder, resulting in compression on the piston head. However, in space, the radiative pressure of our sun is not contained, but is instead free to dissipate outward in all directions.

 

Your comment would only apply if the sun and earth were contained inside of some closed system like a sealed tube, which they are not.

 

 

My point stands. Gravity would overcome any radiative pressure, and flawed analogies and metaphors cannot negate that.

[traveler]

My point stands. Gravity would overcome any radiative pressure, and flawed analogies and metaphors cannot negate that.

 

Gravity wouldn't overcome squat! Your understanding of gravity is highly flawed!

[iNow]

Gravity wouldn't overcome squat! Your understanding of gravity is highly flawed!

I suppose that's possible, but you should still prove it. Where's the math?

 

On the surface, or within the sun... yes, radiative pressure is balanced with (but generally stronger than) gravity (hydrostatic equilibrium IIRC). However, as you move away from the sun by even a tiny amount, the pressure from that radiation is greatly diminished.

 

The earth is not a solar sail, but a massive body which would pull the sun inward as well as the sun pulling on it. (3rd law)

Edited October 1, 2008 by iNow

[traveler]

Prove it. Where's the math?

 

Where's the math to a volcanic eruption?

[iNow]

Where's the math to a volcanic eruption?

 

Yeah, that's what I thought. Never mind, kid. I'm done with you.

 

 

 

EDIT: But not before this:

 

http://en.wikipedia.org/wiki/Radiation_pressure

the radiation of the Sun at the Earth has an energy flux density of 1,370 W/m2, so the radiation pressure is 4.6 µPa (absorbed)

 

Gravity at the sun: 274.1 m/s²

Edited October 1, 2008 by iNow

[traveler]

Yeah, that's what I thought. Never mind, kid. I'm done with you.

 

...and that's what I thought, volcanic eruptions aren't real because there is no math.

[iNow]

I want to introduce you to something called a non-sequitur:

 

http://en.wikipedia.org/wiki/Non_sequitur_(logic)

 

 

It's like you're saying that because bananas are yellow it's 10 degress cooler in Vermont than Oregon.

[traveler]

I want to introduce you to something called a non-sequitur:

 

http://en.wikipedia.org/wiki/Non_sequitur_(logic)

 

 

It's like you're saying that because bananas are yellow it's 10 degress cooler in Vermont than Oregon.

 

No, that would be you saying reality doesn't happen unless someone can calculate it and show the math.

 

Absurd!

[iNow]

No, that would be you saying reality doesn't happen unless someone can calculate it and show the math.

 

Absurd!

 

Now that you've been introduced to non-sequitur, I think it's time you said hello to Mr. Strawman.

 

http://en.wikipedia.org/wiki/Strawman

[traveler]

Now that you've been introduced to non-sequitur, I think it's time you said hello to Mr. Strawman.

 

http://en.wikipedia.org/wiki/Strawman

 

 

Do you have the math for Mr. Strawman? If not, it's not science.

[iNow]

Yep. I thought so.

 

TROLL.

[traveler]

Yep. I thought so.

 

TROLL.

 

Let me know when you have some math for reality, I'd be interested.

[Mr Skeptic]

traveller, you made a claim, and you need to back it up. You don't need maths, just give a reference to someone else who already did the maths, or did the experiment.

 

Perhaps a mod can move this off-topic discussion to its own thread?

[iNow]

...and that's what I thought, volcanic eruptions aren't real because there is no math.

 

Not that your statement is anywhere near appropriate to this thread nor on topic, nor does it support any of your assertions or claims, nor does it negate any of the points which I have made...

 

It's worth pointing out that it's ALSO wrong:

 

http://www.google.com/search?hl=en&rlz=1G1GGLQ_ENUS275&q=equations+for+volcanic+eruption

[Dak]

I want to introduce you to something called a non-sequitur:

 

http://en.wikipedia.org/wiki/Non_sequitur_(logic)

 

 

It's like you're saying that because bananas are yellow it's 10 degress cooler in Vermont than Oregon.

 

In fairness, I think he was trying to reducto ad absurdum you. He was still wrong, m'just saying.

 

Traveller, please follow Mr Skeptic's advice, or just wait until one of our physics experts comes along and tells you wether you're right or wrong.

 

LHC, the sun is about 110 times the size of the earth. it wouldn't fit in the ocean.

[Edtharan]

Nonsense. The heat from the sun would force the Earth away like a piston is forced down on the power stroke of an internal combustion engine.

If gravity couldn't prevent the Sun from blowing the Earth away, what is holding the Sun together? If the sun could push away the Earth, despite its gravity, then why could the Sun not blast its outer layers off just as easily exposing inner layers as new outer layers and then blasting those off as well. The Sun should obliterate itself in no time.

 

Where's the math to a volcanic eruption?

I don't have the equation in front of me, but there would be terms for pressure, structural integrity of the rock, viscosity of the lava and so forth.

 

So yes, there IS equations for a volcanic eruption.

 

There also wouldn't be just one single equation but multiple equations describing individual features of an eruption (although you could put them all together). The various equations would tie together with the output from one being the inputs to another.

 

For example the equation for the height of the plume would use the result of the equation to calculate the force exerted on the material as the eruption occurred.

 

Here is are some places to get started:

Fluid Dynamics

Pressures in gasses

Tensile Strength

 

All of those contain math that relate to eruptions of a volcano.

 

...and that's what I thought, volcanic eruptions aren't real because there is no math

Well that shows that volcanoes must be real. I jsut gave you the maths.

 

Gravity wouldn't overcome squat! Your understanding of gravity is highly flawed!

If you know that much about gravity, could you explain it then? I would be interested, as would any body here. Then we could examine it and see where it states where something different than current theory states would occur and we can revolutionise science and you can get a Nobel Prize.

 

However, this runs the risk of it saying something should happen and then it not happening and your theory getting disproved. But if you are so confident that your theory is correct, then this would not be a discouragement for you.

 

Current theory of gravity has thrown down the gauntlet by making claims as to what will occur in certain circumstances. Does your theory take up the challenge?

 

If we each say the others understanding is flawed, then the only way to resolve it is to test each other's understanding of gravity by using our understanding to make predictions as to what would occur in certain circumstances.

 

 

 

But back on topic...

 

The Sun is much larger than the Earth. This means that the Sun can't fall into the ocean. This means the question is actually nonsense.

 

Because of geometry, if you halve the distance between the Earth and the Sun, then the amount of sunlight (and the energy associated with it) increases by 4 times.

 

If the Earth currently receives around 147 petawatts of energy form the sun, then if we halved the distance between us and the Sun (it is currently around 146,900,000km away), then this would quadruple the amount of energy to 588 petawatts and we are still 73,450,000km away!

 

Keep going by halving the distance and quadrupling the amount of energy until you within the Earth's radius of the Sun and see how much energy would actually be impacting Earth.

 

Long before you actually got that close, the energy form the sun would boil away the ocean and then strip the atmosphere (and the vaporised oceans) from the Earth.

[D H]

http://en.wikipedia.org/wiki/Radiation_pressure

the radiation of the Sun at the Earth has an energy flux density of 1,370 W/m2, so the radiation pressure is 4.6 µPa (absorbed)

 

Gravity at the sun: 274.1 m/s²

 

That's a bit like comparing apples to oranges¹. A better comparison would be to compare the forces on the Earth due to solar radiation pressure and solar gravity at 1AU:²

 

[math]

\aligned

F_{\text{rad}} &= \pi r_e^2 P_{\text{rad}}

\approx 5.9\cdot10^8\,\text{newtons} \\

F_{\text{grav}} &= \frac {G m_e m_s}{R_e^2}

\approx 3.5\cdot10^{22}\,\text{newtons} \\

\frac{F_{\text{rad}}}{F_{\text{grav}}} &\approx 1.7\cdot10^{-14}

\endaligned

[/math]

 

Since the energy flux density of solar radiation and gravitation are both inverse square laws, the ratio of the force due to radiation pressure to the force due to gravity will be essentially constant as a function of distance from the Sun.³

 

Bottom line: Solar radiation pressure is inconsequential to a body the size of the Earth.

 

 

Footnotes:

 

¹Not an apt analogy, as apples and oranges are actually quite comparable and even quite similar.

 

²Calculation here.

 

³Actually, the ratio decreases slightly in close proximity to the Sun as less than half of the Earth will see the full Sun and more than half of the Earth will see at least part of the Sun. Both effects act to effectively reduce the cross section to outward radiation pressure.

[iNow]

Thank you, my good man. I should have just stopped posting and started ignoring the kid when I said I would. I appreciate you stepping in and showing it correctly on my behalf.

[traveler]

Thank you, my good man. I should have just stopped posting and started ignoring the kid when I said I would. I appreciate you stepping in and showing it correctly on my behalf.

 

That's half the problem with modern science, they ignore everything except what they THINK they know to be true, which is then proven wrong. You end up with a house of cards built on a mud foundation.

 

Believe half of what you see and none of what you hear.

[Sisyphus]

¹Not an apt analogy, as apples and oranges are actually quite comparable and even quite similar.

 

As long as we're already doing silly tangents, I feel I must object to this. The article in that link represents a common misunderstanding of the proverb resulting from ambiguity in the English language. The problem arises not in comparing Malus domestica with Citrus sinensis ("apples" and "oranges" taken as wholes), it's comparing individuals of each species. The problem being that the criteria for good apples and the criteria for good oranges are different, so judging one by the other's standards is fallacious. Obviously the former comparison is quite easy, and would never be proverbially impossible.

[Klaynos]

That's half the problem with modern science, they ignore everything except what they THINK they know to be true, which is then proven wrong. You end up with a house of cards built on a mud foundation.

 

Believe half of what you see and none of what you hear.

 

Modern science is fundamentally based on experimentation, sorry but you are just wrong here.

[Mr Skeptic]

That's half the problem with modern science, they ignore everything except what they THINK they know to be true, which is then proven wrong. You end up with a house of cards built on a mud foundation.

 

Believe half of what you see and none of what you hear.

 

I don't believe you.

 

You are right, that science ignores an uncountabley infinite number of possibilities, but I think that is unavoidable. There simply will never be enough people to give half a thought to every possibility, and there never will be. In case you are wondering, uncountably infinite is infinitely more than countably infinite; look it up if you don't believe me.

 

Again you are right that scientists will only believe half of what they see, so they need to see it twice to believe it.

 

And again you are right that we don't believe any of what we hear unless it is data or maths, which, incidentally, is why no one here believes a word you say. And now you admit that they are right to ignore you.

 

It does seem like a few people were curious as to how wrong you were, and did the calculations to show it. Looks like you were mistaken; the radiative pressure would be 170,000,000,000,000 times weaker than gravity, rather than stronger. For a comparison, it would be like you finding a dollar and claiming its enough to pay off the entire US debt ten times over.

[iNow]

Yep. Troll.