<![CDATA[Latest posts for the thread "How much energy would it take to slag an entire planet, oceans and all?"]]> http://www.dakkadakka.com/dakkaforum/posts/list/69.page JForum - http://www.jforum.net How much energy would it take to slag an entire planet, oceans and all?
(I'm working on a crossover so this seems a good starting place as each faction can roast planets. With this I can calculate their big weapons, and from there calculate their shields, all of which would make it easier to determine how much damage each ship can deal and take relative to the others)]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915002.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915002.page GMT How much energy would it take to slag an entire planet, oceans and all? this, you're looking at 3.6x10^27 joules of energy to boil off the oceans of earth and eliminate all ground water.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915014.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915014.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915017.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915017.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915022.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915022.page GMT How much energy would it take to slag an entire planet, oceans and all?
https://what-if.xkcd.com/13/]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915096.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915096.page GMT How much energy would it take to slag an entire planet, oceans and all?
 Konrax wrote:
I would suggest starting with small scale tests in the backyard


The 4th of July isn't too far off. "Celebrate the birth of your country by blowing up a small piece of it!"
]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915099.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915099.page GMT Re:How much energy would it take to slag an entire planet, oceans and all? This site does include a fair bit of maths in comparing Star Trek and Star Wars weapon energies, including considering the energy requirements for blowing up asteroids (ignoring gravity) and planets. A more focused section dealing with planetary bombardment can be found here.
]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915124.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7915124.page GMT How much energy would it take to slag an entire planet, oceans and all?
 Furyou Miko wrote:
According to this, you're looking at 3.6x10^27 joules of energy to boil off the oceans of earth and eliminate all ground water.

Thank you! exactly the sort of thing I'm looking for!

So we have 3.6e27 Joules of energy to boil off all of the water on earth. That's over 8.6x10^17 Tons of TNT, or 860 Petatons.
this


*How do you make it say "this" instead of being the whole URL?
edit: Thanks!

Next step, is how much energy would it take to melt the outer 5 meters of Earth's crust after the water's removed?]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7916731.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7916731.page GMT How much energy would it take to slag an entire planet, oceans and all?
 Bill1138 wrote:

(http://convert-to.com/conversion/energy/convert-j-to-tn.html)
*How do you make it say "this" instead of being the whole URL?


Its [*url=http://www.example.com]This[*/url] without the asterisks.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7916753.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7916753.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7922609.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7922609.page GMT How much energy would it take to slag an entire planet, oceans and all?
First, the specific heat capacity, which is how much energy is required to raise the temperature of a substance by one degree. Use that to work out how much energy you need to raise the substance from its initial temperature to its melting point.

Then you need the latent heat of fusion, which is the energy required to actually melt the substance (equivalently, the energy released as it freezes).

Once you have those numbers, you know how much energy is required to melt a kilogram of that substance. Now you need to work out how much stuff you're melting. To simplify, work out the surface area of the planet, and multiply that by the thickness of the surface layer you want to melt. then multiply that resultant volume by the density of the substance you're thinking about.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7922635.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7922635.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7922724.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7922724.page GMT Re:How much energy would it take to slag an entire planet, oceans and all? 3.6e27 Joules of energy, which is over 8.6x10^17 Tons of TNT, or 860 Petatons.

According to this, the density of the crust's silicate rocks is 2.2 g/cm^3. According to this, Silicon has a density of 2.3290 g/cm^3.

So if I understand correctly, if we calculate the answer with Silicon, the calculated value should be slightly higher than the actual low-end estimate. Correct?


0.0356055615887202 mol = 1 g
1 mol = 28.0855 g

Surface Density of 2.3290 g/cm^3
Silicon has a Molar heat Capacity of: 19.789 J/mol·K
Silicon has a melting point of: 1687 K
Silicon has a heat of fusion of: 50.21 kJ/mol
Earth's average surface temperature is It's 287 K,


So check my math on this...

My Molar Heat Capacity and Heat of Fusion are in mols, so I have to convert the surface density into mols
0.0356055615887202 x 2.329 = 0.08304 mol/cm^3

So I multiply that by the molar heat capacity? That should give me the amount of energy in J to raise the cm^3 by 1 K, correct?
0.08304 x 19.789 = 1.643278 J to raise 1cm^3 of Silicon by 1K.

If Earth's average surface temperature is 287K, and I need to raise it to 1687K, then I need to raise it by 1400K.
1.643278 J x 1400K = 2300.5892 J per cm^3

Then I use Silicon's Heat of Fusion to calculate the amount of energy needed to melt the heated material
0.08304 mol/cm^3 x 50.21 kJ/mol = 4.1694384 kJ/cm^3 or 4169.4384 kJ/cm^3

So the total amount of energy to melt each cm^3 of the Earth's crust from its current state is
2300.5892 J + 4169438.4 J = 4171738.989 J/cm^3

If Earth's Radius is 6371Km, then the surface area is (2 x Pi x R) = 40030.17359Km^2 or 4003017359cm^2

I can multiply the total J/cm^3 by the Surface area and multiply by how deep I want to go to get an estimate of how much energy would be required to do so. Correct? I don't think I can get any more precise than this because of the limitations of significant digits of the numbers I'm working with.
4171738.989 J/cm^3 x 4003017359cm^3 = 1.669954359x10^16J for 1cm deep

1.669954359x10^16J x 500cm = 8.349771795e18J

Add this value to the energy required to vaporize all of the water on earth:
8.349771795e18 + 3.6e27 ~ 3.6e27J?

Can that be right? Is the energy required to vaporize all of the water on earth so much more that that required to melt all of the continents into slag?]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7923122.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7923122.page GMT How much energy would it take to slag an entire planet, oceans and all?
Seventy one percent of earth's surface is ocean.

That means that only 29% of it is land mass. Further, you only have to melt maybe half a mile of the very topmost layer of the surface of that landmass to have 'melted the continents into slag'.

Furthermore to that, the average temperature of the oceans is 16 degrees and water has a relatively high enthalpy - the amount of energy it can store before changing state. That means that to affect a tiny change in the ocean's temperature, you need an insane amount of energy. Also bear in mind that the deeper you go into the ocean, the colder it gets: while the average is 16 degrees, at the bottom of the ocean its more like two degrees once you get more than a few metres from a thermal vent.

The ground, however, gets hotter as to go deeper. near the surface, you're looking at about 15 degrees in the UK, but below the surface that rises by a massive 2 degrees per 100 metres - which means that a mere kilometre under ground, you're looking at a rock temperature of thirty five degrees.

This is why thermal vents exist, incidentally - where the bottom of the ocean meets the rock, you get these vents that constantly pump hot gas into the water at about 400 degrees. This is a really good way to illustrate just how hard it is to heat up the oceans: That's four times the nominal boiling point of water, and it is all lost once you stray a few metres away from the vent, the water temperature is back down to just above freezing.

The end result is that while you need to add a hell of a lot of energy to boil the oceans, the continents already contain a lot of the energy you need to get them turning over.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7923262.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7923262.page GMT How much energy would it take to slag an entire planet, oceans and all?
Love this thread, by the way.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7923329.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7923329.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924023.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924023.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924050.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924050.page GMT Re:How much energy would it take to slag an entire planet, oceans and all? Atomic Rocket I found to be quite informative.

Also useful table of various energy requirements for specific actions:
Energy required to vaporize all the oceans of Terra and dehydrate the crust is 7.0 × 10^27 Joules or 2 Exatons
Energy required to melt the (dry) crust of Terra is 2.9 × 10^28 or 7 Exatons
Energy required blow off Terra's oceans into space is 1.0 × 10^29 or 24 Exatons
Earth's rotational energy is 2.1 × 10^29 or 50 Exatons]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924248.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924248.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924267.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924267.page GMT Re:How much energy would it take to slag an entire planet, oceans and all?
Miradorm wrote:
Atomic Rocket I found to be quite informative.

Also useful table of various energy requirements for specific actions:
Energy required to vaporize all the oceans of Terra and dehydrate the crust is 7.0 × 10^27 Joules or 2 Exatons
Energy required to melt the (dry) crust of Terra is 2.9 × 10^28 or 7 Exatons
Energy required blow off Terra's oceans into space is 1.0 × 10^29 or 24 Exatons
Earth's rotational energy is 2.1 × 10^29 or 50 Exatons

7 Exatons? That must be melting the entire thickness of the crust, because it is drastically higher than what I calculated for the top few meters.

Is there anywhere I can see the math for this? Typically I prefer to know and understand why a number is what it is so I can re-create the process if the need arises.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924427.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924427.page GMT How much energy would it take to slag an entire planet, oceans and all? http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924721.page http://www.dakkadakka.com/dakkaforum/posts/preList/653059/7924721.page GMT