banner1

Home arrow Forum arrow Everything Space Space Science and Astronomy How much energy does the sun give?
Main Menu
Home
News
Links
Wiki
Search
Administrator
FAQ
Contact Us
Science Books
Register
Online Store
Science on the Web
Store - beta
Project Fork
Feature Sections
Encyclopedia Astronuc
ID Watch
Community Menu
Forum
Einstein@Home
Member Blogs
Science Social Network
Science Network Users
Login Form
Welcome, Guest. Please login or register.
Did you miss your activation email?
April 23, 2014, 01:11:24 AM
Username: Password:
Login with username, password and session length

Password reminder
Did you know?

The Platypus is stranger than you think.

Platypuses have no nipples.  After the young hatch, the mother oozes milk from the pores all over her body.

The male platypus has a poison barb on the inside of its hind legs.  The purpose of this weapon is uncertain.

While often compared to the beaver, the platypus is only about 20 inches in length -- more comparable to the size of the muskrat.

The Platypus bill is actually just an elongated muzzle covered with much the same kind of tough skin found on a dog's nose.  This bill contains an electrically-sensitive organ that can detect the electrical signatures of the small aquatic animals it eats.

Author Topic: How much energy does the sun give?  (Read 2711 times)

Offline owlhoot

  • Newbie
  • *
  • Posts: 0
How much energy does the sun give?
« on: January 01, 2003, 05:39:00 PM »
Is there a system for measuring solar output that could tell you how many BTU's the earth is receiving from the sun on average?

The reason I ask is that I want to have some means of computing a habitable zone based on earth norms and would like to know from earth's perspective how much radiant energy the earth gets from the sun. Whatever earth gets is what is required to keep water liquid for the majority of the time. Some stars would have a deeper habitable zone and others shallower depending on size and type.

Any help would be appreciated. I already know that Mars would be getting the square root of what earth gets, and Venus would be getting roughly the square of earth norms. What I need to know is what that energy translates to.

Thanks in advance.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline payloadcontroller

  • Administrator
  • Hero Member
  • *****
  • Posts: 2073
  • Fleet Admiral
    • Novelist Stephanie Osborn
Re: How much energy does the sun give?
« Reply #1 on: January 01, 2003, 08:04:00 PM »
yeahhhh....I got that someplace....gimme some time to try to hunt it up. I hope I can still find it.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »
Ad astra sin bozotii!

Buy Burnout! Click on the banner!


http://www.stephanie-osborn.com

Offline vishniac

  • Human Manifest Destiny proponent
  • Hero Member
  • *****
  • Posts: 1297
Re: How much energy does the sun give?
« Reply #2 on: January 01, 2003, 11:03:00 PM »
There's a JPL mission up there doing just that, ACRIM Sat:
acrim.jpl.nasa.gov/

I didn't search too much but found that graphic:


And the site of Sorce, another mission to go in a few weeks:

http://earthobservatory.nasa.gov/Library/SORCE/sorce_05.html
where I found this other graphic (damn, it doesn't show the w/m2 !!):


and lots of explanations.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »
The popular stereotype of the researcher is that of a skeptic and a pessimist. Nothing could be further from the truth! Scientists must be optimists at heart, in order to block out the incessant chorus of those who say "It cannot be done."
Academician Prokhor Zakharov, University Commencement

Offline owlhoot

  • Newbie
  • *
  • Posts: 0
Re: How much energy does the sun give?
« Reply #3 on: January 02, 2003, 03:46:00 PM »
What does the w/m2 stand for? Something per square meter?
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline payloadcontroller

  • Administrator
  • Hero Member
  • *****
  • Posts: 2073
  • Fleet Admiral
    • Novelist Stephanie Osborn
Re: How much energy does the sun give?
« Reply #4 on: January 02, 2003, 04:43:00 PM »
yeah, those are good graphics.

W/m^2 = Watts per square meter.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »
Ad astra sin bozotii!

Buy Burnout! Click on the banner!


http://www.stephanie-osborn.com

Offline yales

  • Newbie
  • *
  • Posts: 1
Re: How much energy does the sun give?
« Reply #5 on: January 03, 2003, 10:30:00 PM »
Owlhoot, the numbers you are using for Venus and Mars, are too extreme.

The solar flux at Venus is twice Earth's, not the square of Earth's.

The solar flux at Mars's is about half of Earth's, not the square root of Earth's.

====================================
average insolation:

Venus:  2640 watts per square meter
Earth:   1370 watts per square meter
Mars:    590 watts per square meter

====================================


 PLANETARY INSOLATION RELATIVE TO EARTH
(Earth = 1.00)

Planet ---- Relative Distance from Sun --- Relative Insolation
Mercury -------------------- 0.38 -------------------- 6.9
Venus ---------------------- 0.72 -------------------- 1.9
Earth -----------------------1.00 -------------------- 1.00
Mars ------------------------1.5 --------------------- 0.44
Jupiter ---------------------- 5.2 -------------------- 0.037
Saturn ---------------------- 9.5  ------------------- 0.011
Uranus --------------------- 19.1 ------------------ 0.0027
Neptune -------------------  30.0 ------------------- 0.0011
Pluto ----------------------- 39.4 ----------------- 0.00064

==============================================

This chart is good for illustrating why spacecraft use solar cells out to Mars and nuclear energy past the asteroids.

yale
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline owlhoot

  • Newbie
  • *
  • Posts: 0
Re: How much energy does the sun give?
« Reply #6 on: January 04, 2003, 12:51:00 PM »
I beg to differ. The radiation output would follow the inverse square law. This means that when you half the distance from a source of illumination you square the measurable power output.  This is how radioctivity is measured and covers all forms of the electromagnetic spectrum.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Orstio

  • Guest
Re: How much energy does the sun give?
« Reply #7 on: January 04, 2003, 01:45:00 PM »
Here's a link with all the formulas and explanations of terms you should need to do the calculations:

edmall.gsfc.nasa.gov/inv9...iance.html
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline payloadcontroller

  • Administrator
  • Hero Member
  • *****
  • Posts: 2073
  • Fleet Admiral
    • Novelist Stephanie Osborn
Re: How much energy does the sun give?
« Reply #8 on: January 04, 2003, 05:03:00 PM »
Oh, excellent, Orstio. Goddard Space Flight Center. Their info will be very good. Go for it, dude.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »
Ad astra sin bozotii!

Buy Burnout! Click on the banner!


http://www.stephanie-osborn.com

Offline owlhoot

  • Newbie
  • *
  • Posts: 0
Re: How much energy does the sun give?
« Reply #9 on: January 04, 2003, 11:03:00 PM »
Thanks for the link, Orstio. My math isn't what it should be and it seems I need to brush up on the inverse square law. At least I was right in that it applies here. I still need to translate that into real numbers. It looks like half the distance to the source would be 4 times the power, not the power squared. Anyway thanks for the correction. You know, we really need a humble pie icon.:\ :\
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline yales

  • Newbie
  • *
  • Posts: 1
Re: How much energy does the sun give?
« Reply #10 on: January 04, 2003, 11:38:00 PM »
Owlhoot wrote:
Quote
Quote:
I beg to differ


You are confusing the situation. Yes, of course the inverse square law applies, but VENUS IS ONLY 25% CLOSER to the Sun than Earth and MARS IS ONLY 50% FARTHER from the Sun than Earth!

Thus, the inverse square rule gives the exact numbers I use: twice the solar flux at Venus, and 44% at Mars.

You are mistakenly assuming that Venus is HALF the distance to the Sun as Earth, and Mars is TWICE the distance as the Earth.

Not true.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline yales

  • Newbie
  • *
  • Posts: 1
Re: How much energy does the sun give?
« Reply #11 on: January 05, 2003, 12:35:00 AM »
Let's do the calculations:

Inverse Square Law = I = 1/R^2

I= Intensity of Sunlight (or insolation)
R = Distance from Sun
^2 = symbol for squared

---

Insolation at Earth is measured at 1370 watts per square meter

To simplify matters, rather than using miles or kilometers,
 I will use "Astronomical Units" or "AU".

An "Astronomical Unit" (or AU) is defined as the
average distance of the Earth from the Sun (about 93,000,000 miles).

Earth = 1.0 AU
Venus = 0.72 AU
Mars = 1.5 AU

Now, let's apply these data:

=================================================

1) Insolation at Venus compared to Earth

Distance from Sun to Venus = 0.72 AU

I = 1/(0.72)^2

I = 1.9 times

Insolation = 1.9 x 1370 w/m^2 = 2600 w/m^2

Thus we see that sunlight at Venus is TWICE that of Earth,
 not the SQUARE.

=============================================


2) Insolation at Mars compared to Earth

Distance from Sun to Venus = 1.5 AU

I = 1/(1.5)^2

I = 0.44 times

Insolation = 0.44 x 1370 w/m^2 = 600 w/m^2

Thus we see that sunlight at Mars is about HALF that of Earth,
 not the SQUARE ROOT.

==============================================
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline yales

  • Newbie
  • *
  • Posts: 1
Re: How much energy does the sun give?
« Reply #12 on: January 05, 2003, 01:10:00 AM »
Now, back to you original question:
Quote
Quote:
Is there a system for measuring solar output that could tell you how many BTU's the earth is receiving from the sun on average?



Yes, first we multiply the instantaneous power
 to accumulated energy over time:

Our solar power of 1370 watts/meter squared accumulates
to a solar energy of:

-------

4678 BTU's per hour (in Ye Olde English Units)

Note:  this is for one square meter

---------

in a year (or 8760 hours) this converts to :

41,000,000 BTUs per year per square meter

--------------------

Now for the bottom line...

How much solar energy does the Earth intercept in one year:

Diameter of Earth = 12,750 kilometers
Area of Earth's disk = Pi x R^2
Area = 3.14 x (6375)^2
Area = 13,000,000 square kilometers

Therefore the Earth intercepts:

533,000 quadrillion BTUs per year
(THe United States uses 100 quadrillion BTUs
per year for all its energy supply.)

=============================================

All this is less useful than it seems.
It is imperative that we determine how much of this energy is reflected away, radiated away, absorbed, etc
This is an excruciatingly difficult problem.

yale
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

Offline owlhoot

  • Newbie
  • *
  • Posts: 0
life zone
« Reply #13 on: January 05, 2003, 11:39:00 AM »
Thanks for that exhaustive reply, Yales. My question was asked mainly because I wanted to know how much energy was needed to produce a climate like we are used to.

It doesn't matter in the long run how much is reflected away, because our weather patterns make use of it in such a way that we survive on it. What matters is that the energy is there and available.

Mars doesn't get that much energy, and is not likely to be able to be terraformed as a result. Even if it had a denser atmosphere, and more water, it would be too cold, the water would freeze and reflect what little energy there is back into space.

I wanted to know this stuff because we are looking at sunlike stars for potential life zones. My belief is, that even dissimilar stars could support life if the planet was in the right place. Knowing what orbital zone would best support liquid water would narrow the search down considerably. Any planet which orbits in that life zone has the potential of supporting life, even if it does not exist on it yet.

Even a more radiant star would have a possible life zone, although farther away.
« Last Edit: December 31, 1969, 04:00:00 PM by 1079251200 »

 

Valid XHTML 1.0!


Mambo is Free Software released under the GNU/GPL License.