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Science and Astronomy Questions
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| Watsisname | Date: Tuesday, 23.08.2016, 22:12 | Message # 766 |
 Galaxy Architect
Group: Global Moderators
United States
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| Looks very promising, but I would wait a bit more.  This is an interpretation of something weird in their data, and if we are to be convinced of the interpretation it must be verified through its own predictive power. It could also just be something wrong with their experiment or analysis; they must be replicated elsewhere.
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| JackDole | Date: Tuesday, 23.08.2016, 22:55 | Message # 767 |
 Star Engineer
Group: Local Moderators
Germany
Messages: 1742
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| Actually, I am surprised that no one predicted this fifth force. Or does anyone?
But if there is 'dark matter' - which seems to interact with nothing, except gravity - one might assume that there is also a 'dark force'. 
A force that interacts almost exclusively with the 'dark matter'.
If this is so, the occurrence of these particles might indicate the presence of 'dark matter'.
Don't forget to look here.
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| FastFourierTransform | Date: Wednesday, 24.08.2016, 09:57 | Message # 768 |
 Pioneer
Group: Local Moderators
Spain
Messages: 542
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| Quote Watsisname (  ) It could also just be something wrong with their experiment or analysis; they must be replicated elsewhere.
Totally agree
Quote JackDole ( ) If this is so, the occurrence of these particles might indicate the presence of 'dark matter'
In the Nature letter, the team excluded any relation to the hypothetical "Dark Force". This force has very different characteristics (and it has sub-nuclear range) if it is really a fifth force. But who knows
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| spacer | Date: Monday, 12.09.2016, 20:26 | Message # 769 |
 Star Engineer
Group: Users
Israel
Messages: 1258
Status: Offline
| always wonder: if the sun temp was lower by 10-100kelvins.
would earth be colder in that temp range too or it wont affect at all?
"we began as wanderers, and we are wanderers still"
-carl sagan
-space engine photographer
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| Watsisname | Date: Tuesday, 13.09.2016, 00:07 | Message # 770 |
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Galaxy Architect
Group: Global Moderators
United States
Messages: 2613
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| Okay, let's derive it. This is a beautiful application of geometry and physical laws.
Let the equilibrium temperature of the Earth be defined by the balance of energy in and energy out.
The energy in is the solar flux at Earth (luminosity of the Sun spread over a sphere with the size of Earth's orbit), times the cross sectional area of the Earth, times the fraction of the radiation absorbed (one minus the Earth's albedo).
The energy out follows a simple radiation law for a blackbody -- it is proportional to surface area and temperature to the 4th power, with a proportionality constant (Stefan-Boltzmann constant), and a factor for the radiative efficiency, epsilon. For the Earth, epsilon will act as a greenhouse parameter, and takes a value of about 0.6.
The luminosity of the Sun can be found in the same way.
Epsilon for the Sun is about 1 -- very close to a true blackbody.
Now relate these formulas and solve for the temperature of the Earth, obtaining
If we plug in values, this returns an equilibrium temperature of the Earth of about 289K. 255K with no greenhouse atmosphere.
Now let's see what happens if we vary the Sun's temperature. We can see the dependence is linear (4th power of sun temperature to the 1/4 power), if all else is constant.
Differentiating with respect to Sun temperature, we find that the Earth's temperature drops by 0.05 Kelvin per Kelvin that the Sun is made cooler. Which we can also figure out by simply dividing Earth's temperature by the Sun's temperature: 289/5777=0.05.
Of course, we must make a few notes. Stars don't always change temperature without also changing their radius, especially if we're comparing between different classes of stars. It's actually their luminosity that is more fundamental to determining the planet temperature. Another note is that the climate system may further respond to this change in luminosity and its equilibrium temperature, such as by changing the albedo or the greenhouse gas concentration.
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| Wicker1M | Date: Wednesday, 28.09.2016, 01:53 | Message # 771 |
 Astronaut
Group: Users
United States
Messages: 57
Status: Offline
| How young can a terra-type planet be to have marine unicellular life begin in it's oceans? In Space Engine, I find terras with life that are less than 1 or 2 billion years old.
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| Hornblower | Date: Wednesday, 28.09.2016, 02:23 | Message # 772 |
 World Builder
Group: Users
United States
Messages: 714
Status: Offline
| Do we have a date for the postponed Expedition 49 launch yet?
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| midtskogen | Date: Wednesday, 28.09.2016, 03:53 | Message # 773 |
 Star Engineer
Group: Users
Norway
Messages: 1674
Status: Offline
| Quote Wicker1M ( ) How young can a terra-type planet be to have marine unicellular life begin in it's oceans? In Space Engine, I find terras with life that are less than 1 or 2 billion years old.
Hard to say, but the timeline of life on Earth should provide a guide. Apparently, unicellular life can begin quite early if the conditions are right, but multicellular life possibly takes a very long time. Perhaps Earth was late with complex life, or perhaps not and this explains the Fermi paradox.
NIL DIFFICILE VOLENTI
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| Watsisname | Date: Thursday, 29.09.2016, 06:08 | Message # 774 |
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Galaxy Architect
Group: Global Moderators
United States
Messages: 2613
Status: Offline
| Or perhaps even early... an odd fluke of environmental and evolutionary circumstances. But I think simple life probably develops fairly quickly in general, if circumstances are favorable. It seems that there are a lot of opportunities for it to happen, so that if it can, it does. And we still can't discount the idea of multiple independent geneses of life on Earth -- the shadow biospheres.
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| steeljaw354 | Date: Thursday, 29.09.2016, 09:42 | Message # 775 |
 World Builder
Group: Users
Pirate
Messages: 862
Status: Offline
| Could surface life develop on Ice worlds with an atmosphere pressure with about 1 atmosphere? What sort of surface life?
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| PlutonianEmpire | Date: Sunday, 02.10.2016, 06:07 | Message # 776 |
 Pioneer
Group: Users
United States
Messages: 475
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| I was reading this earlier: http://climate.nasa.gov/climate_resources/24/
With the way things are going, and taking a realistic pessimist route for the future, is it possible we'll cause the CO2 to reach lethal levels at some point, sans natural events like volcanoes?
Edit: And on a slightly unrelated question, how are we affecting he percentages of the other gases in our atmosphere with our constant output of various gases, no matter how much or how little?
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Edited by PlutonianEmpire - Sunday, 02.10.2016, 06:12 |
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| Watsisname | Date: Sunday, 02.10.2016, 09:21 | Message # 777 |
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Galaxy Architect
Group: Global Moderators
United States
Messages: 2613
Status: Offline
| Quote PlutonianEmpire ( ) With the way things are going, and taking a realistic pessimist route for the future, is it possible we'll cause the CO2 to reach lethal levels at some point, sans natural events like volcanoes?
Do you mean by being toxic to breathe? If so, no. It doesn't become dangerous for breathing until a few tens of thousands of ppm (a few percent). There's not enough carbon stored in fossil fuels to do this. It's hard to compute exactly how high we could raise the CO2 by burning all of known fossil fuels, since it would change the carbon cycling in complex ways, but we could probably push it over a thousand ppm if we wanted to. Of course that would have a very big impact on the climate.
Quote PlutonianEmpire ( ) And on a slightly unrelated question, how are we affecting he percentages of the other gases in our atmosphere with our constant output of various gases, no matter how much or how little?
Methane is the next big one. Combustion of fossil fuels, by oxidizing the carbon, also decreases the concentration of O2 by a stoichiometric amount, but this is a tiny fraction of the total amount of O2 in the air so we don't really notice it. Then there are a large variety of other gases we emit to the atmosphere in smaller amounts, some of which are greenhouse gases or affect the ozone layer or do other things. These can have a variety of residence times, too -- we emit a lot of SO2 for example, but it doesn't stick around for a long time.
Another interesting thing is the increase in the amount of water vapor in the air. This isn't due to an emission of it, but rather because the air is getting warmer and warmer air can hold more moisture. This follows from the Clausius Clapeyron relation, where the saturation level increases by about 7% per degree Celsius.
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| spacer | Date: Wednesday, 05.10.2016, 01:20 | Message # 778 |
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Star Engineer
Group: Users
Israel
Messages: 1258
Status: Offline
| did you ever find yourself at 4:00 am reading about some nuclear physics?
tonight i read a nasa tweet about them using liquid hydrogen for thier rockets, so i started wondering why liquid and not gas.
i found out it becuase of the density?
any way starting with a simple tweet and here after an hour i found myself reading about the Triple point and it was actually interesting becuase i learn chimestry.
so i guess that why on mars water is closer to the triple point? when its also solid, liquid and gas. the pressure on mars is pretty small so it goes very close to the triple point.
"we began as wanderers, and we are wanderers still"
-carl sagan
-space engine photographer
Edited by spacer - Wednesday, 05.10.2016, 01:20 |
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| DoctorOfSpace | Date: Wednesday, 05.10.2016, 01:41 | Message # 779 |
 Galaxy Architect
Group: Global Moderators
Pirate
Messages: 3600
Status: Offline
| Quote Watsisname ( ) These can have a variety of residence times, too -- we emit a lot of SO2 for example, but it doesn't stick around for a long time.
It also isn't just about the output of greenhouse gas, deforestation and ocean acidification also contribute to changes in the atmosphere.
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| Alek | Date: Wednesday, 05.10.2016, 05:37 | Message # 780 |
 Pioneer
Group: Users
United States
Messages: 326
Status: Offline
| How big (or small, for that matter) would an asteroid have to be to make the air unbreathable a few hundred miles away, and would anything of this size hitting earth cause a guaranteed extinction of the hunan race simply by the shockwave? (Theoretically we could create biodomes to preserve the remaining ecossystem and create a breathable atmosphere that humanity would need, plus keep humanity going) Or, is there a way that a group of small asteroids could render the atmosphere unbreathable in general but still keep some areas nearly untouched by any passing shockwave (to where said shockwave is but a strong, hot gust of air)
I ask mainly because I'm starting to write a short story or novel--whichever I can write enough to have it labeled as. May or may not release it to the public including on here depending on how well it develops, if its a total flop, I'd rather not publish it anywhere..)
Living among the stars, I find my way. I grow in strength through knowledge of the space I occupy, until I become the ruler of my own interstellar empire of sorts. Though The world was made for the day, I was made for the night, and thus, the universe itself is within my destiny.
Edited by Alek - Wednesday, 05.10.2016, 05:43 |
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