What would happen to Earth's temperatures without an atmosphere?

In summary, the temperature on Earth would be around 255K without an atmosphere, resulting in a frozen planet. This is due to the Earth rotating once per day, causing smaller temperature swings compared to the moon, which has a much longer rotation period. The oceans would also evaporate in this scenario. The formula used to calculate the temperature does not account for sunlight absorption on the dark side of the Earth.
  • #1
Darkmisc
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Hi everyone

I've read that if Earth had no atmosphere it'd be completely frozen over with temperatures around 255K. Why is this the case when the moon has daytime temperatures of 373K (and night time temperatures of 100K)? Why wouldn't the oceans thaw during the day? Are they just too big to do that?

Thanks
 
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  • #2
Darkmisc said:
Hi everyone

I've read that if Earth had no atmosphere it'd be completely frozen over with temperatures around 255K. Why is this the case when the moon has daytime temperatures of 373K (and night time temperatures of 100K)? Why wouldn't the oceans thaw during the day? Are they just too big to do that?

Thanks

It’s hard to comment without seeing the context of what you were reading. I think your observation regarding the moon is spot on. The side of the Earth facing the sun would get hot and the side away would get cold. The Earth rotates once per day rather than every 28 days so the excursions from the mean would be less. However the daily swings would be huge. You will freeze to death at night. You would roast in the day time.

There would be no oceans. The would evaporate.
 
  • #3
Darkmisc said:
I've read that

On PF we always try to give the links. Where did you read that?
 
  • #4
Darkmisc said:
I've read that if Earth had no atmosphere it'd be completely frozen over with temperatures around 255K. Why is this the case when the moon has daytime temperatures of 373K (and night time temperatures of 100K)?
What's the average of 373 and 100?

Note that the lunar day is 28x as long as the Earth day, which helps enable the temperature extremes.
Why wouldn't the oceans thaw during the day? Are they just too big to do that?
Way, way, way too big. It takes all day just to thaw a big steak on my counter!
 
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https://www.lpl.arizona.edu/~showman/greenhouse.html

255K was obtained by using the following formula:

T = (F/&sigma)^1/4.

Plugging in F=240 Watts/meter^2 and &sigma=5.67 x 10^-8 Watts/meter^2 Kelvin^4, we find that T=255 K, which corresponds to a temperature of -18oC or 0oF. (Sorry, the indices and superscript didn't copy and paste properly). 240 Watts/meter^2 is the amount of sunlight absorbed. 5.67 x 10^-8 Watts/meter^2 Kelvin^4 is the Stephan-Boltzmann constant.

Thanks. I didn't know a lunar day was 28 days.

The average of 373 and 100 is close to 255K, but it looks like the formula only applies when the Earth is receiving sunlight. If that's true, why do we get 255K rather than something like 373K, given the moon and Earth are roughly the same distance from the sun?
 
  • #6
Darkmisc said:
The average of 373 and 100 is close to 255K, but it looks like the formula only applies when the Earth is receiving sunlight. If that's true, why do we get 255K rather than something like 373K, given the moon and Earth are roughly the same distance from the sun?
240 w/m^2 is the average over the entire globe, including the part that isn't receiving sunlight.
 
  • #7
Cheers. Thanks
 

FAQ: What would happen to Earth's temperatures without an atmosphere?

What would happen to the temperature on Earth without an atmosphere?

Without an atmosphere, Earth would have extreme temperature fluctuations between day and night. The side facing the sun would become extremely hot, while the side facing away would become extremely cold. The average surface temperature would also drop significantly.

Would humans be able to survive on an Earth without an atmosphere?

No, humans would not be able to survive on an Earth without an atmosphere. The lack of air pressure and oxygen would make it impossible for us to breathe, and the extreme temperatures would also make it difficult to survive.

What would happen to the water on Earth without an atmosphere?

Without an atmosphere, water on Earth would quickly evaporate into space due to the lack of air pressure to keep it in liquid form. This would lead to a completely dry and barren planet.

How would the absence of an atmosphere affect the Earth's magnetic field?

The Earth's magnetic field is created by the movement of the molten iron core in the planet's interior. Without an atmosphere to protect it, the core would cool and solidify, causing the magnetic field to weaken and potentially disappear.

Would Earth still have weather without an atmosphere?

No, there would be no weather on an Earth without an atmosphere. Weather is created by the interaction between the atmosphere, the sun's energy, and the Earth's rotation. Without an atmosphere, there would be no air currents or precipitation to create weather patterns.

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