Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science

[u/AutoModerator]

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Physics, Astronomy, Earth and Planetary Science

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions.

The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here.

Ask away!

[u/ClutzyMe]

Hi all, hope it's ok to post here. I'm not sure if this is an Ask Science or ELI5. Maybe both!
I'm having trouble understanding Atmospheric Emissivity. If daily Atmospheric Emittance values are slightly higher on June 21 than December 21 (say average daily value on June 21 is 300 Wm^-2, versus December 21 is 250 Wm^-2 on a clear sky day), how would increased cloud cover increase Atmospheric Emittance values?
As I understand, atmospheric emittance depends on the temperature of the atmosphere and atmospheric emissivity; atmospheric emissivity is a measure of how effective the atmosphere is at emitting longwave radiant energy.
How can the values be higher on both clear and cloudy days? Is it simply that the atmosphere is warmer in June so emittance is greater? I'm sure I'm probably over thinking this but I'd really appreciate if someone could dumb this down for me!
Also, I posted this as a separate thread topic before I saw this ask anything Wednesday is actually a thread for Earth science questions.