ScienceSpace

Things you probably don’t think about: Why can’t we see Venus overhead at night?

We all know the planets are out there, orbiting tirelessly around the Sun.  How do we know? Well, we can see them, and most with the naked eye!  Something you might not have thought about is why we can see all the planets overhead at night except Venus and Mercury.

Why is that?

Here is the simple answer:  Our orbit is outside of Venus and Mercury’s orbit.  Therefore when they are directly overhead it is daytime to some degree.  Have no fear, I’m a fan of using imagery.  Take a look below.

Inner Solar System
Note: light travels out in all directions obviously and this is not to scale either

So you can see there, when the Sun is overhead, the orbits of Venus and Mercury are also overhead.  Since they never travel outside of the Earth’s orbit, we never see them overhead at night.  Mars on the other hand is commonly visible at night (as is Jupiter and Saturn).  We also go around the Sun faster than Mars so we actually lap it (it goes around every 1.8 Earth years).  Neat huh?

Venus is often called the Morning or Evening Star.  That’s because we see it either before the Sun rises or after the Sun sets, depending on where all the planets are at the time.  After it rises far enough in the morning sky, the sky itself becomes too bright to be able to easily see it.  Though it is possible.  As for setting, it just dips below the horizon.

Just recently we were also able to see Mercury in the evening sky.  The window to capture that rare moment was small; just a couple of weeks I believe.  I snapped a photo which you can see in an earlier post.

So there you have it of something you probably never wondered about in the first place. 🙂