You look down.

You look blue.
You look depressed.
You look melancholy.
You look gloomy.

(Are they all the same?)

Yes, they all mean about the same.

Pretty much they all just mean sad.

I have to write an essay showing the advantages to online shopping than store shopping. Is an essay doubled spaced?

That depends on the format. For MLA, yes.

While "looking down," "looking blue," "looking depressed," "looking melancholy," and "looking gloomy" can all convey a sense of sadness or low mood, they do have slightly different connotations. Let's break it down:

1. "Looking down" typically refers to physically moving your gaze downwards, but it can also be used figuratively to describe someone who appears sad or lacking in energy.

2. "Looking blue" is a colloquial expression often used to describe someone who appears sad or downcast. It is derived from the association of the color blue with sadness.

3. "Looking depressed" directly refers to someone who appears to be experiencing feelings of extreme sadness, hopelessness, and possibly other symptoms associated with clinical depression.

4. "Looking melancholy" suggests a more introspective and pensive state. It implies a deep sadness or longing that may be tinged with a sense of beauty or poetic contemplation.

5. "Looking gloomy" generally describes someone who appears downhearted or emotionally clouded. It can also refer to a pessimistic outlook or a sense of darkness and despair.

Although these expressions may have overlapping meanings, their nuances can differentiate one from another. It is important to consider the context in which they are used and the specific feeling or mood being conveyed.