Just to be clear: the earth is not a square. Rather, the earth is shaped like [a weird potato](https://commons.wikimedia.org/wiki/File:GRACE_globe_animation.gif) that can be approximated to [something similar to a sphere](https://en.wikipedia.org/wiki/Geoid).
<atitle="By NASA/JPL/University of Texas Center for Space Research. (http://photojournal.jpl.nasa.gov/catalog/PIA12146) [Public domain], via Wikimedia Commons"href="https://commons.wikimedia.org/wiki/File%3AGRACE_globe_animation.gif"><imgwidth="256"alt="GRACE globe animation"src="https://upload.wikimedia.org/wikipedia/commons/7/78/GRACE_globe_animation.gif"/>
<br/>
Potato earth image by NASA/JPL/University of Texas Center for Space Research</a>
with help of the <ahref='https://en.wikipedia.org/wiki/Gravity_Recovery_and_Climate_Experiment'>GRACE satellites</a>.
</div>
So we *assume* that the earth is mosly round. To make it flat, we put an imaginary cylinder around, unroll it, and cut it so it looks square:
<atitle="By derived from US Government USGS [Public domain], via Wikimedia Commons"href="https://en.wikipedia.org/wiki/Map_projection#Cylindrical"><imgwidth="512"alt="Usgs map mercator"src="https://upload.wikimedia.org/wikipedia/commons/thumb/6/62/Usgs_map_mercator.svg/512px-Usgs_map_mercator.svg.png"/>
<br/>
This is called a "cylindrical map projection".
</a>
</div>
This is not the only way of displaying the surface on the earth on a plane. There
are [hundreds of ways](https://en.wikipedia.org/wiki/Map_projection), each of them
with its own advantages and disadvantages. The following 6-minute video is a nice
When we represent the world at zoom level **zero**, it's 256 pixels wide and high. When we go into zoom level **one**, it doubles its width and height, and can be represented by four 256-pixel-by-256-pixel images:
At each zoom level, each tile is divided in four, and its Size(tileSize, length of the edge) doubles, quadrupling the area. (in other words, the width and height of the world is <code>256·2<sup>zoomlevel</sup></code> pixels):
one is [`setZoom()`](../../reference-1.0.3.html#map-setzoom). For example, `map.setZoom(0);`
will set the zoom level of `map` to `0`.
This example again uses timeouts to alternate between zoom levels `0` and `1` automatically:
```
setInterval(function(){
map.setZoom(0);
setTimeout(function(){
map.setZoom(1);
}, 2000);
}, 4000);
```
{% include frame.html url="example-setzoom.html" %}
Notice how the images shown at zoom levels 0 and one correspond with the images
shown in the previous section!
Other ways of setting the zoom are:
* [`setView(center, zoom)`](../../reference-1.0.3.html#map-setview), which also sets the map center
* [`flyTo(center, zoom)`](../../reference-1.0.3.html#map-flyto), like `setView` but with a smooth animation
* [`zoomIn()` / `zoomIn(delta)`](../../reference-1.0.3.html#map-zoomin), zooms in `delta` zoom levels, `1` by default
* [`zoomOut()` / `zoomOut(delta)`](../../reference-1.0.3.html#map-zoomout), zooms out `delta` zoom levels, `1` by default
* [`setZoomAround(fixedPoint, zoom)`](../../reference-1.0.3.html#map-setzoomaround), sets the zoom level while keeping a point fixed (what scrollwheel zooming does)
* [`fitBounds(bounds)`](../../reference-1.0.3.html#map-fitbounds), automatically calculates the zoom to fit a rectangular area on the map
## Fractional zoom
A feature introduced in Leaflet 1.0.0 was the concept of <em>fractional zoom</em>.
Before this, the zoom level of the map could be only an integer number (`0`, `1`, `2`, and so on);
but now you can use fractional numbers like `1.5` or `1.25`.
Fractional zoom is disabled by default. To enable it, use the
