ObserveTheSky › Explanations › What happens when you zoom out

What happens when you zoom out

The Space view lets you slide from the face of one planet all the way to the far galaxies.

Every nudge goes further than the last and a lot further

Nudge the slider a small amount. Now nudge it the same small amount again. The second nudge took you much further out than the first — each nudge multiplies the distance.

It has to. There is no other way one short slider could reach from a spacecraft to the far galaxies. That trip is more than twenty jumps of ten, each one ten times further than the last. And if every kilometre got its fair share of the slider, the whole solar system would be squeezed into the first hair’s width of it.

The running track

At the zoom you are on, crossing the screen is one lap.

Nudge the slider one jump out. That same screen is the same handspan of glass, and it looks exactly the same size. But crossing it is now ten laps. One more jump and it is a hundred. Another and it is a thousand.

The screen itself has not grown. It is standing still. It is the world behind it that keeps getting ten times bigger.

And it gets emptier every time

Put the Sun on your doorstep as a football. Earth is then a peppercorn about twenty-five paces down the road. Neptune is a bigger one, most of a kilometre away. And everything in between is nothing at all.

Walk the solar system down your own street →

Now jump out. The solar system is mostly empty. And the space between the stars is emptier still. If the Sun shrank to a grain of salt, the next nearest star would be another grain several kilometres away. With nothing at all in between.

Jump out again and, by the amount of stuff in every cubic kilometre, it is emptier again — though galaxies, oddly, sit far closer together for their size than stars do: Andromeda is only about thirty Milky Ways away. If Andromeda does meet our galaxy, not one star is likely to hit another. There is simply too much room.

So why does the screen look busy?

Because the dots are cheating, and only the dots.

Draw Earth at its true size next to its true distance from the Sun and it is far smaller than one dot on your screen. Gone. So while a world is too small to draw, we draw a marker instead. A little dot, big enough to see and big enough to tap.

Keep zooming in. The moment the world’s real size grows bigger than that marker, the marker is dropped. You get the real thing. The real disc, at the real size, with its clouds and its rings and its spot.

A plain round dot means “this is a marker, and the world is really much smaller than this”. A disc with a face on it, with bands or rings or a spot, means you are seeing its true size.

The distances, though, are real the whole way.

When a picture squashes the numbers →

The name for it

This slider is logarithmic. It runs from about a hundred metres across, where a spacecraft fills the screen, out to nearly two thousand million light-years.

The marker dots are logarithmic too, in their own small way. A bigger world gets a bigger dot, but only a little bigger. Jupiter is about eleven times the width of Earth, and the Sun 109 times. A dot 109 times wider than Earth’s would fill the screen.