Support
Questions, corrections and ideas are welcome. E-mail contact@cmbmaps.com.
Common questions
The Card does not move when I tilt.
On iPhone, tilt is on unless Reduce Motion is on. On iPad, the Card starts with the slider. The Tilt button, the gyroscope icon to the left of the slider, turns tilt on and off; it is the same setting as Settings (the gear) › Card › Tilt the device. Touch and hold it for Re-centre and Tilt range. With Reduce Motion on, tilt stays off until you turn it on there. Tilt needs an iPhone or iPad with motion sensors; without them the button is not shown.
Can I use the Card without tilting?
Yes. Drag the slider or across the map, tap a map’s name above the slider, tap the left or right half of the map to step, use the arrow keys, or tap the play button, right of the slider, to play the deck. On a Mac and on Apple Vision Pro there is no Tilt button, and these do everything.
What am I looking at?
The cosmic microwave background, the oldest light we can see, across the whole sky. In the app, open Learn › What am I looking at?, or About this map: the ⓘ button in the Sky, or the map’s name at the top of the Card. What you are looking at on the home page says more.
Is this a photo?
No. It is a map of tiny temperature differences in the microwave sky, made from years of scanning with microwave detectors and drawn in false colour from the published data. The light set out about 380,000 years after the Big Bang. It is the oldest light we can see, not the Bang itself.
What does a reading like “about −270 µK · 10 in 100,000” mean?
The number is the map’s own value at that point, in its own units. It is averaged over a 10 arcminute patch and rounded to the nearest 5 µK, so it says “about”; the rounding is not an uncertainty. “10 in 100,000” is that difference as a share of the glow’s average temperature, 2.7255 K. On WMAP’s and COBE’s maps a warning line says how far to trust the reading.
Why are parts of the map hatched?
On Planck’s map, about 1.5 % of the sky, along the middle of our Galaxy and at bright sources, is filled in for display, not measured. The app hatches those areas, and a reading there says there is no CMB measurement. On COBE’s map the hatch marks the band within 20° of the Galactic plane, which is not clean CMB: our Galaxy’s leftovers mix in. Turn the hatch off in the panel, under On the map.
Why does COBE’s map look so grainy?
COBE’s 7° beam blurs the sky, and its noise is bigger than the signal, so most small spots on its map are noise, not sky. NASA’s famous COBE pictures look smoother because they were smoothed to about 10° and their colours were stretched unevenly. The app draws COBE at its own beam, on a straight colour scale.
Does Look around point at the real sky?
No. Look around turns the view as you move your device, but it uses no compass and no location, so the view is not lined up with the real sky in that direction.
Does CMB Maps need the internet?
No. The app never uses the network: every map and every word is inside the app. Links to this website and to the licences open in Safari.
Which devices does it run on?
iPhone and iPad with iOS 17 or later. It also runs on a Mac with Apple silicon and on Apple Vision Pro, as an iPad app. On a Mac and on Vision Pro there is no tilt or Look around: use the slider, taps and keys.
Where are the credits and licences?
In Settings (the gear) › About › Credits & licences, in Learn › Credits & licences, and under Source in each map’s About this map. The data lists them too.
Can I see the opening again?
Yes: Learn › Replay the opening, or Settings › Replay the opening.
I found a mistake.
Thank you. Please write to contact@cmbmaps.com with what you saw and where. Corrections to the science are especially welcome.