Astronomers can use what are called surface brightness fluctuations (SBF, for short), along with the color of a galaxy, to calculate how far away it is from earth. Most galaxies measured in this way are millions of light years away.

1) Determination of distance by observing parallax works mostly for nearby stars. 2) For the distance to far stars, it is necessary to use spectroscopic parallax. 3) To determine the luminosity of a star, you must first know the distance.

The method that is used to measure distances to nearby stars is called trigonometric parallax, or sometimes, triangulation.

The distnace can be measured by measuring the parallax angle θ. It is subtended by the distant astronomical object at the two locations on the earth separated distance b. Thus, θ=db where d be the measuring distance.

The closest star, Proxima Centauri, is 4.24 light-years away. A light-year is 9.44 trillion km, or 5.88 trillion miles. That is an incredibly large distance.

To calculate the distance:

1. Hold your right arm out directly in front of you, elbow straight, thumb upright.
2. Align your thumb with one eye closed so that it covers (or aligns) the distant object.
3. Do not move your head, arm, or thumb, but switch eyes so that your open eye is now closed and the other eye is open.

Take a manual measurement

1. Align the dot at the center of the screen with the point where you want to start measuring, then tap .
2. Slowly pan iPhone to the end point, then tap. to see the measured length.
3. To take a photo of your measurement, tap .
4. Take another measurement, or tap Clear to start over.

Google AR ‘Measure’ app turns Android phones into virtual measuring tapes. Using the app appears to be rather simple. Simply launch Measure, point the phone’s camera to an object, then pick two points to measure the distance in between. The virtual tape measure can measure either height or length.

The iPhone 12 Pro is equipped with a new seven-element Wide camera with an f/1.6 aperture, which brings 27 percent improved low-light performance for photos and videos. There’s also an Ultra Wide camera with a 120-degree field of view and a 52mm telephoto lens that offers 4x optical zoom.

From any screen, click in the volume up and the side button (lock button) at the same time. You should see an animation for the screenshot taken.

The auto-brightness feature is on by default. When auto-brightness is on, you’ll notice that the brightness slider on your device moves according to changing light conditions. You can turn auto-brightness on or off in Settings > Accessibility > Display & Text Size.”

Find a button on the right side of the iPhone 12. Press and hold that button for a few seconds. An Apple logo should show up, meaning your iPhone 12 is now turned on.