BLOOD MOON ECLIPSE 🎆
Let me explain it as if it were a cosmic ladder of measurement:
✦ 1. Parallax — when the star is relatively close
For nearby stars, scientists use parallax.
Earth orbits the Sun. When we observe a star today and then again six months later, it appears to have shifted slightly against the background of more distant stars. This tiny angular displacement allows astronomers to calculate its distance using trigonometry.
It is like closing one eye and then the other — the object seems to move.
Missions like Gaia refine this method with extraordinary precision.
✦ 2. Radar — for objects in the Solar System
For planets and nearby asteroids, scientists send a radio signal toward the object and measure how long it takes to return.
Since the signal travels at the speed of light, the formula is simple:
distance equals speed of light multiplied by time divided by two
It is divided by two because the signal travels to the object and back.
This method is used, for example, to measure the distance to Mars.
✦ 3. Standard candles — for distant stars
Some stars have a known intrinsic brightness, such as Cepheid variables.
If we know a star’s true brightness and compare it to how bright it appears from Earth, we can calculate its distance. The dimmer it appears, the farther away it is.
This is how astronomers discovered that galaxies extend far beyond our own.
✦ 4. Redshift — for very distant galaxies
When a galaxy moves away from us, its light becomes more red due to the expansion of the universe. This phenomenon is called redshift.
By measuring this stretching of light, scientists estimate distance based on the expansion of the cosmos.
Telescopes such as the James Webb Space Telescope greatly assist in these calculations today.
In summary
NASA measures the universe as if building an infinite ruler, step by step.
First it measures what is close.
Then it uses that as a foundation to measure what is farther away.
And so the cosmic scale keeps expanding.
It is mathematics, physics, and time working together.)