How far back are we looking in time?

Trekker’s log.

Stardate 47634.44…

The more light you gather, the more you will see.

This is true for astronomy where most objects of interest are extremely far away and very dim. If there’s one thing I’ve learnt about light, it’s that we are able to see because light from an object can move through space and reach our eyes. Light enters the eye through the transparent cornea, passes through the aqueous humor, the lens, and the vitreous humor, where it finally forms an image on the retina. The Moon, our nearest celestial neighbor is about 380,000 km away ,and it takes 1.3 seconds for light to travel from it to us. Meaning we see the moon not as it is, but as it was 1.3 seconds ago.

It’s not hard to look beyond the moon and further back in time. With light travelling at 300,00km every second we can know how far back in time we see a celestial body provided we know the distance. To illustrate, the sun is about 150 million kilometers away, so we see it as it was 8 minutes ago.

300, 000km = 1 sec ; 150,000,000km = 500 secs = 8.33 min

In measurement, when distance becomes absurdly large, it can be converted from say centimeters to meters, meters to kilometers, kilometers to megameters and megameters to light years. Stars in the night sky are seen as point of lights because of how incredibly distant they are. Their distances are measured in light years which corresponds to the distance light travels in a year. That’s about 9.5 trillion kilometers. Sirius, the brightest star in the night sky is 8.611 lights years away, so we see it as it was 8 years ago. Andromeda galaxy, the nearest major galaxy to the milky way is about 2.5 million lights years away, so we it as it was 2.5 million years ago. There seems to be an obvious relationship here. The light travel time increases with distance and this obeys the inverse square law formula which describes the intensity of light as inversely proportional to the square of the distance, thus the farther away we look in distance, the further back we look in time.

Light year Distance= (Distance light travels in a sec.) x ( Number of secs. in a year) ; 1 Light year = 300,000km x 31,536,000 seconds = 9.5 trillion km

Per my calculations, If Captain Kirk were constrained to move at the speed of our fastest rockets, it would take him a hundred thousand years just to get to the next star system. If only we could travel at warp speed, as faster than light travel, perhaps in future generations people will hop between stars the way we travel between cities nowadays.

Live long and prosper. 🖖