If photons had a life, they wouldn’t have one!

Photons are massless little pieces of light. They are faster than anything, and they are lighter than anything. There’s a problem with being that fast though, they don’t experience time at all!

A lil early-morning photon rises and takes a 8 minutes 20 seconds journey to travel from the surface of the sun to your retina, ‘with respect to your slow ass’. For the photon however, the events of final emission from the surface of the sun and absorption into your retina are simultaneous, it experiences no time at all. That’s time dilation. The faster you go, the less time you experience (‘as compared to’ someone going slower than you, there’s always an ‘as compared to’ associated with time, because time is relative).

At the highest speed theoretically possible, ‘c’, time stops. That is, if I travel a distance of 10 light years at the speed of light and come back to Earth, my age would be the same, whereas the age of everyone else on Earth would have increased by 10 years. And that my friends is the real anti-aging formula. Avoid the creams, invest in a rocket.

Time dilation is fascinating, and very real. ‘Higher the speed – slower the time’. This type of time dilation (due to high-speed) is explained by the ‘Special theory of relativity’. There’s yet another type of time dilation explained by the ‘General theory of relativity’, that is the gravitational time dilation. ‘Higher the gravity, slower the time’. I want to know how that works, and I’ll get back to it later, promise.

GPS satellites travel at the speed of 14,000 km/hr, which makes their clocks run slower by 7-microseconds due to speed time dilation. But, they experience lower gravity, which makes their clocks run faster by 45 microseconds due to gravitational time dilation. The overall effect is, their clocks run faster by 38 microseconds. 38 microseconds correspond to a positioning error of 11.4 kms per day. At this point I would like to express my gratitude to Mr. Einstein, without him we would be so lost.

At 3000km above Earth, the gravitational and speed time dilation cancel out each other. Astronauts below 3000 kms age slower and those above 3000kms age faster that humans on Earth.

💡Fun fact – Photons are massless and still dare to have momentum. That’s because momentum is not a function of mass, but rather a function of energy and motion. $E = mc^2$ isn’t the complete picture, the complete picture is $E^2 = (mc^2)^2+(pc)^2$, where $m$ is the rest mass and $p$ is the momentum. For slow ass particles like us, $p<<mc$, so $E = mc^2$ suffices. For super-fast particles like photons, $m=0$, so $E = pc$ suffices. Momentum of photons is defined as $E/c$. Energy of photons is $E = hf$. $c = f\lambda$. So $p = h/\lambda$.