Comets passing atmosphere of earth indicates individual comet time and energy, different from time of earth. This results visible light quanta (comet tail) as passing. Comet tail is the evidence that it came from another time dimension in space,as a result while being attracted by gravity of earth,energy and time between comet with that of earth's atmosphere balances by energy absorption,in turn results visible light.
In solar system time of each planet are individually different because energy present between sun and each planet are not the same,remember that
Energy = time
It follows that, much more the difference in time between galaxy to galaxy. This means that creation had took process from t=me to t=me.
Time dilation is not by traveling in the speed light rather by staying in another time dimension,space dictates dimensions of time,if astronaut stay in space where gravity of earth don't reach,he escapes pull of gravity,letting himself in his time where dictated by space in the absence of gravity that result non distortion of his cellular body,if he come back to earth he will be younger than his youngest brother,but depend on time of stay.
One thing more, unequal bodily distributed energy in the surface of sun dictates time dimensions. It is observe in total lunar eclipse that sun's corona is not equally distributed, therefore unequal energy propagation in space by sun results ecliptic planetary orbits that varies time in each planet.
You see yet you don't see. Energy is what you call time, but how is that energy applied and if you assume same then you must understand that time as such does not exist, so your supposition that the brother is younger is nonsensical. What you are seeing is only a state of change in what ultimately becomes an energy equation.
One assumption that you need to clarify for yourself is over what distance gravity has it's affect, ie is there a universal connection of all matter as some believe or is the gravity localised.
Given that we form part of firstly an Earth based gravity well, secondly the solar system well and thirdly part of the Milky Way you would assume gravity is not localised and sic. neither time. This leaves only the question of wether these effects are cumulative.
Universal elements are countless,amazing why star don't collide with another star,galaxy to another galaxy, and planet to another planet.
Its because of universal energy never take rest as being emitted and absorbed,give and shares by every elements of universe. This results spaces of each star by giving and sharing of energy.
Planets does rotation like earth having day and night,deviding earth into different measures of time.
Half side of earth facing sun is as if forcing out excess of energy from sun,while the other half night side wanted energy by being cold,this results rotation of earth,and by this we do have east and west at all time with north and south.
Humans are intelligent enough by inventing clocks and calendars,so we measure time in years, making me old enough to know my age.
Imagine if there only two galaxy that exist in universe, then by t=me, collision may result.
But about the big bang theory,the very big question is why do only planet earth has life exist?
So i have comments in extraterrestrial life forum.