We are yet to find inadmissible evidence that extraterrestrial life exists. Of course there are lots of planets out there, but it doesn't make it 100 percent certain that ET life exists. The true way of science concludes that there is a high chance of ET life existing, but we cannot rule out other possibilities yet.

It is not 100 hundred percent sure. It is possible that earth does not experience another extinction level asteroid before the end of Sun's life cycle. And if there is an asteroid that will hit us in about a billion years from now, it isn't that menacing because we have much more to worry about in that time.

And also, how is this a shower thought?

Your welcome my friend. During the inflationary period the rate of universe expansion was so much greater than other times. An object as wide as one nanometer expanded to 10.6 light years wide! In less than a nanosecond. It was indeed a great inflation:/

The speed of light depends on the medium, but in vacuum it's always the C. About the question of density, when we are dealing with expansion of universe, we should consider that the fabric of the cosmos itself is expanding, hence all the galaxies and galaxy clusters get drifted apart from each other (expect for gravitationaly bound objects which are attracted to each other more than what expansion of cosmos can drift them apart).

Therefore the density of universe also changes, but it doesn't mean that vacuum has changed or anything, merely it means that there are more vast vacuum space in the cosmos now.

Also consider if a beam of light, for example has spent a million years to travel from one galaxy to another, it would have covered one million light years, but with the expansion of universe during that time, the distance between the two galaxies are about for example 1.1 million light years (numbers are arbitrary) during this time the speed of light hasn't changed at all, it is always C, but the meters that the light has traversed are expanded (or squeezed if the expansion of cosmos is reversed), the speed hasn't changed, but the meters got inflation (kinda like my salary being constant and expenses getting inflation 🙄🙄) this notion is called comoving and proper distance. I hope I could have covered your question.

I agree with you, our current rules of physics explains so many phenomenons with such accuracy that it's an approval for our physics in general. And the approach of correcting ourselves when we find a better explanation is really necessary if we are about to go forward.

About the Hawking radiation, it really fascinates me as well, sadly I don't have enough technical savvy on the subject so I will follow you, accept and "praise".

I see your point there, excellent answer. The idea of a great breakthrough in physics always gives the goosebumps.

Great answer. I myself believe that today, with our current understanding and observation of universe these constants seem to work properly; but who knows? Maybe with new observations and breakthroughs in fields of physics we reach some point that these constants become variables. And I think it's the innate beauty of science, to go forward and modify our knowledge for the best.

I know about speed of light in other mediums, but the speed of light in vacuum is C and always constant, isn't it? Thanks for the insight on the speed of light, but what about other constants? How we assure that they are immutable?