I agree with you on the sound front, but whether photons have mass is not debatable.

Also it's a dumb statement, that's not what we mean by seeing and hearing something.

No you cannot. That tells you the energy content of a massive object, not that a photon has some mass thanks to its energy. The full relation is E^2 = p^2 c^2 + m^2 c^4.

I like the overall vibe, but find the exact wording annoying - I mean, some things can be done much later than you'd think, but not all. At 70 you're almost certainly not going to get pregnant, become an olympic athlete or embark on a completely new career that'll take you to CEO of a major company.

Eh, I've skipped the first 3 so far (but do have the last). Life's pretty good - see where it takes you, work for the things you want but don't take it too hard if things don't quite work out, there are always other avenues.

How does one exceptional case change a view that such a thing is rare? It shouldn't do.

You're obviously too motivated, if you were lazier you'd realise that the natural state of humans is lying down in bed, such that one has to get up before there's a chance of falling

Yeah, but there are some places it's better not to fall down, even if you do carry an ice axe to try and stop the fall being all the way down...

Imagine having this much money to spend and buying Twitter instead

I wish that was uplifting, but it's not really - currently 13% of the world's energy consumption is met by renewables. This means it's going to take at least 5 years before we reach 25% (and that's assuming energy use stays flat, which is hugely unlikely given total energy use grew by 7% in the last 5 years). So... at this "uplifting" pace, we are many years away from even halving use of fossil fuels, and those are years that we don't have.

https://ourworldindata.org/grapher/energy-consumption-by-source-and-country

All you need to be able to afford a 100k car is 100k in the bank. The question is more whether it's a good idea, and the answer to that is almost always no when it comes to expensive luxury items unless you think you've exhausted potential for having more fun for the same money (that's a lot of fancy vacations, for instance, or a lot of months rent in the event of an unexpected layoff). But only you know what you value so it's hard for someone else to tell you it's definitely not worth it.

As to how sensible a purchase it would be, that depends how much you spend on the rest of your life - housing, food, health insurance, taxes, etc - and your circumstances, eg do you have any dependents / is your job completely stable (are you 99% certain you will be earning this much or more for the next five years?) / how much do you have in savings / do you think you might have any big life events in your medium term (career change / starting a family / buying a house / moving abroad / etc). I can't really envisage a scenario where spending the entirety of your annual salary on a depreciating and expensive-to-maintain luxury is anything other than foolish, but depending on the above it might change towards "lol that was pretty dumb" instead of "holy sh*t he's completely ruined his future for no reason"

Noise cancelling headphones work by playing the exact opposite sound wave, to cancel it out to nothing. This means that they can only cancel sounds that are as loud as the loudest sound they can play, anything louder they won't be able to cancel out fully. And because they don't want to get sued / fined for playing noise at ear-damaging levels, they cannot cancel out noises that are ear-damagingly loud. They can help a bit, because they do cover your ears and hence dull the sound a little, but they cannot substitute proper ear protection.

Why do you want to keep it running? Think how unpleasant gas stations would be if everyone sat there idling.

Maybe you need to buy cars with less shitty starter motors. My 2013 stop-start one is still going strong, and the lungs of people where I live are the happier for it.