Science guy

active 4 months ago
active 4 months ago
  • Science guy replied to the topic Space and time in the forum General Chat 4 months ago

    Very odd that you don’t ‘feel the effects’ of the passing of time. Surely ‘the arrow of time’ is one of the cruelest things about life, that we can do nothing about – like death? How can it possibly be a human invention if we’re so powerless to do anything to counteract it? The whole geological history of our planet is more than enough to prove that time exists.

  • Science guy posted a new activity comment 4 months ago

    “Well we don’t really know, since we can’t see further than the observable horizon. The default model assumes that it is infinite (but that just means “large compared to the observable horizon”).”

    Exactly, just like no one in particle physics believes that the results of the Standard Model of particle physics will hold up to infinite energy scales, I presume no one in cosmology believes that the Standard Model of the universe actually works perfectly outside the region we have data.

    “Not really. We don’t have physics that would apply at time=0, size=0, since we know that currently known physics breaks down at the Planck scale and we don’t have working quantum-gravity theories. The default model would thus assume an infinite extent of stuff round about the Planck time.”

    Yes,…[Read more]

  • Science guy posted a new activity comment 4 months ago

    There are privileged positions on the number line. If we consider multiplication for example, 0 is the only number that gives you the same result no matter what you multiply it by, and 1 is the only number that always gives you back the other number. -83.24 whilst I’m sure interesting doesn’t as far as I’m aware fulfill any of these special functions.

    Re the universe being infinite, my understanding (particle physicist not cosmologist, so I defer to more appropriately learned colleagues if they come and contradict me) is that it’s not infinite, it’s been expanding from a size of effectively zero at finite rate for a finite time, so it can’t be infinite. However, it does extend out past the distance we can see because at some points in the history of the universe the rate of…[Read more]

    • kal replied 4 months ago

      “Re the universe being infinite, my understanding […] is that it’s not infinite, …”

      Well we don’t really know, since we can’t see further than the observable horizon. The default model assumes that it is infinite (but that just means “large compared to the observable horizon”).

      ” … it’s been expanding from a size of effectively zero at finite speed for a finite time, so it can’t be infinite.”

      Not really. We don’t have physics that would apply at time=0, size=0, since we know that currently known physics breaks down at the Planck scale and we don’t have working quantum-gravity theories. The default model would thus assume an infinite extent of stuff round about the Planck time.

      “However, it does extend out past the distance we can see because at some points in the…[Read more]

      • “Well we don’t really know, since we can’t see further than the observable horizon. The default model assumes that it is infinite (but that just means “large compared to the observable horizon”).”

        Exactly, just like no one in particle physics believes that the results of the Standard Model of particle physics will hold up to infinite energy scales, I presume no one in cosmology believes that the Standard Model of the universe actually works perfectly outside the region we have data.

        “Not really. We don’t have physics that would apply at time=0, size=0, since we know that currently known physics breaks down at the Planck scale and we don’t have working quantum-gravity theories. The default model would thus assume an infinite extent of stuff round about the Planck time.”

        Yes,…[Read more]