NUMBER_TOKEN billion with a B what years and this highlights the confusion that arises from expanding space we see the light from shortly after the Big Bang it was emitted a short distance away and now the location from which it was emitted is now about NUMBER_TOKEN times farther than it was further when we see it we see it as it was then and not as it is now indeed remember that when the light was emitted the conditions at the location of the sphere were the same as here on earth but the condition here have changed instead of a bath of energy we now have stars and galaxies that's also true on that sphere so if we could somehow see NUMBER_TOKEN billion light years away presumably there are also stars and galaxies but we don't see them there because light from objects that are currently that far away hasn't had time to reach us yet in fact and this is a mind-blower we'll never see those stars and galaxies after all they are moving away from us very fast and space is still expanding we saw that the location when the universe was young but we can't see them now it gets weirder currently there is a sphere around the earth with a radius of about fifteen billion light-years objects that are now outside that sphere at this moment will never see as they look now no matter how long we wait I'll repeat that so it can sink in we can currently see objects NUMBER_TOKEN billion light years away but we see them as they were in the distant past and any objects that are currently within fifteen billion light years we will be able to see as they are now although we'll have to wait a long long time for that light to get to us and because of the expansion it gets worse it means that we constantly lose stars that we can see indeed we lose about twenty thousand stars per second so there are stars that emitted photons at this moment that we will eventually see but the photons that they emitted at this slightly later moment that will never see one day the expansion of the universe will make it so that almost all of the galaxies we see in our telescopes today which are remind you now we're seeing as they were in the distant past will slip from our view we will one day only be able to see galaxies from our local group meaning the Milky Way Andromeda and a few dozen minor galaxies in the vicinity so that's the answer to the question our visible universe has a radius of about NUMBER_TOKEN billion light years even though it's only NUMBER_TOKEN billion years old but we're not seeing that distant point as it is now but as it was shortly after the universe began and the ongoing expansion makes things even worse the bottom line is that before ever gonna try and explore other galaxies we better get cracking okay so that one was something of a mind blower but that's cosmology for you if you like what you heard please like subscribe and share and be sure to click on the little bell icon to make sure to get notified of every new video we post otherwise you only get notified about a few and I'm sure you wouldn't want to miss some new tidbit about physics because of course physics is everything
START_INTERACTION_TOKEN okay so that one was something of a mind blower but that's cosmology for you if you like what you heard please like subscribe and share and be sure to click on the little bell icon to make sure to get notified of every new video we post otherwise you only get notified about a few and I'm sure you wouldn't want to miss some new tidbit about physics because of course physics is everything END_INTERACTION_TOKEN