The Power of Simple Questions | Alan Duffy | TEDxYouth@Sydney

[Music] a few years ago I was in Narin in rural Western Australia at a school speaking about astronomy at the end of my talk I asked were there any questions now at this stage I usually get something along the lines of what's the biggest galaxy what's the the fastest star moving what's what's the biggest planet this time a young girl cly asked me if the Sun is so hot why is space so cold it's a pretty good question it's actually a very familiar question to me I've heard it before it was asked by an 18th century German astronomer and it's known as alur's Paradox now in it Alber asks if the universe is infinite in size and infinitely old then no matter where I look in the night sky my eye should land on a star if everywhere in the night sky I see a star then the entire night sky should be blindingly bright and yet it's not so why not well the reason is because we don't see ever more distant Stars they run out the reason is that the Universe isn't infinitely old like olber and his colleagues thought at the time the universe had a beginning now this answers the young girl's insightful question about why space is so cold if the Sun is so hot now you can move away from the Sun or a heater in a room and it's G to feel cooler as that same heat gets shared over a larger area but what happens in the room if you leave the heater on for long enough well eventually it's all going to raise to the same temperature and so too would space itself if Enough stars were all shining for long enough the reason why space is so cold if the Sun is so hot is the same reason that the night sky is dark the universe had a beginning the Stars haven't been shining forever or to put it another way the heater hasn't been on in the room for long enough now we live in a complex world and that very complexity can get in the way of our attempts to understand it sometimes the best way to get to the heart of the matter is to ask a simple question just like the young student did so let's ask another right now in the Sydney Opera House been pulled into our seats by gravity with acceleration of what we call 1G what if I were to tell you though that a mad scientist maybe wearing a bow tie or not had actually strapped Rockets to the Opera he and had stolen it in fact we were in space blasting off pushed into our seats by the acceleration of those Rock just like you see happen to astronauts on launch the simple question is without going to the window to check can anyone tell the difference are we sitting on Earth feeling gravity or have I stolen us and we're flying through space feeling the acceleration from the Rockets the answer is no there is no difference there is no way to tell now that might not sound like much but it was that simple question and that Insight that led Albert Einstein to formulate the general theory of relativity now what else happens aboard this Starship opera house I'm at the top at the bottom near the Rockets is of course who else but Albert Einstein and we perform an experiment Albert has a flashlight every second going to flash it on and off and I'm going to just sit and measure how long it takes those flashes to arrive if we're just floating in space well I'm just going to see them arrive every second what if we're accelerating so now the Rockets are firing and we're traveling up in the time it takes for the light from the flashlight from Albert's flashlight to reach me I've moved up a little so the light has had to travel a little bit further to reach me so the light has taken a little bit longer to reach me so now I'm going to measure a little bit longer between the flashes no matter how much I tell Einstein to sort his his timing out to get it on the second I'll always see it taking longer his time everything he's doing will actually be appearing to me to be taking a little bit longer his time is running more slowly relative to mine no turns out for those of you who are worried I haven't sold in the opera house we are actually safe on Earth but you can't tell the difference that's what the simple question led us to understand so what we learned from the case of acceleration in the Rockets still happens here on Earth so when Einstein and I do this experiment again I'm still going to see these flashes take a little bit longer than a second I'm still going to see his time passing more slowly because he's closer to the Earth than I am now that might seem ridiculous that The Closer you are to the Earth the slower time passes turns ey that we actually have really accurate clocks in space that show exactly this thing they're called the global positioning satellites or GPS super accurate clocks far from the earth they quickly get out of sync with the more slowly ticking clocks on Earth in fact if you don't correct for this effect the satnav in your phone would be off by a dozen kilometers within the day all of this everything from understanding the difference or not between acceleration and gravity the change of time and the fact your GPS Works comes from asking a simple question and the Insight gained from that there's a last question I want to share with you today and it's one I try to answer at work what if the world was filled with invisible stuff I don't just mean hard to see I mean fundamentally doesn't shine or absorb light this stuff still has mass so it still has gravity but without interacting with light it'd be like a ghost flying through and between the atoms of solid matter that you and I the Wolves even the very planet is made of that's actually not such a hard trick by the way most of the atom is empty space the only reason I can't put my hand through a table is because the electric field and atoms of my hand repel the electric field in the atoms of the table but light is just an electromagnetic field so if you're something that doesn't care about light then you certainly won't be bothered by this electric field and you'll fly straight through solid matter as if it was empty space if there was enough of this ghostlike invisible stuff you'd see objects like stars move in strange and unexpected ways pulled by the gravity of an unseen partner what if I were to tell you when astronomers look into the night sky we do see the stars move in strange and unexpected ways not just the Stars the entire galaxy itself seems to be held together by enormous amounts of unexplained gravity so much gravity in fact fact that for every atom we have in the universe we need five times more of this invisible ghostlike stuff lying between the galaxies giving the extra gravity so maybe we should turn the question around what if the universe wasn't filled with invisible stuff well for starters the G would fly apart simple questions can be powerful things and the best of these questions offer amazing insight into the world around us three simple questions today led us to realize that the Universe had a beginning that time is relative and that the Galaxy is held together by ghosts simple questions can be anything but simple to answer or to put it simply if you want to understand something complex ask a simple question thank you [Applause] [Music]

Channel: TEDx Talks

Views: 118,071

Keywords: TEDxTalks, English, Australia, Science (hard), History, Physics, Rocket science, Science

Id: C5P4Yc-GiU8

Length: 10min 19sec (619 seconds)

Published: Sat Aug 15 2015