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# Would we see it coming?

 Posts: 1,516 Add as FriendChallenge to a DebateSend a Message 10/22/2015 9:55:40 PMPosted: 2 years agoTheoretical question. If light travelled at 60 mph and a car that is 60 miles away drives towards me at 30mph it would take 2 hours to reach me. If the car leaves at 8am it would arrive at my location by 10pm. But because light takes an hour to reach me, from my perspective, I would only see the car leave at 9am but it would arrive at 10am. In other words it would seem to travel 60 mph. But if 60 mph is the speed of light, shouldn't it seem to leave there and arrive here at the same moment?
 Posts: 729 Add as FriendChallenge to a DebateSend a Message 10/22/2015 11:47:47 PMPosted: 2 years agoI know the answer - the problem with f5's puzzles is finding a way to put it into language that cannot be misunderstood!!Basically, in the first part we ignore the hour that the light takes to reach us so we get a flight time of 1 hour, when in reality the flight time was 2 hours.So although the car's speed 'seemed' to be 60 (on the basis of distance divided by the wrong flight time of 1 hour), the car wasn't really going at the speed of light.If it had really been going at the speed of light then you wouldn't see it coming, but in the case here it was really going at half c, so you would (albeit very blue shifted!).
 Posts: 1,516 Add as FriendChallenge to a DebateSend a Message 10/23/2015 9:56:05 PMPosted: 2 years agoAt 10/22/2015 11:47:47 PM, kp98 wrote:I know the answer - the problem with f5's puzzles is finding a way to put it into language that cannot be misunderstood!!Basically, in the first part we ignore the hour that the light takes to reach us so we get a flight time of 1 hour, when in reality the flight time was 2 hours.So although the car's speed 'seemed' to be 60 (on the basis of distance divided by the wrong flight time of 1 hour), the car wasn't really going at the speed of light.If it had really been going at the speed of light then you wouldn't see it coming, but in the case here it was really going at half c, so you would (albeit very blue shifted!).Lol stop spoiling my fun. I was asking the people who don't know.
 Posts: 24 Add as FriendChallenge to a DebateSend a Message 10/25/2015 2:44:54 PMPosted: 2 years agoAt 10/22/2015 9:55:40 PM, Furyan5 wrote:Theoretical question. If light travelled at 60 mph and a car that is 60 miles away drives towards me at 30mph it would take 2 hours to reach me. If the car leaves at 8am it would arrive at my location by 10pm. But because light takes an hour to reach me, from my perspective, I would only see the car leave at 9am but it would arrive at 10am. In other words it would seem to travel 60 mph. But if 60 mph is the speed of light, shouldn't it seem to leave there and arrive here at the same moment? : :Yes. Without light information, the car wouldn't exist.
 Posts: 6,033 Add as FriendChallenge to a DebateSend a Message 10/25/2015 8:32:38 PMPosted: 2 years agoAt 10/22/2015 9:55:40 PM, Furyan5 wrote:Theoretical question. If light travelled at 60 mph and a car that is 60 miles away drives towards me at 30mph it would take 2 hours to reach me. If the car leaves at 8am it would arrive at my location by 10pm. But because light takes an hour to reach me, from my perspective, I would only see the car leave at 9am but it would arrive at 10am. In other words it would seem to travel 60 mph. But if 60 mph is the speed of light, shouldn't it seem to leave there and arrive here at the same moment?This isn't a relativity question, Furyan. You're just confusing what you know with when you know it.Try restating it this way:Bored and broke, your girlfriend walks across town to your place, walking at 5mph, and leaving at 9am.As she leaves, she encounters your friend on a bicycle, and asks him to let you know she's on her way, as her prepaid phone is out of calls too.Traveling at 10mph, your friend arrives at 10am, and tells you that he saw your girlfriend on her way an hour ago. You now know that she left at 9am, and can guess that she's still about an hour away -- but you didn't know any of that until 10am.
 Posts: 1,516 Add as FriendChallenge to a DebateSend a Message 10/25/2015 8:53:35 PMPosted: 2 years agoAt 10/25/2015 8:32:38 PM, RuvDraba wrote:At 10/22/2015 9:55:40 PM, Furyan5 wrote:Theoretical question. If light travelled at 60 mph and a car that is 60 miles away drives towards me at 30mph it would take 2 hours to reach me. If the car leaves at 8am it would arrive at my location by 10pm. But because light takes an hour to reach me, from my perspective, I would only see the car leave at 9am but it would arrive at 10am. In other words it would seem to travel 60 mph. But if 60 mph is the speed of light, shouldn't it seem to leave there and arrive here at the same moment?This isn't a relativity question, Furyan. You're just confusing what you know with when you know it.Try restating it this way:Bored and broke, your girlfriend walks across town to your place, walking at 5mph, and leaving at 9am.As she leaves, she encounters your friend on a bicycle, and asks him to let you know she's on her way, as her prepaid phone is out of calls too.Traveling at 10mph, your friend arrives at 10am, and tells you that he saw your girlfriend on her way an hour ago. You now know that she left at 9am, and can guess that she's still about an hour away -- but you didn't know any of that until 10am.As always you miss the point completely. If I was watching her the whole time I would see her leave at 9am. The car I am watching and from my perspective it leaves at 9 and arrives 12 min later.
 Posts: 6,033 Add as FriendChallenge to a DebateSend a Message 10/26/2015 3:41:02 AMPosted: 2 years agoAt 10/26/2015 1:16:34 AM, trojan wrote:At 10/25/2015 11:17:15 PM, RuvDraba wrote:At 10/25/2015 8:53:35 PM, Furyan5 wrote:If I was watching her the whole time I would see her leave at 9am.Light transmission isn't instantaneous, Furyan, so it's like the friend on the bicycle. The bicycle being faster than your girlfriend, you receive news of her departure after she leaves, but before she arrives. During the time it takes the news to reach you, she's also traveling. If she sent a friend on a bicycle with an update every half hour, and it took her two hours to walk, and the bicycles all traveled the same route at twice her walking speed, then you'd receive four updates, each precisely 30 minutes apart, but out of date by different periods due to the diminishing distance between you.The first report, sent at 9am, is sent when she's two hours away, but takes an hour to reach you, since the bike is twice as fast. It's 10am when you get the report, but in that time, she has also traveled for an hour. So the report says she was two hours away, but she's actually only one hour away when you get the report -- so it's an hour out.Yet when she sends her last report, half an hour from your door, the cyclist takes only 15 minutes to arrive, but in that time she has traveled for 15 minutes too. The cyclist tells you she was 30 minutes away when he saw her, yet in fact she's now only 15 minutes away. So reports that started an hour out, are now only 15 minutes out.One would be silly to believe a report still current at 10am when the cyclist can tell us that it was transmitted an hour ago at 9am. But if we forgot to factor that in, then we'd also believe she was traveling faster than she really was, since she'd arrive at 11am, only an hour after we received the first message.(By the way, a sound effect called the 'Doppler' effect -- where the pitch of a a vehicle's engine rises as it approaches -- is also related to the decreasing distance between observer and observed. [https://en.wikipedia.org...]) : :Only if you believe that light, sound, time, space and matter are real things. If we're experiencing life in a simulation, then none of these things are real. They're only perceived to be real from each unique created perspective.Hi Brad,Hope you're well!There's no way of knowing that we are not all in some simulation, that's true. However, we can be reasonably confident about some qualities regarding whatever constitutes the reality we're in.One is that the objective is shared and persistent. I don't mean that it persists forever; only that it persists to observation -- including observable signs of history; and that this information is as reliable as any other information we have.Within those reasonable assumptions, I'll stick by what I wrote earlier. :) And beyond those assumptions I think we'd probably be off-topic. :)