RC

# In philosophy, foundationalism is the view that certain basic beliefs are justified without reference to other beliefs. Such beliefs are said to be justified "foundationally". The general strategy of foundationalism is to break a chain of reasoning at its weakest linkâ€”to show that one need not accept any of the beliefs which are reached by a chain of reasoning, if one does not accept its starting point.

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##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington

##### Farnaz M.

Simon Fraser University

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### Video Transcript

welcome to our fourth example video. Looking at relativity, This video we're going to consider the problem of exploding stars. We have star A and star be And at the moment that you are halfway in between the two stars. So there's a distance d in between them and Europe position D over to at the moment that you are exactly half paid in between them traveling with a speed towards star be of 0.85 So 85% of the speed of light is your speed when you are exactly halfway in between them traveling with the speed you observe in your reference frame that the stars explode simultaneously. So the question then is do you see the flashes simultaneously? And this is actually kind of a silly question. We just said that in your reference frame, that is the reference frame that travels around centered at your navel or wherever you prefer to put it. That in your reference frame, you observed that the stars have exploded simultaneously. That means that the light arrives at you simultaneously because you are halfway in between them. So yes, absolutely. You see the two flashes simultaneously now, uh, The reason this problem confuses people is because they're still thinking, Oh well, I'm traveling at 0.85 speed of light and the stars explode simultaneously with respect to me, so that means they explode at the same time. And then I moved some distance while the light from B travels towards me and the light from a travels towards me. Therefore, I see the light from B first. No, that is wrong. That is, with respect to a completely separate reference frame that would be saying that they are exploding at the same time with respect to some other reference frame. But we said that they exploded, that they explode simultaneously with respect to your reference frame. The only way you have for defining that is if the light and since you're halfway in between, is if the light arrives at you from both stars at the same exact time. And that UIs simultaneity, someone standing off to the side who's moving out on Li se will say 0.1 C to the left instead of zero point I've see to the right and is at a different position, would not observe the stars to exploded simultaneously. They would have a completely different observation since yours was that they did explode simultaneously

RC
University of North Carolina at Chapel Hill

#### Topics

Quantum Physics

Atomic Physics

Nuclear Physics

Condensed Matter Physics

##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington

##### Farnaz M.

Simon Fraser University