Something has been bugging me... Concerns Physics. - Page 2

[ARCHIVED THREAD] - Something has been bugging me... Concerns Physics. (Page 2 of 3)

Posted: 10/11/2004 9:56:47 AM EDT

[#1]

Quoted:
Quoted:
Quoted:

So because the air in the car is also going the same speed everything in the car would act like it was just not moving at the speed of the car?

Correct.

BTW, here's an interesting experiment...take a helium balloon with you in the car...when you brake sharply, the balloon will actually move to the REAR of the car instead of the front...freaky...

Now why is that?
Sudden change in air pressure as the air in the car shifts towards the windshield as you slow. The pressure at the windshield is higher than the pressure at the back window. The helium balloon is more affected by the air pressure differential in the cabin of the vehicle than it is by momentum. This also works when you accelerate (opposite direction of air and balloon travel) but you can stop faster than you can accelerate, so the behavior is more pronounced when braking.

As to the fly, wait till that sucker's in the air, then lock up the brakes and watch him bounce off the inside of the windshield.

Yup...but that's only half of the story...it's actually an example of relativity...read THIS...

Posted: 10/11/2004 9:58:40 AM EDT

[#2]

Its the same rule that applies to combat aircraft.

How do the bullets not come right back and strike the plane?

Because they're already travelling the plane's speed.

So they travel at the plane's speed plus the speed of their original property.

Posted: 10/11/2004 9:59:20 AM EDT

[#3]

Remember, all the Laws of Physics are strictly enforced. Always. Without exception.

Posted: 10/11/2004 10:04:55 AM EDT

[#4]

Quoted:
Quoted:
Quoted:
Even better question is what happens when a spaceship doing 99.999% of the speed of light shines it headlights forward? Since light speed is constant does the light not move forward for you to see? Now if you shine said light backwards from a ship going same speed does it almost stand still? Now my brain hurts.

The beam of light will leave the headlight at the speed of light relative to the headlight. Same thing going backwards.

I don't think that is correct. If it were so, then the speed of light is variable, and a merely arbitrary measurement. Explain Red/Blue shift if the light from fast objects experiences this.

Zaphod has it right. One major consequence of (special) relativity is that light has the same speed in all reference frames. That means that the headlight sees the light departing at 3x10^8 m/s, and a "stationary" observer also sees it moving at 3x10^8 m/s.

Red & blue shifts are about frequency (or wavelength), not velocity. Light from a distant star is still moving toward you at 3x10^8 m/s, it's just that its wavelength seems longer (frequency seems lower); that's why it's red-shifted. Similarly for blue-shift.

Posted: 10/11/2004 10:12:51 AM EDT

[#5]

Does this have any thing to do with the urban legend about the guy who survived the WTC collapse by going to the roof and riding the thing down?

Posted: 10/11/2004 10:15:23 AM EDT

[#6]

Quoted:
Quoted:
Quoted:
Quoted:
Even better question is what happens when a spaceship doing 99.999% of the speed of light shines it headlights forward? Since light speed is constant does the light not move forward for you to see? Now if you shine said light backwards from a ship going same speed does it almost stand still? Now my brain hurts.

The beam of light will leave the headlight at the speed of light relative to the headlight. Same thing going backwards.

I don't think that is correct. If it were so, then the speed of light is variable, and a merely arbitrary measurement. Explain Red/Blue shift if the light from fast objects experiences this.

Zaphod has it right. One major consequence of (special) relativity is that light has the same speed in all reference frames. That means that the headlight sees the light departing at 3x10^8 m/s, and a "stationary" observer also sees it moving at 3x10^8 m/s.

Wait a second! If both observer and headlight see the light radiating at the same speed, then that would have to mean that the light is moving slower relative to the headlight than to the observer, right? How could Zaphod be right when he says that the light travels at the speed of light WRT the headlight?

Red & blue shifts are about frequency (or wavelength), not velocity. Light from a distant star is still moving toward you at 3x10^8 m/s, it's just that its wavelength seems longer (frequency seems lower); that's why it's red-shifted. Similarly for blue-shift.

Right, that is exactly my point! Light is traveling the same speed, but the waves are being bunched up more or stretched out more.

I fail to see how Zaphod is correct or how you are disagreeing with me.

light can never travel more than 186,282 miles/sec. WRT the universe. If a flashlight is traveling through the universe lens forward at 1 mile per second, it's beam would only be going 186,281 miles per second WRT to the flashlight, but still 186,282 WRT the universe.

Right?

Posted: 10/11/2004 10:15:33 AM EDT

[#7]

Quoted:
Quoted:
ding ding ding!

We have a winner
Einstein's theory of relativity

Quoted:
Relativity.

The fly is not flying in relation to the
ground, but in relation to the car. Same
reason why if you jump in a downward
traveling elevator, you do not leviate.

No, we don't.

The reason you don't levitate in a descending elevator is because your acceleration downward due to gravity is greater than the acceleration of the elevator (which is zero when the elevator is at top speed).

If the elevator was free-falling, you WOULD levitate, a-la the Vomit Comet.

Einstein's theory of relativity has much bigger fish to fry. Oh, and the fly IS moving in relation to the ground. If it's moving forward at 30 mph when the car is going 60mph, the fly is doing 90 mph in relation to the ground.

I may very well be wrong about this... but I can't see how you would ever levitate in an elevator, even if it were falling.

The elevator would take up most of the shaft, and thus hit a lot of resistance from the air, however... your body wouldn't have any resistance, and thus would only be effected by gravity. So, the elevator would actually be slowed down enough by the wind resistance, that you would still be "standing" on the floor (probably crapping would be more realistic).

This would be the same concept as when you drop a book and a piece of paper, side by side... the book hits the ground first, but if you place the paper on top of the book, they will both fall at the same rate.

Then again, I could very well be wrong... feel free to correct me if it's needed.

Posted: 10/11/2004 10:18:59 AM EDT

[#8]

According to relativity, you cannot just add velocities directly...you have to calculate their sum using the formula w = (u + v)/(1 + uv/c^2). More info can be found HERE.

This equation always applies, regardless of velocity...of course, the difference is infinitesimal at normal, everyday velocities. If I am standing in a railroad car moving at exactly 50 MPH, and I throw a ball at exactly 50 MPH in the same direction as the car is moving, the combined forward velocity of the ball is very close to, but not exactly 100 MPH. Of course, at those low velocities we just use Newtonian physics and say it's 100 MPH, because you cannot measure with infinite precision.

Posted: 10/11/2004 10:19:08 AM EDT

[#9]

Quoted:
Quoted:
Quoted:
ding ding ding!

We have a winner
Einstein's theory of relativity

Quoted:
Relativity.

The fly is not flying in relation to the
ground, but in relation to the car. Same
reason why if you jump in a downward
traveling elevator, you do not leviate.

No, we don't.

The reason you don't levitate in a descending elevator is because your acceleration downward due to gravity is greater than the acceleration of the elevator (which is zero when the elevator is at top speed).

If the elevator was free-falling, you WOULD levitate, a-la the Vomit Comet.

Einstein's theory of relativity has much bigger fish to fry. Oh, and the fly IS moving in relation to the ground. If it's moving forward at 30 mph when the car is going 60mph, the fly is doing 90 mph in relation to the ground.

I may very well be wrong about this... but I can't see how you would ever levitate in an elevator, even if it were falling.

The elevator would take up most of the shaft, and thus hit a lot of resistance from the air, however... your body wouldn't have any resistance, and thus would only be effected by gravity. So, the elevator would actually be slowed down enough by the wind resistance, that you would still be "standing" on the floor (probably crapping would be more realistic).

This would be the same concept as when you drop a book and a piece of paper, side by side... the book hits the ground first, but if you place the paper on top of the book, they will both fall at the same rate.

Then again, I could very well be wrong... feel free to correct me if it's needed.

You are right. The only way to be in a free fall in the elevator would be to have the elevator decending at 9.8 m/s^2. If the elevator were merely falling at terminal velocity, you could stand on the floor.

Posted: 10/11/2004 10:19:45 AM EDT

[#10]

Quoted:
Its the same rule that applies to combat aircraft.

How do the bullets not come right back and strike the plane?

Because they're already travelling the plane's speed.

So they travel at the plane's speed plus the speed of their original property.

I dont think this is correct, as there are aircraft that could not be armed with a cannon because if it were fired at speed, it might shoot itself down...

BTW this is one of the reasons I LOVE this board. I would bet that DU never has conversations like this.

Posted: 10/11/2004 10:23:08 AM EDT

[#11]

Quoted:
Quoted:
Its the same rule that applies to combat aircraft.

How do the bullets not come right back and strike the plane?

Because they're already travelling the plane's speed.

So they travel at the plane's speed plus the speed of their original property.

I dont think this is correct, as there are aircraft that could not be armed with a cannon because if it were fired at speed, it might shoot itself down...

BTW this is one of the reasons I LOVE this board. I would bet that DU never has conversations like this.

If a plane were fast enough and the bullets had a low enough Ballistic Coefficient, then it is possible for the bullets to slow down fast enough to allow the plane to catch up with them before they drop enough. Speeds would have to be VERY high though, since the BC of 20 mikety-mike is probably pretty high.

Posted: 10/11/2004 10:32:46 AM EDT

[#12]

Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Even better question is what happens when a spaceship doing 99.999% of the speed of light shines it headlights forward? Since light speed is constant does the light not move forward for you to see? Now if you shine said light backwards from a ship going same speed does it almost stand still? Now my brain hurts.

The beam of light will leave the headlight at the speed of light relative to the headlight. Same thing going backwards.

I don't think that is correct. If it were so, then the speed of light is variable, and a merely arbitrary measurement. Explain Red/Blue shift if the light from fast objects experiences this.

Zaphod has it right. One major consequence of (special) relativity is that light has the same speed in all reference frames. That means that the headlight sees the light departing at 3x10^8 m/s, and a "stationary" observer also sees it moving at 3x10^8 m/s.

Wait a second! If both observer and headlight see the light radiating at the same speed, then that would have to mean that the light is moving slower relative to the headlight than to the observer, right? How could Zaphod be right when he says that the light travels at the speed of light WRT the headlight?

Because space and time are relative, while the speed of light is absolute. If you are on a spaceship traveling at 99% of the speed of light, and you shine a headlight forward, you will observe the light beam traveling away from you at the speed of light. A stationary observer will also observe the headlight beam to be traveling at the speed of light. To the stationary observer, the spaceship's passengers' time will slow down, and the spaceship's length will decrease as it approaches the speed of light. This change in perceived space and time allows the spaceship's passengers to see the light beam traveling away at the speed of light while the stationary observer also sees the same light beam traveling at the speed of light.

And that's special relativity.

Posted: 10/11/2004 10:36:32 AM EDT

[#13]

Quoted:
The fly doesn't have any trouble moving about in a car for the same reason you don't have any trouble using a lavatory in an airplane. Would it make sense to expect that you couldn't walk up the aisle in an airplane?

But you are in physical contact with the plane while you are walking (at least I am) the fly is not in physical contact.

Posted: 10/11/2004 10:46:16 AM EDT

[#14]

Quoted:
light can never travel more than 186,282 miles/sec. WRT the universe. If a flashlight is traveling through the universe lens forward at 1 mile per second, it's beam would only be going 186,281 miles per second WRT to the flashlight, but still 186,282 WRT the universe.
Right?

Nope, sorry.

The light is going exactly the same speed relative to the flashlight or the universe. That's fundamental to special relativity. The example you give is fine for sound waves. The velocity of a sound wave is basically the velicoty of the wave in the source's frame plus the velocity of the source relative to the universe. (This is true because the speed of sound is much less than the speed of light). Light doesn't work that way, however. Light goes the speed of light, period. If a flashlight is going 0.5*c through the universe, the light it puts out is moving 1.0*c both relative to the flashlight and relative to the universe, not 1.5*c. The "doppler effect" is different for light than it is for sound, because velocities don't add linearly when you're near the speed of light.

For an excellent treatment, check out "Relativity Simply Explained" by Martin Gardner (Dover Press, $12 softcover). It's short and simple, and I think it does a great job of introducing Special and General Relativity without a bunch of distracting math.

Posted: 10/11/2004 10:54:51 AM EDT

[#15]

Quoted:
Quoted:
The fly doesn't have any trouble moving about in a car for the same reason you don't have any trouble using a lavatory in an airplane. Would it make sense to expect that you couldn't walk up the aisle in an airplane?

But you are in physical contact with the plane while you are walking (at least I am) the fly is not in physical contact.

That doesn't make any difference. You can jump up and down on the plane, water will fall straight into the wash basin, and you can even stand up to pee without adjusting for windage.

The fly is only concerned with 1 thing, the speed of the air around him. This is the same reason, BTW that you can't waterski in the back of a P/U truck driving down the highway with the bed filled up with water. Water skiing only works if you are moving ~22 mph in relation to the water.

Posted: 10/11/2004 10:59:38 AM EDT

[#16]

Quoted:
Quoted:
Quoted:
The fly doesn't have any trouble moving about in a car for the same reason you don't have any trouble using a lavatory in an airplane. Would it make sense to expect that you couldn't walk up the aisle in an airplane?

But you are in physical contact with the plane while you are walking (at least I am) the fly is not in physical contact.

That doesn't make any difference. You can jump up and down on the plane, water will fall straight into the wash basin, and you can even stand up to pee without adjusting for windage.

The fly is only concerned with 1 thing, the speed of the air around him. This is the same reason, BTW that you can't waterski in the back of a P/U truck driving down the highway with the bed filled up with water. Water skiing only works if you are moving ~22 mph in relation to the water.

I don't know about you but I always have to adjust for windage when I pee. Plane or no plane.

Posted: 10/11/2004 11:07:45 AM EDT

[#17]

Quoted:
Quoted:
light can never travel more than 186,282 miles/sec. WRT the universe. If a flashlight is traveling through the universe lens forward at 1 mile per second, it's beam would only be going 186,281 miles per second WRT to the flashlight, but still 186,282 WRT the universe.
Right?

Nope, sorry. The light is going exactly the same speed relative to the flashlight or the universe. That's fundamental to special relativity. The example you give is fine for sound waves. The velocity of a sound wave is basically the velicoty of the wave in the source's frame plus the velocity of the source relative to the universe. (This is true because the speed of sound is much less than the speed of light). Light doesn't work that way, however. Light goes the speed of light, period. If a flashlight is going 0.5*c through the universe, the light it puts out is moving 1.0*c both relative to the flashlight and relative to the universe, not 1.5*c. The "doppler effect" is different for light than it is for sound, because velocities don't add linearly when you're near the speed of light.

For an excellent treatment, check out "Relativity Simply Explained" by Martin Gardner (Dover Press, $12 softcover). It's short and simple, and I think it does a great job of introducing Special and General Relativity without a bunch of distracting math.

Let me see if I am interpreting you and mace correctly. Light is always moving at the speed of light relative to you BECAUSE, time for you is slowing down proportionately to make the speed of light APPEAR to be moving faster.

A guy flying a spaceship at 99% the speed f light, flicks on his headlights, sees the light illuminate an object 186,282 miles away in 1+ second, but the guy on the side of the road sees the light in 2 seconds. The reason is, that the guy on the ship is actually living in super-slow motion, thus causing the light to appear to be traveling along at almost double the speed of light. In reality, the light was only moving 1,862.82 miles per second faster than the ship, and the ship actually is 1,862.82 miles away from the object when the light hits it, and is only 931 miles away from the object when the pilot sees the object.

The point is, that time slows down in proportion to the percentage of the speed of light. If you go 1%C faster than everybody, then you are passing through time ~1% slower then everybody else.

Right? Did I finally get this correct?

Posted: 10/11/2004 11:08:26 AM EDT

[#18]

Quoted:
Quoted:
The fly doesn't have any trouble moving about in a car for the same reason you don't have any trouble using a lavatory in an airplane. Would it make sense to expect that you couldn't walk up the aisle in an airplane?

But you are in physical contact with the plane while you are walking (at least I am) the fly is not in physical contact.

It is in physical contact with the air. Assuming you're in an enclosed car, windows closed, no massive holes or anything, not only the air, but everything inside the moving car is behaving exactly the same as if it was stopped. There is no test you can perform on anything inside the car that will tell you what it's speed is relative to anything outside the car.

If you flew a model helicopter around in the cargo bay of a C5 Galaxy cruising at 500 mph, it'd be no different from flying it around in the same plane on the ground.

Posted: 10/11/2004 11:09:45 AM EDT

[#19]

Quoted:
Quoted:
Quoted:
Quoted:
The fly doesn't have any trouble moving about in a car for the same reason you don't have any trouble using a lavatory in an airplane. Would it make sense to expect that you couldn't walk up the aisle in an airplane?

But you are in physical contact with the plane while you are walking (at least I am) the fly is not in physical contact.

That doesn't make any difference. You can jump up and down on the plane, water will fall straight into the wash basin, and you can even stand up to pee without adjusting for windage.

The fly is only concerned with 1 thing, the speed of the air around him. This is the same reason, BTW that you can't waterski in the back of a P/U truck driving down the highway with the bed filled up with water. Water skiing only works if you are moving ~22 mph in relation to the water.

I don't know about you but I always have to adjust for windage when I pee. Plane or no plane.

Wow! 580+ MPH windage when you pee!? That is like aiming at the shaver outlet to hit the john!

Posted: 10/11/2004 11:10:57 AM EDT

[#20]

Instead of thinking of the air in the car- which is correct. Think along these lines:

An objects speed can only be measured in relation to a point of reference. So in actuallity if you take the "fly" in the car. He isnt going 60mph but actually going 1060 if you take into account the earths rotation...but then again if you calcualate in the speed that the earth is going around the sun and the rotation and the car, then the fly actually is going around at 68,060 mph!

Posted: 10/11/2004 11:12:31 AM EDT

[#21]

Quoted:
The fly is only concerned with 1 thing, the speed of the air around him. This is the same reason, BTW that you can't waterski in the back of a P/U truck driving down the highway with the bed filled up with water. Water skiing only works if you are moving ~22 mph in relation to the water.

That's an excellent example...

...I'm just wondering what made it come to mind.

Posted: 10/11/2004 11:15:06 AM EDT

[#22]

Quoted:
Quoted:
Quoted:
light can never travel more than 186,282 miles/sec. WRT the universe. If a flashlight is traveling through the universe lens forward at 1 mile per second, it's beam would only be going 186,281 miles per second WRT to the flashlight, but still 186,282 WRT the universe.
Right?

Nope, sorry. The light is going exactly the same speed relative to the flashlight or the universe. That's fundamental to special relativity. The example you give is fine for sound waves. The velocity of a sound wave is basically the velicoty of the wave in the source's frame plus the velocity of the source relative to the universe. (This is true because the speed of sound is much less than the speed of light). Light doesn't work that way, however. Light goes the speed of light, period. If a flashlight is going 0.5*c through the universe, the light it puts out is moving 1.0*c both relative to the flashlight and relative to the universe, not 1.5*c. The "doppler effect" is different for light than it is for sound, because velocities don't add linearly when you're near the speed of light.

For an excellent treatment, check out "Relativity Simply Explained" by Martin Gardner (Dover Press, $12 softcover). It's short and simple, and I think it does a great job of introducing Special and General Relativity without a bunch of distracting math.

Let me see if I am interpreting you and mace correctly. Light is always moving at the speed of light relative to you BECAUSE, time for you is slowing down proportionately to make the speed of light APPEAR to be moving faster.

A guy flying a spaceship at 99% the speed f light, flicks on his headlights, sees the light illuminate an object 186,282 miles away in 1+ second, but the guy on the side of the road sees the light in 2 seconds. The reason is, that the guy on the ship is actually living in super-slow motion, thus causing the light to appear to be traveling along at almost double the speed of light. In reality, the light was only moving 1,862.82 miles per second faster than the ship, and the ship actually is 1,862.82 miles away from the object when the light hits it, and is only 931 miles away from the object when the pilot sees the object.

The point is, that time slows down in proportion to the percentage of the speed of light. If you go 1%C faster than everybody, then you are passing through time ~1% slower then everybody else.

Right? Did I finally get this correct?

Now my head hurts.

Posted: 10/11/2004 11:15:41 AM EDT

[#23]

Quoted:
Quoted:
The fly is only concerned with 1 thing, the speed of the air around him. This is the same reason, BTW that you can't waterski in the back of a P/U truck driving down the highway with the bed filled up with water. Water skiing only works if you are moving ~22 mph in relation to the water.

That's an excellent example...

...I'm just wondering what made it come to mind.

I was picturing myself transporting an aquarium, and picturing fish skipping off the surface of the water at 55+ MPH.

Honest!

Posted: 10/11/2004 11:19:49 AM EDT

[#24]

So if a tree falls on top of a mime in the middle of the forest, and nobody's around to hear it, does anyone care?

Posted: 10/11/2004 11:26:49 AM EDT

[#25]

Quoted:
Instead of thinking of the air in the car- which is correct. Think along these lines:

An objects speed can only be measured in relation to a point of reference. So in actuallity if you take the "fly" in the car. He isnt going 60mph but actually going 1060 if you take into account the earths rotation...but then again if you calcualate in the speed that the earth is going around the sun and the rotation and the car, then the fly actually is going around at 68,060 mph!

But what if I am driving against the earth's rotation?

Posted: 10/11/2004 11:27:59 AM EDT

[#26]

Quoted:
But the ball comes down quickly. The fly can fly around for a long time. Would it not loose its velocity that it got from the car pretty quick?

Here's where you are getting confused.

You are trying to analyze the wrong system, or better said, using the wrong frame of reference to do your analysis.

The fly is flying inside the car. The speed of the air inside the car, relative to the inside of the car and the fly, is zero. The fly is flying in still air as long as it stays inside, no matter how fast the car is moving. The fly orients itself by using the interior of the car as its frame of reference, so it can actually hover in "space" by maintaining its relationships to the car's interior.

The moment the fly steps outside, its world went from 70 mph to 0, and it gets left behind in a hurry.

Posted: 10/11/2004 11:28:08 AM EDT

[#27]

Quoted:
I understand that if you are traveling in a car at 60 mph and holding a ball when you toss it in the air it does not go flying back to the rear of the car because it is also traveling at 60mph.

How come a fly can fly around inside a car that is traveling at 60 mph? It would seem to me that the fly who is flying is independent of the car and would not have the forward momentum of the car. You would think that when it first took off in the car that it would be fine, but would loose it's momentum pretty fast and would slam against the rear windshield. But tell that to the damn fly who was doing circles around my head while I was driving down the highway this weekend.

This has been driving me crazy for years, I hope someone can answer this.

All matter that makes up the car, and is contained by the car is propelled to 60mph by the car's engine...

The air inside the car is moving with the car too, (if it was not, you'd have a 60mph wind in your face) thus the fly can fly in it... Since you, the car, and the air in it are all moving at the same relative velocity, you appear to be not moving. When you move at a higher velocity (say you crawl around in the car, or the fly flies) then you have apparent motion....

Posted: 10/11/2004 11:28:16 AM EDT

[#28]

Quoted:
Quoted:
Instead of thinking of the air in the car- which is correct. Think along these lines:

An objects speed can only be measured in relation to a point of reference. So in actuallity if you take the "fly" in the car. He isnt going 60mph but actually going 1060 if you take into account the earths rotation...but then again if you calcualate in the speed that the earth is going around the sun and the rotation and the car, then the fly actually is going around at 68,060 mph!

But what if I am driving against the earth's rotation?

67,940!!!

Posted: 10/11/2004 11:31:54 AM EDT

[#29]

Quoted:
Quoted:
Quoted:
Quoted:
light can never travel more than 186,282 miles/sec. WRT the universe. If a flashlight is traveling through the universe lens forward at 1 mile per second, it's beam would only be going 186,281 miles per second WRT to the flashlight, but still 186,282 WRT the universe.
Right?

Nope, sorry. The light is going exactly the same speed relative to the flashlight or the universe. That's fundamental to special relativity. The example you give is fine for sound waves. The velocity of a sound wave is basically the velicoty of the wave in the source's frame plus the velocity of the source relative to the universe. (This is true because the speed of sound is much less than the speed of light). Light doesn't work that way, however. Light goes the speed of light, period. If a flashlight is going 0.5*c through the universe, the light it puts out is moving 1.0*c both relative to the flashlight and relative to the universe, not 1.5*c. The "doppler effect" is different for light than it is for sound, because velocities don't add linearly when you're near the speed of light.

For an excellent treatment, check out "Relativity Simply Explained" by Martin Gardner (Dover Press, $12 softcover). It's short and simple, and I think it does a great job of introducing Special and General Relativity without a bunch of distracting math.

Let me see if I am interpreting you and mace correctly. Light is always moving at the speed of light relative to you BECAUSE, time for you is slowing down proportionately to make the speed of light APPEAR to be moving faster.

A guy flying a spaceship at 99% the speed f light, flicks on his headlights, sees the light illuminate an object 186,282 miles away in 1+ second, but the guy on the side of the road sees the light in 2 seconds. The reason is, that the guy on the ship is actually living in super-slow motion, thus causing the light to appear to be traveling along at almost double the speed of light. In reality, the light was only moving 1,862.82 miles per second faster than the ship, and the ship actually is 1,862.82 miles away from the object when the light hits it, and is only 931 miles away from the object when the pilot sees the object.

The point is, that time slows down in proportion to the percentage of the speed of light. If you go 1%C faster than everybody, then you are passing through time ~1% slower then everybody else.

Right? Did I finally get this correct?

Now my head hurts.

Damn. You ain't kiddin'!

The best example I found was in Hawking's book, which I think is "The Universe In A Nutshell".

A spaceship is travelling near the speed of light. The two crewmembers stand at opposite ends of the ship along the direction of travel. The guy in back illuminates the guy in front with a flashlight. They both see the beam moving at 186,000 mps. As such, the light beam takes a measureable amount of time to get from the flashlight to the second crewmember.

Now comes the hard part.

There is a ground controllman standing on the surface of a planet as th ship flies by. He sees the light turn on just as the crewmembers do. To him, the light beam is also moving at 186,000 mps. However, since the ship is moving as well, the distance the light beam travels is longer according to the plane of reference of the observer than to the crewmembers. In other words, the crewmembers saw the beam cross the space between them (i.e. - the length of the cabin). The observer saw the light beam cross the entire distance the SHIP travelled in that time (i.e. - much farther than the length of the cabin).

So, if S=vt (where S is distance, v is velocity, and t is time), the equation for the crewmembers will use a different value of S than for the observer. Since v is a constant (the speed of light), then t MUST change between the crewmembers and the observer.

Since S for the observer is greater than for the observer, t must increase. As such, time slows down aboard the spaceship in reference to the observer. By the same token, time seems to speed up outside the spaceship in relation to the crewmembers.

Capiche?

Posted: 10/11/2004 11:33:35 AM EDT

[#30]

Quoted:
Quoted:
Quoted:
Instead of thinking of the air in the car- which is correct. Think along these lines:

An objects speed can only be measured in relation to a point of reference. So in actuallity if you take the "fly" in the car. He isnt going 60mph but actually going 1060 if you take into account the earths rotation...but then again if you calcualate in the speed that the earth is going around the sun and the rotation and the car, then the fly actually is going around at 68,060 mph!

But what if I am driving against the earth's rotation?

67,940!!!

Correct, when measured from a point fixed in relation to outer space.

Posted: 10/11/2004 11:36:14 AM EDT

[#31]

Quoted:
Quoted:
Quoted:
light can never travel more than 186,282 miles/sec. WRT the universe. If a flashlight is traveling through the universe lens forward at 1 mile per second, it's beam would only be going 186,281 miles per second WRT to the flashlight, but still 186,282 WRT the universe.
Right?

Nope, sorry. The light is going exactly the same speed relative to the flashlight or the universe. That's fundamental to special relativity. The example you give is fine for sound waves. The velocity of a sound wave is basically the velicoty of the wave in the source's frame plus the velocity of the source relative to the universe. (This is true because the speed of sound is much less than the speed of light). Light doesn't work that way, however. Light goes the speed of light, period. If a flashlight is going 0.5*c through the universe, the light it puts out is moving 1.0*c both relative to the flashlight and relative to the universe, not 1.5*c. The "doppler effect" is different for light than it is for sound, because velocities don't add linearly when you're near the speed of light.

For an excellent treatment, check out "Relativity Simply Explained" by Martin Gardner (Dover Press, $12 softcover). It's short and simple, and I think it does a great job of introducing Special and General Relativity without a bunch of distracting math.

Let me see if I am interpreting you and mace correctly. Light is always moving at the speed of light relative to you BECAUSE, time for you is slowing down proportionately to make the speed of light APPEAR to be moving faster.

A guy flying a spaceship at 99% the speed f light, flicks on his headlights, sees the light illuminate an object 186,282 miles away in 1+ second, but the guy on the side of the road sees the light in 2 seconds. The reason is, that the guy on the ship is actually living in super-slow motion, thus causing the light to appear to be traveling along at almost double the speed of light. In reality, the light was only moving 1,862.82 miles per second faster than the ship, and the ship actually is 1,862.82 miles away from the object when the light hits it, and is only 931 miles away from the object when the pilot sees the object.

The point is, that time slows down in proportion to the percentage of the speed of light. If you go 1%C faster than everybody, then you are passing through time ~1% slower then everybody else.

Right? Did I finally get this correct?

Erm... that one's much harder. I know just enough to have an idea of how to do it correctly. Sorta. Lemme think about it.

Posted: 10/11/2004 11:37:34 AM EDT

[#32]

Quoted:
............ As such, time slows down aboard the spaceship in reference to the observer. By the same token, time seems to speed up outside the spaceship in relation to the crewmembers.

Capiche?

I think that should read the way we observe light instead of time

Posted: 10/11/2004 11:37:35 AM EDT

[#33]

Quoted:
The point is, that time slows down in proportion to the percentage of the speed of light. If you go 1%C faster than everybody, then you are passing through time ~1% slower then everybody else.

Right? Did I finally get this correct?

Almost perfect! The true factor is

gamma = 1 / sqrt(1 - v^2/c^2)

This is the factor by which time expands (or distance contracts) from the perspective of a moving subject. When v is very small relative to speed of light, things are the way we're used to thinking about them ("classical"):

v/c ~= 0, gamma ~= 1

When you're near the speed of light, this quantity blows up fast.

Posted: 10/11/2004 11:40:16 AM EDT

[#34]

Quoted:
Instead of thinking of the air in the car- which is correct. Think along these lines:

An objects speed can only be measured in relation to a point of reference. So in actuallity if you take the "fly" in the car. He isnt going 60mph but actually going 1060 if you take into account the earths rotation...but then again if you calcualate in the speed that the earth is going around the sun and the rotation and the car, then the fly actually is going around at 68,060 mph!

Don't forget that our solar system is orbiting the galactic core and our galaxy, along with others in the Local Group, are falling towards the Virgo Cluster of Galaxies...it all depends on your vantage point...

Posted: 10/11/2004 1:26:40 PM EDT

[#35]

OK, all of you are wrong. SWO_daddy was almost right, but not quite there.

Quoted:
Here's where you are getting confused.

You are trying to analyze the wrong system, or better said, using the wrong frame of reference to do your analysis.

The fly is flying inside the car. The speed of the air inside the car, relative to the inside of the car and the fly, is zero. The fly is flying in still air as long as it stays inside, no matter how fast the car is moving. The fly orients itself by using the interior of the car as its frame of reference, so it can actually hover in "space" by maintaining its relationships to the car's interior.

The moment the fly steps outside, its world went from 70 mph to 0, and it gets left behind in a hurry.

Since I adopted the BlammO-centric worldview, my understanding of the universe has increased exponentially and all apparent conflicts with the laws of physics are now resolved. The BlammO-centric worldview is is founded on the concept that I am the center of my universe. I never move in relation to anything else -- everything moves in relation to me. As I walk, I cause the world to rotate beneath me. Other people move in relation to the world and to me, but I remain steadfastly in the center of my universe.

It works out very nicely. For example, let's say that Footrat or Capitalist has posted a picture of Alizee and it's displayed on a monitor at the end of the hall. Naturally, I will want to rotate my universe so that the monitor is closer to the center (me). I simply stand up, and walk in such a way that the world rotates beneath me and the monitor is brought closer. I haven't moved -- the world did.

This is just another way I manage to save energy. However, since the universe has mass (and therefore inertia), it still takes energy for me to rotate it to my liking. But when you recognize the relatively small amount of energy it takes for me to move the entire universe, you have to admit I'm pretty efficient.

Now, I'm working on a subset of my worldview that allows me to claim myself as the source of all energy in the universe as well so I won't have to work so hard at being lazy.

Posted: 10/11/2004 1:46:54 PM EDT

[#36]

OH shit! If that bothers you stay out of airplanes for when you hit an air pocket you drink comes out of your cup then drops straght back in.

BTW, you want to have fun? Throw your ball up and then hit the accellerator before the ball falls.

Tj

Posted: 10/11/2004 1:51:57 PM EDT

[#37]

Quoted:
OK, all of you are wrong. SWO_daddy was almost right, but not quite there.

Quoted:
Here's where you are getting confused.

You are trying to analyze the wrong system, or better said, using the wrong frame of reference to do your analysis.

The fly is flying inside the car. The speed of the air inside the car, relative to the inside of the car and the fly, is zero. The fly is flying in still air as long as it stays inside, no matter how fast the car is moving. The fly orients itself by using the interior of the car as its frame of reference, so it can actually hover in "space" by maintaining its relationships to the car's interior.

The moment the fly steps outside, its world went from 70 mph to 0, and it gets left behind in a hurry.

Since I adopted the BlammO-centric worldview, my understanding of the universe has increased exponentially and all apparent conflicts with the laws of physics are now resolved. The BlammO-centric worldview is is founded on the concept that I am the center of my universe. I never move in relation to anything else -- everything moves in relation to me. As I walk, I cause the world to rotate beneath me. Other people move in relation to the world and to me, but I remain steadfastly in the center of my universe.

It works out very nicely. For example, let's say that Footrat or Capitalist has posted a picture of Alizee and it's displayed on a monitor at the end of the hall. Naturally, I will want to rotate my universe so that the monitor is closer to the center (me). I simply stand up, and walk in such a way that the world rotates beneath me and the monitor is brought closer. I haven't moved -- the world did.

This is just another way I manage to save energy. However, since the universe has mass (and therefore inertia), it still takes energy for me to rotate it to my liking. But when you recognize the relatively small amount of energy it takes for me to move the entire universe, you have to admit I'm pretty efficient.

Now, I'm working on a subset of my worldview that allows me to claim myself as the source of all energy in the universe as well so I won't have to work so hard at being lazy.

And that is why BlammO is the adviser to personal energy conservation in my administration.

eta - He has some very interesting and attractive ideas.

Posted: 10/11/2004 1:53:42 PM EDT

[#38]

Quoted:
Quoted:
............ As such, time slows down aboard the spaceship in reference to the observer. By the same token, time seems to speed up outside the spaceship in relation to the crewmembers.

Capiche?

I think that should read the way we observe light instead of time

NO! That's the whole point!

BOTH groups observe light IDENTICALLY. Since distance (space) changes, but velocity (of light) doesn't, then TIME MUST change.

Get it?

Posted: 10/11/2004 1:53:43 PM EDT

[#39]

Open your window, thats the answer.

Posted: 10/11/2004 2:30:38 PM EDT

[#40]

Does this work with bees ?

Regards,
Mild Bill

Posted: 10/11/2004 3:20:08 PM EDT

[#41]

Quoted:
loost momentum is a terrible thing.

WTF? From you, of all people.

Posted: 10/11/2004 3:24:42 PM EDT

[#42]

Quoted:
The air in the car is travelling at 60 MPH, so the fly isn't affected, but if the fly were to be shooed out the window, I'm sure it would LOSE momentum rapidly as the speed of the car exceeds the flys top speed by a large margin.
I would like to see a slo-mo of how the fly copes with the transition from 60 to 3 MPH in a few seconds. He says whoa, I bet.

That'd be the equilivant of you or I punching out of an aircraft going over Mach 2.5.

In other words, "My day just took a turn for the worst."

Posted: 10/11/2004 3:27:29 PM EDT

[#43]

Quoted:

So because the air in the car is also going the same speed everything in the car would act like it was just not moving at the speed of the car?

Correct.

BTW, here's an interesting experiment...take a helium balloon with you in the car...when you brake sharply, the balloon will actually move to the REAR of the car instead of the front...freaky...

because the air in the car bounced off the windshield and dash while the rear end also lifts up.

Posted: 10/11/2004 3:32:12 PM EDT

[#44]

Quoted:

because the air in the car bounced off the windshield and dash while the rear end also lifts up.

...Huh?

I think there's more physics involved than "AIR RUSHING IN CAR" involved. Also, how would the rear end lifting up affect the balloon at all? The balloon is floating...

Posted: 10/11/2004 11:59:06 PM EDT

[#45]

Quoted:
Quoted:
This has been driving me crazy for years, I hope someone can answer this.

Short drive???

putt???

Tower of Terror - that's easy , no more physical connection between you and the coin and if you push it up it leaves your fingers at a certain speed and then it starts being accelerated down at 32 fps per second. So it will slow to zero and then fall at the normal acceleration due to gravity. You however are being accelerated faster down by the ride mechanism. Ergo the feeling of your lunch heading north in your southbound gullet. Same thing with your drink (or you, if walking around in the plane) your momentum, the liquid continues in it's original motion as the plane pulls you down, drinks momentum, wants to continue in the original motion, and when you are pulled down by the seat belt, it isn't really being held down by anything other than surface tension at that point.

I once saw three wives all find different seats on a Southwest flight when their husbands all started discussing similar topics to this during a gate hold. When the fly takes off here in the plane does the lessening of the weight on the structure get over ridden by the impact of the down draft created by the fly's wings. Does the momentum of the fly when moving forward independent of the aircraft subtract from the sum of momentums due to conservation of momentum, and the conversation went downhill to include a discussion of whether or not the weight of the food being digested by the fly and burned to create kinetic energy, effect on the air conditioning, needing to burn more fuel, to cool more air because of the heat generated by the fly. Total thrust, drag, lift, gravity effects. Do two flys flying in opposite direction cancel each other out?? etc.

I can't understand why the wives left us, I mean them.

Posted: 10/12/2004 12:08:59 AM EDT

[#46]

Quoted:
Quoted:
Quoted:
This has been driving me crazy for years, I hope someone can answer this.

Short drive???

putt???

Tower of Terror - that's easy , no more physical connection between you and the coin and if you push it up it leaves your fingers at a certain speed and then it starts being accelerated down at 32 fps per second. So it will slow to zero and then fall at the normal acceleration due to gravity. You however are being accelerated faster down by the ride mechanism. Ergo the feeling of your lunch heading north in your southbound gullet. Same thing with your drink (or you, if walking around in the plane) your momentum, the liquid continues in it's original motion as the plane pulls you down, drinks momentum, wants to continue in the original motion, and when you are pulled down by the seat belt, it isn't really being held down by anything other than surface tension at that point.

I once saw three wives all find different seats on a Southwest flight when their husbands all started discussing similar topics to this during a gate hold. When the fly takes off here in the plane does the lessening of the weight on the structure get over ridden by the impact of the down draft created by the fly's wings. Does the momentum of the fly when moving forward independent of the aircraft subtract from the sum of momentums due to conservation of momentum, and the conversation went downhill to include a discussion of whether or not the weight of the food being digested by the fly and burned to create kinetic energy, effect on the air conditioning, needing to burn more fuel, to cool more air because of the heat generated by the fly. Total thrust, drag, lift, gravity effects. Do two flys flying in opposite direction cancel each other out?? etc.

I can't understand why the wives left us, I mean them.

How do you know you even went anywhere? The windows could have been High rez displays meant to trick you into believing that you were moving, thus cancelling out your entire theory of the fly.

Posted: 10/12/2004 12:25:00 AM EDT

[#47]

Quoted:
You would think that when it first took off in the car that it would be fine, but would loose it's momentum pretty fast and would slam against the rear windshield. .

Well, tell me what force is going to cause the fly to loose its momentum? Outside, you have air resistance (friction), but inside the car you have none. Imagine you threw something in space. There's nothing to stop it, so it will go damn near forever. Similar concept with the fly inside the moving car as it relates to your momentum perception.